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The aerobiology of the aecial state of the commandra blister rust, Cronartium comandrae Peck, in Alberta. Powell , John Martin 1969

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THE AEROBIOLOGY OF THE AECIAL STATE OF THE COMANDRA BLISTER RUST, CRONARTIUM COMANDRAE PECK, I N ALBERTA by JOHN MARTIN POWELL B . S c , U n i v e r s i t y o f London, 1956 M . S c , M c G i l l U n i v e r s i t y , 1959 A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n t h e Department o f BOTANY We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , I969 0 J o h n M a r t i n P o w e l l 1969 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced deg ree a t the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r ee t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y I f u r t h e r a g r ee t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Depar tment o r by h i s r e p r e s e n t a t i v e s I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n Depar tment o f Z> 0>"T A NY  The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8 , Canada i ' ABSTRACT Cronartium comandrae Peck is a heteroecious native rust which is damaging to several Pinus species in North America. It grows peren-n i a l l y in the li v i n g bark of hard pines producing pycniospores and aeciospores, and develops annually on species of Comandra and Geocaulon producing urediospores, teliospores and basidiospores. Studies were carried out to determine the effect of various meteorological and biological environmental factors on the aeciospore aerobiological phase of the rust. The main aspects considered included the factors affecting aeciospore production and release; and the factors affecting aeciospore transport, dispersion, deposition, germination and v i a b i l i t y . Aeciospore production occurred from mid May to late August, with the peak period between late May and mid June. An average aecium produced spores for 35-50 days, and individual cankers produced spores for up to 95 days. Much variation occurred from year to year and between trees. Aecial production was interfered with by the activity of rodents, insects and other fungi on the canker and through resinosis, which pro-bably accounted for a 50-55$ reduction of the potential aeciospore pro-duction in any year. Fresh rodent damage was recorded on U0-52$ of the cankers at about 20 locations in the years I966 to -I968, insect damage on 39-^6$, Tuberculina and Cladosporium infection on YJ-33?o, and resinosis on 67-71$. Rodent damage was mainly caused by squirrels. Some 6k micro-f l o r a l organisms were isolated from the cankers and spores. Tuberculina  maxima was mainly responsible for k i l l i n g the infected canker bark and i i g r e a t l y r e d u c e d t h e p r o d u c t i o n o f a e c i o s p o r e s . P e n i c i l l i u m spp. and an u n d e s c r i b e d C l a d o s p o r i u m were a l s o p r o m i n e n t on t h e c a n k e r s b u t p l a y e d a l e s s e r r o l e i n r e d u c i n g p r o d u c t i o n . One hundred and s e v e n t e e n s p e c i e s o f i n s e c t s , m i t e s and s p i d e r s were a s s o c i a t e d w i t h t h e r u s t c a n k e r . E p u r a e a  o b l i q u u s , an u n i d e n t i f i e d c e c i d o m y i i d a e and P a r a c a c o x e n u s g u t t a t u s were t r u e m y c e t o b i o n t s . V a r i o u s o t h e r s p e c i e s caused damage t o t h e ca n k e r , i n c l u d i n g D i o r y c t r i a , P i s s o d e s s c h w a r z i and C y l i n d r o c o p t u r u s d e l e o n i . D a i l y a e c i o s p o r e p e r i o d i c i t y showed s p o r e s t o be n o r m a l l y d i s -p e r s e d between 0800 and 1900 h o u r s , w i t h some e v i d e n c e o f a d o u b l e peak between 1000 and 1600 h o u r s , and l i t t l e d i s p e r s a l between 2000 and 0700 h o u r s . T u r b u l e n t a t m o s p h e r i c c o n d i t i o n s were a s s o c i a t e d w i t h a l l peak a e c i o s p o r e c o n c e n t r a t i o n s . Heavy r a i n s i n i t i a l l y i n c r e a s e d s p o r e c oncen-t r a t i o n s , b u t no d i s p e r s a l o c c u r r e d d u r i n g l o n g humid c o o l p e r i o d s . S p o r e d e p o s i t i o n c o n c e n t r a t i o n s were v e r y s t e e p c l o s e t o s o u r c e , and showed a t y p i c a l h o l l o w c u r v e d e p o s i t i o n g r a d i e n t . Spore c o n c e n t r a t i o n s f r o m a r t i f i c i a l r e l e a s e p o i n t s were s i m i l a r l y r e d u c e d w i t h d i s t a n c e f r o m s o u r c e , l a r g e l y b y d i f f u s i o n . A e c i o s p o r e s had an average v e l o c i t y o f 3.23 cm/sec i n c a lm a i r . R a p i d d e p l e t i o n o f spor e c o n c e n t r a t i o n o c c u r r e d under t h e f o r e s t canopy, m a i n l y b y s e d i m e n t a t i o n , a l t h o u g h a e c i o s p o r e s had good im-p a c t i o n e f f i c i e n c y . A e c i o s p o r e s g e r m i n a t e d on w a t e r agar o v e r t h e t e m p e r a t u r e r a n g e 1-30°C, w i t h optimum f o r g e r m i n a t i o n and germ t u b e g r o w t h c l o s e t o 15°C. Most a e c i o s p o r e s g e r m i n a t e d w i t h i n k-5 h o u r s , w i t h a r e d u c t i o n i n r a t e o f germ t u b e e l o n g a t i o n a f t e r 8 h o u r s and l i t t l e i n c r e a s e a f t e r 2k h o u r s . F r e e w a t e r was n e c e s s a r y f o r g e r m i n a t i o n ; a l l s p o r e s s w e l l e d p r i o r t o g e r m i n a t i o n . A e c i o s p o r e s g e r m i n a t e d e q u a l l y w e l l i n t h e d a r k and l i g h t , i i i and g e r m i n a t e d o v e r t h e pH ra n g e k.5-8. G e r m i n a t i o n r e s p o n s e on sugar media was b e t t e r t h a n on some o t h e r media, b u t a d d i t i o n o f a l t e r n a t e h o s t m a t e r i a l t o me d i a d i d not improve g e r m i n a t i o n . D a i l y a e c i o s p o r e c o l l e c t i o n s gave h i g h g e r m i n a t i o n p e r c e n t a g e s f o r 2-k weeks, b u t much l o w e r p e r c e n t a g e s d u r i n g l a t e r s p o r u l a t i o n p e r i o d . A e c i o s p o r e g e r m i n a t i o n was l o w e r f r o m exposed t h a n p r o t e c t e d a e c i a , and wet s p o r e s g e r m i n a t e d p o o r l y . V i a b i l i t y was r e d u c e d b y c o n t a m i n a t i o n f r o m a s s o c i a t e d f u n g i . A e c i o s p o r e s l o s t v i a b i l i t y v e r y r a p i d l y when ex-pos e d t o t e m p e r a t u r e s above 25°C; t e m p e r a t u r e s c l o s e t o 0°C were most f a v o u r a b l e . H i g h h u m i d i t y a f f e c t e d v i a b i l i t y , b u t u l t r a d r y c o n d i t i o n s were a l s o a d v e r s e . D i r e c t s u n l i g h t r e d u c e d v i a b i l i t y r a p i d l y . G e n e r a l l y , d a i l y c o n d i t i o n s f a v o u r i n g d i s p e r s a l were l e a s t f a v o u r a b l e f o r g e r m i n a t i o n and v i a b i l i t y r e t e n t i o n . i v TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS i v LIST OF TABLES i x LIST OF FIGURES x i i i ACKNOWLEDGMENTS x x i v INTRODUCTION 1 THE ORGANISM 5 HISTORY OF THE FUNGUS 5 DISTRIBUTION AND HOSTS 10 D i s t r i b u t i o n o f t h e r u s t on P i n u s 11 D i s t r i b u t i o n o f t h e r u s t on S a n t a l a c e a e Ik L I F E CYCLE 2k SYMPTOMS 37 DAMAGE kl AREA OF STUDY 1+8 LOCATION, PHYSIOGRAPHY AND GEOLOGY 48 SOILS 50 CLIMATE 50 VEGETATION 6 l STUDY LOCATIONS 62 V AECIOSPORE PRODUCTION 65 PERIODS OF AECIOSPORE PRODUCTION AND ENVIRONMEfflTAL FACTORS AFFECTING SPORULATION 65 Methods 65 R e s u l t s 66 D i s c u s s i o n 75 BIOLOGICAL FACTORS AFFECTING AECIOSPORE PRODUCTION 78 Methods 78 R e s u l t s 82 M i c r o f l o r a 82 M i c r o f a u n a 91 Rodents 102 Response o f t h e t r e e 107 D i s c u s s i o n 109 AECIOSPORE DISPERSAL 128 METEOROLOGICAL FACTORS AFFECTING DISPERSAL 128 Methods and M a t e r i a l s 128 E x p e r i m e n t a l s i t e s 128 Spore c o l l e c t o r s 131 M e t e o r o l o g i c a l i n s t r u m e n t s 136 R e s u l t s 139 D i u r n a l p e r i o d i c i t y o f m e t e o r o l o g i c a l f a c t o r s , and t h e m i c r o c l i m a t e o f s t u d y l o c a t i o n 1 139 D i u r n a l s p o r e p e r i o d i c i t y l 4 l E f f e c t o f r e l a t i v e h u m i d i t y and t e m p e r a t u r e 146 E f f e c t o f r a i n f a l l 150 v i E f f e c t o f dew 15I4. E f f e c t o f w i n d 155 A v a i l a b i l i t y o f s p o r e s 155 S e a s o n a l s p o r e p e r i o d i c i t y 156 AECIOSPORE DISPERSAL FROM A NATURAL POINT SOURCE 159 Methods and M a t e r i a l 159 R e s u l t s 162 OTHER DATA ON DISTANCE OF AECIOSPORE DISPERSAL 171 AECIOSPORE DISPERSAL EXPERIMENTS FROM POINT SOURCES 173 M a t e r i a l s and Methods 173 E x p e r i m e n t a l arrangement 175 E x p e r i m e n t a l p r o c e d u r e 179 A n a l y s i s o f d a t a l 8 l R e s u l t s 18U C o n c e n t r a t i o n p a t t e r n s l8k Change o f c o n c e n t r a t i o n w i t h d i s t a n c e l8h RATE OF FALL OF AECIOSPORES I N CALM AIR 197 M a t e r i a l s and Methods 197 R e s u l t s 200 AECIOSPORE DISPERSAL DISCUSSION 205 M e t e o r o l o g i c a l f a c t o r s and s p o r e p e r i o d i c i t y 205 S p o r e d i s p e r s a l 213 AECIOSPORE GERMINATION 228 FACTORS AFFECTING AECIOSPORE GERMINATION 230 Methods and M a t e r i a l s 230 v i i Spore m a t e r i a l and methods of handling 230 Methods f o r e x p l o r a t o r y experiments 231 Methods f o r subsequent experiments . 23^ R e s u l t s 2k0 E f f e c t of temperature on germination 2k0 E f f e c t of humidity on germination 2k7 S w e l l i n g of spores on ... l i q u i d media 2^9 E f f e c t of h y d r a t i o n of spores on germination 251 E f f e c t of l i g h t on germination 252 E f f e c t of hydrogen i o n concentration on germination 255 E f f e c t of substrate on germination 257 a. Various agar media 257 b. A d d i t i o n of sucrose to media 259 c. Presence of host leaves on, or l e a f e x t r a c t s i n the media 2.6o D i s c u s s i o n 262 DAILY AECIOSPORE GERMINATION 270 Methods and M a t e r i a l s 270 R e s u l t s and D i s c u s s i o n 272 AECIOSPORE VIABILITY 283 Methods and M a t e r i a l 283 R e s u l t s 287 E f f e c t of temperature on spore v i a b i l i t y 287 E f f e c t o f humidity on spore v i a b i l i t y 292 • E f f e c t of l i g h t on spore v i a b i l i t y 29U v i i i D i s c u s s i o n 297 SUMMARY AM) CONCLUSION 302 LITERATURE CITED 321 APPENDIX I 353 APPENDIX I I 356 i x LIST OF TABLES TABLE Page I Monthly and annual c l i m a t i c summaries f o r Kananaskis, 53 l a t . 51°02'W, long. 115°03'W; e l e v . k,560 f t MSL, f o r the p e r i o d o f record (1939-1968). I I Monthly and annual c l i m a t i c summaries f o r s e l e c t e d 54 s t a t i o n s i n the Marmot Creek Research Basin, l a t . 50°57'N, long. 115° 1 0 % elev. 5,300-^8,000 f t MSL (1962-1967). I I I Monthly temperature and p r e c i p i t a t i o n averages at Kan- 55 anaskis Boundary Ranger S t a t i o n , l a t . 50°55'N, long. 115°08'W, elev. 4,800 f t MSL (1962-1968)., and Pigeon Mountain Lookout, l a t . 51°03'N, long. 115°04% el e v . 6,000 f t MSL (1960-1968), compared w i t h those at Kananaskis f o r a s i m i l a r p e r i o d (1963J-I968). IV Date of beginning and end of Cronartium comandrae 67 aeciospore production, and main s p o r u l a t i o n p e r i o d at a number of l o c a t i o n s i n the years 1964 - 1968' i n c l u s i v e . V Date of beginning and end of spore production, and 68 : t o t a l number of days of production from i n d i v i d u a l cankers at l o c a t i o n 1 from 1965 to 1968 i n c l u s i v e . Main spore production p e r i o d i s i n c l u d e d f o r 3 to 6 cankers f o r the years 1965 to I967. VI Average number of days and range o f days of ae c i o - 74 spore production f o r i n d i v i d u a l p u s t u l e s on s e v e r a l cankers i n 1966 and I967 at l o c a t i o n 1. V I I Summary of sequence of s p o r u l a t i o n f o r 30 and 20 74 p u s t u l e s on two cankers at l o c a t i o n 1 i n 1967. V I I I The recorded incidence of Tuber c u l i n a maxima on 83 Cronartium comandrae cankers on lodgepole pine and the t o t a l number of a c t i v e and i n a c t i v e cankers ob-served at var i o u s l o c a t i o n s i n southwest A l b e r t a during the years 1964 to 1968. IX The incidence of Tuber c u l i n a maxima on observed 87 a c t i v e and i n a c t i v e Cronartium comandrae cankers at 7 l o c a t i o n s during the years 1964 to 1968. X X The number of Cronartium comandrae a e c i a l cankers ( l ) producing aeciospores, (2) s p o r u l a t i n g but i n f e c t e d w i t h Tuberculina, (3) w i t h i n a c t i v e a e c i a l zones i n -fecte d w i t h Tuberculina, (k) w i t h i n a c t i v e or dead cankers, at two l o c a t i o n s during the years 1966 to 1968. XI The recorded incidence of Cladosporium tax. sp. 1 on Cronartium comandrae cankers observed at v a r i o u s l o c a t i o n s i n southwest A l b e r t a during the years I965 to 1968. X I I The incidence of i n s e c t damage on Cronartium comandrae cankers on lodgepole pine and the num-ber o f cankers observed at v a r i o u s l o c a t i o n s i n southwest A l b e r t a during the years 1964 to 1968. 92 X I I I The incidence of new rodent damage on Cronartium 10k comandrae cankers, and the number of cankers observed at va r i o u s l o c a t i o n s i n southwest A l b e r t a during the years 1966 to I968. XIV The percentage incidence of f r e s h rodent chewing 106 of Cronartium comandrae cankers at s e l e c t e d l o c a t i o n s d u r ing the years 1966 to 1968. XV XVI The incidence of f r e s h r e s i n o s i s on Cronartium  comandrae cankers on lodgepole pine and the number of cankers observed at a number of l o c a -t i o n s i n southwest A l b e r t a during the years 1966 to 1968. The h o u r l y mean temperature, r e l a t i v e humidity and wind speed at two canker s t a t i o n s , compared w i t h records from the Bay s t a t i o n f o r temperature and humidity, and from Kananaskis f o r wind speed, f o r the p e r i o d May 17 to J u l y 11, 1966. 109 iko XVII Number of aeciospores deposited on n a t u r a l l e a f surfaces c o l l e c t e d along the four c a r d i n a l r a d i i at v a r i o u s d i s t a n c e s from a s p o r u l a t i n g Cronartium  comandrae canker on J u l y 7, 1968, at l o c a t i o n 3-170 X V I I I Average number of aeciospores deposited per square centimeter on spore c o l l e c t o r coated s l i d e s at d i s -tances of 5, 10 and 15 feet along ei g h t r a d i i a-round a s p o r u l a t i n g Cronartium comandrae canker at l o c a t i o n 33 on 9 days between June 2k and J u l y 15, 1968. 170 x i XIX P a r t i c u l a r s of experiments on d i s p e r s i o n of Cron- l80 artium comandrae aeciospores from a p o i n t source. XX T o t a l number of spores trapped at one foot above 185 ground at each distance on a l l r a d i i . XXI T o t a l number of spores trapped at 5 and 10 f e e t a- 185 bove ground at 20, 50, 100 and 150 f e e t on f i v e r a d i i . XXII R e s u l t s of Experiment X, showing number of spores 190 trapped on an area of 13-5 sq cm at the one foot l e -v e l at each sampling p o i n t . X X I I I Comparison of the observed and expected concentra- 195 t i o n of spores at four distances from the 5 f o o t r e l e a s e p o i n t during ei g h t t e s t s . XXIV Percentages of i n d i v i d u a l t e s t s of aeciospores 201 of Cronartium comandrae deposited 3 meters from p o i n t of l i b e r a t i o n on gl a s s s l i d e s exposed suc-c e s s i v e l y f o r 15 second periods i n a closed c y l i n -der. XXV Average r a t e of f a l l i n s t i l l a i r of ten aeci o - 202 spore t e s t s . XXVI Number of aeciospore clumps deposited 3 meters from 203 p o i n t of l i b e r a t i o n on glass s l i d e s exposed s u c c e s s i v e l y f o r 15 second periods i n a closed c y l i n d e r . XXVII Average r a t e of f a l l i n s t i l l a i r of dry and wet 20k aeciospores during two t e s t s . XXYIII Average l e n g t h and width (|a) of aeciospores 205 deposited on s l i d e s during the dry and wet-spore t e s t s o f r a t e o f f a l l . XXIX Average number of germ tubes per spore, and the 2^3 range of the average f o r four t e s t s e r i e s at var i o u s temperatures. XXX Average l e n g t h and width ( i n microns) of 25 a e c i o - 250 spores from 5 f r e s h or stored samples. Measure-ments were made on dry spores and when spores were placed on a Czapek-Dox agar medium. XXXI Average germination percentages f o r spores 252 stored f o r v a r i o u s periods of time at -k°C, and then germinated, dry or a f t e r 2k hours hy-d r a t i o n i n a saturated humidity, on Czapek-Dox agar at 15°'C. X l l E f f e c t of l i g h t and dark c o n d i t i o n s on percent germination and germ tube growth of three s e r i e s of aeciospore samples, germinated on Czapek-Dox agar at 15-C or under f l u c t u a t i n g outside tem-peratures f o r 2k hours. E f f e c t of dark and three colored l i g h t wave bands on percent germination and germ tube growth of three s e r i e s of aeciospore samples, germinated at 15°C on Czapek-Dox agar f o r 2k hours. Average percentage and range of germination of two s e r i e s of aeciospores a f t e r 2k hours on d i f f e r e n t media at 15°C. Average number of germ tubes and lengths of germ tubes per spore f o r three samples on seven d i f f e r e n t media a f t e r 2k hours at 15°C. Average germination percentages o f f i v e a e c i o -spore samples stored at s i x temperatures and germinated on water agar at 15°C a f t e r v a r i o u s i n t e r v a l s of storage. Average germination percentages o f aeciospore samples stored f o r four to s i x days at v a r i o u s temperatures and germinated on water agar at 15°C Average percentage germination of a number of spore samples given two methods of r a p i d c o o l i n g and stored at -20°C f o r periods between 7 and 18 days, and then germinated on water agar at 15°C f o r 2k hours. A p o r t i o n of the l i q u i d n i t r o g e n cooled spores was r a p i d l y thawed f o r one minute at 38°C p r i o r t o seeding on the agar. Average number of germ tubes per spore and average l e n g t h of longest germ tube i n three dry-humid treatments a f t e r v a r i o u s i n t e r v a l s of storage. x i i i LIST OF FIGURES Figure Page 1 D i s t r i b u t i o n of Cronartium comandrae on 15 Pinus species i n western Canada. 2 D i s t r i b u t i o n of Cronartium comandrae on 16 Pinus species i n eastern Canada. 3 A e r i a l stems of Geocaulon l i v i d u m , w i t h 17 a x i l l a r y greenish f l o w e r s . h A e r i a l stems of Comandra umbellata ssp. 17 p a l l i d a , w i t h t e r m i n a l white flowers about to break open. 5. S e r i e s of a e r i a l stems of Comandra umbellata 17 ssp. p a l l i d a , which branch j u s t below the s o i l , and are attached to an underground rhizome. Some a e r i a l stems dead from pre-vious year. 6 Large haustorium of Comandra umbellata ssp. 17 p a l l i d a attached to Populus tremuloides Michx. r o o t , w i t h smaller haustorium on smaller r o o t . 7 D i s t r i b u t i o n of Cronartium comandrae on the 22 S a n t a l a c e a e , Comandra umbellata and Geocaulon ' l i v i d u m , i n western Canada. 8 D i s t r i b u t i o n o f Cronartium comandrae on the 23 Santalaceae, Comandra umbellata and Geocaulon l i v i d u m , i n eastern Canada. 9 Transverse s e c t i o n s taken from the c e n t r a l 26 p o r t i o n of four Cronartium comandrae cankers on lodgepole pine showing e c c e n t r i c growth caused by the r u s t . Note the r e s i n impreg-n a t i o n of the outer sapwood. 10 Transverse s e c t i o n s taken from the c e n t r a l 26 p o r t i o n of f i v e Cronartium comandrae cankers on lodgepole pine showing e c c e n t r i c growth caused by the r u s t . x i v Transverse s e c t i o n taken through the a e c i a l zone of a Cronartium comandrae canker showing the a e c i a s i t u a t e d i n the bark t i s s u e s . Note the r e s i n impregnation of the bark between aeci a , and the s w e l l i n g of the outer r i n g - o f sapwood caused by the fungus. P y c n i a l drops on the p y c n i a l zone of a Cronar-tium comandrae canker on the stem and branches of a lodgepole pine. Note the s w e l l i n g of the stem a s s o c i a t e d w i t h the canker. Group of p y r i f o r m pycniospores of Cronartium  comandrae. X 2500. P y r i f o r m aeciospores of Cronartium comandrae showing s i z e and shape v a r i a t i o n of the spore t a i l . X 700. P y r i f o r m aeciospores of Cronartium comandrae showing the spore w a l l ornamentation. X 700. Canker.of Cronartium comandrae on a young branch of Pinus contorta, w i t h the p e r i d i a of the a e c i a s t i l l unruptured and forming t y p i c a l b l i s t e r s pushing through the bark. Canker of Cronartium comandrae w i t h abundant ruptured a e c i a covering the a e c i a l zone. B r i g h t orange-colored aeciospores of Cronartium  comandrae covering the exposed a e c i a of the canker. Young canker of Cronartium comandrae on Pinus  c o n t o r t a w i t h rough bark covering the o l d a e c i a l zone around the branch stub t h a t acted as entry p o i n t to the stem. Abundant a e c i a were produced around the o l d a e c i a l zone. S l i g h t hypertrophy of the young Pinus c o n t o r t a stem caused by Cronartium comandrae, w i t h c h a r a c t e r i s t i c rough, cracked bark, i n the o l d e r canker area caused by a e c i a r u p t u r i n g . T y p i c a l b a s a l stem canker of Cronartium coman-drae showing o l d e r rough bark zone and current year a e c i a l zone w i t h many dispersed aeciospores caught i n the c r e v i c e s of the bark. XV 22 Aeciospores of Cronartium comandrae, stained' 33 w i t h HC1 - Giemsa, each w i t h two n u c l e i . X 700. 23 Aeciospore of Cronartium comandrae, st a i n e d w i t h 33 HC1 - Giemsa, w i t h two n u c l e i . X 1200, 2k I n i t i a t i o n o f aeciospore germination, w i t h four 33 germ tubes developing through the spore w a l l , a f t e r 1 hour. X 1200. 25 Cronartium comandrae aeciospore w i t h s e v e r a l 33 germ tubes, but only one germ tube w e l l developed a f t e r 6 hours. Note the short-m u l t i p l e branches on the non-septate germ tube. X 380. 26 Group of germinated aeciospores w i t h t y p i c a l 33 branching of germ tubes a f t e r 2k hours. X 125. 27 Aeciospore of Cronartium comandrae w i t h one 3^ developed germ tube, a f t e r 3 hours. Note the non-septate c o n d i t i o n of the germ tube and t h a t the two n u c l e i have migrated towards the t i p of the germ tube. X 830. 28 Germ tubes of two Cronartium comandrae aeci o - - 3^+ spores a f t e r 3 hours, showing development of a globose and club-shaped appressorium on the developed germ tube, i n t o which the two n u c l e i have migrated. X 700. 29 Germ tube development of a Cronartium comandrae 3^+ aeciospore a f t e r 3 hours, showing a globose ap-pressorium w i t h two n u c l e i and an i n f e c t i o n peg. x 1080. 30 Germ tube development of two Cronartium coman- 3^ drae aeciospores a f t e r 3 hours, showing two types of a p p r e s s o r i a each w i t h two n u c l e i and an i n f e c t i o n peg. X 6l0. 31 U r e d i a of Cronartium comandrae on c e n t r a l p o r t i o n 35 of a Comandra umbellata ssp. p a l l i d a l e a f . Dark s t r u c t u r e s on bottom are young t e l i a . 32 T e l i a of Cronartium comandrae on both surfaces 35 of a p o r t i o n - o f a Comandra umbellata ssp. p a l l i d a l e a f . x v i Branch i n f e c t i o n o f Cronartium comandrae on Pinus contorta, w i t h mycelium causing s w e l l i n g i n the main stem around the branch stub. Tree w i t h dead spike-top above a canker of Cronartium comandrae g i r d l i n g the t r e e ; lower branches are p r o g r e s s i v e l y k i l l e d by downward growth of r u s t . Heavy r e s i n o s i s forming a d r i e d c r u s t over a p o r t i o n of a Cronartium comandrae stem canker. Note rough bark of o l d branch canker (upper l e f t ) which served as entry f o r the r u s t to the stem. Annual rodent damage on a l a r g e Cronartium  comandrae stem canker on Pinus contorta. Note the s t r i p of d r i e d dead bark not removed on each annual v i s i t , and the abundant exudation of r e s i n . Rodentcdamage on a Cronartium comandrae stem canker around a branch which acted as an entry p o i n t f o r the r u s t i n t o the stem. Sporu-l a t i o n of the a e c i a l zone can be seen outside the chewed area. Map of the lower Kananaskis R i v e r V a l l e y , A l b e r t a , showing the l o c a t i o n s o f the main study areas. Study l o c a t i o n 1, on the Kananaskis Forest Experiment S t a t i o n , near the northeast shore of B a r r i e r Lake, showing the l o c a t i o n of i n f e c t e d lodgepole pine, Comandra p l a n t p l o t s , and i n -struments used during the study. Summary of the d a i l y maximum and minimum temperatures and r e l a t i v e humidity taken from hygrothermograph records, the d a i l y r a i n f a l l , and the phenology of the a e c i a l , p y c n i a l , u r e d i a l and t e l i a l s t a t e s of Cronartium  comandrae, May to August i n I965 and 1966. Summary of the d a i l y maximum and minimum tem-peratures and r e l a t i v e humidity taken from hy-grothermograph records, the d a i l y r a i n f a l l , and the phenology of the a e c i a l , p y c n i a l , u r e d i a l and t e l i a l s t a t e s of Cronartium comandrae, May to August i n I967 and 1968. XV11 A p l a s t i c screening c y l i n d r i c a l - s l e e v e cage used f o r c o l l e c t i n g i n s e c t s from Cronartium  comandrae cankers on stems of Pinus contorta. Rough, cracked bark of the a e c i a l zone of a Cronartium comandrae canker i n f e c t e d w i t h the purple mold, Tuberculina maxima, which i s conspicuous as a darker area where the surface bark has been removed, or cracked. B a s a l canker of Cronartium comandrae w i t h t y p i c a l rough bark i n a e c i a l zone and showing evidence of i n s e c t damage. Note e x i t holes and Lepidoptera f r a s s at top of canker, and f u r t h e r f r a s s i n lower rough zone. Pupal chambers of Pissodes schwarzi scored i n t o the sapwood throughout the Cronartium  comandrae canker area on s m a l l Pinus c o n t o r t a stem. View of s i t e no. 2 at study l o c a t i o n 1, showing a 24-hour impaction spore c o l l e c t o r by Cronartium comandrae canker no. 2721 on a s m a l l Pinus contorta, and instruments f o r r e c o r d i n g the weather. Instruments are, from l e f t to r i g h t , b l a c k porous d i s c atmometer, instrument s h e l t e r c o n t a i n i n g hygrothermograph, Wallin-Polhemus dew d u r a t i o n recorder on ground, mast w i t h anemometer cups f o r wind speed recorder and spore c o l l e c t o r . (Rain gauge i s out of the p i c t u r e ) Standard Stevenson screen i n an opening, con-t a i n i n g hygrothermograph and thermometers used as reference weather s t a t i o n at study area 1, w i t h a b i - m e t a l actinograph f o r r e c o r d i n g i n -coming r a d i a t i o n seen at the back. A r e c o r d -i n g r a i n gauge and a wind d i r e c t i o n recorder (out of the p i c t u r e ) were maintained at t h i s open s i t e . A H i r s t spore trap w i t h sampling o r i f i c e one foot above ground, close to a Comandra um-b e l l a t a p l o t . x v i i i 49 Seven-day p o l l e n sampler of the Sarvas type, 130 used to c o l l e c t aeciospores at set distances from s p o r u l a t i n g Cronartium comandrae cankers. Spores pass through the sampler o r i f i c e and are deposited on a vaseline-coated'sampling band placed around a c l o c k - d r i v e n drum housed w i t h i n the i n t a k e c y l i n d e r . 50 A 24-hour impaction spore c o l l e c t o r , w i t h the 133 sealed l i d removed to show the a c r y l i c p l a s t i c d i s c h o l d i n g 24 microscope s l i d e s upon which spores are deposited, and the fan f o r drawing a i r through the box at a c o n t r o l l e d r a t e . 51 A 24-hour impaction spore c o l l e c t o r i n opera- 133 t i o n , w i t h i t s sampling o r i f i c e placed close to the sporulating surface of a Cronartium  comandrae canker. 52 C e n t r a l instrument power and r e c o r d i n g box, 133 w i t h Thorntbmte f o u r - u n i t wind speed r e g i s t e r recorder ( l e f t ) , wind d i r e c t i o n recorder, and d i g i t a l p r i n t o u t recorder w i t h p o l a r o i d camera f o r wind speed recorder system ( r i g h t ) . Behind are the transformers and r e c t i f i e r s f o r reducing the 110 v o l t power supply and c o n t r o l l i n g an output of 12 v o l t s f o r operation of wind i n -struments, dew instruments and 24-hour impaction spore c o l l e c t o r s . A standby 12 v o l t b a t t e r y i s a l s o present. 53 Set of anemometer cups of the Thornthwaite 133 wind speed r e g i s t e r recorder system operated at canker height near a s p o r u l a t i n g Cronartium  comandrae canker. 54 Mean d i u r n a l aeciospore p e r i o d i c i t y curves 143 f o r three cankers over v a r y i n g periods of t r a p p i n g i n the years 1964 to I967, expressed as a percentage of the peak geometric mean hou r l y concentration. 55 Frequency of h o u r l y maximum aeciospore concen- l45 t r a t i o n s from three Cronartium comandrae can-kers on 91 dry and 40 r a i n y days i n 1966 and 95 dry and 29 r a i n y days i n 1967, during the main spore production p e r i o d s . 56 Average hou r l y aeciospore concentrations 147 c o l l e c t e d from three Cronartium comandrae cankers i n June 1966. x i x Average h o u r l y aeciospore concentrations c o l l e c t e d from three Cronartium comandrae cankers from June 6 to 25, I967. Average hou r l y aeciospore concentration c o l -l e c t e d from Cronartium comandrae canker no. 2713 during periods without r a i n (average 19 to 2k days) i n June 1966, compared w i t h the aver-age h o u r l y a i r temperature, r e l a t i v e humidity and wind speed. Hourly number of aeciospores c o l l e c t e d from Cronartium comandrae canker no. 25l6 during the p e r i o d June 7 to J u l y 3, I965, r e l a t e d to hourl y a i r temperature, r e l a t i v e humidity, r a i n f a l l , incoming r a d i a t i o n and wind speed. Hourly number of aeciospores c o l l e c t e d from Cronartium comandrae canker no. 2721 during the p e r i o d May 29 to June 95 1966, r e l a t e d to a i r temperature, r e l a t i v e humidity, r a i n -f a l l , incoming r a d i a t i o n and wind speed. D a i l y number of aeciospores c o l l e c t e d from two Cronartium comandrae cankers during the 1966 spore production p e r i o d , p l o t t e d on semi-log s c a l e . D a i l y number of aeciospores c o l l e c t e d from Cronartium comandrae canker no. 2713 during I965, I966 and 1967, p l o t t e d on semi-log s c a l e . P a t t e r n of aeciospore d e p o s i t i o n around Cronartium comandrae canker no. 2713 during a ICH5- hour p e r i o d on June 23, 1967-The average percentage change of aeciospore d e p o s i t i o n concentration w i t h distance on eight r a d i i around Cronartium comandrae canker no. 2713 on June 23, 1967, and the percentage change on the southeast r a d i i , p l o t t e d on semi-log s c a l e . P a t t e r n of aeciospore d e p o s i t i o n around Cronartium comandrae canker no. 2689, on three days (0800 to IcOO'J-hours) i n June 1968. XX The average percentage change o f aecio -spore d e p o s i t i o n w i t h d i s t a n c e around Cronartium comandrae canker no. 2689, on three days (0800 to l600 hours) i n June 1968, p l o t t e d on semi-log s c a l e . Spore-ejector used f o r l i b e r a t i n g a e c i o -spores i n d i s p e r s a l experiments from p o i n t source. Compressor u n i t v w i t h connecting rubber tubing, f o r r e g u l a t i n g a i r flow f o r r e -lease of aeciospores i n d i s p e r s a l experiments. W i n d - d i r e c t i o n a l p l a s t i c s l i d e holder spore c o l l e c t o r s (without microscope s l i d e s ) used f o r c o l l e c t i n g aeciospores i n d i s p e r s a l experiments and from n a t u r a l sources. P o r t i o n of spore c o l l e c t o r network, w i t h c o l l e c t o r s on d i f f e r e n t r a d i i at var i o u s distances from r e l e a s e p o i n t . Wind d i r e c t i o n vane and wind speed anemometer can be seen to the l e f t o f the stand f o r the spore-ejector. Note spore c o l l e c t o r s at 5 and 10 f e e t on the masts. P o r t i o n of spore c o l l e c t o r network w i t h c o l l e c t o r s on d i f f e r e n t r a d i i at var i o u s distances from spore-ejector at r e l e a s e p o i n t . Wind speed anemometer at l e f t of s p o r e - e j e c t o r . Diagram of p o i n t source aeciospore d i s p e r s a l experiment sampling g r i d , w i t h 113 sampling c o l l e c t o r s l a i d out f o r southwest winds. Spore c o l l e c t o r s were a l s o l o c a t e d at the 300 and kOO foot distances along the m i d - l i n e . Aeciospore concentration p a t t e r n s at three sampling heights f o r a spore r e l e a s e one foot above ground (Experiment V I I ) . Aeciospore concentration patterns at three sampling heights f o r a spore r e l e a s e f i v e • f e e t above ground (Experiment X ) . xx i Composite aeciospore concentration p a t t e r n s at three sampling heights f o r a l l e i g h t spore r e l e a s e s f i v e f e e t above ground (Experiments I I - VI, V I I I - X ) . V e r t i c a l p r o f i l e s of aeciospore concen-t r a t i o n p atterns along the m i d - l i n e of the sampling network f o r two spore r e -leases at one foot (Experiments I and V I I ) , and two spore r e l e a s e s f i v e f e e t above ground (Experiments V and X ) . V e r t i c a l p r o f i l e s of aeciospore concen-t r a t i o n p atterns along the m i d - l i n e and f o r k5° and 90° sectors of the sampling network, f o r one spore r e l e a s e at f i v e f e e t above ground (Experiment V I I I ) . Composite v e r t i c a l p r o f i l e s of aeciospore concentration p a t t e r n s along the m i d - l i n e and f o r ^5° and 90° sectors of the sam-p l i n g network, f o r a l l e ight spore r e l e a s e s f i v e f e e t above ground (Experiments I I -VI, V I I I - X ) . E f f e c t of temperature on per cent germina-t i o n of three Cronartium comandrae aecio-spore samples a f t e r 2k hours on water agar (pH 6 .8 ) . E f f e c t of temperature on Cronartium com-andrae aeciospore germination. Average percent germination of f i v e s e r i e s and v a r i o u s numbers of r e p l i c a s w i t h three to f i v e samples each, a f t e r 2k hours on water agar. Average l e n g t h of. germ tubes of three Cronartium comandrae aeciospore samples germinated oh water agar (pH 6.8). a f t er 2k hours at v a r i o u s temperatures. (a) Length of longest germ tube per spore, (b) Length of a l l germ tubes per spore. Inf l u e n c e of v a r i o u s temperatures on r a t e of Cronartium comandrae aeciospore germina-t i o n a f t e r v a r i o u s time i n t e r v a l s on water agar. x x i i 83 Average r a t e of germination of three Conartium 246 comandrae aeciospore samples at d i f f e r e n t tem-peratures and a f t e r v a r i o u s time i n t e r v a l s on water agar. 8 4 Average l e n g t h of the longest germ tube from 2 4 8 three to f i v e Cronartium comandrae aeciospore samples germinated on..water agar at d i f f e r e n t temperatures and a f t e r v a r i o u s time i n t e r v a l s . 85 E f f e c t o f hydrogen i o n concentration on germ- 256 i n a t i o n of Cronartium comandrae aeciospores a f t e r 24 hours at 15 and 20°C. 86 E f f e c t of hydrogen i o n concentration on 256 germination of Cronartium comandrae aec i o -spores a f t e r 2 4 hours at 5, 15 and 25°C. Spore samples were stored f o r 4 and 6 weeks at 0°C p r i o r to use. 87 Average d a i l y per cent germination of f i v e 273 to seven Cronartium comandrae aeciospore samples a f t e r 24 hours on water agar at 15°C, f o r the years 1965, 1966 and 1967. 88 D a i l y per cent germination of aeciospores 275 from two Cronartium comandrae cankers f o r the years 1965, 1966 and 1967. 89 V a r i a t i o n i n the d a i l y per cent germination 276 of aeciospores from seven Cronartium com-drae cankers i n I965. 90 D a i l y per cent germination of aeciospores 277 from f i v e i n d i v i d u a l a e c i a of a Cronartium comandrae canker during the 1966 s p o r u l a t i o n p e r i o d . 91 D a i l y per cent germination of aeciospores from 278 f i v e i n d i v i d u a l a e c i a of a Cronartium comandrae canker during the I967 s p o r u l a t i o n p e r i o d . 92 Average per cent germination o f three Cronartium 288 comandrae aeciospore samples stored at three temperatures, and germinated on water agar at 15°C a f t e r v a r i o u s hours o f storage. XX 111 Average per cent germination of f i v e Cronartium comandrae aeciospore samples stored i n a wet, dry or u l t r a dry atmos-phere, and germinated on water agar at 15°C a f t e r v a r i o u s i n t e r v a l s of storage. E f f e c t of exposure of Cronartium comandrae aeciospores to d i r e c t l i g h t f o r v a r y i n g lengths of time on c l e a r sunny days (June 16, and J u l y 5, 1966; June 23, 1967), and on a cloudy day (June 16, 1967). x x i v ACKNOWLEDGMENTS I wish to express my sin c e r e g r a t i t u d e to the l a t e Dr. J . E. Bi e r f o r h i s enlightened guidance and communicative enthusiasm throughout-much of t h i s i n v e s t i g a t i o n . I wish a l s o to thank Dr. R. J . Bandoni, Dr. A. L. F a r l e y , Dr. P. G. Haddock, Dr. T. M. C. Taylor, Dr. G. H. N. Towers, and Dr. B. J . van der Kamp, f o r t h e i r counseling and as s i s t a n c e i n the pr e p a r a t i o n o f the t h e s i s . Thanks are extended to the Canada Department of F i s h e r i e s and F o r e s t r y f o r permission to use, f o r t h i s t h e s i s , data gathered i n the course o f work on a Department p r o j e c t . A p p r e c i a t i o n i s expressed to Mr. W. Morf and Mr. L. S. Skaley, t e c h n i c i a n s of the Forest Research Laboratory, Calgary, A l b e r t a , f o r a s s i s t a n c e i n the c o l l e c t i o n of data. Thanks are due to Dr. B. C. Sutton, F o r e s t Research Laboratory, Canada Department of F i s h e r i e s and F o r e s t r y , Winnipeg, Manitoba, f o r the i d e n t i f i c a t i o n o f the m a j o r i t y of the f u n g i . Other s p e c i a l i s t s who con-t r i b u t e d to the i d e n t i f i c a t i o n of va r i o u s f l o r a l groups are: Dr. A. M. Adams, H o r t i c u l t u r a l Experiment S t a t i o n , Ontario Department of A g r i c u l t u r e , Vineland S t a t i o n , Ontario; Dr. F. D. Cook, Department o f S o i l Science, U n i v e r s i t y of A l b e r t a , Edmonton, A l b e r t a ; Dr. Y. H i r a t s u k a , Forest Research Laboratory, Canada Department of F i s h e r i e s & F o r e s t r y , Calgary, A l b e r t a ; and Dr. D. B. P r e s t , Department of B a c t e r i o l o g y , U n i v e r s i t y of Wisconsin, Madison, Wisconsin. Many i n s t i t u t i o n s provided Cronartium comandrae ma-t e r i a l f o r the d i s t r i b u t i o n a l aspects o f t h i s study, and I would l i k e to e s p e c i a l l y thank the curators of the f o l l o w i n g h e r b a r i a f o r t h e i r a s s i s -tance: Arthur Herbarium, Purdue U n i v e r s i t y , L a f a y e t t e , Indiana; The xxv N a t i o n a l Fungus C o l l e c t i o n s , B e l t s v i l l e , Maryland; The New York B o t a n i c a l Garden, New York; Mac Donald College, Ste. Anne-de-Bellevue, Quebec; The W. P. Fraser Memorial Herbarium, U n i v e r s i t y of Saskatchewan, Saskatoon, Saskatchewan; U n i v e r s i t y of A l b e r t a , Edmonton, A l b e r t a ; M y c o l o g i c a l Herbarium, Canada Department of A g r i c u l t u r e , Ottawa; Ontario; and the M y c o l o g i c a l Herbaria, Canada Department of F i s h e r i e s and F o r e s t r y , at Calgary, Quebec, V i c t o r i a and Winnipeg. I am indebted to the f o l l o w i n g taxonomic s p e c i a l i s t s of the Entomology Research I n s t i t u t e , Canada Department of A g r i c u l t u r e , Ottawa, Ontario, who made a u t h o r i t a t i v e i d e n t i f i c a t i o n s o f f a u n a l m a t e r i a l : Dr. E. C. Becker, Dr. D. Brown, Mr. W. J . Brown, Dr. J . M. Campbell, Dr. T. N. Freeman, Dr. M. Ivanochko, Mr. G. Lewis, Dr. E. E. L i n d q u i s t , Miss M. R. MacKay, Mr. J . E. H. M a r t i n , Dr. W. R. M. Mason, Dr. J . F. McAlpine, Mr. C. D. F. M i l l e r , Dr. A. Mutuura, Dr. 0. Peck, Dr. B. V. Peterson, Dr. W. R. Richards, Mr. R. de Ruette, Dr. L. K..Smith, Dr. J . R. Vockeroth and Mr. G. S. Walley. Other s p e c i a l i s t s who c o n t r i b u t e d to the i d e n t i f i c a t i o n of v a r i o u s f a u n a l groups are: Dr. G. A. Bradley, Forest Research Laboratory, Canada Department of F i s h e r i e s & F o r e s t r y , Winnipeg, Manitoba; Dr. C. W. O'Brien, Department of Entomology, Univer-s i t y of C a l i f o r n i a , Berkeley, C a l i f o r n i a ; Dr. C. V. G. Morgan, Entomology Laboratory, Canada Department of A g r i c u l t u r e , Summerland, B r i t i s h Colum-b i a ; Dr. C. T. Parsons, Manchester Depot, Vermont; Mr. B. A. Sugden, Forest Entomology Laboratory, Canada Department of F i s h e r i e s & F o r e s t r y , Vernon, B r i t i s h Columbia; Dr. A. L. T u r n b u l l , Department of B i o l o g i c a l Science, Simon Fraser U n i v e r s i t y , Burnaby, B r i t i s h Columbia; and Dr. T. A. Woolley, Department of Zoology, Colorado State U n i v e r s i t y , F o r t C o l l i n s , xxv i Colorado. Thanks are extended to my w i f e , Margaret, who proof-read the manuscript during i t s p r e p a r a t i o n , and to Miss Barbara Brown who typed the f i n a l manuscript. - 1 -INTRODUCTION A knowledge of the e f f e c t of environment on a pathogen during that p a r t of i t s l i f e c y c l e when i t i s outside the host i s of prime im-portance to an understanding of the f a c t o r s i n f l u e n c i n g the spread and i n t e n s i f i c a t i o n of an airborne disease. For a pathogen to be able to spread and i n t e n s i f y e f f e c t i v e d i s p e r s a l must be achieved. This i m p l i e s the p r o d u c t i o n of spores i n p o s i t i o n s from which they can be tran s p o r t e d and deposited a l i v e on host p l a n t s under c o n d i t i o n s and i n q u a n t i t i e s t h a t w i l l lead to i n f e c t i o n . The environmental c o n d i t i o n s under which a pathogen can i n t e n s i f y have been f a i r l y a c c u r a t e l y defined f o r a few diseases, but estimates of the distance of spread or l o s s through non-v i a b i l i t y under d i f f e r e n t environmental c o n d i t i o n s have been l a r g e l y guesses. Besides a f f e c t i n g d i s p e r s a l , environment a l s o a f f e c t s the pro-d u c t i o n of inoculum on the host, spore germination and subsequent i n f e c -t i o n of the host, a l l o f which should t h e r e f o r e be considered i n t h i s phase of disease epidemiology. Factors o f the environment are both l i -m i t i n g and opt i m a l f o r spore s u r v i v a l and germination and must be known before i n f e c t i o n can be p r e d i c t e d . The phase i n the l i f e c y c l e of a pathogen, when a spore s t a t e proceeds independently of i t s hosts, con-cerns the f i e l d of aerobiology. Gregory (1961) considered aerobiology as "the study of p a s s i v e l y airborne-.macro-organisms t h e i r i d e n t i t y , behaviour, movements and s u r v i v a l " . This phase has been stud i e d i n a few diseases a f f e c t i n g a g r i c u l t u r a l crops ( C a r t e r 1963; H i r s t and Stedman 1961, 1962; J a r v i s 1962; Meredith 1961a, 1961b; Shanmuganathan and - 2 -Arulpragasam 1966; TSireeramulu 1 9 6 2 ; Wilson and Baker 1 9 4 6 ) , but few-studies have i n v o l v e d aspects of the aerobiology of f o r e s t pathogens (Bega i 9 6 0 ; R i s b e t h 1959; i^reeramulu 1 9 6 3 ; Van A r s d e l et a l . 1 9 6 1 ) . The comandra b l i s t e r r u s t , Cronartium comandrae Peck, an im-por t a n t n a t i v e disease damaging s e v e r a l species of hard pine i n North America, was s e l e c t e d f o r t h i s study, because of i t s d i s t i n c t i v e a e c i o -spore, a unique p y r i f o r m shape, which i s e a s i l y i d e n t i f i e d against the background a i r spora. Except f o r an o u t l i n e of the C_. comandrae r u s t — i t s h i s t o r y , d i s t r i b u t i o n , l i f e c y c l e , symptoms and damage, t h i s study i s l i m i t e d to the a e r o b i o l o g i c a l aspects of the a e c i a l s t a t e of the r u s t . The r u s t has been known on p i n e f o r n e a r l y 90 years and was f i r s t recorded i n western Canada from A l b e r t a i n 1907 on lodgepole pine, Pinus c o n t o r t a Dougl., and from B r i t i s h Columbia i n 1913 on ponderosa pine P. ponderosa Laws. (Arthur and Kern 1 9 1 4 ). Widespread damage by C_. comandrae i n western North America was not recorded u n t i l the mid -1950's (Mielke 1957), but during the l a s t decade there have been s e v e r a l r e -ports (Andrews and H a r r i s o n 1959; K r e b i l l 1 9 6 5 ; Peterson 1 9 6 2 a ) , and it -has r e c e n t l y become a p l a n t a t i o n problem i n other p a r t s o f North America ( C o r d e l l et a l . 1 9 6 7 ; Dance and Lynn 1 9 6 5 ; Wolfe et a l . 1 9 6 8 ) . The genus Cronartium i n c l u d e s the world's most damaging t r e e r u s t f u n g i (Peterson 1 9 6 2 b ) ; C. comandrae has been reported the most d e s t r u c t i v e stem r u s t on hard pines of western North Americai•(Peterson 1 9 6 2 a ; Hawksworth 1 9 6 4 ) . Hawksworth ( 1 9 6 4 ) suggested t h a t C. comandrae was one of the three major diseases of P. contorta. The l i f e - c y c l e of C. comandrae has been summarized by Hedgcock - 3 -and Long ( 1 9 1 5 a ) , Mielke ( 1 9 6 1 ) , and Mielke et a l . ( 1 9 6 8 ) , but the e n v i r -onmental c o n d i t i o n s under which each spore s t a t e develops or survives are not w e l l known. C. comandrae i s a heteroecious r u s t which grows p e r e n n i a l l y i n the l i v i n g bark of hard pines, and develops annually on the a l t e r n a t e hosts of the genera Comandra and Geocaulon. The pine i s i n f e c t e d during the l a t e summer and f a l l ; the p y c n i a appear i n the summer 2 or 3 years a f t e r i n i t i a l i n f e c t i o n , and a e c i a are produced the f o l l o w i n g year. The a e c i o -spores are d i s p e r s e d and i n f e c t the a l t e r n a t e hosts, where s e v e r a l genera-t i o n s of u r e d i a may be produced. T e l i a f o l l o w the u r e d i a l s t a t e , and these germinate t o produce ba s i d i o s p o r e s which are able to i n f e c t pine, com-p l e t i n g the l i f e c y c l e of the r u s t . Heavy pine i n f e c t i o n occurs at i n f r e -quent i n t e r v a l s ( K r e b i l l 1 9 6 5 ; Mielke 1957; Peterson 1 9 6 2 a ; Wagener i 9 6 0 ) g i v i n g r i s e to the use of the term "wave" years of i n f e c t i o n . This sug-gests that s a t i s f a c t o r y environmental c o n d i t i o n s f o r i n f e c t i o n do not occur every year, or even every decade. C h a r a c t e r i s t i c a l l y a n a t i v e pathogen i s i n s t a b l e balance w i t h i t s hosts and n a t u r a l environment, but i f t h i s balance i s upset then l o c a l or widespread epidemics w i l l r e s u l t . For an outbreak — an i n t e n s i f i c a t i o n or spread of the comandra b l i s t e r r u s t to occur, environmental f a c t o r s would have to be n o n - l i m i t i n g f o r three se-parate a e r o b i o l o g i c a l phases during the l i f e c y c l e of the r u s t i n any one year. Although the present study concentrates on the f i r s t phase of a e c i o -spore s p o r u l a t i o n on pine to d i s p e r s a l and germination on the a l t e r n a t e host, s i m i l a r f a c t o r s would a l s o a f f e c t the r e p e t i t i v e u r e d i a l phase on the a l t e r n a t e host, and the phase between b a s i d i o s p o r e production on the a l t e r n a t e host and i n f e c t i o n on s u s c e p t i b l e p i n e . The b a s i d i o s p o r e phase, - k -i s probably the most c r i t i c a l f o r determining outbreaks or wave years of pine i n f e c t i o n . The b a s i d i o s p o r e phase was not s e l e c t e d f o r study here, as i t s spore s t a t e was not very s u i t a b l e f o r d i s t a n c e d i s p e r s a l s t u d i e s . The i n f o r m a t i o n gained i n t h i s study can be r e l a t e d to the probable aero-b i o l o g y of the other r u s t spore s t a t e s , and to t h a t of other important Cronartium r u s t s , and f o r e s t pathogens i n general. The a e r o b i o l o g i c a l aspects which p l a y a r o l e i n the sequence of development of each spore s t a t e of the r u s t and which must be considered i n any aerobiology phase, i n c l u d e both m e t e o r o l o g i c a l and b i o l o g i c a l en-vironmental f a c t o r s . The main aspects which are considered i n the present study i n c l u d e , a) the character of the aeciospores, t h e i r p r o d u c t i o n and r e l e a s e , b) the boundary l a y e r and t u r b u l e n t f a c t o r s o f the atmosphere as they, a f f e c t escape, t r a n s p o r t , d i s p e r s i o n and d e p o s i t i o n of aeciospores, c) the environmental f a c t o r s a f f e c t i n g aeciospore germination, d) the environmental e f f e c t s on aeciospore v i a b i l i t y during these events, and e) b i o l o g i c a l f a c t o r s a f f e c t i n g aeciospore production, d i s p e r s a l , germina-t i o n and v i a b i l i t y . - 5 -THE ORGANISM HISTORY OF THE FUNGUS In the 1870*s C. H. Peck described two new r u s t f u n g i . T h i r t y -f i v e years l a t e r they were connected as the a e c i a l and t e l i a l s t a t e s of the same fungus. I n l875.Peck described as a new species, under the name Periderm!um pyriforme, a c a u l i c o l o u s or stem-inhabiting Peridermium w i t h a e c i a having obovate, p y r i f o r m , or oblong-pyriform spores, from a s p e c i - . men c o l l e c t e d by J . B. E l l i s on pine branches at Newfield, New Jerse y . Peck was informed by E l l i s t h a t the c o l l e c t i o n may have been made i n Georgia, and placed by accident among h i s New Jersey specimens. Arthur and Kern (l9lk), a f t e r examining the type specimen, b e l i e v e d the i n -s c r i p t i o n on the o r i g i n a l specimen voucher was c o r r e c t . There are s t i l l no records of any c o l l e c t i o n of t h i s r u s t i n Georgia. Hedgcock and Long (1915b) suggested Pinus r i g i d a M i l l , was the host of the type s p e c i -men, as t h i s was the only n a t i v e species of pine i n the type l o c a l i t y which was found i n f e c t e d elsewhere (Vermont). I n 1879 Peck described the second fungus, the t e l i a l s t a t e on the stems of Comandra p a l l i d a A.DC. from Colorado, as a new species, Cronartium comandrae. He st a t e d that t h i s species appeared to be a p a l e r form of the same species which occurred on leaves of Comandra umbellata (L.) Nutt. A specimen of C. comandrae was c o l l e c t e d by E l l i s on _C. umbellata ( E l l i s and Everhart, North American Fungi, No. 1082) near New-f i e l d , New Jersey, i n 1879, which was used by Hedgcock and Long (1915a) as more evidence t h a t the type l o c a t i o n f o r P. pyriforme was c o r r e c t . An - 6 -e a r l y c o l l e c t i o n by T. G-. Lea from Ohio On Thesium umbellatum (C. umbel-l a t a ) was given the name Cronartium asclepiadeum Kze. var. T h e s i i by Berkeley ( l 8 4 5 ) , to d i s t i n g u i s h the r u s t from the European C. a s c l e p i a -deum. Berkeley s t a t e d then that t h i s v a r i e t y might be a d i s t i n c t species. I n 1895 Lagerheim, elev a t e d i t to species status and termed i t Cronar-tium t h e s i i . In the meantime Peck (1879) had c o r r e c t l y given the t e l i a l s t a t e of the r u s t f u l l species status as C. comandrae, i t s present v a l i d name. Fol l o w i n g Peck's d e s c r i p t i o n of Peridermium pyriforme, con-s i d e r a b l e confusion developed i n the use of t h i s b i n o m i a l , which produced many m i s - i d e n t i f i c a t i o n s of specimens and erroneous r e p o r t s of the occur-rence of the comandra r u s t . The:specimens which probably i n i t i a t e d t h i s confusion were c o l l e c t i o n s by E l l i s of Peridermium r u s t s from near the type l o c a t i o n of P. pyriforme at Newfield. One was c o l l e c t e d on Pinus inops A i t (P. v i r g i n i a n a M i l l s ) i n May 1882 ( i s s u e d as P. pyriforme, Wo. 1021, E l l i s , North American Fungi), and the others were c o l l e c t e d on P. v i r g i n i a n a i n A p r i l 1890, and on P. r i g i d a i n May 1890 (both i n the Herbarium, New York B o t a n i c a l Garden). The l a t t e r two were o r i g i n a l l y l a b e l l e d Peridermium p i n i W a l l r . , a European Peridermium, but were l a t e r r e f e r r e d to P. pyriforme. However, these have now been r e f e r r e d to P. comptoniae (Arth.) Orton and Adams. These l a t e r c o l l e c t i o n s of E l l i s lead Arthur and Kern (1906) and Arthur (1907a) to describe as P. p y r i -forme what i s now known as P. comptoniae, completely i g n o r i n g Peck's d e s c r i p t i o n s t a t i n g that the aeciospores were p y r i f o r m . C l i n t o n (1908) l a t e r connected t h i s so c a l l e d P. pyriforme (P. comptoniae) w i t h - 7 -Cronartium comptoniae A r t h . , a t e l i a l s t a t e o c c u r r i n g on Comptonia  p e r e g r i n a (L.) Coult. and Myr i c a spp. P r i o r to t h i s , Underwood and E a r l e (1896) had cast doubt on the status of P. pyriforme and had sug-gested that i t was p o s s i b l y a synonym of Peridermium cerebrum Peck, a species described i n 1873. They suggested t h i s , because they found the s t r i k i n g p y r i f o r m spores of P. pyriforme occurred " i n both forms of P. cerebrum as they occur i n the South". This i n d i c a t e s f u r t h e r con-f u s i o n of the i d e n t i t y of Peridermium forms on pine, as only the t r u e P. pyriforme has p y r i f o r m spores. Hedgcock and Long (1913) described a c a u l i c o l o u s species of Peridermium w i t h ovoid to p y r i f o r m aeciospores on Pinus c o n t o r t a c o l -l e c t e d by E. B e t h e l from Colorado, as a new species, Peridermium b e t h e l i . Unable to compare the specimen of B e t h e l w i t h type m a t e r i a l of P. p y r i -forme , they r e l i e d (Hedgcock and Long 1915a) on the published statement of Arthur and Kern (1906) which concluded that Peck's d e s c r i p t i o n was inaccurate concerning the p y r i f o r m shape of the aeciospores. Arthur and Kern (1913 5 1914), however, discarded t h e i r o r i g i n a l i n t e r p r e t a t i o n of P. pyriforme a f t e r seeing a specimen submitted i n 1913 by W. P. Frase r , c o l l e c t e d on Pinus ponderosa at Vernon, B r i t i s h Columbia. This specimen had the t y p i c a l p y r i f o r m spores described o r i g i n a l l y by Peck. Arthur and Kern (1914) speculated t h a t the a l t e r n a t e s t a t e s o f t h i s Peridermium would be found on species of Comandra, as t h i s genus had the only unattached species of Cronartium then known. A I907 c o l -l e c t i o n of P. pyriforme on Pinus c o n t o r t a from D e v i l ' s Lake (now Lake Minnewanka), Banff, A l b e r t a , by E. W. D. Holway, gave support to t h i s - 8 -s p e c u l a t i o n , as Holway wrote on the packet t h a t the Peridermium on pine was undoubtedly a s s o c i a t e d w i t h a Cronartium on Comandra. Orton and Adams (igik) found true P. pyriforme on Pinus pungens Lamb., and Cronartium comandrae on Comandra umbellata w i t h i n ho f e e t of the i n -f e c t e d pine. They concluded t h a t t h i s Cronartium was the a l t e r n a t e s t a t e of P. pyriforme. They a l s o suggested t h a t P. b e t h e l i was a synonym of P. pyriforme. Hedgcock and Long (lyik) s u c c e s s f u l l y i n f e c t e d Comandra  umbellata w i t h aeciospores of P. pyriforme, confirming the l i f e c y c l e of the r u s t and gave i t the new combination Cronartium pyriforme. In the f o l l o w i n g year (1915a) they gave the morphology, l i f e h i s t o r y , and d i s t r i -b u t i o n of t h i s r u s t as then known under the new combination C. pyriforme. Kirkwood (1915) i n o c u l a t e d Pinus ponderosa w i t h spores from Comandra ( p a l l i d a ? ) through i n c i s i o n s i n the bark, which r e s u l t e d i n the develop-ment of r u s t hyphae w i t h i n the bark and wood of-.--the pine. This was the f i r s t r e cord of the s u c c e s s f u l t r a n s f e r of C. comandrae from Comandra t o pine. He als o s u c c e s s f u l l y i n o c u l a t e d Comandra p l a n t s w i t h aeciospores from pine. More r e c e n t l y , Andrews e t a l . (1963) reported s u c c e s s f u l i n -f e c t i o n of Pinus c o n t o r t a w i t h b a s i d i o s p o r e s of C. comandrae. T e l i a l horns were placed among and above the needles, w i t h p y c n i a being observed a year l a t e r . Boyce (1916) f i r s t described the p y c n i a and pycniospores of C. comandrae from a c o l l e c t i o n on Pinus ponderosa made i n J u l y 1916 i n C a l i f o r n i a . I n the same year, Weir and Hubert (1917) observed p y c n i a and pycniospores o c c u r r i n g on P. ponderosa and P. contorta, confirming the f i n d i n g s of Boyce. Meinecke (1929) t r i e d u n s u c c e s s f u l l y f o r 6 years to i n o c u l a t e d i r e c t l y from pine to pine w i t h aeciospores. This i n d i c a t e s _ 9 -t h a t C. comandrae was only heteroecious and can not be autoecious as i s Peridermium h a r k n e s s i i J.P. Moore (Meinecke 19 l6 , 1920, I929; Hedgcock and Hunt 1920). Many e a r l y herbarium specimens of C. comandrae are s t i l l l a -b e l l e d w i t h synonyms or combinations o f them. Some e a r l y c o l l e c t i o n s were placed under the form-genus Aecidium (Farlow 1905) i n s t e a d of P e r i -dermium, some of which were even n o n - a e c i a l c o l l e c t i o n s (eg. Aecidium  asclepiadeum var. t h e s i i on Comandra p a l l i d a from Kamloops, B r i t i s h Columbia). Hedgcock and Long (1915a) gave Caeoma comandrae Peck as a synonym of Cronartium pyriforme. Caeoma comandrae was described by Peck (1884) from a specimen c o l l e c t e d by M. E. Jones on Comandra p a l l i d a i n Utah., However, a recent check of the New York B o t a n i c a l Garden Herbarium, where Hedgcock and Long reported the specimen deposited, r e -vealed no specimen he l d as Caeoma comandrae, but one held as Uredo  comandrae by the same c o l l e c t o r . This specimen proved to be P u c c i n i a  comandrae Peck, a species a l s o described by Peck i n 1884 but from a c o l -l e c t i o n by T. S. Brandeges i n Washington T e r r i t o r y . This leaves the question of the v a l i d i t y of Caeoma comandrae as a synonym i n doubt, as i t has not been l i s t e d by others. - 10 -DISTRIBUTION AND HOSTS Comandra b l i s t e r r u s t has been reported on one introduced and ten n a t i v e hard pine species i n North America, ranging from New Brunswick to the Yukon and southward to Tennessee, northern Alabama, M i s s i s s i p p i , New Mexico and C a l i f o r n i a . I t has not been reported from A l a s k a (Cash 1953; Laurent, p e r s o n a l communication 1966) or Mexico although suscept-i b l e pines do occur. I t has not been introduced outside North America but i s a p o t e n t i a l l y dangerous r u s t to na t i v e hard pines of Europe and A s i a . The u r e d i a l and t e l i a l s t a t e s of the r u s t have been recorded over a s i m i l a r range on the a l t e r n a t e hosts, Comandra and Geocaulon of the f a m i l y Santalaceae. The e a r l i e s t l i s t s of d i s t r i b u t i o n and hosts were given by Hedgcock and Long (1915a) and by Arthur (1907b, 1925, 1927, 1934). More recent c o l l e c t i o n s have extended the known d i s t r i -b u t i o n of the r u s t and r e - i d e n t i f i c a t i o n has e l i m i n a t e d some of the e a r l i e r r e p o r t s . A l l the Cronartium comandrae m a t e r i a l has been seen i n the f o l l o w i n g h e r b a r i a (Herbarium codes are those used i n the "index Herb-ariorum", Lanjouw and S t a f l e u (196U): CFB, DAOM, DAVFP, PUR, UBC, WIN, and c r i t i c a l . . ' m a t e r i a l has been seen from the f o l l o w i n g h e r b a r i a : BPI, MISSA, NY. L i s t s or in f o r m a t i o n have been obtained from the f o l l o w i n g h e r b a r i a not included above: ALTA, FFB, MFB, MONT, QFB, QMP, SASK, WINF, WSP, MacDonald College, Ste. Anne-de-Bellevue, and many of the r e g i o n a l l a b o r a t o r i e s of the United States F o r e s t S e r v i c e . - 11 -D i s t r i b u t i o n o f the Rust on Pinus Pinus attenuata Lemm. This host was not recorded by Arthur (1934) or more r e c e n t l y , by Peterson (1962b), but there are specimens from Grant Pass, Oregon, c o l l e c t e d by J . R. Weir, Sept. 6, 1916, i n the PUR and BPI h e r b a r i a . A recent p u b l i c a t i o n by Peterson (1967) does i n c l u d e t h i s pine as a host. Pinus banksiana Lamb. Arthur (1934) reported C. comandrae occurred on t h i s host i n Michigan, Wisconsin, A l b e r t a and Saskatchewan. Hedgcock and Long (1915b) reported s e v e r a l c o l l e c t i o n s from Michigan and. Minnesota on P. d i v a r i c a t a (=_P. banksiana). I t was a l s o reported from New Brunswick (Davidson and Newall 1957), Quebec (Pomerleau 1942), Ontario (Conners 1934) and Mani-toba ( R i l e y et a l . 1952). Pinus c o n t o r t a Dougl. Recorded by Arthur (1934) from Colorado, Idaho, Wyoming and A l b e r t a . Hedgcock and Long (1915b) reported the occurrence i n Michigan, and Peterson (1962b) i n C a l i f o r n i a , Montana, Oregon, Utah and Washington. Al s o recorded i n B r i t i s h Columbia ( Z i l l e r 1953) and the Yukon (Molnar i960). In I968 two specimens were c o l l e c t e d from the Cypress H i l l s , Saskatchewan (CFB 8406, 8407). Pinus e c h i n a t a M i l l . Four recent r e p o r t s of the r u s t on t h i s host are from M i s s o u r i (Berry et a l . 1961), Arkansas (U.S. Forest Service I962; P o o l i n g et a l . 1964), and Tennessee (Powers et a l . I967). - 12 -Pinus j e f f r e y i Grev. & B a l f . Peterson (1962b) reported t h i s species as a host i n C a l i f o r n i a and Oregon, and I have seen specimens c o l l e c t e d by Lewis, from near the S i s k i y o u N a t i o n a l F o r e s t , Oregon (BPI, PUR). Pinus ponderosa Laws. Arthur (193^) reported i t from C a l i f o r n i a , Colorado, Montana, Oregon, South Dakota, Utah, Washington and B r i t i s h Columbia. Peterson (1962b) added the st a t e s of Ar i z o n a , Idaho, Nevada and Wyoming. C o l l e c -t i o n s on P. ponderosa var. a r i z o n i c a (Engelm.) Shaw are included i n t h i s d i s t r i b u t i o n . P l a n t a t i o n s of ponderosa pine have r e c e n t l y been reported i n f e c t e d i n Tennessee (Powers et. a l . 1967). Pinus pungens Lamb. Orton and Adams (l^lh) reported the r u s t from Pennsylvania. Pinus r i g i d a M i l l . There i s a n o n - v e r i f i a b l e specimen from t h i s host, c o l l e c t e d at Mt. Calvary, New Je r s e y i n 1917 (PUR), but Hedgcock and Long (1915b) reported a c o l l e c t i o n from Vermont. Pinus s y l v e s t r i s L. The r u s t has been reported on t h i s introduced pine, from Wash-ington (Shaw 1958) and Connecticut (Spaulding 1958). In Canada i t has been reported from Manitoba (Thomas 1953), Saskatchewan (Ives et a l . I968), and A l b e r t a (Powell and Morf 1965). Specimens from Roscommon, Michigan are deposited i n the BPI and PUR h e r b a r i a , n e i t h e r i s v e r i f i a b l e , - 13 -and i s probably C. comptoniae. A specimen c o l l e c t e d i n 1887 i n the Mis-s o u r i B o t a n i c a l Garden, St. L o u i s , M i s s o u r i (Arthur and Kern I906) and now i n the BPI herbarium, was l a b e l l e d Peridermium pyriforme, but i s ' probably Cronartium comptoniae as i t does not have the p y r i f o r m spores. Pinus taeda L. M i l e s (1934) f i r s t reported the r u s t on t h i s host from M i s s i s -s i p p i , and more r e c e n t l y i t has been, reported from p l a n t a t i o n s i n Tennessee and the northeastern corner of Alabama (Powers et a l . 1967). Pinus v i r g i n i a n a M i l l . There i s a lQlk c o l l e c t i o n by Hedgcock from Peterburg, Penn-s y l v a n i a , i n the PUR herbarium a t t r i b u t e d to t h i s host, but the c o l l e c t i o n i s not v e r i f i a b l e , and was not l i s t e d by Hedgcock and Long (1915a, 1915b) or Arthur (193*+). Peterson (1967) reported a Pinus sp. specimen as . l i k e l y from t h i s p ine. C o r d e l l et a l . (1967) noted t h a t p l a n t e d and n a t u r a l P. v i r g i n i a n a were not i n f e c t e d i n Tennessee, although at s e v e r a l l o c a t i o n s they were intermixed w i t h i n f e c t e d P. taeda. Other r e p o r t s The introduced species P. n i g r a A r n o l d and P. p i n a s t e r A i t . have a l s o been reported as hosts of C. comandrae (Boyce 19^3; Spaulding 1958; Mielke 196I; V e r r a l l 1964), but Peterson (1962b) p o i n t s out th a t these were based on a re p o r t by C l i n t o n (1912) at the time when P e r i -dermium pyriforme was o f t e n l i n k e d w i t h C. comptoniae (Arthur and Kern I906; C l i n t o n 1908). There i s al s o a I918 n o n - v e r i f i a b l e specimen l a -b e l l e d as C. comandrae from Roscommon, Michigan on P. n i g r a i n the BPI - Ik -herbarium. Peterson. (1966b) i n d i c a t e d the erroneous r e p o r t (Gremmen 1964). of P. r e s i n o s a as a host f o r C. comandrae i n Vermont. The c o l l e c t -i o n upon which t h i s r e p o r t was based was again C. comptoniae. The d i s t r i b u t i o n of C. comandrae on Pinus spp. i n western and eastern Canada i s shown i n F i g s . 1 and 2. D i s t r i b u t i o n of the r u s t on Santalaceae Two genera of the Santalaceae serve as a l t e r n a t e hosts f o r C. comandrae. The d i s t r i b u t i o n f o r the genus Comandra has r e c e n t l y been modified as P i e h l (1965) rearranged the genus, and placed what were f i v e species (C. umbellata (L.) Nutt., C. c a l i f o r n i c a Eastw., C. r i c h a r d s i a n a Fernald, C_. p a l l i d a A. DC., C. elegans (Rochel) Reichenb.) as four sub-species of one species (C. umbellata). This i s not too s a t i s f a c t o r y , e s p e c i a l l y i n Canada, as h i s d i s t r i b u t i o n map i n d i c a t e s that there are large zones which have intermediates between two subspecies. However, h i s arrangement has been followed, as i t does e l i m i n a t e the previous problem of d i s t i n g u i s h i n g between C_. umbellata and C. r i c h a r d s i a n a , "since they are now one subspecies (ssp. umbellata). E a r l i e r , F e r n a l d (1928) had separated the species C. l i v i d a Richardson from the genus Comandra, and formed a new genus, Geocaulon w i t h G. l i v i d u m (Richardson) Fernald as the type. P i e h l (1965) agreed w i t h t h i s separation, as Geo-caulon has s e v e r a l features that separate i t from Comandra. Both Comandra and Geocaulon are hemiparasites ( F i g s . 3, k, 5 and 6 ) . S e v e r a l papers have l i s t e d the p l a n t species upon which Comandra i s p a r a s i t i c (Brooks '.v 1937; F i s h e r 1922; Harrington 19^5; Hedgcock 1915; Moss 1926; P i e h l . F i g . 1. D i s t r i b u t i o n of Cronartium comandrae on Pinus species i n western Canada. F i g . 2. D i s t r i b u t i o n of Cronartium comandrae on Pinus species i n eastern Canada. F i g . 3- A e r i a l stems of Geocaulon l i v i d u m , w i t h a x i l l a r y greenish f l o w e r s . F i g . k. A e r i a l stems of Comandra umbellata ssp. p a l l i d a , w i t h t e r -m inal white flowers about to break open. F i g . 5. S e r i e s of a e r i a l stems of Comandra umbellata ssp. p a l l i d a , which branch j u s t below the s o i l and are attached to an . underground-rhizome. Some a e r i a l stems dead from previous year. F i g . 6. Large haustorium of Comandra umbellata ssp. p a l l i d a a t t a -ched to Populus tremuloides Michx. r o o t , w i t h smaller haustorium on smaller r o o t . 17 -- 18 -1 9 6 5 ) 5 but I am aware of only one published r e p o r t f o r Geocaulon (Moss 1926, as C. l i v i d a ) . Geocaulon i s a genus w i t h a d i s t i n c t l y northern d i s t r i b u t i o n i n North America, extending from Newfoundland to Alaska, and only as f a r south as northern New England, Wisconsin, Michigan, Minnesota, Idaho and Washington (Fernald 1928; H a r r i s 1965; Hitchcock et a l . 1964; Raup 1947 p i . X X I I ) . Comandra umbellata (L.) Nutt. ssp. umbellata P i e h l (=C. umbellata; CJ. r i c h a r d s i a n a ) . Arthur (1934) reported C. comandrae occurred on t h i s host i n C a l i f o r n i a , Delaware, I l l i n o i s , Indiana, Iowa, Massachusetts, Michigan, M i s s i s s i p p i , New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsyl-van i a , Washington, Wisconsin, Ontario and Quebec. P i e h l ' s (1965') d i s -t r i b u t i o n map suggests that the records f o r C a l i f o r n i a , Oregon, and Washington were on the ssp. c a l i f o r n i c a and not umbellata. Hedgcock and Long (1915a) reported a. c o l l e c t i o n from Vermont, and Powers et a l . (1967) record i t from Alabama and Tennessee. Specimens from the D i s -t r i c t of Columbia and Minnesota are deposited i n the BPI herbarium. C o l -l e c t i o n s l i s t e d as C. umbellata or C. r i c h a r d s i a n a from Manitoba and Saskatchewan are i n the UBC and WINF h e r b a r i a , and are probably t r u e C. umbellata spp. umbellata, or an intermediate between t h i s and ssp. p a l -l i d a . Comandra umbellata (L.) Nutt. ssp. p a l l i d a (A.DC.) P i e h l ( =C. p a l l i d a ) Arthur (1934) reported i t from A r i z o n a , Colorado, Idaho, Iowa, Minnesota, M i s s o u r i , Montana, New Mexico, North Dakota, Oregon, South - 19 -Dakota, Utah, Washington, Wyoming, A l b e r t a , B r i t i s h Columbia, Northwest T e r r i t o r i e s and Saskatchewan. Hedgcock and Long ( 1915a) reported c o l -l e c t i o n s from Nebraska, and a c o l l e c t i o n from Michigan i s deposited i n the PUR herbarium. There i s a specimen of t h i s host from Texas i n the BPI herbarium, and one reported as Comandra sp. (NY herbarium) which should probably be r e f e r r e d to ssp. p a l l i d a . Bisby ( 1 9 3 8 ) reported i t s occurrence i n Manitoba, and Conners ( 1 9 3 4 ) i n Ontario. There i s some doubt about the specimen upon which Arthur ( 1 9 3 4 ) based h i s Northwest T e r r i t o r i e s r e c o r d . J . A. Parmelee (personal communication 1966) be-l i e v e d t h i s r ecord was based on the DAOM specimen, No. l 8 6 l , from near M a r t i n Cabin, Slave Lake A l b e r t a , c o l l e c t e d i n 1929, and that A rthur i n t e r p r e t e d 'Slave Lake' as Great Slave Lake, Northwest T e r r i t o r i e s , i n s t e a d of Lesser Slave Lake, A l b e r t a . However, Arthur ( 1 9 2 7 ) i n c l u d e d the Northwest T e r r i t o r i e s i n h i s d i s t r i b u t i o n l i s t p r i o r to the c o l l e c t i o n of the above DAOM specimen. There i s no record of Comandra from the Northwest T e r r i t o r i e s or the Yukon i n the DAO or CAN h e r b a r i a , or more r e g i o n a l h e r b a r i a .(ALTA, CAFB, UAC, UBC), and i t has not been c o l l e c t e d north of about 59°N. l a t i t u d e i n A l b e r t a . P o r s i l d and Cody ( 1 9 6 8 ) , i n t h e i r c h e c k l i s t of v a s c u l a r p l a n t s i n the c o n t i n e n t a l Northwest T e r r i -t o r i e s , i n d i c a t e d t h a t C_. p a l l i d a was expected to occur, but at present there i s no rec o r d from the. area. Comandra umbellata (L.) Nutt, ssp. c a l i f o r n i c a (Eastw.) P i e h l . I am aware of no herbarium specimens under t h i s subspecies name, but according to P i e h l ' s ( 1 9 6 5 ) d i s t r i b u t i o n map, the specimens recorded by Hedgcock and Long ( 1 9 1 5 a ) and Arthur ( 1 9 3 4 ) under C. - 20 -umbellata from C a l i f o r n i a , Oregon, and Washington, should be ssp. c a l i f o r -n i c a . Geocaulon l i v i d u m (Richardson) F e r n a l d Arthur (1934) gave the f o l l o w i n g d i s t r i b u t i o n of the r u s t on t h i s host (as Comandra l i v i d a ) , Wisconsin, Manitoba and Quebec. Z i l l e r and Molnar (1953) f i r s t r eported the occurrence i n B r i t i s h Columbia, and Molnar (i960) i n the Yukon. Baranyay et a l . (1962) f i r s t reported the i n f e c t e d host i n A l b e r t a , and a year l a t e r Baranyay and Bourchier (1963) reported i t i n the Northwest T e r r i t o r i e s , though i n a c c u r a t e l y reported to be on Comandra. A c o l l e c t i o n made i n 1937 by D. V. Baxter (DAOM 5558 and PUR 48514) from Great Slave Lake, Northwest T e r r i t o r i e s , and l a b e l l e d Comandra sp. proved to be G. l i v i d u m . Other unreported herbarium specimens, some l a b e l l e d as C. l i v i d a , extend the known d i s -t r i b u t i o n to Idaho (NY), Washington (DAOM) and Ontario (DAOM). Other r e p o r t s Arthur (1934) r e f e r r e d to Buckleya d i s t i o c h o p h y l l a (Nutt.) Torr. as a host of C_. comandrae i n Tennessee. This species i s no longer regarded as a host of C. comandrae, as Hepting (1957) made the connection o f the Cronartium o c c u r r i n g on Buckleya w i t h Peridermium  appalachianum Hepting and Cummins, g i v i n g the combination Cronartium  appalachianum Hepting, a r u s t which occurs i n North C a r o l i n a , Tennessee and V i r g i n i a . The d i s t r i b u t i o n of C_. comandrae on Comandra and Geocaulon i n western and eastern Canada i s shown i n F i g s . 7 and 8. Very r e c e n t l y a - 21 -d i s t r i b u t i o n map f o r C. comandrae on Pinus spp. and Comandra spp.has been p u b l i s h e d by K r e b i l l (1968b). G e n e r a l l y h i s northern d i s t r i b u t i o n l i n e f o r Canada does not extend f a r enough north, e s p e c i a l l y i n the Yukon and Northwest T e r r i t o r i e s , and i n Manitoba and Quebec. The c o l -l e c t i o n from Great Whale R i v e r , has been misplaced i n Ontario i n s t e a d of Quebec. F i g . 7. D i s t r i b u t i o n o f Cronartium comandrae on the Santalaceae, Comandra umbellata and Geocaulon l i v i d u m , i n western Canada. F i g . 8. D i s t r i b u t i o n of Cronartium comandrae on the Santalaceae, Comandra umbellata and Geocaulon l i v i d u m , i n eastern Canada. - 2k -LIFE CYCLE Pine i n f e c t i o n by Cronartium comandrae u s u a l l y takes place during summer and autumn through the needles on branches or main stems (Andrews et a l . I963). I t i s p o s s i b l e that the fungus i n f e c t s young t r e e s d i r e c t l y through the bark or through wounds (Kirkwood 1915)5 but t h i s mode of entry i s of minor importance. P e n e t r a t i o n of the needle by the germ tube of the b a s i d i o s p o r e or sporidium may be through the stomatal pore or d i r e c t l y through the epidermal c e l l s . Following;pene-t r a t i o n a mass of hyphae develops w i t h i n the needle t i s s u e near the p o i n t of i n f e c t i o n , then hyphal growth penetrates downwards through the v a s c u l a r bundle of the needle and i n t o the bark which becomes d i s c o l o r e d The length of the p e r i o d between needle i n f e c t i o n and bark d i s c o l o r a t i o n the i n c u b a t i o n p e r i o d , v a r i e s according to the length o f growing season, the seasonal weather, and the distance the hyphae must grow between p o i n t of i n f e c t i o n and the bark. The mycelium of the fungus, which branches i r r e g u l a r l y , r a m i f i e s i n t e r c e l l u l a r l y through a l l l i v e pine bark t i s s u e s , and extends i n t o the outer sapwood t i s s u e s , mainly i n the medullary rays (Adams 1919; K r e b i l l 1968a). K r e b i l l found the advancing hyphae i n the phloem, never more than 2.cm.beyond the v i s i b l e s w e l l i n g of the i n f e c t e d stem. The i n f e c t e d bark increased i n th i c k n e s s due to the i n t e r c e l l u l a r hyphae and expanding parenchyma c e l l s . With the i n -crease i n th i c k n e s s the conducting sieve c e l l s i n the phloem c o l l a p s e . One or more u n i c e l l u l a r h a u s t o r i a may penetrate i n t o a s i n g l e parenchyma c e l l from the i n t e r c e l l u l a r hyphae. K r e b i l l a l s o r e p o r t e d h a u s t o r i a sometimes present i n sieve elements and xylem ray t r a c h e i d s , and noted - 25 -t h a t the h a u s t o r i a v a r y i n s i z e and morphology depending on t h e i r p o s i -t i o n . Peterson (1966a) reported the i n t e r e s t i n g occurrence o f C. comandrae hyphae i n t i s s u e s of the dwarf m i s t l e t o e , Arceuthobium ameri-canum Nutt. ex Engelm., on Pinus contorta, w i t h h a u s t o r i a p e n e t r a t i n g i n t o Arceuthobium parenchyma c e l l s . The r e a c t i o n o f the sapwood to i n -f e c t i o n i s a decrease or c e s s a t i o n of growth i n the canker area ( F i g s . 9 and 10). Resinosus a l s o occurs and the r e s i n may thoroughly impregnate the bark and outer sapwood ( F i g s . 9? 10 a n ( i l l ) • The p y c n i a l or spermogonium s t a t e appears as a d i s t i n c t c r u s t -l i k e l a y e r of p a r a l l e l pycniophores or spermatiophores pushing up between the outer l a y e r of c o r t i c a l parenchyma c e l l s and the o v e r l y i n g t h i n w a l l e d c e l l s of the phellogen (Adams 1919). The pycniophores a r i s e from a zone of i n t e r t w i n e d u n i n u c l e a t e hyphae which make up the base of each pycnium. The pycniophores c o n t a i n a s i n g l e nucleus which d i v i d e s , one nucleus m i g r a t i n g i n t o the immature pycniospore or spermatium which are abstr a c t e d from the f r e e ends o f the pycniophores at ma t u r i t y . The pycn-iospores appear to escape through the i r r e g u l a r c r a c k i n g of the over-l y i n g pheHum t i s s u e , and are exuded w i t h a t h i n g e l a t i n o u s f l u i d to form orange-colored d r o p l e t s ( F i g . 12) , which e v e n t u a l l y dry on the sur-face o f the bark to form dark-colored spots c a l l e d " p y c n i a l s c a r s " . Insects are a t t r a c t e d to the d r o p l e t s and help d i s t r i b u t e the pycniospores. The pycniospores are 3 to k by 3 to 7M-, p y r i f o r m i n shape ( F i g . 13) , and probably have a sexual f u n c t i o n s i m i l a r to th a t shown by P i e r s o n (1933) f o r pycniospores of Cronartium r i b i c o l a F i s c h e r . The p y c n i a appear one to three years a f t e r the i n i t i a l i n f e c t i o n and precede the a e c i a l s t a t e F i g . 9- Transverse sec t i o n s taken from the c e n t r a l p o r t i o n of ' four Cronartium comandrae cankers on lodgepole pine showing e c c e n t r i c growth caused by the r u s t . Note the r e s i n impregnation of the outer sapwood. F i g . 10. Transverse sec t i o n s taken from the c e n t r a l p o r t i o n of f i v e Cronartium comandrae cankers on lodgepole pine • showing e c c e n t r i c growth caused by the r u s t . F i g . 11. Transverse s e c t i o n taken through the a e c i a l zone of a Cronartium comandrae canker showing the a e c i a s i t u a t e d i n the bark t i s s u e s . Note the r e s i n impregnation of the bark between a e c i a , and the s w e l l i n g of the outer r i n g of sapwood caused by the fungus. - 26 -F i g . 12. P y c n i a l drops on the p y c n i a l zone of a Cronartium coman-drae canker on the stem and branches of a lodgepole pine. Note the s w e l l i n g of the stem a s s o c i a t e d w i t h the canker. F i g . 13. Group of p y r i f o r m pycniospores of Cronartium comandrae. x 2500. F i g . Ik. P y r i f o r m aeciospores of Cronartium comandrae showing s i z e and shape v a r i a t i o n o f the-spore t a i l . X 700. F i g . 15. P y r i f o r m aeciospores of Cronartium comandrae showing the spore w a l l ornamentation. X 700. - 28 -on the i d e n t i c a l area by at l e a s t one season. The p y c n i a occur i n t i s -sues j u s t beneath the periderm (Adams 19195 K r e b i l l 1968a) and o v e r l i e the a e c i a which develop s e v e r a l c e l l s deeper i n the cortex ( F i g . l l ) . H i r a t s u k a and Cummins (1963) found that the Cronartium species were the on l y r u s t s to develop an i n t r a c o r t i c a l pycnia, and one of the few r u s t genera i n which p y c n i a l growth was indeterminate. Pycniospore product-io n u s u a l l y begins i n June, or s h o r t l y a f t e r the main a e c i a l p r o d u c t i o n p e r i o d , and i n some seasons they may continue to be produced i n t o October. The p r i m o r d i a of the a e c i a appear as a mass of uninucleate hyphal c e l l s , o r i g i n a t i n g i n the c o r t i c a l parenchyma of the host some 3 to 8 c e l l s below the phellogen (Adams 1919)- The c e l l s o f the c e n t r a l p o r t i o n of the matured primorddfa become d i f f e r e n t i a t e d f i r s t to form b i -nucleate b a s a l c e l l s . Each of the f i r s t b a s a l c e l l s formed cuts o f f an i n t e r c a l a r y c e l l and a c e l l which becomes metamorphosed to form a p e r i -d i a l c e l l of the c e n t r a l arch. The peridium so formed c o n s i s t s o f a continuous membrane one to three c e l l s t h i c k , and the aecium i s d e l i m i t e d by the p e r i p h e r a l p e r i d i a l chains. The b i n u c l e a t e b a s a l c e l l s cut o f f chains of c e l l s which f u r t h e r d i v i d e i n t o an i n t e r c a l a r y c e l l and an aeciospore. The c e l l w a l l s of the aeciospores begin to t h i c k e n when they are about the t h i r d or f o u r t h spore from the b a s a l c e l l . The aeci o -spores then become acuminate above (Adams 1919? Arthur 193^) or below (Arthur and Kern l^lk; Hedgcock and Long 1915a) to give a t y p i c a l p y r i -form shape, are quite v a r i a b l e i n s i z e , 17 to 37 by 38 to 77u, w i t h c o l o r l e s s 2 to 3u t h i c k w a l l s , which are f i n e l y verrucose w i t h s m a l l i r -r e g u l a r t u b e r c l e s ( F i g s . Ik and 15) . As the a e c i a continue to mature the F i g , 16. Canker of Cronartium comandrae on a young "branch of Pinus  contorta, w i t h the p e r i d i a of the a e c i a s t i l l unruptured and forming t y p i c a l b l i s t e r s pushing through the bark. F i g . 17. Canker of Cronartium comandrae w i t h abundant ruptured a e c i a covering the a e c i a l zone. F i g . 18. B r i g h t orange-colored aeciospores of Cronartium comandrae covering the exposed a e c i a of the canker. - 29 -- 30 -o v e r l y i n g host t i s s u e becomes r a i s e d and g r a d u a l l y ruptures exposing the white b l i s t e r s c o n s i s t i n g of the peridium ( F i g . 16) e n c l o s i n g a powdery mass of p y r i f o r m orange-yellow aeciospores ( F i g . 1 8 ) . The a e c i a ( F i g s . 17 and 18) are produced over the area which p r e v i o u s l y produced pycnia, and occur over or between p y c n i a l scars, u s u a l l y i n the year f o l l o w i n g p y c n i a l production, although a e c i a may not occur u n t i l the second year or even l a t e r . Aeciospore p r o d u c t i o n v a r i e s w i d e l y w i t h seasonal con-d i t i o n s , l o c a l i t y , and bark t h i c k n e s s . I n the study area the main p e r i o d of production began i n l a t e May and continued i n t o J u l y and up to the end of August at a reduced r a t e . In some years the cankers may produce a second crop of aeciospores l a t e i n the season, but i n the current year p y c n i a l zone. There may be a great v a r i a t i o n between i n d i v i d u a l a e c i a from one canker which can prolong the production p e r i o d , but u s u a l l y production from an i n d i v i d u a l aecium only l a s t s f o r two to f i v e weeks. Frequently the i n d i v i d u a l a e c i a are so close together that s e v e r a l ap-pear to coalesce to form one l a r g e i r r e g u l a r aecium. A f t e r the aeci o -spores are r e l e a s e d , the peridium d i s i n t e g r a t e s , and bark n e c r o s i s oc-curs around the a e c i a l ruptures. Adams (1919) reported that a new cork l a y e r i s formed below the a e c i a , and the dead t i s s u e i s sloughed o f f or remains as a rough, deeply-cracked bark ( F i g s . 19, 20 and 2 l ) . K r e b i l l (1968a) found no evidence of the development of a secondary cork l a y e r beneath a e c i a , but a l a y e r occurred at times beneath p y c n i a . The mature aeciospores, which are g e n e r a l l y dispersed by the wind to s u s c e p t i b l e Comandra or Geocaulon p l a n t s , are b i n u c l e a t e ( F i g s . 22 and 2 3 ) . Upon germinating one to s i x germ tubes may emerge through F i g . 19. Young canker of Cronartium comandrae on Pinus c o n t o r t a w i t h rough bark covering the o l d a e c i a l zone around the branch stub that acted as entry p o i n t to the stem. A-bundant a e c i a were produced around the o l d a e c i a l zone. F i g . 20. S l i g h t hypertrophy of the young Pinus c o n t o r t a stem caused by Cronartium comandrae, w i t h c h a r a c t e r i s t i c rough, cracked bark, i n the o l d e r canker area caused by a e c i a r u p t u r i n g . F i g . 21. T y p i c a l b a s a l stem canker of Cronartium comandrae showing older rough bark zone and current year a e c i a l zone w i t h many dispersed aeciospores caught i n the c r e v i c e s of the bark. - 32 -the spore w a l l ( F i g . 2h), but u s u a l l y the two n u c l e i migrate i n t o one of the developing germ tubes ( F i g . 25) and only t h i s germ tube continues to elongate to any extent. The germ tubes have m u l t i p l e short branches which may occur i r r e g u l a r l y throughout the length of the germ tube ( F i g s . 26 and 27). The germ tubes are non-septate, w i t h the two n u c l e i continu-i n g to migrate toward the t i p of the tube during e l o n g a t i o n . I f condi-t i o n s are s u i t a b l e an appressorium forms ( F i g . 28) from which an i n -f e c t i o n peg may develop ( F i g s . 29 and 30) and penetrate the host through the stomata to i n f e c t and develop a b i n u c l e a t e mycelium. This type of aeciospore germination i s t y p i c a l of the heteroecious r u s t s , and i s i n marked contrast to that of the autoecious r u s t s ( H i r a t s u k a 1968; H i r a t -suka et a l . 1966; P o w e l l and Morf 1966). The stem, l e a f p e t i o l e s , leaves, f l o r a l b r a c t s and f r u i t s of the a l t e r n a t e host may a l s o be i n f e c t e d . One to three weeks a f t e r aeciospore i n f e c t i o n , the u r e d i a appear on the sur-face of the leaves as s m a l l y e l l o w p u s t u l e s ( F i g . 31)• The u r e d i a de-velop from a hyphal plexus o f t e n beneath a stoma of the host l e a f (Moss I 9 2 8 ) . The v e r t i c a l hyphae a r i s e i n a p a l i s a d e f a s h i o n and become d i -v i d e d i n t o three c e l l s ; the p e r i d i a l , i n t e r c a l a r y and sporogenous c e l l s . At a l a t e r stage the i n t e r c a l a r y c e l l s disorganize, the b a s a l sporogenous c e l l s give r i s e to s p o r e - i n i t i a l s , and the p e r i d i a l c e l l s give r i s e to the peridium of the u r e d i a l sorus. The peridium of the u r e d i a l sorus q u i c k l y ruptures exposing a, mass of e l l i p t i c a l to g l o b o i d , orange-yellow urediospores, 16 to 23 by 19~28u, w i t h n e a r l y c o l o r l e s s 1.5 to 2\x t h i c k w a l l s , which are s p a r s e l y e c h i n u l a t e . The urediospores are e a s i l y disseminated by wind or i n s e c t s and are able to germinate and r e - i n f e c t F i g . 22. Aeciospores o f Cronartium comandrae, st a i n e d w i t h HC1-Giemsa, each w i t h two n u c l e i . X 700. F i g . 23. Aeciospore of Cronartium comandrae, s t a i n e d w i t h HC1-C-iemsa, w i t h two n u c l e i . X 1200. F i g . 2k. I n i t i a t i o n of aeciospore germination, w i t h four germ tubes developing through the spore w a l l , a f t e r 1 hour. X 1200. F i g . 25. Cronartium comandrae aeciospore w i t h s e v e r a l germ tubes, but only one germ tube w e l l developed a f t e r 6 hours. Note the short m u l t i p l e branches on the non-septate germ tube. X 380. F i g . 26. Group of germinated aeciospores w i t h t y p i c a l branching of germ tubes a f t e r 2k hours. X 125. - 33 -F i g . 27. Aeciospore of Cronartium comandrae w i t h one developed germ tube, a f t e r 3 hours. Note the non-septate c o n d i t i o n of the germ tube and th a t the two n u c l e i have migrated towards the t i p o f the germ tube. X 830. F i g . 28. Germ tubes of two Cronartium comandrae aeciospores a f t e r 3 hours, showing development of a globose and club-shaped appressorium on the developed germ tube, i n t o which the two n u c l e i have migrated. X 700. F i g . 29. Germ tube development o f a Cronartium comandrae a e c i o -spore a f t e r 3 hours, showing a globose appressorium w i t h two n u c l e i and an i n f e c t i o n peg. X 1080. F i g . 30. Germ tube development of two Cronartium comandrae a e c i o -spores a f t e r 3 hours, showing two types of a p p r e s s o r i a each w i t h two n u c l e i and an i n f e c t i o n peg. X 6l0. F i g . 31. U r e d i a of Cronartium comandrae on c e n t r a l p o r t i o n of a Comandra umbellata ssp. p a l l i d a , l e a f . Dark s t r u c t u r e s on bottom are young t e l i a . F i g . 32. T e l i a of Cronartium comandrae on both surfaces of a por-t i o n of Comandra umbellata ssp. p a l l i d a l e a f . - 35 -- 36 -the same a l t e r n a t e host, thus spreading and i n t e n s i f y i n g the i n f e c t i o n during the summer, o f t e n over a distance of a hundred miles or more. In the present study u r e d i a l i n f e c t i o n s were found hundreds of miles out on the P r a i r i e s away from any pine source. A l l p a r t s of Comandra p l a n t s were h i g h l y s u s c e p t i b l e t o i n f e c t i o n at any stage i n t h e i r develop-ment. Four to seven generations of the u r e d i a l s t a t e may be produced i n a s i n g l e season, i f weather co n d i t i o n s permit, which g r e a t l y increases the p o s s i b i l i t i e s of pine i n f e c t i o n . T e l i a may form about two to three weeks a f t e r the u r e d i a ap-pear on the p l a n t s and may occur on l e s i o n s i n i t i a t e d by u r e d i a or on new l e s i o n s l a t e i n the season. The t e l i a are reddish-brown, slender, o f t e n curved, h a i r - l i k e s t r u c t u r e s , 80 to 120u t h i c k and about 1 mm i n length, which stand up from the host t i s s u e ( F i g . 32). They are com-posed of columnar rows of t e l i o s p o r e s , 12 to 16 by 28 to kk\i, w i t h n e a r l y c o l o r l e s s , 2 to 3M- t h i c k , smooth w a l l s , h e l d together i n a g e l a -t i n o u s matrix. I n time, u s u a l l y under moist c o n d i t i o n s , each t e l i o s p o r e germinates i n s i t u by means of a f i v e - c e l l e d promycelium, each of the four upper c e l l s bearing one s m a l l t h i n - w a l l e d globose b a s i d i o s p o r e , 2 t o 6 by 2 to 6\i, on the t i p of a stout sterigma. The b a s i d i o s p o r e s are disseminated by the wind, and i f deposited on s u s c e p t i b l e pine needles w h i l e s t i l l v i a b l e , can germinate under favourable c o n d i t i o n s and i n -f e c t the pine, thus completing the l i f e c y c l e of the fungus. - 37 -SYMPTOMS The f i r s t v i s i b l e s i g n of comandra b l i s t e r r u s t i n f e c t i o n on a pine i s a yellow-brown spot on a needle. This i s at the p o i n t of i n -f e c t i o n , but i t i s d i f f i c u l t to d i s t i n g u i s h m a c r o s c o p i c a l l y from s i m i l a r spots caused by other agencies. In the f i r s t , second or t h i r d season f o l l o w i n g i n f e c t i o n an area of the bark a t the base of the needle f a s c -i c l e becomes d i s c o l o r e d , and a s m a l l spindle-shaped s w e l l i n g may develop. This i s the beginning of a canker, which mostly begins on needle-bearing branches and stems. I n f e c t i o n s on main stems u s u a l l y enter v i a s m a l l branches ( F i g . 3 3 ) . M y c e l i a l growth i n the host t i s s u e i s more r a p i d l o n g i t u d i n a l l y than l a t e r a l l y , and more r a p i d towards the base than the t i p of the branch or stem. Reddish-orange p y c n i a l drops appear on the bark two or more years a f t e r i n f e c t i o n . In subsequent years the p y c n i a form i n a zone behind the p e r i p h e r y o f the i n f e c t e d t i s s u e and outside the a e c i a l zone. P y c n i a l drops are not v i s i b l e long; they may be eaten by l a r v a l and adu l t i n s e c t s , dry up, or be washed by r a i n . " P y c n i a l s c a r s " may s t i l l be seen i f the bark i s r e l a t i v e l y smooth. A e c i a appear as white b l i s t e r s pushing through the bark over p y c n i a l zones of the previous years. The a e c i a l p e r i d i a rupture r e l e a s -i n g masses of orange aeciospores. A e c i a are only present i n one area f o r one season as the p y c n i a l and a e c i a l zones c o n t i n u a l l y form around the pe r i p h e r y o f the canker. Not a l l a e c i a appear as b l i s t e r s through the bark. In thick-barked trees the a e c i a are o f t e n b u r i e d and the aeciospores F i g . 33- Branch i n f e c t i o n of Cronartium comandrae on Pinus contorta, w i t h mycelium causing s w e l l i n g i n the main stem around the branch stub. Fig,. 35-. Heavy r e s i n o s i s forming a d r i e d c r u s t over a p o r t i o n of a Cronartium comandrae stem canker. Note rough bark of o l d branch canker (upper l e f t ) which served as entry f o r the r u s t to the stem. F i g . 3^. Tree w i t h dead spike-top 'above a canker of Cronartium comandrae g i r d l i n g the t r e e ; lower branches are progres-s i v e l y k i l l e d by downward growth of r u s t . - 39 -appear through cracks i n the bark. On removing the bark large areas of a e c i a w i t h aeciospores are exposed. Under n a t u r a l c o n d i t i o n s only a sm a l l p r o p o r t i o n of these aeciospores would be dispersed. Some t r e e s , e s p e c i a l l y those w i t h marked r e s i n o s i s , seldom produce aeciospores, and i t i s d i f f i c u l t to e s t a b l i s h the l i m i t s of the canker m i c r o s c o p i c a l l y . Where a e c i a have been produced, the bark cracks and the cambium and u n d e r l y i n g wood d i e . As the fungus grows the branch or stem even-t u a l l y i s g i r d l e d and p a r t s beyond the canker d i e . Spike-topped t r e e s ( F i g . 3*0 and flagged branches are conspicuous symptoms of the disease. When cankers develop on the main stem, the canker zone i s o c c a s i o n a l l y c o n s t r i c t e d i n s t e a d of swollen, as increased diameter growth of the healthy stem continues above and below the canker during canker g i r d -l i n g . Resin exudation i s a conspicuous symptom of disease, e s p e c i a l l y on Pinus c o n t o r t a ( F i g . 35). Much of the r e s i n o s i s i s caused by the fungus but some i s caused by rodents chewing the succulent i n f e c t e d bark of the canker. Rodent damage i s usua l l y a good i n d i c a t i o n of the pre-sence of the disease. ( F i g s . 36 and 37). The f i r s t symptom of the r u s t on the a l t e r n a t e host i s the y e l -low s w e l l i n g s of the developing u r e d i a l s o r i , which rupture to r e l e a s e the urediospores. A few weeks l a t e r the t e l i a l "horns" are e a s i l y v i s i -b l e developing on the same area as the u r e d i a l s o r i or from new l e s i o n s . U r e d i a and t e l i a may be present over the whole p l a n t . There i s some c h l o r o s i s of the leaves i n h e a v i l y i n f e c t e d p l a n t s , s l i g h t evidence of reduced l e a f growth and d e f o l i a t i o n i s u s u a l l y premature. F i g . 36. Annual rodent damage on a la r g e Cronartium comandrae stem canker on Pinus contorta. Note the s t r i p of d r i e d dead bark not removed on each annual v i s i t , and the abundant exudation of r e s i n . F i g . 37. Rodent damage on a Cronartium comandrae stem canker a-round a branch which acted as an entry p o i n t f o r the r u s t i n t o the stem. S p o r u l a t i o n of the a e c i a l zone can be seen outside the chewed area. - ko -- 1+1 -DAMAGE Comandra b l i s t e r r u s t damage i n n a t u r a l pine stands i s not u s u a l l y s p e c t acular, i n f e c t i o n being l i m i t e d to some extent by the d i s -t r i b u t i o n of i t s a l t e r n a t e hosts, which, although ranging over much of North America, are r e s t r i c t e d l o c a l l y to s m a l l areas. Comandra umbel-l a t a i s r a r e l y found w i t h i n pine stands as i t favours dry open areas, but Geocaulon l i v i d u m occurs on wetter areas w i t h i n spruce-pine stands. Heavy pine i n f e c t i o n i s u s u a l l y found adjacent to areas of i n f e c t e d a l -ternate hosts. The r u s t a t tacks t r e e s of a l l ages and s i z e s and causes m o r t a l i t y by b a s a l or stem g i r d l i n g . The p e r i o d between i n i t i a l i n f e c -t i o n and death o f the t r e e may be as much.as t h i r t y years, or more, and then only a few tre e s d i e each year. Seedlings may be k i l l e d w i t h i n a few years f o l l o w i n g i n f e c t i o n , because the r u s t can enter through needles on the main stem and the fungus soon g i r d l e s the s m a l l stem. The fungus c h a r a c t e r i s t i c a l l y enters the main stem of the o l d e r t r e e v i a branch i n -f e c t i o n s . The fungus only grows one to. three inches down the branch each year so that the rust.may be present i n the branch many years be-fore i t reaches the main stem. I f the branch i s k i l l e d before the r u s t reaches the main stem, the main stem w i l l not u s u a l l y become i n f e c t e d . Dead tops or spike-tops were common damage features i n mature stands where the fungus had g i r d l e d the stem thereby k i l l i n g the upper stem and branches. C h i l d s (1968) showed t h a t downward growth on the stem by the r u s t i s l e s s than 6 inches per year, thus the lower p o r t i o n of the t r e e may l i v e f o r many years i f vigorous lower branches remain. I n f e c t i o n w i t h i n a stand may have occurred i n only a few years, or even i n one year, when c o n d i t i o n s - h2 -f o r i n f e c t i o n were favourable and a supply of basi d i o s p o r e s was a v a i l -able. S e v e r a l r e p o r t s show that pine i n f e c t i o n by:the r u s t i s i n -frequent. Observations were made f o r over 50 years i n an i n f e c t e d Pinus  ponderosa stand i n S i s k i y o u County, C a l i f o r n i a , and i t appeared t h a t current damage was from i n f e c t i o n kO years ago w i t h l i t t l e or no recent i n f e c t i o n ( C a l i f o r n i a Forest Pest C o n t r o l A c t i o n C o u n c i l 1958; U. S. Forest S e r v i c e 1955; Wagener i 9 6 0 ) . I n f e c t i o n of P. ponderosa i n south-ern Nevada was reported as sporadic by Wagener ( i 9 6 0 ) w i t h a wave of i n f e c t i o n by the r u s t i n .1932 or 1 9 3 3 " and almost no new i n -f e c t i o n on pine since Wagener ( 1 9 5 0 ) reported the r u s t on P. ponderosa i n a southeastern Idaho p l a n t a t i o n " . . . . c h i e f l y on the 19^0 and 19^1 growth of branches and no evidence was found i n I 9 6 2 to i n d i c a t e any more recent i n f e c t i o n ( K r e b i l l , p e r s o n a l communication 1 9 6 2 ) . L i t t l e or no recent i n f e c t i o n was found on P. ponderosa i n the Black H i l l s , South Dakota, and areas of Colorado i n stands where damage was reported 2 5 - 3 5 years p r e v i o u s l y (Peterson 1 9 6 2 a ) . Peterson ( 1 9 6 2 a ) pre-sented evidence that i n f e c t i o n occurred two to s e v e r a l decades ago on P. co n t o r t a i n the Bighorn and Shoshone N a t i o n a l F o r e s t s , Wyoming, w i t h almost no recent i n f e c t i o n . One of the f i r s t r e p o r t s of damage i n the United States was made by Boyce (Hedgcock and Long 1915a) i n Klamath N a t i o n a l F o r e s t , C a l i -f o r n i a , where he found 34% of the young P. ponderosa dead and a f u r t h e r 17% i n f e c t e d i n a stand r e p r e s e n t i n g average r a t h e r than heavy i n f e c t i o n . Meinecke ( 1 9 2 8 ) reported 35% of P. ponderosa dead or doomed i n an area - k3 -near Mt. Lassen, C a l i f o r n i a , and c a l c u l a t e d t h a t t h i s r e s u l t e d i n a 21$ r e d u c t i o n of f o r e s t cover. Other r e p o r t s o f damage to P. ponderosa have been noted from other p a r t s of C a l i f o r n i a (U.S. For e s t S e r v i c e 195'5, 1956), a 30-year o l d p l a n t a t i o n i n Caribou N a t i o n a l F o r e s t , Idaho (Wegener 1950), Charleston Mountains, southern Nevada (Wegener i960), the Black H i l l s of South Dakota (Hedgcock and Long 1915a; L u c k i n b i l l 1935)> and the east side of the Cascade Range i n Oregon and Washington ( C h i l d s 1968). Damage to young P. pungens i n Pennsylvania was noted by Adams and Orton (191^) and Hedgcock and Long (1915a); the l a t t e r reported t h a t 58$ of the pine which were producing a e c i a at the end of June were dead by autumn from the g i r d l i n g e f f e c t of the fungus. U n t i l r e c e n t l y , P. co n t o r t a was considered only an o c c a s i o n a l host f o r t h i s pathogen (Mielke 1957) although Peterson (1962a) quotes an unpublished I925 r e p o r t by Be t h e l of damage to t h i s host i n Colorado. Mielke (1957) reported mature stands covering s e v e r a l square miles where 50 - 98$ of the tre e s were i n f e c t e d i n areas of Idaho, Utah and Wyoming. Andrews and H a r r i s o n (1959) a l s o reported s e v e r e l y i n f e c t e d P. c o n t o r t a stands i n Wyoming adjacent to sagebrush areas supporting the a l t e r n a t e host. Peterson (1962a) studied damage on 2k p l o t s i n i n f e c t e d stands i n northern Wyoming and found 21$ of the t r e e s i n f e c t e d . The stands were l a r g e l y 50 - 100 years o l d w i t h i n f e c t i o n centered i n t i s s u e u s u a l l y over 20 years o l d , w i t h the cankers at an average height o f 12 f e e t . K r e b i l l (1965) s t u d i e d i n f e c t e d stands i n 12 N a t i o n a l Forests l o c a t e d from c e n t r a l Montana to northern Utah and found t h a t some cankers were 100 years o l d , and that there had been a b u i l d up between 1910 to 19^5, - 44 -w i t h only sparse recent i n f e c t i o n . I n most cases over 90% of- the sampled cankers were i n trunks and from one-fourth to one-half of these had caused spiketops. The centers of cankers ranged from 1.5 to 69 f e e t above ground w i t h the mean height around 26 f e e t . About 90% of the cankers had been scarred by rodent chewing. I n one sample p l o t 26% of a l l l i v e lodgepole pines were i n f e c t e d , and there was considerable e v i -dence of recent m o r t a l i t y by r u s t g i r d l i n g . R e cently C. comandrae has become a problem i n young p l a n t a t i o n s of P. ponderosa and P. taeda i n the Cumberland P l a t e a u area of eastern Tennessee and northeastern Alabama (Powers et a l . 1967). Powers e t a l . r e p o r t p l a n t a t i o n s w i t h over 9°% of the l e s s than 10 y e a r - o l d t r e e s i n -f e c t e d , and one case, w i t h 57% of the 2 y e a r - o l d P. taeda t r e e s i n f e c t e d . More r e c e n t l y , C o r d e l l et a l . (1967) reported t h a t 40% of the P. taeda p l a n t a t i o n s l e s s than 10 years o l d were i n f e c t e d on the Cumberland Pla t e a u , and on these p l a n t a t i o n s 6% of the t r e e s were i n f e c t e d . They als o detected severe i n f e c t i o n and m o r t a l i t y i n a P. ec h i n a t a p l a n t a t i o n i n the same area. C. comandrae i s a l s o proving a p l a n t a t i o n problem on P. ec h i n a t a i n the C l a r k N a t i o n a l Forest, M i s s o u r i (Berry et a l . 1961), and Ozark N a t i o n a l Forest, Arkansas (Dooling et a l . 1964). I n the l a t t e r area 44% of the t r e e s on three p l o t s planted i n 1958 i n the B u f f a l o D i s -t r i c t were dead by 1967 (Dooling 1967). Wolfe et a l . (1968) r e c e n t l y found t h a t the r u s t was now present on a l l 8 d i s t r i c t s of the Ozark N a t i o n a l Forest, being observed i n 19% of the P. echi n a t a stands examined. In Canada there have been few recorded r e p o r t s o f extensive damage, although the r u s t has been reported as f a i r l y common throughout - 45 -the P r a i r i e Provinces. I n 1959 two area r e p o r t s of m o r t a l i t y were r e -corded i n P. con t o r t a stands: one i n young t r e e s near Robb, A l b e r t a (Thomas et a l . i960) , and the other i n the Teslin-Whitehorse area o f the Yukon w i t h 5 - 10$ of the s a p l i n g s i z e t r e e s i n f e c t e d (Molnar i960) . L a t e r , Baranyay and Stevenson (1964) reported 3$ of the l i v i n g t r e e s on seven 0.05-acre p l o t s i n 20 y e a r - o l d regeneration near Robb were i n f e c t e d by C. comandrae, the range between p l o t s v a r y i n g from 1.4 to 10.8$. I n eastern Canada, 22$ of the t r e e s i n a P. banksiana p l a n t a t i o n at Thunder Bay, Ontario, were i n f e c t e d (Dance and Lynn 1965), and more than 10$ of young P. banksiana i n a sm a l l area at Sa i n t Urbain, Quebec, were i n f e c t e d (Martineau and O u e l l e t t e 1966). Meinecke (1928), Horton (1955), and Mielke et a l . (1968) men-t i o n the value o f the r u s t as a b i o t i c t h i n n i n g agent causing m o r t a l i t y i n overstocked young pine stands. Peterson (1962a), however, s t a t e s that m o r t a l i t y caused by the r u s t "could seldom or never be w r i t t e n o f f as harmless or b e n e f i c i a l n a t u r a l t h i n n i n g " . He found t h a t the i n f e c t e d t r e e s were l a r g e r , and that suppressed t r e e s d i d not respond to r e l e a s e by the r u s t . He a l s o found t h a t over h a l f the i n f e c t e d l i v e lodgepole pine t r e e s had a lower v i g o r r a t i n g than they would have i f r u s t - f r e e . C h i l d s (1968) found t h a t t o p - k i l l i n g of P. ponderosa by the r u s t was not i n d i c a t i v e of h i g h - r i s k t r e e s , unless the remaining crown was s m a l l and of poor v i g o r . Nordin (195*0 reported the r u s t was more pr e v a l e n t i n pure than i n mixed stands i n A l b e r t a . Damage a p p r a i s a l surveys c a r r i e d out i n a s s o c i a t i o n w i t h the present s t u d i e s , i n d i c a t e d that 44$ o f t t h e 725 t r e e s on a 0.1 acre p l o t - k6 -i n a 20 y e a r - o l d P. banksiana stand south of Rae, N.W.T., were i n f e c t e d i n I965 w i t h an average of 1.6 i n f e c t i o n s per tree;.. By 1966, 7.9% of the i n f e c t e d t r e e s had died and many others had dead tops ( J . A. Baranyay, unpublished data I965, I966). Nearly a t h i r d o f the cankers noted i n I965 were i n a c t i v e i n 1966, but many new a c t i v e cankers were recorded. A 1966 survey on a 0.1 acre p l o t i n a 25 y e a r - o l d P. con t o r t a stand near Saskatchewan R i v e r Crossing, Banff N a t i o n a l Park, A l b e r t a , i n d i c a t e d 32.7% of the tre e s i n f e c t e d by the r u s t , Peridermium s t a l a c t i f o r m e A r t h . . & Kern, and 10% by C. comandrae ( J . A. Baranyay, unpublished data 1966). Over h a l f the C_. comandrae i n f e c t e d t r e e s were dead by 1968. A I92U p l a n t a t i o n of Pinus s y l v e s t r i s near Beaver Mines, A l b e r t a , was reported to have extensive rodent damage, some w i t h f r e s h chewing which l e a d me to suspect a r u s t i n f e c t i o n . A f t e r considerable search, one s t r i p of a c t i v e canker w i t h spores was found at the edge of a chewed area ( P o w e l l and Morf 1965). Of 50 t r e e s t a l l i e d a l l had rodent damage, suggesting r u s t i n f e c t i o n was once widespread throughout the p l a n t a t i o n . H e a v i l y i n -f e c t e d C. umbellata ssp. p a l l i d a grew w i t h i n a few f e e t i n an open meadow. About 500 cankers were measured and observed on trees v a r y i n g i n age from 3 to 125 years from 23 areas i n the Rocky Mountains and Foot-h i l l s regions of A l b e r t a . The average height of the center of the can-kers was l.k f e e t , w i t h the highest centered at 15 f e e t . The average length of the cankers was 1.2 f e e t , w i t h the longest 15 f e e t . In 1966 and 1967, kkO l i v e cankers were tagged (103 i n 1967), but by 1968 101 of of these were dead, of which only 13 were branch cankers. Canker m o r t a l i t y at one l o c a t i o n amounted to 82%, and at another 55%5 both occurred i n 10 - kl -to 20 y e a r - o l d stands. I n a regeneration area where few tre e s were over 5 years o l d , kk% of the t r e e s w i t h cankers died i n one year. T o t a l t r e e i n f e c t i o n i n t h i s area amounted to 23% on a 0.22 acre p l o t i n 19°75 but i t was u n l i k e l y t h a t any of the i n f e c t e d t r e e s would s u r v i v e f o r more than a few years at the current m o r t a l i t y r a t e . The reg e n e r a t i o n oc-curred i n an area of Comandra and chances f o r f u r t h e r i n f e c t i o n i n these young age tre e s were high. - hd -AREA OF STUDY LOCATION, PHYSIOGRAPHY AND GEOLOGY The main area of study was r e s t r i c t e d to a p o r t i o n of the Kananaskis R i v e r v a l l e y centered on the Kananaskis Forest Experiment S t a t i o n some 5 miles south of Seebe, A l b e r t a ( F i g . 38), where the f o o t -h i l l s merge w i t h the f r o n t range of the Rocky Mountains. The Kananaskis Forest Experiment S t a t i o n , an area of about 2k square m i l e s , i s bounded to the north by the Stoney In d i a n Reservation, and on a l l other sides borders on the Bow R i v e r F o r e s t , of the A l b e r t a Rocky Mountains Forest Reserve. The Kananaskis R i v e r , which flows north to j o i n the Bow R i v e r at Seebe, l i e s i n a north-south v a l l e y s i t u a t e d between two of the east-ern s e r i e s of ranges of the Rocky Mountains. In the northern p a r t of the v a l l e y the Kananaskis Range l i e s to the west and the F i s h e r Range to the east. The a l t i t u d e of the area v a r i e s between U,200 and 95 500 f e e t , w i t h timber l i n e between 6,500 and 7 , 0 0 0 f e e t . B a r r i e r Lake i s a man-made water body over four miles long, f i l l i n g a p o r t i o n o f the f l a t -bottomed U-shaped v a l l e y between the northern end of the Kananaskis Forest Experiment S t a t i o n and a p o i n t about a mile south o f the Evans -Thomas Creek. The v a l l e y bottom, which at some p o i n t s i s !§• miles wide, i s f l a n k e d at many places by te r r a c e s of g l a c i a l t i l l and morainic ma-t e r i a l , and l a c u s t r i n e and a l l u v i a l d e p o s i t s ; evidence of previous g l a c i a t i o n s and r e t r e a t s to which the area was subjected. From approxi-mately the 5,000 f o o t l e v e l the slopes r i s e g r a d u a l l y or p r e c i p i t o u s l y to masses of upthrust and f o l d e d sedimentary rocks deposited from F i g . 38- Map o f t h e l o w e r K a n a n a s k i s R i v e r V a l l e y , A l b e r t a , show-i n g t h e l o c a t i o n s o f t h e main s t u d y a r e a s . - k9 -- 50 -Cambrian to Cretaceous times, which form the mountains and ri d g e tops of the ranges. The g e o l o g i c a l formations, of the area were stud i e d by Bawling (1905) and Beach (19U3). SOILS A p r e l i m i n a r y survey of the s o i l s of the area was made by Crossl e y (1951), who found w e l l drained a l l u v i a l s o i l s and eroded s o i l and rock areas dominant i n the f l o o d p l a i n s of the Kananaskis R i v e r and i t s major east bank t r i b u t a r i e s . Shallow stomy/ l i t h o s o l s o i l s are pro-minent on moderate to steep slopes where e r o s i o n i s q u i t e r a p i d . The dominant s o i l s on the lower slopes of the v a l l e y are grey podzols of calcareous or non-calcareous o r i g i n , w i t h brown podzols and podzols gen-e r a l l y at higher e l e v a t i o n s . L o c a l i z e d areas support hangmoor peat, h a l f -bog and sod s o i l s , which r e s u l t from excessive moisture, poor drainage, or s o i l s at high a l t i t u d e s under grass or open f o r e s t . Brown f o r e s t s o i l s , and l o c a l i z e d chernozem and re n d z i n a s o i l s are found around the northern end of B a r r i e r Lake and to the north, where the F o o t h i l l s abut against the Rocky Mountains. A f o r e s t land c l a s s i f i c a t i o n map, based on s u r f i c i a l m a t e r i a l , was r e c e n t l y prepared f o r some of the Kananaskis Research Forest (Duffy and England I967), and a ge n e r a l i z e d s o i l s map was prepared f o r the Marmot Creek b a s i n ( J e f f r e y 1965). CLIMATE The main c l i m a t i c c h a r a c t e r i s t i c of the Kananaskis V a l l e y i s - 51 -i t s v a r i a b i l i t y , t y p i c a l of most mountain regions i n c o n t i n e n t a l l o c a t i o n s . This v a r i a b i l i t y i s only now becoming more a c c u r a t e l y determined through the increase i n the number of c l i m a t o l o g i c a l s t a t i o n s i n the v a l l e y , and e s p e c i a l l y through the i n t e n s i v e instrumentation a s s o c i a t e d w i t h the A l b e r t a Watershed Research Program i n the b a s i n of Marmot Creek (Munn and S t o r r 1967), and other s p e c i a l i z e d p r o j e c t s (MacHattie 1966, 1967). Kananaskis ( e l e v a t i o n k,560 f e e t MSL, l a t i t u d e 51°02'N, longitude 1 1 5 ° 0 3 ' W) i s the only s t a t i o n w i t h a r e l a t i v e l y long c l i m a t o l o g i c a l record upon which acceptable average conditions can be based, but even some of the parameters recorded at t h i s s t a t i o n are based on short term, and some-times i r r e g u l a r p e r i o d s . This s t a t i o n i s l o c a t e d 300 f e e t to the east of study l o c a t i o n 1 ( F i g s . 38 and 39)j on a k n o l l on the edge of a large grassed c l e a r i n g , open to the south and east, w i t h k-0 f o o t trees im-mediately to the north, thus the s i t e i s not p a r t i c u l a r l y t y p i c a l of t h i s f o r e s t e d r e g i o n . A l l other c l i m a t o l o g i c a l s t a t i o n s i n the lower Kananaskis v a l l e y have been e s t a b l i s h e d during the l a s t decade, and again records f o r some parameters a r e • i n t e r m i t t e n t , and i n the case of Pigeon Lookout ( e l e v . 6,000 f t MSL, l a t . 51°03'N, long. 1 1 5 ° 0 V w ) depend on the d u r a t i o n of the summer f o r e s t f i r e season. Tables I, I I and I I I , give the c l i m a t i c summaries f o r the m e t e o r o l o g i c a l parameters recorded at Kananaskis, Kananaskis Boundary Ranger S t a t i o n ( e l e v . k,800 f t MSL, l a t . 50°55'W, long. 115°08'W), Pigeon Lookout, and f o r a few s t a t i o n s i n the Marmot Creek Basin ( e l e v . 5,200 to 9,200 f t MSL, l a t . 5 0 ° 5 7 % long. 115°10'W). Data f o r Kananaskis, Kananaskis Boundary and Pigeon Lookout s t a t i o n s were e x t r a c t e d from the "Monthly Record", Canada Department of F i g . 39- Study l o c a t i o n 1, on the Kananaskis Forest Experiment S t a t i o n , near the northeast shore of B a r r i e r Lake, showing the l o c a t i o n of i n f e c t e d lodgepole pine, Comandra p l a n t p l o t s , and instruments used during the study. Table I. Monthly and annual climatic summaries for Kananaskis, lat. 51°02'N, long. 115 03'W, elev. 4,560 ft MSL, for the period of record (1939 - 1968). TEMPERATURE "F 1 JAN FEB MAR. APR MAY JUN JUL AUG SEP OCT NOV DEC YEAI Daily mean 15.2 2 0 . 4 2 4 . 8 34.3 45.0 51.4 57-6 55.7 48.7 4 0 . 9 27.2 21 .8 36. c Extreme maximum 59 61 64 75 82 88 93 92 86 80 66 64 93 Extreme minimum -50 -42 -41 -24 - 7 23 23 29 15 - 8 -32 -44 -50 1 PRECIPITATION inches Total 1.05 1.41 i . 4 o 2.49 3.06 4 . 0 8 2.49 2.78 2.28 1.44 1.15 1.17 24.7S Snowfall 10.24 14.07 12.89 20.18 7.48 1.53 0.00 0.16 0.34 8 .88 10.52 11.24 9 7 . 5 : SUNSHINE DURATION hours 2 Average 69 138 150 246 214 236 308 254 163 121 71 61 2031 Per cent of possible 26 41 59 45 48 62 57 43 37 27 25 43 Years of data 1 2 2 l 2 4 5 5 5 2 1 1 WIND SPEED mph3 Mean 6.8 6 . 8 5.9 5-9 5-3 5-4 5.0 4 . 8 5-1 7.2 7-2 7.7 6 .1 WIND DIRECTION FREQUENCY <j? North 8 9 10 .'8 8 8 7 8 ' 5 . 4 6 6 7 Northeast 8 9 9 5 9 10 7 9 9 6 7 8 8 East 12 14 l l 10 14 13 14 14 13 9 9 9 12 Southeast 9 6 6 3 8 10 .10 10 10 9 8 10 8 South 4 5 6 4 6 5 8 10 7 5 4 5 • 6 Southwest 29 "27 • 28 39 23 25 26 25 29 40 38 37 30 West 17 20 21 18 26 20 17 15 16 16 18 17 18 Northwest 5 5 10 9 8 7 9 7 7 6 5 5 7 Calm 9 9 6 4 4 3 2 3 5 5 6 6 5 Years of wind data 12 13 12 10 17 20 21 22 14 15 11 12 -Data for period August 1939 to December 1968 Data for 1939-19^1, 1946-1947 and 1968, largely summers on 3 D a t a for 1939-1941, 1946-1968 (summers only 1946-1954). Table I I . Monthly and annual c l i m a t i c summaries f o r s e l e c t e d s t a t i o n s i n the Marmot Creek Research Basin, l a t . 50°57'N, long. 115°10'W, elev. 5,300 - 8,000 f t MSL ( 1962. - 1967). S t a t i o n E l e v a t i o n Jan Feb Mar Apr 'May Jun J u l Aug Sep Oct Nov ( f e e t ) MEAN DAILY TEMPERATURE °F Confluence 1 5300 14.9 24.1 23.0 30.6 ko.2 49 .2 56.9 56.2 48 .4 39-6 23.4 Confluence 5 5800 12.8 2 2 . 6 21.2 31.0 38.3 47-3 54.3 53-5 46.2 36.9 2 2 . 1 Cabin 5 6800 12.6 17.4 15.9 21.9 34.2 43.2 53.0 51.4 4 2 . 3 32.7 19.4 MEAN DAILY MAXIMUM TEMPERATURE °F Confluence 1 5300 22.4 32.5 31-2 38.9 50.0 59-9 68.9 68.0 59-6 48 . 1 31.0 Confluence 5 5800 21.4 33-0 31-7 4l.O 48 .7 58.8 67 .8 6 6 . 8 57-7 46 .9 30-3 Cabin 5 6800 19.5 26.5 25.6 30.8 43.9 52.8 66.0 6 2 . 8 51-9 4 o . 6 26 .6 MEAN DAILY MINIMUM TEMPERATURE °F Confluence 1 5300 7.4 15.7 l 4 . 7 21.5 30.4 38.5 kk.$ 4 4 . 3 137-2 ; .30.3. .15.8 Confluence 5 5800 4 . 2 12.1 10.6 20.9 28.0 35-8 4 0 . 9 4 0 . 1 34 .6 2 7 . 1 14.0 Cabin 5 6800 5-6 8 .3 6.2 12.9 24 .5 33-6 39-9 39-9 32.6 2 4 . 8 12.2 TOTAL PRECIPITATION inches Confluence 1 5300 - - - - - - - - - - 4 .26 2.17 2.29 1-84-Confluence 5 5800 1.26 1.26 1.34 2.54 3.06 4.55 2.50 2.53 2.04 2.17 2.25 Cabin 5 6800 - - - - - - - - - - 3-47 2.26 3.09 2.33 MEAN WIND SPEED mph and DIRECTION Confluence 4 5600 4 .3 5-2 5-3 4 .7 5-2 4.8 5-2 5-1 k.8 5.9 4 .2 W N W S , W, SE / NW / N W , , W „ w 'w N ms , Ws (W) (SE) (W/SE) (SE) (N W / S E ) (NW/SE) (SW) ( N W ) Upper Ridge 8000 - - - - . - - - - - - - - 10.7 8 .1 9 . 7 12.4 11.2 -- NW/SW SW/W SW SW sw/w MEAN EVAPORATION inches Confluence 5 5750 - - - - — — — 3-29 4 .86 3-88 2.70 lAnemometer moved to 150 f t tower at 5,900 f t i n J u l y 1967, p r e v i o u s l y on 33 f t tower. Dec 17.2 15.3 14.7 24.2 23.4 21.3 10.2 7-3 8.0 k.9 13.5 w Years Yr T,of , x Record 35-3 5 33.4 5 2 9 . 8 2-4 44.5 44.0 39.0 1.55 27 .1 4 . 9 NW/W 5 5 2-4 25.9 5 23 .0 5 2 0 . 7 2-4 6 4-6 4 2-3 2-3 2-4 1-4 4-6 Table I I I . Monthly temperature and p r e c i p i t a t i o n averages at Kananaskis Boundary Ranger S t a t i o n , l a t . 50°55'N, long. 115°08'W, elev. 4 , 8 0 0 f t MSL ( 1 9 6 2 - 1 9 6 8 ) 1, and Pigeon Mountain Lookout, l a t . 51°03'N, long. 1 1 5 ° 0 V W , elev. 6 , 0 0 0 f t MSL ( 1 9 6 0 - 1 9 6 8 ) % compared w i t h those at Kananaskis f o r a s i m i l a r p e r i o d (1963-I968). S t a t i o n JAW FEB MAR APR MAY JUW JUL AUG SEP OCT WOV DEC YR MEAN TEMPERATURE °F Kananaskis Boundary 1 2 . 9 1 9 . 2 2 3 - 5 3 0 . 8 1+2.5 4 9 . 5 5 6 . 3 5 4 . 8 48 .8 42 .2 24 .6 1 2 . 3 3 4 . 8 Pigeon Lookout 2 -- - - - - - - - - 47*3 5 6 . 1 5 5 - 1 ^ 5 - 3 Kananaskis 1 5.I 2 6 . 7 2 5 . 6 3 4 . 5 4 3 . 6 5 0 . 6 5 7 - 4 5 5 - 8 4 9 . 3 4 0 . 9 2 6 . 3 1 8 . 1 3 6 . 2 TOTAL PRECIPITATION inches Kananaskis Boundary 1 . 4 5 I . 8 7 1 . 6 l 1 .72 3 - 0 2 ' 4 . 7 4 1 . 6 8 2 . 0 5 2 . 0 3 1 .62 1 .71 2 . 5 9 2 6 . 0 9 Pigeon Lookout 2 -- -- -- -- 5 . 9 8 2 . 7 1 2 . 2 9 3 . 0 9 I . 9 9 Kananaskis l . l 4 0 . 8 2 1 .57 3 - 3 9 3-22 5-12 I . 8 3 2 . 4 7 2 . 7 8 1 . 4 3 1-33 1-88 2 6 , 9 8 •^-Temperature data began 1963. 2Temperature data 1963, I965-I968; P r e c i p i t a t i o n data i 9 6 0 , I962-I968. - 56 -Transport (very recent months from the C l i m a t o l o g i c a l S t a t i o n Report, Forms 230k and 2 3 0 6 ) , and those from Marmot Creek s t a t i o n s . from the "Compilation of Hydrometeorological Record, Marmot Creek Basin", V o l -ume I - I I I , Water Survey of Canada, Department of Energy Mines and Resources, Calgary, A l b e r t a . The winter climate i s c h a r a c t e r i z e d by an a l t e r n a t i o n of c o l d , dry, r a t h e r s t i l l p e r i o d s , w i t h periods of comparatively warm, dry, windy, chinook a i r , which gives to the general area of southwestern A l b e r t a one of the gre a t e s t w inter temperature ranges. I n December 1968, Kananaskis experienced a 108°F temperature range. The v a r i a t i o n i n winter weather i s determined l a r g e l y by type and c i r c u l a t i o n of a i r masses. The main c i r c u l a t i o n i s from the north and west which r e s u l t s i n the predominance of maritime P o l a r (mP) and c o n t i n e n t a l A r c t i c (cA) a i r masses, w i t h the o c c a s i o n a l occurrence of unstable and very c o l d maritime A r c t i c (mA) a i r masses (Penner 1 9 5 5 ) . Maritime T r o p i c a l (mT) a i r masses may occasion-a l l y enter the r e g i o n a l o f t from the south i n winter ascending the P o l a r airmasses but never reaching the surface (Anonymous 1 9 5 6 ). Week-long periods of thawing may occur i n a l l w inter months when mP a i r enters the region, w i t h temperatures i n the 50's not being uncommon. LongLey (1967b) found t h a t Kananaskis, on average, had 29 Chinook days (above !+0°F) during the winter months December to February, which was two more than Calgary, and 19 more than Banff. In c o n t r a s t , periods of sub-zero temperatures of a d u r a t i o n of a week or more are comparatively r a r e . Ex-treme low temperatures occur when s t a b l e cA a i r stagnates over the eastern s l o p e s o f the Rockies and western P r a i r i e s . Often twjr. c 1. _ :'• '..*;: - 57 -temperatures i n the v a l l e y are lower than on the higher slopes as c o o l a i r c o l l e c t s i n the v a l l e y under i n v e r s i o n c o n d i t i o n s , and Chinook a i r , or warm a i r masses under subsidence are only experienced at the higher l e v e l s . The Chinook i s c h a r a c t e r i z e d by a strong w e s t e r l y flow of mP a i r w i t h lee waves forming troughs and c r e s t s roughly p a r a l l e l to the mountain ranges, which r e s u l t , when warm dry a i r i s drawn i n t o a mid-l a t i t u d e low pressure center i n the lee of the Rocky Mountains. The a i r descends the leeward side of the mountains at the dry a d i a b a t i c lapse r a t e which b r i n g s high temperatures and low h u m i d i t i e s to the areas where the Chinook reaches the ground. Condensation and clouds form near the c r e s t of each standing wave w i t h the ascending of a i r , g i v i n g the w e l l known Chinook Arch. Much of the red b e l t c o n i f e r f o l i a g e i n j u r y observed on v a l l e y slopes, which i s very prominent i n some seasons, has been a t t r i b u t e d to the abrupt a l t e r n a t i o n s of c o o l a r c t i c a i r and warm chinook a i r (Henson 1952; MacHattie 1963). The winters are r e l a t i v e l y dry, o nly about 30% of the annual p r e c i p i t a t i o n at Kananaskis (Table I ) occurs during the s i x winter months, October to March. Snow accounts f o r n e a r l y 40% of the annual p r e c i p i t a t i o n of about 25 inches at Kanan-a s k i s , but much of t h i s f a l l s i n A p r i l , which i s the highest s n o w f a l l month. The h e a v i e s t s i n g l e s n o w f a l l on record at Kananaskis occurred i n June 1951 when 33 inches f e l l i n two days. At the higher l e v e l s of the v a l l e y , S t o r r (1967) found that 70 to 75% of the annual p r e c i p i t a t i o n occurred as snow or a mixture of r a i n and snow. June i s the wettest month of the year, and August the month of g r e a t e s t p r e c i p i t a t i o n v a r i a b i l i t y . The v a r i a t i o n of summer p r e c i p i t a t i o n and temperature depends upon the - 58 -d u r a t i o n and frequency of su b s i d i n g dry mP a i r from the west, mT a i r from the Gulf of Mexico which may b r i n g considerable moisture to the Front Ranges, and i n l a t e summer and autumn the c o n t i n e n t a l T r o p i c a l (cT) a i r which may penetrate from the south and give hot, dry s p e l l s . I n sp r i n g and autumn, mA a i r may enter the r e g i o n f o r a few days but i t i s absent i n summer. V a l l e y bottom s t a t i o n s r e c e i v e l e s s p r e c i p i t a t i o n than v a l l e y slope s t a t i o n s . S t o r r ( 1 9 6 7 ) found t h a t on the average sum-mer r a i n f a l l increased about 1 .5 inches per thousand f e e t i n the east-f a c i n g Marmot Creek b a s i n w i t h a l e v e l l i n g o f f at about 7 , 6 0 0 f e e t MSL. Although the years of record o f sunshine are short, the low t o t a l hour values f o r May and June, when l e s s than 50 per cent of the p o s s i b l e d u r a t i o n was recorded (Table I ) , ' r e f l e c t the passage of lows j u s t to the south of the area which b r i n g cloudy, moist a i r to the r e g i o n . There i s g e n e r a l l y l e s s v a r i a t i o n i n the summer month temperatures than i n winter temperatures. Temperatures above 8o°F are experienced i n s e v e r a l months but the high e l e v a t i o n of the area, a l l above 4 , 2 0 0 f e e t , i s r e s p o n s i b l e f o r c o o l summer nights and lower daytime tempera-tures than occur on the hot, dry P r a i r i e s to the east. Maximum tempera-tures u s u a l l y occur near the end of J u l y . D i f f e r e n c e s i n the average d a i l y maximum and minimum temperatures during the summer months are approximately 10 to 15°F between the upper and lower areas of the v a l l e y (Munn and S t o r r 1 9 6 7 ) . F r o s t s can occur i n any month, and the average f r o s t - f r e e p e r i o d f o r the years 1951 to 1964 at Kananaskis was 62 days, w i t h the average date of the l a s t s p r i n g f r o s t , June 2 1 , and the f i r s t autumn f r o s t , August 22 (Longley 1 9 6 7 a ) . During the summer - 59 -months there were many occurrences of low night r e l a t i v e h u m i d i t i e s i n the Kananaskis v a l l e y (MacHattie 1966) when chinook-type winds occurred. Webb ( 1 9 6 5 ) showed th a t these low humidity nights were a s s o c i a t e d w i t h a i r subsidence under conditions f a vouring lee wave formation. MacHattie (.1966) found t h a t d a i l y minimum hu m i d i t i e s were' remarkably independent of v e g e t a t i o n cover, s i t e and topography, and t h a t the increase w i t h e l e v a t i o n was very s l i g h t from v a l l e y bottom to 1 , 0 0 0 f e e t e l e v a t i o n up the v a l l e y s i d e s . N i g h t l y maximum hu m i d i t i e s were more v a r i a b l e and f r e q u e n t l y decreased a b r u p t l y w i t h e l e v a t i o n j u s t above v a l l e y bottom (11% i n 300 f e e t ) w i t h a more gradual decrease above t h i s l e v e l ( l e s s than 1% per 100 f e e t ) . The mean monthly wind speeds at Kananaskis were higher i n the winter months, when chinooks are frequent, than i n the summer months (Table I ) . December had the highest mean wind speed and J u l y , c l o s e l y f o l l owed by August, the lowest. The strongest winds come from the south-west or west at a l l times of the year. The dominant wind d i r e c t i o n i n p r a c t i c a l l y a l l months of the year was from the southwest, although i n c e r t a i n years winds from the southeast or east were dominant i n some of the summer months. MacHattie ( 1967) i n d i c a t e d t h a t t h i s southeast wind component was dominant at n i g h t , although of only low speed, and was t y p i c a l of a downvalley wind coming from the Lusk Creek s u b - v a l l e y . He showed that the wind components across the main v a l l e y had a more pro-nounced day-night cycle than the wind components along the v a l l e y , both at Kananaskis and i n Marmot Creek at 5680 f e e t . No appreciable d i u r n a l o s c i l l a t i o n of winds occurred up and down the v a l l e y at Kananaskis i n - 6o -summer, but he found t h a t the southwest component could be dominant f o r most of the day, or under c e r t a i n conditions, during only the d a y l i g h t hours. I n the summer months there was u s u a l l y a marked maximum wind speed i n mid- and l a t e - a f t e r n o o n , w i t h a minimum o c c u r r i n g around sun-r i s e . At a v a l l e y bottom s t a t i o n near the confluence of Marmot Creek and the Kananaskis R i v e r there was a morning-evening slope wind c y c l e , w i t h the wind blowing toward the more i n t e n s e l y i n s o l a t e d slope. Munn and S t o r r (1967) a l s o showed the prominence of the northwest-southeast sub v a l l e y winds i n August at the 5,600 f o o t l e v e l on Marmot Creek. They found a wind speed maximum j u s t before s u n r i s e w i t h a downvalley wind, and another maximum i n the e a r l y afternoon w i t h an u p v a l l e y wind. The minima, about 0800 and 1800 hours, were as s o c i a t e d w i t h wind s h i f t s from downvalley to u p v a l l e y and v i c e v e r s a . At the Confluence h s t a t i o n at 5,600 f e e t (Table I I ) , v e r y close to the l o c a t i o n used by Munn and S t o r r (1967), there was a l s o a high occurrence of downvalley northwest winds i n many months, and of u p v a l l e y southeast winds i n the months March to J u l y , but at the r i d g e s t a t i o n at 8000 f e e t , the winds were predominantly from the southwest, and at a monthly mean v e l o c i t y two or more times those of the lower s t a t i o n . A comparison of monthly mean temperatures and monthly p r e c i -p i t a t i o n f o r the p e r i o d 1963 to 1968 (Table I I I ) , showed th a t Kananaskis had warmer summer months than Kananaskis Boundary by about 1 ° , and warmer winter months by as much as 7 ° . During the winter months Kananaskis r e -ceived l e s s p r e c i p i t a t i o n , but more during the summer months than Kanan-a s k i s Boundary. Temperatures at Pigeon Lookout were 1° cooler i n J u l y - 61 -and August, and 3 to 5° cooler i n June and September than at Kananaskis, and Pigeon Lookout g e n e r a l l y r e c e i v e d more p r e c i p i t a t i o n . Monthly temp-eratures were al s o g e n e r a l l y lower i n the Marmot Creek Basin (Table I I ) than at Kananaskis. P r e c i p i t a t i o n from A p r i l to June was higher at Kananaskis than i n Marmot Creek. VEGETATION The area f a l l s l a r g e l y w i t h i n the S rub-alpine Forest Region (Rowe 1 9 5 9 ) ; which i s found between the approximate l i m i t s of 5 , 0 0 0 and 6 , 5 0 0 f e e t , where the climax species are Engelmann spruce, P i c e a  engelmanni Parry, and western white spruce, P i c e a glauca (Moench) Voss var. a l b e r t i a n a (S. Brown) Sarg., although large areas are covered by the sub-climax species, lodgepole pine. At higher e l e v a t i o n s , between 6, 500 f e e t and the t i m b e r l i n e , the A l p i n e Forests are c h a r a c t e r i z e d by the dominance of a l p i n e f i r , Abies l a s i o c a r p a (Hook.) Nutt., and a l p i n e l a r c h , L a r i x l y a l l i i P a r i . At the northern end of the Kananaskis v a l l e y , Douglas f i r , Pseudotsuga m e n z i e s i i (Mirb.) Franco, a climax species of the Montane Fo r e s t Region i s present on warm, dry slopes at lower e l e -v a t i o n s (up to 4 , 7 5 0 f e e t ) . Balsam poplar, Populus b a l s a m i f e r a L. occurs on the a l l u v i a l s o i l s of the v a l l e y , and trembling aspen, P. tremuloides Michx., competes w i t h lodgepole pine, as a pioneer species f o l l o w i n g f i r e , on the lower slopes of the v a l l e y where brown f o r e s t s o i l s predomin-ate. F i r e has been the most important f a c t o r i n f o r e s t stand development i n the area, and throughout the Sub-alpine and F o o t h i l l s F o r e s t Regions of A l b e r t a (Horton I 9 5 6 ; Smithers 1 9 6 2 ). Smithers ( 1 9 5 6 ) records a - 62 -major f i r e i n the area around 1865, and other important f i r e s occurred i n 1910, 1920 and. 1936. This lead to lodgepole pine stands of even age, sometimes overstocked w i t h very high d e n s i t i e s per acre. A number of workers have stud i e d the s i l v i c a l and e c o l o g i c a l c h a r a c t e r i s t i c s of lodgepole pine i n the area and much of t h i s work has been summarized by Smithers (1962). Forest cover maps have r e c e n t l y been pu b l i s h e d f o r the Kanan-a s k i s Forest Experiment S t a t i o n (Canada Department o f F o r e s t r y and R u r a l Development, I 9 6 7 ) , and Marmot Creek Watershed Research Basin (Depart-ment of F o r e s t r y of Canada, I 9 6 5 ) , which i n d i c a t e the major species pre-sent, t h e i r average height c l a s s , and crown closure d e n s i t y , as w e l l as showing p o o r l y drained and rock outcrop areas. The f o r e s t and a l p i n e cover types and h a b i t a t types of the Marmot Creek Watershed Research Basin, w i l l be pu b l i s h e d by K i r b y and O g i l v i e i n 1969. This w i l l r e -present the f i r s t d e t a i l e d e c o l o g i c a l v e g e t a t i o n r e p o r t f o r any.area i n the Kananaskis v a l l e y . The r e p o r t describes eleven f o r e s t h a b i t a t types and ten a l p i n e h a b i t a t types, and i n d i c a t e s t h a t kQfo of the Marmot Creek Basin c o n s i s t s of non-productive f o r e s t area — a l p i n e f o r e s t , meadow and rock. The r e s t of the area i s l a r g e l y of the s p r u c e - f i r - p i n e cover type, w i t h areas of pine and pine-aspen cover types at lower e l e v a t i o n s , where they became e s t a b l i s h e d a f t e r the 1936 f i r e . STUDY LOCATIONS The study l o c a t i o n s ( F i g . 38) occurred i n both mixed and even aged stands of lodgepole pine, except l o c a t i o n 8 which was i n a grass - 63 -c l e a r i n g . The even aged stands were approximately 10, 2k, 28, 32 and kO y e a r s - o l d , and became e s t a b l i s h e d a f t e r f i r e . There was al s o one regeneration area w i t h few trees over 5 years o l d ( l o c a t i o n 9). The mixed stand ( l o c a t i o n l ) had trees ranging i n age from 7 to 60 years, w i t h most t r e e s grouped i n the 21 or 52 year age c l a s s . L o c a t i o n 3 was s i t u a t e d i n the lower l e v e l s of the Marmot Creek Watershed Research Basin near the c l i m a t o l o g i c a l s t a t i o n , Confluence 1 (Table I I ) . Laboratory experiments w i t h aeciospores, d a i l y counts and ger-minations t e s t s , were carried;.'out i n the l a b o r a t o r y at the Kananaskis Forest Experiment S t a t i o n , or at the Forest Research Laboratory, C a l -gary. The spore d i s p e r s a l and m i c r o c l i m a t i c studies were c a r r i e d out at l o c a t i o n s 1, 2, 3 and 8 ( F i g . 38). The aeciospore c o l l e c t i o n s f o r d a i l y germination t e s t s came from l o c a t i o n 1. Spore c o l l e c t i o n s f o r ex-perime n t a l purposes came from most of the l o c a t i o n s . C o l l e c t i o n s of the asso c i a t e d m i c r o f l o r a and microfauna came from l o c a t i o n s 1, 2, 3, 5 and 7. Measurements and observations of canker growth and a c t i v i t y , and the incidence of ass o c i a t e d m i c r o f l o r a , microfauna and rodent damage, were made at a l l . l o c a t i o n s except l o c a t i o n 8. Besides the main area of study, a d d i t i o n a l i n f o r m a t i o n was obtained from many p o i n t s w i t h i n the Sub-alpine, Montane and F o o t h i l l s Forest Regions between Robb (53°13'N, ll6°58'W) and Waterton Lakes Na-t i o n a l Park (49°03'N, 113°55'W"). The in f o r m a t i o n mainly c o n s i s t e d of measurements and observations of canker growth and a c t i v i t y , and i n c i -dence of ass o c i a t e d m i c r o f l o r a and microfauna. C o l l e c t i o n s of the associated m i c r o f l o r a were made from a number of p l a c e s . M a t e r i a l f o r - 6k -the r e a r i n g o f a s s o c i a t e d microfauna from Pinus c o n t o r t a was obtained from B a r i l Creek, Saskatchewan R i v e r Crossing, C l i n e R i v e r , and near Robb, and from P. banksiana, kO miles south of Rae, N.W.T. Extensive survey f o r d i s t r i b u t i o n a l data were carried- out over the southern p o r t i o n of the Province south of 56°N. A d d i t i o n a l d i s t r i -b u t i o n data and m a t e r i a l f o r r e a r i n g a s s o c i a t e d microfauna was gathered by personnel of the Forest I n s e c t and Disease Survey i n the course of t h e i r r e g u l a r d u t i e s . - 65 -AECIOSPORE PRODUCTION PERIODS OF AECIOSPORE PRODUCTION AND ENVIRONMENTAL  FACTORS AFFECTING SPORULATION ": • ' Methods A e c i a l cankers were observed at r e g u l a r i n t e r v a l s from e a r l y May to October at l o c a t i o n s 1 and 2 ( F i g . 38) i n the years 196k to .1968, at l o c a t i o n 3 from 1966 to 1968 and at l o c a t i o n 9 i n 1968. At l o c a t i o n 1 observations were made 2 or .3 times a week i n the years 196k to I967 and weekly i n 1968. At l o c a t i o n 2 observations were made s e v e r a l times a week i n 196k and once or twice a week from 1965 onwards. Locations 3 and 9 were v i s i t e d at l e a s t once a week. I n some years observations were made on a d a i l y b a s i s on s e l e c t e d t r e e s at l o c a t i o n 1 to e s t a b l i s h i n i -t i a t i o n o f s p o r u l a t i o n and d u r a t i o n of 'production from i n d i v i d u a l cankers and i n d i v i d u a l a e c i a l p u s t u l e s . S p o r u l a t i o n was considered to have com-menced w i t h the rupture of the peridium of the aecium and the r e l e a s e of the f i r s t aeciospores, and to have ceased when no f u r t h e r aeciospores were present i n the ruptured aecium. Three to 30 i n d i v i d u a l p u s t u l e s were marked on i n d i v i d u a l a e c i a l cankers w i t h l e t t e r e d or numbered p i n s p r i o r to r u p t u r i n g o f the p e r i d i a . E f f o r t s were made to s e l e c t i s o l a t e d p u s t u l e s which, would not coalesce w i t h nearby p u s t u l e s . Observations of aeciospore s p o r u l a t i o n were a l s o made at other l o c a t i o n s at i r r e g u l a r i n t e r v a l s i n the va r i o u s years and provide general i n f o r m a t i o n on the s p o r u l a t i o n p e r i o d . D a i l y temperatures, r e l a t i v e humidity, r a i n f a l l , wind and r a d i a t i o n data were recorded on hygrothermographs, r a i n gauges and r a i n f a l l recorder, wind speed and d i r e c t i o n recorder and actinograph - 66 -placed at l o c a t i o n 1 from mid May to l a t e August. L o c a t i o n of i n s t r u -ments and i n f e c t e d t r e e s i s shown i n F i g . 39 j a n d- a d d i t i o n a l d e t a i l s of the instruments are given i n the aeciospore d i s p e r s a l s e c t i o n . For A p r i l and the f i r s t h a l f of May i n each year weather data was obtained from the K a n a n a s k i s ' c l i m a t o l o g i c a l s t a t i o n , 330 f e e t from the nearest i n f e c t e d t r e e of the study area. Weather data was als o recorded at l o c a t i o n s 2 and 3 f o r the p e r i o d of study. I n a d d i t i o n to observing the phenology of aeciospore produc-t i o n i n the d i f f e r e n t years at the va r i o u s l o c a t i o n s , the phenology of the other spore s t a t e s of the fungus was observed. At l o c a t i o n 1, Comandra p l a n t s were observed two or three times a week f o r the presence of the u r e d i a l and t e l i a l s t a t e s on four p l o t s , each one square meter i n area ( F i g . 3 9 ) - Some observations were al s o made on the phenology of lodgepole pine and Comandra p l a n t s at t h i s l o c a t i o n . r'''y.v'.Vi;. R e s u l t s Table IV summarizes the beginning and end of aeciospore sporu-l a t i o n at l o c a t i o n s 1, 2,t:3 and 9 f o r 1964 to 1968, and i n d i c a t e s the main spore production p e r i o d . Aeciospore production v a r i e d w i d e l y w i t h seasonal c o n d i t i o n s and l o c a l i t y . Aeciospore s p o r u l a t i o n began from mid-May to e a r l y June. At higher e l e v a t i o n s the p e r i o d was one to two weeks l a t e r , and tre e s on s i t e s w i t h a north or west aspect were l a t e r i n i n i t i a t i n g s p o r u l a t i o n than those w i t h a south or east aspect. The main p e r i o d of aeciospore s p o r u l a t i o n l a s t e d 1 three to f i v e weeks, us-u a l l y commencing at the beginning of June, although i n I 9 6 5 and 1968 spore production was concentrated i n a two week p e r i o d . For three years, s p o r u l a t i o n ended i n the second 1 -half of J u l y , but i n the other two years - 67 -Table IV. Date of beginning and end of Cronartium comandrae aeciospore production, and main s p o r u l a t i o n p e r i o d at a number of l o c a -t i o n s i n the years 1964 - 1968 i n c l u s i v e . Year L o c a t i o n no. Began Ended Main P e r i o d 1964 1 June 2 J u l y 19 June 3 - June 30 2 June 1 J u l y 18 June 8 - J u l y 7 I 9 6 5 1 May 24 J u l y 30 May 30 - June 13 2 May 18 J u l y 24 # 1966 1 May 13 Aug. 18 May 26 - J u l y 3 2 May 26 Aug. 10+ June 1 - J u l y 4 3 Aug. l 6 1967 1 May 31 Sept. 1 June 5 - J u l y 8 2 May 30 Aug. 3+ June 10 - J u l y 10 3 May 31 Aug. 17 June 12 - J u l y 10 1968 1 June 6 J u l y 18 June 18 - June 2 8 2 May 31 J u l y 22+ June 13 - June 2 3 3 JJune 2 J u l y 31 June 18 - June 28 9 June 2 J u l y 30 June 13 - June 28 * Information not complete spore production continued to the middle or end of August. I n I966 a sporadic and very l i g h t resumption of aeciospore production, induced p o s s i b l y by warm weather, occurred at l o c a t i o n 2 i n September and October. The s c a t t e r e d a e c i a l p u s t u l e s , r a r e l y more than 2 mm i n diameter, occurred i n the p y c n i a l zone of the same year. Table V gives the date of beginning and end of spore production f o r a number of cankers at l o c a t i o n 1 f o r the years 1965 to I 9 6 8 . F i g s . 40 and 4 l summarize the weather and phenology data f o r the v a r i o u s r u s t s t a t e s at l o c a t i o n 1 i n the same years.' Most a e c i a l cankers i n any one year began s p o r u l a t i o n at approximately the same time although some can-kers were c o n s i s t e n t l y e a r l y , e.g. #2721, but others were l a t e , e.g. #2712. From observations there was a tendency f o r s p o r u l a t i o n to occur Tree No. Began 2516 June 1*+ Table V'., 1965 Date of beginning and end of spore production, and total number of days of production from individual cankers at location 1 from 1965 to 1968 inclusive. Main spore production period is included for 3 to 6 cankers for the years 1965 to 1967. Ended July 30 2710 May 10 July 2k 2711 2712 2713 2715 2716 2717 2719 2720 2721 May 29 June 1+ May 27 June 8+ June h No data May 2k May 30+ May 22 2722 May 2k 2723 May 2k 2728 June 2+ June 26 July 26 July 26 July 17 July 20 July 16 June 20 July 12 July 5 July k July 22 Main period June 5-11 July 2-10 May 30-June 11 June 24-27 June 5-13 June 5-17 May 26-June 11 Total no. of days 57+ 60 29 56+ 61 40+ kl 5k 22+ 52 1+3 k2 51+ 1966 Began Ended No production June 1 June 15 (1 pustule only) May 2k May 30 May 20 June 19 Aug. 18 Aug. 15 10 May 26 Aug Tree dead June 2+ July 30 May 26 Aug. 15 Tree dead May 13 July 27 May 22 July 8 Tree dead May 25 July 8 Main period June 2-, July k May 25-July 3 May 22-July 3 Total no. of days 1U 27 81 77 59+ 82 76 kd k5 1967 Began Ended Tree dead May 28 Aug. 25 May 31 June 5 June 2 June 23 Aug. k Sept. 1 June 6 Aug. 7 June 2 May 30 Aug. 15 Aug. 15 Main period Total no. of days June 2-June 25 June 11--July 18 June 5-Aug. 7 May 30 June 27 (tree dead July 18) May 31 July 7 May 31 Aug. 10 90 2k 60 92 63 75 78 29 38 72 1968 Began Ended June 6 July 6 No production June 15 July 8 June' 8 June 30 (tree dead July 22) Total no. of days 31 June 10 July 16 June 10 July 18 June 10 July 3 June 6 July 18 0 2k 23 Canker area dead — 37 39 21+ >*3 C A co F i g . hO. Summary of the d a i l y maximum and minimum temperatures : and r e l a t i v e humidity taken from hygrothermograph records, the d a i l y r a i n f a l l , and the phenology, of the a e c i a l , py-c n i a l , u r e d i a l and t e l i a l s t a t e s of Cronartium comandrae, " May to August i n 1965 and 1966. - 69 -10 15 20 15 30 10 15 20 25 30 10 15 20 15 30 10 15 10 MAXIMUM 20 AND MINIMUM T E M P E R A T U R E °C -10 RELATIVE 2 4 HUMIDITY 16 NO.OF H O U R S 80 AND 100% * 0 2.0 1.5 RAINFALL INCHES 1.0 0.5 0 A E C I O S P O R E S P Y C N I O S P O R E S U R E D I O S P O R E S TEL IOSPORES K> 15 20 25 30 MAY 10 15 20 25 30 JUNE 10 15 20 25 30 JULY 5 10 15 20 A U G U S T 10 15 10 25 30 10 15 20 25 30 10 15 20 25 30 MAXIMUM j o AND MINIMUM T E M P E R A T U R E "> °C RELATIVE HUMIDITY 16 NO. OF H O U R S 80 AND 100% RAINFALL 1.0 INCHES AEC IOSPORES PYCNIOSPORES UREDIOSPORES TEL IOSPORES 10 13 20 25 30 MAY 10 15 20 25 30 JUNE 15 20 25 30 JULY 5 10 15 20 A U G U S T 80n HUMIDITY 100| % Light Moderate Heavy F i g . 1+1. Summary of the d a i l y maximum and minimum temperatures and r e l a t i v e humidity taken from hygrothermograph records, the d a i l y r a i n f a l l , and the phenology of the a e c i a l , py-c n i a l , u r e d i a l and t e l i a l s t a t e s of Cronartium comandrae, May to August i n 1967 and 1968. - 70 -10 15 20 25 30 10 IS 20 25 30 10 15 20 25 30 10 15 20 MAXIMUM 20 AND MINIMUM T E M P E R A T U R E 1 0 °C -10 24 r RELATIVE HUMIDITY 1 6 NO. OF H O U R S 8 80 AND 100% o 2.0 1.5 1.0 0.5 RAINFALL INCHES A E C I O S P O R E S P Y C N I O S P O R E S UREDIOSPORES TEL IOSPORES l_ MAXIMUM AND MINIMUM T E M P E R A T U R E °C RELATIVE HUMIDITY NO. OF H O U R S 8 80 AND 100% o RAINFALL INCHES A E C I O S P O R E S PYCNIOSPORES UREDIOSPORES TEL IOSPORES L_ 5 10 15 20 25 30 MAY 10 15 20 25 30 10 15 20 25 30 5 JUNE 10 15 20 25 30 10 15 20 25 30 JULY 10 15 20 25 30 1 1 5 10 15 20 A U G U S T 10 15 20 25 30 MAY 80n HUMIDITY , 100i % U g h , Moderate Heavy 10 15 20 25 30 JUNE 10 15 20 25 30 JULY NR = No Record 5 10 15 20 A U G U S T - 71 -f i r s t from cankers on the smaller branches, seedlings and young t r e e s , a l l having t h i n smooth bark, somewhat l a t e r on large branches w i t h t h i c k e r bark, and l a t e r s t i l l on stems of o l d e r t r e e s w i t h a t h i c k e r rough bark. This was probably because the developing a e c i a were deeper seated i n the t h i c k e r roughened bark than i n t h i n smoother bark, and because of the mechanical problems of r u p t u r i n g t h i c k bark. U s u a l l y the a e c i a l b l i s t e r s of t h i c k barked cankers erupted i n the bark f i s s u r e s , but removal of bark o f t e n exposed a large a e c i a l area underneath where spores remain unexposed f o r much of the season. Cankers on trees i n the open or on a south or east aspect of a t r e e a l s o began s p o r u l a t i o n s l i g h t l y e a r l i e r than those in a dense stand or l o c a t e d w i t h a dominantly west or north aspect. Even on trees which were n e a r l y g i r d l e d by the fungus, s p o r u l a t i o n began from pustules on the southeast or south aspect and was l a s t from those on the north. Cankers a few f e e t up the stem als o sporulated before b a s a l cankers s i t u a t e d i n the t h i c k e r bark zone of a t r e e . I n i t i a t i o n of s p o r u l a t i o n was about two to three weeks a f t e r evidence of shoot bud break on the lodgepole pine which u s u a l l y commenced i n l a t e A p r i l or e a r l y May. S i m i l a r l y , growth of Comandra p l a n t s began before aeciospore s p o r u l a t i o n . Growth amounted .to an i n c h or more of a e r i a l p l a n t development by May 12 i n 1965 and May 10 i n I966, and the Comandra p l a n t s were f l o w e r i n g by the l a s t week i n May i n favourable s i t e s . Development was l a t e r i n 1967 and 1968. I n 1963 and I96U Comandra p l a n t s were f i r s t noted as producing urediospores at l o c a t i o n 1 on June 18 and 28 r e s p e c t i v e l y . I n l a t e r years the incidence of i n f e c t i o n and u r e d i a l and t e l i a l development was recorded on Comandra p l a n t s on the four p l o t s at .-.location 1 ( F i g . 39) . Each p l o t having an average of 53 - 72 -a e r i a l shoots each year. These p l o t s were l a i d out w i t h i n 100 f e e t of i n f e c t e d t r e e s , and i n most cases were w i t h i n 1+0 f e e t . I n 1966 no i n -f e c t i o n s were.recorded on the p l a n t s u n t i l 39 days (on June 28) a f t e r aeciospore r e l e a s e from the adjacent t r e e s ( F i g . 1+0). A s i m i l a r long i n t e r v a l occurred i n 1965 ( F i g . 1+0), but i n I968 ( F i g . l+l) u r e d i a were present 12 days (on June 17) a f t e r the f i r s t aeciospores were recorded. E a r l y springs may advance and l a t e springs r e t a r d somewhat the advent of a e c i a l production. S p o r u l a t i o n was three weeks e a r l i e r i n 1966 than i n 1968. E a r l y May (May 1-15) was u n u s u a l l y warm i n 1966 there being twice the number of degree days above 0°C than i n the same p e r i o d i n 1967 and 1968, and one and a h a l f times the number i n 1965. During May 1966 the r e g i o n was i n f l u e n c e d by a prevalence of mP a i r , but i n 1967 and 1968, May was dominated by mA and cA a i r masses. Wo cA a i r was experienced i n May 1966", but t h i s a i r mass was present f o r a few days i n the f i r s t h a l f of May 1967 and 1968, b r i n g i n g w e l l below normal tem-peratures to the r e g i o n . May 1965 d i d not experience the c o l d cA a i r , as occurred i n 1967 and 1968, but was dominated by mA a i r during the month. The presence of warmer a i r masses, w i t h t h e i r corresponding warmer surface temperatures, could w e l l account f o r s p o r u l a t i o n being e a r l i e r i n 1966 than the other years, and~.'why s p o r u l a t i o n was delayed to a l e s s e r extent i n 1965 compared w i t h 1967 and 1968. A p r i l had a l s o been warmer i n I965 and 1966 than i n the l a t t e r two years. I n i t i a t i o n of s p o r u l a t i o n i n most years seemed to s t a r t on a day of, or a day f o l l o w i n g , r a i n , suggesting that moisture was r e q u i r e d to rupture the p e r i d i a . The end of the main spore production p e r i o d o f t e n coincided w i t h a heavy r a i n f a l l which washed the spores from the a e c i a . This was most n o t i c e a b l e i n 1965 and - 73 -I966. The warm dry weather of J u l y 1966 and 1967 tended to extend the spore production p e r i o d . There was a great range i n the d u r a t i o n of spore production from i n d i v i d u a l cankers. (Table V) and pustules (Table V i ) . P e r i o d of spore production on some tre e s was c o n s i s t e n t l y short, e.g. #2711, and on others long, e.g. #2713 and 2719. G e n e r a l l y production tended to be longest on the l a r g e s t t r e e s , s h o r t e s t on the sma l l e s t , w i t h the i n t e r -mediates i n between. As w e l l as v a r i a t i o n i n the spore d u r a t i o n from i n -d i v i d u a l cankers there was considerable range between i n d i v i d u a l p u s t u l e s on the same canker (Table V i ) . I n both years i n d i v i d u a l p u s t u l e s pro-duced spores f o r a shorter p e r i o d on #2715, & younger, t h i n suppressed t r e e , than on the o l d e r dominant t r e e , #2719- Tree #2717 was s i m i l a r to #2719, but #2710 was again a smaller diameter t r e e , and on average, sporulated f o r a shorter p e r i o d although the pustu l e s p o r u l a t i o n range was s i m i l a r . P u s t u l e s tended to sporulate f i r s t towards the center of a canker and l a s t towards the periphery. G e n e r a l l y pustules on one canker sporulated at about the same time, although on occasion there could be two waves of pustul e s p o r u l a t i o n , as occurred on t r e e #25l6 i n 1965 (Table V) which accounted f o r the two main periods of spore p r o d u c t i o n . Table V I I summarizes the sequence of development of i n d i v i d u a l pustules on two cankers i n I967, and shows how a large percentage of the pustules rupture w i t h i n a few days of each other and produce spores f o r very s i m i -l a r periods of time. - 7h -Table VI. Average number of days and range o f days of aeciospore production f o r i n d i v i d u a l p u s t u l e s on s e v e r a l cankers i n 1966 and 1967 at l o c a t i o n 1. Year Canker No. No. of pustules Spore Production followed Aver. no Range of days 1966 2715 8 21 17-38 2719 6 k6 21-64 1967 2715 20 3k 25-58 2719 9 60 43-75 2710 30 52 37-87 2717 3 60 53-71 Table V I I . Summary of sequence of s p o r u l a t i o n f o r 30 and 20 pu; t u l e s on . two cankers at l o c a t i o n 1 i n 1967. Canker Date State o f Aeciospore pustules No. Closed Ruptured S p o r u l a t i o n F i n i i Main Diminished 2710 May 31 13 2 15 0 0 June 1 6 4 20 0 0 June 3 4 1 25 -0 0; June 6 ,'0 5 25 0 0 June 8 0 1 29 0 0 June 9 0 0 30 0 0 June 23 0 0 Ik 16: 0 June 28 0 0 :o 30 0 J u l y 25 0 0 0 . 11 19 Aug. 9 0 0 0 6 24 2715 June 7 19 1 "0 0 0 June 8 12 7 1 0 0 June 9 9 10 1 . 0 0 June 12 4 14 2 0 0 June 16 2 6 12 0 0 June 17 0 3 17 0 0 June 22 0 0 20 0 0 J u l y 4 0 0 0 20 0 J u l y 25 0 0 0 k 16 - 75 -"V ' ' D i s c u s s i o n Annual production of the a e c i a may be short l i v e d on s m a l l seedlings, young trees and s m a l l diameter branches. Production may only l a s t f o r two or at the most, three years on t h i s s m a l l diameter stem or branch m a t e r i a l before the fungus e f f e c t i v e l y g i r d l e s and k i l l s the stem or branch. I f branch i n f e c t i o n s are s u f f i c i e n t l y close to the main stem the fungus w i l l grow i n t o the main stem and continue to pro-duce spores annually, although there i s o f t e n a year without a e c i a l production at time of t r a n s f e r from a k i l l e d branch to the stem. On large branches and stems w i t h t h i c k bark, a e c i a may be produced annually u n t i l t hat p o r t i o n beyond the canker i s k i l l e d . a s a r e s u l t of the g i r d -l i n g a c t i o n of the fungus. This may r e q u i r e many years and depends on the s i z e and s t a t e of the i n f e c t e d t r e e . K r e b i l l (1965) found t h a t the m a j o r i t y o f cankers of h i s study o r i g i n a t e d from 20 to 50 years ago, and t h a t a few were more than 100 years o l d . I n the present study some tree s under observation succumbed every year, but the p e r i o d of study was not long enough to f o l l o w f r e s h stem cankers from i n i t i a l stem i n -f e c t i o n to stem g i r d l i n g , although one branch to stem i n f e c t i o n had a l -most g i r d l e d a 1.4 i n c h d.b.h. stem i n three years. Evidence of annual rodent chewing on one 10.0 i n c h d.b.h. t r e e i n d i c a t e d t h a t the i n f e c t i o n had been present f o r at l e a s t 13 years and probably f o r 20 years. Dur-in g the p e r i o d of i n f e c t i o n there i s an annual increase i n canker s i z e , thus t h e o r e t i c a l l y , a greater volume o f aeciospores i s produced each succeeding season u n t i l death of the a f f e c t e d p a r t occurs. I n most cases, however, a e c i a l . p r oduction i s i n t e r f e r e d w i t h by the a c t i v i t y o f other f u n g i , i n s e c t s or rodents, at l e a s t i n some p o r t i o n of the canker, - 76 -and there i s o f t e n a r e d u c t i o n i n annual a e c i a l p r o d u c t i o n d e s p i t e the increased canker s i z e . The e f f e c t of these b i o l o g i c a l agents on produc-t i o n i s discussed l a t e r . Mielke (19^3) noted the c o r r e l a t i o n between s i z e of canker, age of host t i s s u e s and bark t h i c k n e s s , and aeciospore production f o r C. r i b i c o l a . Death o f stem or branch cankers i n any one year i n one l o c a l i t y w i l l g r e a t l y reduce the volume of aeciospores pro-duced the f o l l o w i n g year i n the same area. I n 1968, a dying t r e e pro-duced only two a e c i a l pustules whereas i n the three previous y e a r s " i t had produced abundant spores (#2713, Table V). I n 1968 i n f e c t i o n on the nearby Comandra p l a n t s was low and l a t e o c c u r r i n g , whereas i n other years i t appeared about 10 days a f t e r the f i r s t aeciospores were r e l e a s e d and was abundant. Widespread canker death may t h e r e f o r e be a f a c t o r con-t r i b u t i n g to the wavelike 'character of spread and i n t e n s i f i c a t i o n of the r u s t . K r e b i l l (1968c) has r e c e n t l y p u b l i s h e d i n f o r m a t i o n on the phenology o f C!. . comandrae i n the Rocky Mountain S t a t e s . Data from a number of p l o t s showed great v a r i a t i o n i n d u r a t i o n of aeciospore pro-duction, varying, from 3 to 17 weeks, but ae c i a were only abundant through June and J u l y . Development of a e c i a was e a r l i e s t at the low-est e l e v a t i o n s , and the d u r a t i o n of a e c i a was s h o r t e s t at the higher e l e v a t i o n s . Boyce (1916) reported t h a t CJ. comandrae a e c i a u s u a l l y commence s p o r u l a t i o n i n l a t e A p r i l or e a r l y May, and f i n i s h by l a t e June or e a r l y J u l y . Spaulding (1922) gives the d u r a t i o n of C_. r i b i c o l a aeciospore production i n d i f f e r e n t years f o r a number of areas i n east-ern North America. Duration i n most years l a s t e r f o r k8 to 90 days, although he gives extremes of 12 and lk-0 days. The 12 day p e r i o d appears - 77 -to be very short e s p e c i a l l y as he records closed b l i s t e r s appearing kl days e a r l i e r I The long aeciospore p e r i o d r e s u l t e d from l a t e a e c i a being noted i n mid-September at Amery, Wisconsin, p o s s i b l y a second p e r i o d of a e c i a l production as occurred at l o c a t i o n 2 of the present study i n I966. Pennington ( c i t e d i n Spaulding 1922) noted that more a e c i a were produced per canker i n 1919 than i n 1918 i n the Adirondacks, a l s o that there were more new s p o r u l a t i n g cankers. However, he b e l i e v e d that fewer aeciospores were set f r e e i n 1919 than i n 1918, from r e s u l t s of spore-trapping and observations on f i r s t generation u r e d i a . York ( c i t e d i n Spaulding 1922), working i n the White Mountains, found t h a t a e c i a matured f o r about 30 days on s i n g l e cankers, but may take longer on l a r g e r branch or stem cankers. Rhoads (1920) followed p r o d u c t i o n of 300 a e c i a on v a r i o u s t r e e s i n Maine from the time they f i r s t broke on May 3- He found t h a t by May 20, only 63 a e c i a were s t i l l s p o r u l a t i n g , by May 29 only 19 and none by June k. Others have reported periods of 20 to 30 days, and more than Ik days ( c i t e d i n Spaulding 1922) f o r aeciospores to be produced by an i n d i v i d u a l aecium. I n western North America, Lachmund (1933) reported t h a t C_. r i b i c o l a aeciospore p r o d u c t i o n at low e l e v a t i o n s may begin as e a r l y as l a t e February although more u s u a l dates occur i n l a t e March or e a r l y A p r i l . A t the higher e l e v a t i o n s s p o r u l a t i o n u s u a l l y begins by June. The main aeciospore production p e r i o d occurs between mid May and mid J u l y , and heavy spore production may extend i n t o August. Lachmund a l s o noted t h a t , r a t h e r f r e q u e n t l y at lower e l e v a t i o n s , a sporadic and l i g h t aeciospore production may occur i n October or November. The a e c i a were c h a r a c t e r i s t i c a l l y s m a l l , and t h i s second wave of aeciospore p r o d u c t i o n - 78 -occurred under the i n f l u e n c e of warm f a l l weather i n years having an e a r l y s p r i n g . He a l s o noted i t s occurrence on C. comptoniae and C_. filamentosum Pk. cankers (Lachmund 1929). Dates o f aeciospore produc-t i o n given by Mielke and Kimmey (1935) i n d i c a t e d t h a t the main aeciospore p e r i o d occurs from m i d - A p r i l to mid-June, but may be a month l a t e r at higher e l e v a t i o n s . Mielke (19*1-3) s t a t e d t h a t during warm and dry springs the main a e c i a l s p o r u l a t i o n may only l a s t two or three weeks, but during c o o l , wet springs may l a s t two or more months. Lachmund (1933) noted that t h i c k bark tended to r e t a r d a e c i a l production, and Mielke (19*1-3) f u r t h e r discusses t h i s f a c t o r i n r e l a t i o n to the d i f f e r e n t s o f t pine species t h a t C. r i b i c o l a i n f e c t s . Lachmund (1933) found t h a t f o r cankers t h a t produce p y c n i a f o r the f i r s t time i n a given year only 57$ produce a e c i a the f o l l o w i n g s p r i n g , the r e s t produce a e c i a i n the second year, although a few do not produce a e c i a u n t i l subsequent years. . Cankers a f f e c t e d by secondary organisms may not produce a e c i a at a l l . BIOLOGICAL FACTORS AFFECTING AECIOSPORE PRODUCTION ;[••.:) Methods Observations were made on the frequency and type of as s o c i a t e d f u n g i seen on the a e c i a l zone of cankers at d i f f e r e n t l o c a t i o n s . These f u n g i were i s o l a t e d from the canker, c u l t u r e d and i d e n t i f i e d . On one occasion pieces of a e c i a l canker were shaken i n d i s t i l l e d water f o r sev-e r a l hours, and the r e s u l t i n g s o l u t i o n streaked on agar p l a t e s . Micro-organisms which developed on the streaks were i s o l a t e d and c u l t u r e d . A large number of f u n g i , yeasts and b a c t e r i a were f r e q u e n t l y found as-s o c i a t e d w i t h f r e s h and stored spore c o l l e c t i o n s . These microorganisms - 79 -were allowed to e s t a b l i s h c o l o n i e s on t e s t agar media f o r a few days before being i s o l a t e d and grown i n pure c u l t u r e s f o r i d e n t i f i c a t i o n . Records were kept of the frequency of these a s s o c i a t e d microorganisms during the d a i l y germination t e s t s at l o c a t i o n 1 from 1965 to I967 i n an e f f o r t to e s t a b l i s h the importance o f the va r i o u s microorganisms. Tentative i d e n t i f i c a t i o n s were made ,;6f many of the i s o l a t e s of organisms f r e q u e n t l y encountered. Many!isolates, i n c l u d i n g the l e s s f r e q u e n t l y o c c u r r i n g , were i d e n t i f i e d or v e r i f i e d by taxonomic s p e c i a l i s t s . I n s e c t s were observed to be i n f e s t i n g the r u s t cankers i n most areas v i s i t e d , and i n many of these areas the frequency and amount of i n s e c t damage was noted. On a few occasions i n s e c t s were c o l l e c t e d d i r e c t l y from the a e c i a l canker surface and placed i n p r e s e r v a t i o n v i a l s . • To gain a b e t t e r i d e a of the number of i n s e c t s which used the r u s t can-ker as a h a b i t a t niche f o r a l l or p a r t of t h e i r l i f e c y c l e a c y l i n d r i c a l -sleeve i n s e c t cage was developed which could be pla c e d around the r u s t canker on the i n f e c t e d t r e e stem or branch ( E l l i o t t and P o w e l l 1966). The cage was constructed of p l a s t i c screening and cotton f a b r i c closed by an open-ended z i p p e r , the cage being attached to the t r e e by nylon draw-s t r i n g s at each end ( F i g . k-2). The drawstrings held the cage i n p o s i t i o n when the zip p e r was opened f o r removal of i n s e c t s , but to ensure t h a t a l l i n s e c t s were c o l l e c t e d , the cage was removed and a l l f o l d s of the cage m a t e r i a l examined. Ten to 12 cages were operated at l o c a t i o n 2 from 1965 to 1968, 8 to 10 cages at l o c a t i o n 3 from 1966 to 1968, and 1 or 2 cages near l o c a t i o n 1 f o r the same p e r i o d . The cages were v i s i t e d f o r i n s e c t c o l l e c t i o n at weekly i n t e r v a l s from mid May to October. Many of the cages were l e f t on the tre e s overwinter and were p r o t e c t e d by l / 2 - i n c h F i g . k2. A p l a s t i c s c r e e n i n g c y l i n d r i c a l - s l e e v e cage u s e d f o r c o l -l e c t i n g i n s e c t s f r o m C r o n a r t i u m comandrae c a n k e r s on stems o f P i n u s c o n t o r t a . - 8o -- 81 -wire mesh to prevent damage from bears or other mammals. I n many cases a cage was l e f t around a canker f o r two or more seasons, thus any i n -sects w i t h a long l i f e c y c l e would have been obtained. I n each year some new cankers were caged i n each area. In a d d i t i o n to the above c o l l e c t i o n methods, i n s e c t s were reared from i n f e c t e d cankers which were placed i n cardboard or metal r e a r i n g containers i n the i n s e c t a r y . These containers were u s u a l l y placed i n a c o o l area (about 2-5°C) f o r a p e r i o d of 3 to k months i n an e f f o r t to s a t i s f y any i n s e c t requirements o f a diapause p e r i o d . Each c o l l e c t i o n f o r r e a r i n g came from a s i n g l e canker, or as many as 20 can-kers. The c o l l e c t i o n s came from many l o c a t i o n s i n A l b e r t a , a few from the Northwest T e r r i t o r i e s , and in c l u d e d some C_. comandrae cankers on Pinus banksiana. G e n e r a l l y the l a r g e r c o l l e c t i o n s f o r r e a r i n g were made i n September or October, thus any i n s e c t s which overwintered i n the s o i l had u s u a l l y departed the environs of the canker by t h i s time. I t was o f t e n noted l a t e i n the season, t h a t a number of l a t e i n s t a r l a r v a e or pupae had c o l l e c t e d at the bottom of the cage, thwarted i n t h e i r e f f o r t s to crawl or drop to the s o i l surface. C o l l e c t e d or reared i n s e c t s were pinned, mounted or placed i n an appropriate amount of a l c o h o l f o r pre-s e r v a t i o n . Aeciospores t h a t had passed through ad u l t or immature i n s e c t s were checked f o r v i a b i l i t y by attempting to germinate spores obtained from f a e c a l p e l l e t s . Estimates were a l s o made of the number of spores i n the f a e c a l p e l l e t s from some species, and whether the f a e c a l p e l l e t s were composed e n t i r e l y of spores or p a r t l y of bark and other m a t e r i a l from the canker area. - 82 -O b s e r v a t i o n s were made on t h e f r e q u e n c y o f o l d and f r e s h r o d e n t chewing a s s o c i a t e d w i t h t h e r u s t c a n k e r a t about 20 l o c a t i o n s i n t h e y e a r s 1966 t o 1968 and a t a few l o c a t i o n s i n 196k and 1965. A t most l o c a t i o n s i n I967 and I968 t h e amount o f chewing and i t s e f f e c t on f u t u r e a e c i a l p r o d u c t i o n was n o t e d . The e f f e c t o f r e s i n f l o w on a e c i o -s p o r e p r o d u c t i o n was n o t e d . R e s u l t s M i c r o f l o r a A l l t h e i d e n t i f i e d m i c r o f l o r a l o r g a n i s m s t h a t were i s o l a t e d f r o m a e c i o s p o r e c o l l e c t i o n s o r d i r e c t l y f r o m t h e a e c i a l zone o f t h e ca n k e r a r e g i v e n i n A p p e n d i x I . The l i s t g i v e s a t o t a l o f 6k o r g a n i s m s , a l t h o u g h t h e number might be r e d u c e d i f or g a n i s m s o n l y i d e n t i f i e d t o genus p r o v e d t o be i d e n t i c a l w i t h o t h e r s i d e n t i f i e d t o s p e c i e s . The l i s t i n c l u d e s 8 b a c t e r i a and 56 f u n g i , i n c l u d i n g 5 y e a s t s o r y e a s t - l i k e f u n g i . The f u n g i and y e a s t s l a r g e l y b e l o n g t o t h e c l a s s D e u t e r o m y c e t e s (43) w i t h t h e l a r g e s t number b e l o n g i n g t o t h e f a m i l y M o n i l i a c e a e ( 2 6 ) . W i t h i n t h e M o n i l i a c e a e , 18 b e l o n g t o P e n i c i l l i u m and i t s c l o s e l y r e -l a t e d g e n e r a P a e c i l o m y c e s and S p i c a r i a . Many o f t h e s e o r g a n i s m s a r e p r o b a b l y o n l y a i r s p o r a c o n t a m i n a n t s a l t h o u g h , as such, t h e y may w e l l a f f e c t t h e v i a b i l i t y o f t h e a e c i o s p o r e s w i t h w h i c h t h e y come i n t o con-t a c t . S e v e r a l o f t h e s e o r g a n i s m s a r e common s o i l i n h a b i t i n g f u n g i , e.g. Mucor, B o t r y t i s , A s p e r g i l l u s , P e n i c i l l i u m and E p i c o c c u m . P o l y p o r u s  a d u s t u s W i l l d . ex F r . i s known t o be a p r o m i n e n t p a t h o g e n on s p e c i e s o f P o p u l u s , b u t was i s o l a t e d f r o m a v e r y l a r g e number o f spo r e c o l l e c t i o n s a t l o c a t i o n 1 i n 1966. An u n i d e n t i f i e d s t e r i l e m y c e l i u m w i t h clamp con-n e c t i o n s was a l s o q u i t e common i n t h e same y e a r . - 83 -Two of the organisms were commonly found s p o r u l a t i n g on the a e c i a l zone o f the canker and played a l a r g e r o l e i n reducing aeciospore production and aeciospore v i a b i l i t y . They were the purp l e mold, Tu b e r c u l i n a maxima Rost. ( F i g . 4 3 ) , and an undescribed dark green species, Cladosporium tax. sp. 1. The l a t t e r fungus does not f i t any of the species described from r u s t s and has been given a taxonomic niche, number X L I I , i n the Commonwealth M y c o l o g i c a l I n s t i t u t e , Kew, England, by Dr. M. B. E l l i s (B. C. Sutton,personal communication 1966). Table V I I I summarizes the incidence of T. maxima and the num-ber of cankers observed during the years 1964 to 1968 at 3 to 23 l o c a t i o n s . Table V I I I . The recorded incidence of Tu b e r c u l i n a maxima on Cronartium  comandrae cankers on lodgepole pine and the t o t a l number of a c t i v e and i n a c t i v e cankers observed at va r i o u s l o c a t i o n s i n southwest A l b e r t a during the years 1964 to 1968. Year No. of No. of T o t a l no. of Tu b e r c u l i n a Per cent l o c a t i o n s l o c a t i o n s a c t i v e and i n f e c t e d T u b e r c u l i n a observed w i t h no i n a c t i v e can- cankers i n f e c t e d T u b e r c u l i n a kers observed 1964 5 2 38 7 18.5 1965 3 0 26 5 19.2 I966 20 6 31+1 82 24 .0 1967 23 10 424 55 13.2 1968 22 9 313 42 13-4 The number of cankers f o r which observations were recorded v a r i e d each year depending on the number of l o c a t i o n s v i s i t e d and on canker m o r t a l i t y . The number of cankers observed at any one l o c a t i o n v a r i e d from 1 to 51 w i t h most l o c a t i o n s having 15 to 20 a c t i v e cankers i n the i n i t i a l year F i g . U-3. Rough, cracked bark of the a e c i a l zone of a Cronartium  comandrae canker i n f e c t e d w i t h the purple mold, Tuber-c u l i n a maxima, which i s conspicuous as a darker area where the surface bark has been removed, or cracked. - 8k -- 85 -observations were recorded. On subsequent v i s i t s the same cankers were observed, but some had become i n a c t i v e through the a c t i o n of T u b e r c u l i n a or other agents.. T^ maxima was not observed at s i x of the l o c a t i o n s i n any year, and the numbers of cankers i n f e c t e d at other l o c a t i o n s v a r i e d from year to year. Examples of the v a r i a t i o n . i n d i f f e r e n t years i s given f o r 7 l o c a t i o n s i n Table IX. At A l t r u d e , V i c a r y and Marmot Creeks, and the area near Saskatchewan R i v e r Crossing, there was l e s s t r e e m o r t a l i t y r e s u l t i n g from canker i n f e c t i o n s , but considerable m o r t a l i t y was ob-served at the other l o c a t i o n s , e s p e c i a l l y at C l i n e R i v e r , where the stands were g e n e r a l l y s l i g h t l y younger. At C l i n e R i v e r the s i t e was p a r t i c u l a r l y dry and 25 trees succumbed during a two year p e r i o d . The number of T u b e r c u l i n a i n f e c t e d trees at A l t r u d e Creek and at the Wedge has remained r e l a t i v e l y constant, but the number has f l u c t u a t e d at the other l o c a t i o n s , w i t h a peak year i n 1966 at most l o c a t i o n s . On some cankers the T u b e r c u l i n a completely covered the a e c i a l zone and prevented any aeciospore production. On other cankers only s m a l l areas were covered and aeciospore production continued from the u n i n f e c t e d areas. Tuberculina d i d not appear to sporulate to any degree on the p y c n i a l zone, but was most abundant on the a e c i a l zone. T u b e r c u l i n a was pre-sent from the beginning of aeciospore production, although there was a marked increase i n the production of i t s purple spores as the season advanced. I n i t i a l l y i t appeared as a purple, v e l v e t y l a y e r , but soon a mass of spores were produced which continued w e l l past the normal a e c i o -spore s p o r u a l t i o n p e r i o d . No evidence could be found t h a t T u b e r c u l i n a was a hyperparasite of the r u s t , but i t was c e r t a i n l y a p a r a s i t e on the r u s t canker, not being found outside the r u s t zone on the t r e e . I t was - 86 -u s u a l l y r e s t r i c t e d to the current year's a e c i a l zone, or what would normally have been the a e c i a l zone i f a e c i a l p r oduction had not been a f f e c t e d , although on occasions i t spread i n t o o l d a e c i a l zones or i n t o the current p y c n i a l zone. Only current season a e c i a l or p y c n i a l cankers appeared to be s u s c e p t i b l e to T u b e r c u l i n a as no cankers-which had been i n a c t i v e the previous season were recorded w i t h Tuberculina. In 1966 and 1967 a general view was obtained t h a t the amount of a e c i a l zone covered by T u b e r c u l i n a increased as the season progressed. In I968 e i g h t cankers w i t h Tuberculina, i n i t i a l l y covering between 5 and 40% of the a e c i a l zone, were checked at weekly i n t e r v a l s and there appeared to be no appreciable increase i n the amount of the a e c i a l zone covered by Tuberculina. Although there may be o n l y a s l i g h t increase i n the Tuber- . c u l i n a covered area during the aeciospore production p e r i o d , there was g e n e r a l l y an increase i n the f o l l o w i n g season, and i n many cases no aeciospores were produced. When the p y c n i a l zone became i n f e c t e d there was no aeciospore production the f o l l o w i n g year, thus T u b e r c u l i n a was a favourable b i o l o g i c a l c o n t r o l of C. comandrae. Tub e r c u l i n a appeared to hasten the death of the r u s t i n f e c t e d bark. A t r e e p r a c t i c a l l y g i r d l e d s o l e l y by C. comandrae tended to l i v e and continue producing aeciospores f o r at l e a s t a year, but one g i r d l e d by C. comandrae and i n f e c t e d by T u b e r c u l i n a was soon k i l l e d . At the two l o c a t i o n s w i t h T u b e r c u l i n a ob-servations f o r f i v e years no t r e e was i n f e c t e d by T u b e r c u l i n a f o r more than three years, and at the l o c a t i o n s w i t h three years of data no t r e e was recorded w i t h T u b e r c u l i n a f o r more than two years. Generally, Tu-b e r c u l i n a i n f e c t e d the whole of the canker and the canker became i n a c t i v e , but o c c a s i o n a l l y one area of the canker escaped i n f e c t i o n and aeciospore Table IX. The incidence of Tu b e r c u l i n a maxima on observed a c t i v e and i n a c t i v e Cronartium  comandrae cankers at 7 l o c a t i o n s during the years 196k to 1968. Year A l t r u d e Creek V i c a r y Creek M i s t Creek No. of cankers (A) No. i n f e c t e d (B) (A) (B) (A) (B 1964 5* 3 10 1 - -1965 2* 2 - - - -1966 7 5 23 9 20 k 1967 8 3 22 3 15 6 1968 5 0 21 0 11 l * Incomplete t a l l y Marmot Creek The Wedge C l i n e R i v e r Saskatchewan RiVer Crossing (A) (B) (A) (B) (A) (B) (A) (B -• - 12* 3 - - - -- - 10* 2 - - - -25 13 16 3 33 9 17 k 25 6 20 2 18 2 16 6 2k 5 15 ' 5 7 0 16 2 - 88 -production continued from t h i s area f o r a year or two. Table X shows some of the e f f e c t of Tuberculina and other f a c t o r s on continued ae c i o -spore production at two l o c a t i o n s . At both l o c a t i o n s there was a t r e n d f o r the number of cankers producing aeciospores to decrease and the num-ber of cankers becoming i n a c t i v e to in c r e a s e . Most of these cankers were i n a c t i v e as a r e s u l t of Tuberculina, although i n both areas a few cankers were i n a c t i v a t e d through rodent chewing. When the cankers w i t h aeciospore producing zones or zones i n f e c t e d w i t h T u b e r c u l i n a were tagged at Marmot Creek i n 1966,'.a number of other i n a c t i v e cankers were observed i n the stand but not tagged. None of these cankers became a c t i v e a f t e r I966 and evidence i n d i c a t e d that many were probably i n -a c t i v a t e d by Tuberculina. From the evidence of the present study the Table X. The number of Cronartium comandrae a e c i a l cankers ( l ) producing aeciospores, (2) s p o r u l a t i n g but i n f e c t e d w i t h Tuberculina, (3) w i t h i n a c t i v e a e c i a l zones i n f e c t e d w i t h Tuberculina, (4) w i t h i n a c t i v e or dead cankers, at two l o c a t i o n s during the years I966 to 1968. Year Cankers producing aeciospores.; 1966 19 1967 14 10 1966 14 1967 12 1968 4 A e c i a l zone A e c i a l zone a c t i v e w i t h i n a c t i v e w i t h Tu b e r c u l i n a T u b e r c u l i n a Marmot Creek 7 6 3 3 l 4 Saskatchewan R i v e r Crossing 2 1 3 4 2 2 0 Other i n a c t i v e cankers 0 Dead cankers 10 0 3 12 0 0 1 0 0 1 - 8 9 ' -b u i l d up and spread of T u b e r c u l i n a i n an i n f e c t e d stand i s slow, but once e s t a b l i s h e d i t i s e f f e c t i v e i n i n a c t i v a t i n g the canker and markedly reducing the aeciospore production. Germination t e s t s o f T u b e r c u l i n a spores gave average per cent germination of about 80$. V i a b i l i t y was maintained f o r a p e r i o d of at l e a s t a year. The r o l e of Cladosporium tax sp. 1. i n reducing aeciospore production i s not as c l e a r . G e n e r a l l y i t became obvious only on the a e c i a l zone towards the end of the aeciospore production p e r i o d , although evidence of Cladosporium i n f e c t i o n could be observed at the beginning of the aeciospore s p o r u l a t i o n p e r i o d on the o l d a e c i a l zones of the canker. The fungus was t y p i c a l l y shades of dark green although at times, i t appeared black-green. I t sporulated abundantly i n the l a t t e r h a l f of the summer and covered both the a e c i a l and p y c n i a l zones of the canker. Some evidence was obtained t h a t i t p a r a s i t i z e d the r u s t a e c i o -spores, and i t was an extremely common i s o l a t e from spore c o l l e c t i o n s where i t s : mycelium was found throughout many c o l l e c t i o n s . When present i n stored spore c o l l e c t i o n s , the v i a b i l i t y of the aeciospores was u s u a l l y reduced to zero. The incidence of Cladosporium i s shown i n Table XI f o r the years 1965 to 1968, and was g e n e r a l l y lower than f o r Tu b e r c u l i n a at most l o c a t i o n s . The percentage f o r 1965 was obtained from a very s m a l l l o c a t i o n sample, a n d ' i f percentages from the same three l o c a t i o n s were only considered i n the other years percentages of 19 .0 , 23 .4 and 15.8 were obtained, values much higher than those f o r the l a r g e r l o c a t i o n sample. Nearly h a l f (46$) of the Cladosporium i n f e c t i o n s occurred on the same cankers as T u b e r c u l i n a was observed, but due to the very low incidence i n 1968, Cladosporium was only recorded from two - 90 -Table X I . The recorded incidence of Cladosporium tax. sp. 1 on Cron-artium comandrae cankers observed at va r i o u s l o c a t i o n s i n southwest A l b e r t a during the years I965 to 1968. Year 1965 1966 1967 1968 No. of l o c a t i o n s observed 3 21 23 21 No. of l o c a t i o n s w i t h no Cladosporium 1 7 10 16 T o t a l no. of cankers observed 26 341 424 313 Cladosporium i n f e c t e d cankers 47 40 .14 Per cent Cladosporium i n f e c t e d 3 0 . 8 13-8 9-5 4 . 5 l o c a t i o n s i n a l l three years. The low incidence of 1968 may have been due to most of the observations being made by another observer and a l s o be-cause many l o c a t i o n s were v i s i t e d at a s l i g h t l y e a r l i e r date than i n other years. G e n e r a l l y a higher percentage of the Cladosporium i n f e c t i o n s was a s s o c i a t e d w i t h a c t i v e s p o r u l a t i n g a e c i a l zones than occurred w i t h T u b e r c u l i n a and only a few occurred on non-sporulating cankers which didn' t a l s o have Tuberculina. Cladosporium was recorded on a few tre e s f o r four years and on many, aeciospores were produced f o l l o w i n g two or even three years of Cladosporium i n f e c t i o n , thus Cladosporium d i d not appear to act as a b i o l o g i c a l c o n t r o l agent of the r u s t i n the same way as Tuberculina. Despite the low annual incidence of Cladosporium, 80$ of the cankers at Marmot Creek were i n f e c t e d by Cladosporium during the three yecar:. r e c o r d i n g p e r i o d , and 68$ of the cankers at The Wedge during a four year p e r i o d , Cladosporium was not observed at f i v e l o c a t i o n s i n any year, and at a f u r t h e r f i v e l o c a t i o n s o n ly one canker was observed i n f e c t e d i n three years of observing. Other organisms observed i n f e c t i n g the a c t i v e zone of the - 91 -a e c i a l canker were white m y c e l i a l growths, which were l a t e r i d e n t i f i e d as Fusarium sp., MonociIlium sp., Coniothyrium olivaceum Bonard., and Sclerophoma p i t y o p h i l a (Cda.) Htihn. Their incidence i n any year was very low, l e s s than 1% i n the years I966 to 1968. At one l o c a t i o n they were present on 9% of the cankers i n 1967, DUT-- were not observed at t h i s l o c a t i o n i n 1968. P e n i c i l l i u m spp., notably P. tardum Thorn, P. god l e w s k i i Z a l e s k i , P. rugulosum Thorn, P. funiculosum Thorn s e r i e s , P. brevi-compactum Dierckx. and P. nr. r o l f s i i Thorn, were a l l i s o l a t e d on one or s e v e r a l occasions from the a e c i a l zone, but a l l were probably i n c i d e n t a l and not p a r a s i t i c . A l t e r n a r i a t e n u i s auct. and Epicoccum  nigrum Link were al s o o c c a s i o n a l l y i s o l a t e d from the current year a e c i a l zone, along w i t h Sporobolomyces sp., Rhodotorula spp., and b a c t e r i a belonging to Ar t h r o b a c t e r sp., Pseudomonas and a number of u n i d e n t i f i e d species. A number of secondary organisms, not p a r a s i t i c on the r u s t , were found to f r u i t on non-current year a e c i a l zones of o l d cankers, such as L a c h n e l l u l a a r i d a ( P h i l l . ) Dennis, but they were only observed i n f r e q u e n t l y on C. comandrae, being more p l e n t i f u l on P. s t a l a c t i f o r m e can-kers . Microfauna Insect damage was widespread on C. comandrae cankers. Table X I I records the incidence of obvious i n s e c t damage on the cankers ob-served during the years 1964 to 1968 at 3 to 22 l o c a t i o n s . Data f o r 1964 and 1965 are based on only a s m a l l sample of observed cankers and are t h e r e f o r e l e s s r e l i a b l e , although the percentages are close to the range of the other years. Insect damage was recorded at each l o c a t i o n on at l e a s t one occasion. At four l o c a t i o n s more than 60% of the cankers - 92 -Table X I I . The incidence of i n s e c t damage on Cronartium comandrae cankers on lodgepole pine and the number of cankers ob-served at various l o c a t i o n s i n southwest A l b e r t a during the years 1964 to 1968. Year Wo. of l o c a t i o n s observed No. of l o c a t i o n s w i t h no damage T o t a l no. of cankers observed Cankers w i t h i n s e c t damage Per cent • i n s e c t damage 1964 4 2 47 15 31.9 1965 3 1 22 13 59-1 1966 20 4 299 137 4 5 . 8 1967 22 2 4o4 154 3 8 . 8 I968 22 5 317 132 ' 41 .6 had some evidence of damage i n each of the years I966 to 1968, and at one l o c a t i o n over 88% were damaged each year. Much of the f l u c t u a t i o n i n incidence was r e l a t e d to as s o c i a t e d rodent damage, as w i t h the r e -moval of i n f e c t e d bark there was l i t t l e s u i t a b l e h a b i t a t remaining f o r the i n s e c t s . Table X I I records only the obvious i n s e c t damage, o f t e n recorded on only one annual v i s i t to a canker, and must be considered an underestimate of the incidence of damage. Often signs cf i n s e c t damage were not v i s i b l e on the canker surface f o r aeciospores may cover the b o r i n g holes, o r i n s e c t s may mine t h e i r way i n t o the canker through bark c r e v i c e s . Insects may al s o have been present i n the a e c i a and were not v i s i b l e without i n v e s t i g a t i o n , t h i s was e s p e c i a l l y so of young l a r v a l i n s t a r s which only became v i s i b l e at a l a t e r stage. Some lar v a e a l s o took on the c o l o r of the spores when feeding on them and even a t r a i n e d eye could e a s i l y miss them i n a mass of aeciospores. Insect-damage took s e v e r a l forms, o f t e n the r u s t i n f e c t e d bark was h e a v i l y chewed and there was much b o r i n g w i t h i t s a s s o c i a t e d f r a s s ( F i g . 4 4 ) . F i g . kk. B a s a l canker of Cronartium comandrae w i t h t y p i c a l rough bark i n a e c i a l zone and showing evidence of i n s e c t damage. Note e x i t holes and Lepidoptera f r a s s at top of canker, and f u r t h e r f r a s s i n lower rough zone. F i g . 45. Pupal chambers of Pissodes schwarzi scored i n t o the sap-wood throughout the Cronartium comandrae canker area on sm a l l Pinus c o n t o r t a stem. - 93 -- 9*+ -At the time of a e c i a l s p o r u l a t i o n the i n s e c t s , both larvae and adu l t forms, fed e x t e n s i v e l y on the aeciospores, reducing the number a v a i l a b l e f o r d i s p e r s a l . They s i m i l a r l y fed on the pycniospores and the p y c n i a l drops which have a high concentration of sugars. Often the aeciospores became matted together and gave a mealy, bleached appearance, having l o s t t h e i r v i a b i l i t y ' . Much of the canker became a mass of i n s e c t f a e c a l p e l l e t s composed almost e x c l u s i v e l y of aeciospores, or w i t h cer-t a i n species of i n s e c t s , a mixture of i n f e c t e d bark and spores. The phloem i n f e c t e d t i s s u e o f t e n became a mass of feeding g a l l e r i e s and pupal chambers ( F i g . 45). The i n s e c t f r a s s o f t e n hung together on the surface of the canker as large aggregates h e l d together by i n s e c t s i l k . The d i f f e r e n t forms of i n s e c t damage were l a r g e l y d i c t a t e d by the species of i n s e c t i n h a b i t i n g the canker. In the s p r i n g and e a r l y summer the i n s e c t s occurred mainly i n the current a e c i a l zone and past a e c i a l zones towards the center of the canker. As the season advanced the l a r v a l forms and v i s i t i n g a d u lts were a t t r a c t e d more to the s p o r u l a t i n g p y c n i a l zone. By l a t e summer and e a r l y f a l l the whole p y c n i a l zone was h e a v i l y damaged. Many, i n s e c t s overwintered i n the canker, thus i n s e c t s were o f t e n present i n an a e c i a l p u s t u l e before the peridium of the pustu l e broke open. On some occasions cankers were so h e a v i l y i n f e s t e d w i t h larvae that very few aeciospores were dispersed from the canker d e s p i t e being produced i n great abundance. Many of these aeciospores were eaten by l a r v a e , but many others were aggregated together and held by f i n e s i l k threads. A l l the i d e n t i f i e d microfauna — i n s e c t s , mites and s p i d e r s , t h a t were c o l l e c t e d from the exposed surface of the canker or were reared from the i n f e c t e d cankers are given i n Appendix I I . The l i s t contains a - 95 -t o t a l of 117 species. A few of the organisms o n l y i d e n t i f i e d to genus, many being immatures or of the nondiagnostic sex, may be i d e n t i c a l w i t h others i d e n t i f i e d to species. The l i s t i n c l u d e s 98 i n s e c t s , 17 mites and 2 s p i d e r s . The most important insect:, orders represented were the Coleoptera w i t h 25 species belonging to 12 f a m i l e s , the D i p t e r a w i t h 17 species i n 9 f a m i l i e s , the Hymenoptera w i t h 2k species i n 7 f a m i l i e s , the Lepidoptera w i t h 10 species i n k f a m i l i e s , and the Collembola w i t h 8 species i n 2 f a m i l i e s . The number of specimens of each species c o l l e c t e d or reared from the cankers i s recorded i n Appendix I I . In many cases not a l l specimens of a species were removed from a canker, a l s o on numerous occasions the more common or f r e q u e n t l y o c c u r r i n g species were not c o l l e c t e d from a canker. This group of common species are u s u a l l y i n d i c a t e d i n the l i s t by a p l u s (+) f o l l o w i n g the number, which i n d i c a t e s t h a t they were f a r more common than the number of specimens c o l l e c t e d would i n d i c a t e . Mycetocoles, or animals a s s o c i a t e d w i t h f u n g i , have.been c l a s s i f i e d i n three main categories: mycetobionts, mycetophiles and mycetoxenes (Benick 1952). Animals which cannot complete t h e i r develop-ment without u t i l i z i n g the fungus as food are known as mycetobionts. Mycetophiles are those organisms t h a t are not a b s o l u t e l y dependent upon f u n g i f o r development, w h i l e organisms that are simply chance v i s i t o r s or users of the fungus are termed mycetoxenes. Many of the species c o l l e c t e d from the canker i n the present study are probably mycetoxenes — u s i n g the canker as s h e l t e r or food, or seeking out species upon which they feed which happen to be u s i n g the canker. Many of the Hymenoptera probably f a l l i n t o t h i s l a s t category as they are l a r g e l y - 96 -p a r a s i t i c on other i n s e c t s . A few of the species c o l l e c t e d appear to be true mycetobionts — the Coleoptera, Epuraea obliquus Hatch, and two d i p t e r a , an u n i d e n t i f i e d Cecidomyiidae and Paracacoxenus guttatus Hardy and Wheeler. These three were very important i n reducing the production of aeciospores and w i l l be discussed i n some d e t a i l . Among the others c o l l e c t e d there appeared to be a number of mycetophiles which were u t i l i -z i n g the fungus but known more commonly to develop i n other h a b i t a t s . The most commonly observed species on the cankers were the o r i b a t i d mite, Ceratozetes sp., the f l a t brown n i t i d u l i d b e e t l e , Epuraea  obliquus i n the l a r v a l and adu l t stages, v a r i o u s d i p t e r a l a r v a e , i n c l u d -i n g Paracacoxenus guttatus and an u n i d e n t i f i e d Cecidomyiidae, and larvae of a number of Lepidoptera. Epuraea obliquus was prominent on the canker throughout the a e c i a l and p y c n i a l s p o r u l a t i o n p e r i o d . A d u l t b e e t l e s were observed i n unruptured p u s t u l e s , and on two occasions a b e e t l e was observed chewing through the peridium and e f f e c t i v e l y r u p t u r i n g the p u s t u l e . Evidence from r e a r i n g s and from f i n d i n g specimens at the bottom of cages i n d i -cated that the larvae probably pupate and overwinter i n the s o i l or d u f f l a y e r , from which the adu l t seeks out the canker on emerging i n the s p r i n g . Some may pupate i n the canker zone, but b e e t l e s were only reared once d i r e c t l y from l o g s . A d u l t b e e t l e s were f a i r l y common from' mid May u n t i l August, and a few were present on the cankers through to September" or l a t e r ( l a t e s t c o l l e c t e d October 17, 1966). Ge n e r a l l y from one to six'were observed on an i n d i v i d u a l canker. Epuraea were observed on 80$ of the cankers at l o c a t i o n 2 i n 1965, and at l e a s t 50$ of the cankers i n 1966 and 1968. A s i m i l a r high incidence was recorded at - 97 -l o c a t i o n 3 i n the years 1966 to 1968. The f i r s t l a r v a e were found from mid June onwards, and some were c o l l e c t e d as l a t e as October 9 i n 1968, although i n other years few were observed a f t e r August. The adults and l a r v a e became covered w i t h aeciospores; the average number of spores on the body of 8 b e e t l e s was 580, and on 3 l a r v a e was 1198. A t the time of aeciospore production the Epuraea e x i s t e d e n t i r e l y on spores. A number of f a e c a l p e l l e t s was examined from b o t h adults and la r v a e , and only spores and p e r i d i a l c e l l s were present. The number of spores i n l 6 p e l l e t s was counted from adult b e e t l e s and gave an average of 586 spores, very few of which r e t a i n e d t h e i r form. These spores were checked f o r v i a b i l i t y but none germinated. The number of a e c i o -spores made i n v i a b l e through being eaten by the Epuraea b e e t l e s and l a r v a e •was enormous. Counts of adu l t Epuraea p e l l e t s from C_. comptoniae, which has a smaller aeciospore, gave lk^8 spores per p e l l e t . The l a r v a e fed e x t e n s i v e l y on the p y c n i a l drops c o n t a i n i n g the pycniospores, and were observed crawling from one drop to another. G e n e r a l l y the la r v a e oc-curred i n l a r g e r numbers on an i n d i v i d u a l canker than the a d u l t s , but r a r e l y more than 12 were counted. Epuraea a l s o fed e x t e n s i v e l y on Tuber-c u l i n a and to a l e s s e r extent on Cladosporium. The la r v a e and b e e t l e s o f t e n c a r r i e d a l a r g e number of spores on t h e i r bodies, which made them appear purple, and probably a s s i s t e d i n d i s p e r s i n g the spores over the canker zone to areas not i n f e c t e d by Tuberculina. I n a l l thar- t r a v e l s , the l a r v a e tended to leave slime t r a i l s to which aeciospores became a t -tached. Other spores became attached to f a e c a l p e l l e t s , and these attached spores were e f f e c t i v e l y prevented from being dispersed. On one occasion three b e e t l e s were allowed to crawl over a malt agar p l a t e to a s c e r t a i n what spores they might be c a r r y i n g . On t h i s occasion c o l o n i e s of - 98 -Cladosporium herbarum and Cladosporium tax. sp. 1 developed. Epuraea and other i n s e c t s no doubt act as c a r r i e r s o f many f u n g i and b a c t e r i a , and may w e l l be r e s p o n s i b l e f o r a number of s o i l organisms being present among the aeciospores. Epuraea obliquus were c o l l e c t e d or reared from s i x d i f f e r e n t l o c a t i o n s (#1, 2, 3, 5, 7 and 9) i n the study area on C. comandrae, and were reared from two canker c o l l e c t i o n s on P. banksiana, one from a p o i n t 33 miles southwest of Rae, N.W.T., and the other from Twatinaw i n northern A l b e r t a . I t was probably much more widespread than the c o l l e c t i o n s would i n d i c a t e , f o r i t was c o l l e c t e d on a number of other stem r u s t s i n the r e g i o n . A d d i t i o n a l c o l l e c t i o n data i s given f o r some of my E. obliquus c o l l e c t i o n s on pine stem r u s t s i n the paper by Parsons (1967). D i p t e r a larvae were commonly observed e a t i n g among the a e c i o -spores and often-caused the aeciospores t o become-aggregated together i n a mass o f f i n e s i l k and gave a mealy bleached appearance to the spores. These la r v a e were o f t e n present i n very large numbers on an i n d i v i d u a l canker and as many as f i f t y were counted. Between 25 and 70$ of the cankers at l o c a t i o n s 2 and 3 were observed w i t h dipterous larvae i n the various years. An average of 253 aeciospores were counted attached to the bodies of two young l a r v a e . The larvae took on the c h a r a c t e r i s t i c orange-yellow c o l o r of the spores. I n f f a c t , s i m i l a r dipterous larvae feeding on the white form of P. s t a l a c t i f o r m e (Powell 1966), were a l l white i n c o l o r . These dipterous larvae belong to at l e a s t two species and probably more, although the larvae of only two species were con-s i s t e n t l y c o l l e c t e d . One i s an u n i d e n t i f i e d Cecidomyiidae which u s u a l l y occurred i n l a r g e r numbers. Cecidomyiidae larvae on C. comandrae cankers - 99 -were c o l l e c t e d from l o c a t i o n s 1, 2, 3, and A l t r u d e Creek, B a r i l Creek and Saskatchewan R i v e r Crossing. Dr. J . R. Vockeroth (personal com-munication 1966) considered the larvae c o l l e c t e d i n large numbers from the u r e d i a l and t e l i a l s t ates of C. comandrae on Comandra p l a n t s , i n widel y s c a t t e r e d l o c a l i t i e s , and from a l t e r n a t e host p l a n t s of P. s t a l a c t i f o r m e to be the same species. U n f o r t u n a t e l y , only one Cecido-myiidae a d u l t f l y was c o l l e c t e d from the cankers during the study p e r i o d and could only be i d e n t i f i e d to genus, belonging to the t r i b e L e s t r e m i i n i . This was obtained from a canker cage i n June. Larvae of one Cecidomyiidae c o l l e c t i o n were i d e n t i f i e d as belonging to sub-family Lestremiinae. Cecidomyiidae larvae were f i r s t c o l l e c t e d i n the l a t t e r h a l f of June on C. comandrae cankers, and an odd one could s t i l l be found i n September and October. The other common dipterous l a r v a e were t e n t a t i v e l y i d e n t i -f i e d i n I965 as Dros o p h i l i d a e or Lauxaniidae, but were l a t e r reared to adult and i d e n t i f i e d as the d r o s o p h i l i d Paracacoxenus guttatus (McAlpine I968), a d u l t s of which had been reared or c o l l e c t e d e a r l i e r . This was the f i r s t i n f o r m a t i o n on the h a b i t a t of t h i s species and on the l a r v a l and pupal stages. Paracacoxenus had only been reported once p r e v i o u s l y from sweepings over muddy ground along streams or lakes i n a f o r e s t e d area. P. guttatus were c o l l e c t e d from cankers at l o c a t i o n s 1, 2, 3 and 5 i n the study area, and adults were c o l l e c t e d when v i s i t i n g the p y c n i a l drops of exposed cankers. A d d i t i o n a l data i s given f o r some of my Paracacoxenus c o l l e c t i o n s i n the paper by McAlpine (1968). The Paracaco-xenus l a r v a e , l i k e the Cecidomyiidae l a r v a e , fed e x t e n s i v e l y on the aeci o -spores and p y c n i a l drops. Adults were taken i n d i f f e r e n t years between June lk and October 17, but larvae were not observed u n t i l mid J u l y i n - 100 -most years. Specimens of another important d i p t e r a genus, which l a r g e l y occurred i n overwinter r e a r i n g s , belonged to one or more species of Bradysia. These emerged over a long p e r i o d of time i n the i n s e c t a r y and the larvae presumably fed e x t e n s i v e l y on the i n f e c t e d bark, although they were not observed doing so i n the f i e l d . S e v e r a l adult S c i a r i d a e , a l l of which were i d e n t i f i e d as Bradysia. were c o l l e c t e d i n the f i e l d . A S t a p h y l i n i d a e b e e t l e , of the genus Atheta was al s o very prominent i n r e a r i n g s , but was not observed i n the f i e l d . Coleoptera that were observed i n the f i e l d , other than the Epuraea, and were ap-p a r e n t l y feeding i n the i n f e c t e d canker t i s s u e s and p o s s i b l y on the spores, belonged to some of the f o l l o w i n g genera: Fissodes, C y l i n d r o -copturus, C o r t i c a r i a , Melanopthalma and Ernobius. The Cu r c u l i o n i d a e , Pissodes schwarzi Hopkins and Cylindrocopturus d e l e o n i Buchanan were observed feeding on t h e ' a e c i a l zone o f the canker, and t h e i r feeding g a l l e r i e s and pupal chambers ( F i g . h^) could be found i n the i n f e c t e d r u s t t i s s u e s . These weevils probably hasten the death of the t r e e as t h e i r l a r v a l g a l l e r i e s u s u a l l y scored the outer sapwood. P. schwarzi and C. d e l e o n i were c o l l e c t e d or reared from m a t e r i a l from l o c a t i o n s 1, 3, 5, and from C l i n e R i v e r , Saskatchewan R i v e r Crossing, and an area 3 mies northeast of Robb, w h i l e P. schwarzi was a d d i t i o n a l l y c o l l e c t e d from the Yukon, and C. d e l e o n i from l o c a t i o n 2. The a d u l t C o r t i c a r i a , -Melanopthalma and Ernobius observed i n the f i e l d , were a l l c o l l e c t e d between l a t e May and the end of J u l y at l o c a t i o n s 1, 2 and 3. Three genera of Lepidoptera were f r e q u e n t l y encountered i n the canker, t h e i r damage was c h a r a c t e r i z e d by aggregates of f r a s s at the entrances to t h e i r feeding g a l l e r i e s and over t h e i r pupal chambers - 101 -which were o f t e n found i n the f i s s u r e s of the rough c e n t r a l p o r t i o n of the canker. The great e s t damage was done by the l a r g e r larvae of D i o r y c t r i a zimmermani Grt., or specimens i d e n t i f i e d o n ly as D i o r y c t r i a sp., which could o f t e n be seen momentarily on the surface of the canker, and which pupated i n a s i l k - l i n e d chamber i n the i n f e c t e d t i s s u e . These larvae mine e x t e n s i v e l y i n t o the phloem t i s s u e and destroy l a r g e areas of the a e c i a l and p y c n i a l zone o f the canker. D i o r y c t r i a were c o l l e c t e d or reared from l o c a t i o n s 1, 2, 3 and 55 Saskatchewan R i v e r Crossing and C l i n e R i v e r , as w e l l as a number of other p o i n t s i n A l b e r t a , the North-west T e r r i t o r i e s , and the Cypress H i l l s , Saskatchewan. The larvae of the L a s p r e y r e s i a and Coleotechnites (Recurvaria) were much smaller, but s t i l l caused some damage i n the current or o l d a e c i a l zone. On occasion an empty cocoon could, be found s t i c k i n g out from the canker surface, or fromtthe a s s o c i a t e d r e s i n c r u s t . -The o r b a t i d mite, Ceratozetes sp., was present at s e v e r a l l o -cations i n the study area -and could be found on most i n f e c t e d t r e e s . However, i t was not r e s t r i c t e d to the canker area but could be found on many areas of the stem and apparently l i v e d i n the s o i l or d u f f l a y e r . Large numbers were o f t e n found i n the a e c i a l zone of the canker from the beginning of spore production, but were encountered l e s s o f t e n as aeci o -spore s p o r u l a t i o n ended. A few of the other mites could have been phyto-phagous, but most are probably 'classed as mycetoxenes. The Eupodidae and Tydeid mites taken from aeciospore c o l l e c t i o n s were approximately the same c o l o r as the spores, and were probably, feeding on them. Aphids of the genus Cin a r a were observed covering the whole a e c i a l and p y c n i a l zone of a few cankers, and were attended by species - 102 -of ant belonging to Lasius and Camponatus. The aphids f ed e x t e n s i v e l y on the aeciospores and l a t e r on the p y c n i a l drops, they probably a l s o ob t a i n n u t r i e n t s from the i n f e c t e d bark t i s s u e s . I n one case the ants associated w i t h the Cih a r a had b u i l t up e a r t h to enclose the canker and aphids, e f f e c t i v e l y preventing aeciospore d i s p e r s a l . The aphids were of t e n found sucking the a e c i a l area o f the canker and had worked i n un-der the bark. Of the other orders of insects, some of the Collembola and Thysanoptera probably scavenged on the a e c i a l zone of the canker, and ate spores. The Hymenoptera, excluding the Formicidae, were l a r g e l y p a r a s i t i c on Coleoptera, Lepidoptera or D i p t e r a species i n h a b i t i n g the canker and t h e r e f o r e were i n c i d e n t a l . A l l others given i n the l i s t may a l s o f a l l i n t o t h i s i n c i d e n t a l or mycetoxenes category, and were c e r t a i n l y not mycetobionts and probably not mycetophiles. Rodents Rodent damage was widespread at most l o c a t i o n s . The Richardson red s q u i r r e l , Tamiasciurus hudsonicus r i c h a r d s o n i (Bachman), B r i t i s h Columbia v a r y i n g hare, Lepus americanus columbiensis Rhoads, and the dusky porcupine, E r e t h i z o n dorsat um nigrescens A l l e n , were a l l observed chewing on the a e c i a bearing bark at one time or another, and judging from t e e t h marks, chipmunks and mice were a l s o r e s p o n s i b l e f o r removing some bark. Rodents g e n e r a l l y removed a l l the bark down to the sapwood, but u s u a l l y r e s t r i c t e d t h e i r a c t i v i t y , except i n the case of porcupines, to the i n f e c t e d bark. They showed a preference f o r the p y c n i a l and a e c i a l zones, but o f t e n ate the i n f e c t e d bark outside the p y c n i a l zone. The gnawing r a r e l y extended i n t o non-infected healthy bark. I n most - 103 -cases the rodents f a i l e d to eat the e n t i r e diseased area, enabling the r u s t to produce a e c i a i n l i m i t e d bark areas, or to continue to grow beyond the chewed area where p y c n i a l and a e c i a l s p o r u l a t i o n would again take place i n fu t u r e years. I n some cases the rodents hastened the death o f the t r e e by completely g i r d l i n g the stem or by removing the one remaining l i v e i n f e c t e d s t r i p of bark. Such trees would g e n e r a l l y succumb to the attack of the r u s t i n a year or two. I n many cases the rodent-chewing helped to suppress or destroy the canker f o r around the edge of the chewed areas c a l l u s t i s s u e developed. I n s e v e r a l 20 to 30 year o l d stands a f a i r p r o p o r t i o n of the tre e s showed o l d chewed areas where presumably a r u s t canker was .once a c t i v e , but had been i n a c t i v a t e d - b y rodent chewing. In these cases the whole canker area was chewed out and presumably no i n f e c t e d bark remained from which the r u s t could continue to i n f e c t the t r e e and produce a e c i a . One of the most s t r i k i n g cases of t h i s form of b i o l o g i c a l c o n t r o l encountered i n the present study, was the case of the P. s y l v e s t r i s p l a n t a t i o n near Beaver Mines, already r e f e r r e d to i n the s e c t i o n on damage. Rodent damage was c h a r a c t e r i s t i c of i n f e c t e d t r e e s , as i n i n -f e c t e d stands only r u s t i n f e c t e d t r e e s showed evidence of rodent damage. The one exception to t h i s was an area of porcupine damage where the por-cupine had been l e s s s e l e c t i v e although s t i l l showing a preference f o r r u s t i n f e c t e d t r e e s . Rodents appeared to only a t t a c k t r e e s which had a c t i v e l y producing pycnial and a e c i a l zones, and p r e f e r e d the p y c n i a l zones. Most of the damage probably occurred during the winter or e a r l y s p r i n g , but.some damage was recorded s p o r a d i c a l l y throughout the summer and e a r l y f a l l . I n many cases, cankers showed evidence of annual rodent v i s i t s . - 10k Each year the rodents removed the succulent p y c n i a l zone near the l i m i t s of the canker o f t e n l e a v i n g a t h i n s t r i p of c a l l u s t i s s u e adjacent to the previous year's chewed area. An example of such annual chewing i s shown i n F i g . 36, which had probably been v i s i t e d f o r at l e a s t 10 conse-c u t i v e years. Often the rodents removed a l l the p y c n i a l zone and some of the a e c i a l zone, completely r i n g i n g the canker, but l e f t untouched the center of the canker composed o f dead bark t i s s u e s . At l o c a t i o n s 2 and 3, where many of the cankers were p r o t e c t e d by i n s e c t cages, i t was not uncommon to di s c o v e r , i n the sp r i n g , t h a t the rodents had chewed the newly i n f e c t e d bark beyond the top and bottom of the cage. There were als o a few cases where the rodents damaged the i n s e c t cage and were able to chew the canker beneath. During the p e r i o d 1966 to 1968, kkY cankers were observed f o r rodent damage, and of these 320 or 71.7$ r e c e i v e d some damage i n one of the years or i n many cases each year. This percentage was s l i g h t l y lower than would have occurred normally as some 20 of the cankers were pr o t e c t e d by i n s e c t cages during two or three years of the p e r i o d . Fresh chewing was only recorded on 6 of these "protected" cankers, f a r lower than the average rodent damage incidence at these l o c a t i o n s . Table X I I I Table X I I I . The incidence of new rodent damage on Cronartium comandrae cankers, and the number of cankers observed at v a r i o u s l o -cations i n southwest A l b e r t a during the years 1966 to 1968. Year Wo. of l o c a t i o n s T o t a l no. of No. of can- Per cent observed cankers kens w i t h new new rodent observed rodent damage damage 1966 19 333 133 " 39-9 1967 21 385 166 4 3 . 1 1968 21 307 158 51.5 - 105 -shows the incidence of f r e s h rodent damage recorded each year and the number of cankers observed, excluding the cankers w h o l l y or p a r t l y pro-t e c t e d by i n s e c t cages. At two l o c a t i o n s no rodent damage was recorded i n any of the years. These, were areas of young open grown i n f e c t e d t r e e s . G e n e r a l l y the g r e a t e s t incidence of damage occurred i n the o l d e r stands where damage by s q u i r r e l s was predominant. At some l o c a t i o n s the rodent p o p u l a t i o n must remain high, but at others considerable f l u c t u a t i o n must occur. Table XIV shows the percentage incidence of f r e s h canker chewing at a number of selected' l o c a t i o n s . At M i s t Creek the stand was very open which may have accounted f o r the lower incidence, a l s o l e s s cankers were a c t i v e i n I968 which perhaps reduced t h e i r n a t u r a l a t t r a c t i v e n e s s to the rodents. The l a t t e r f a c t o r may a l s o be r e s p o n s i b l e f o r the lower i n c i -dence of rodent damage at Honeymoon and Ribbon Creeks i n 1968, as much of the a c t i v e p o r t i o n s of cankers had been removed i n the two previous years. The l a s t three l o c a i o n s given i n Table XIV were about h a l f a mile apart, but Saskatchewan R i v e r Crossing 2 was an o l d e r stand and probably more s u i t a b l e as permanent s q u i r r e l t e r r i t o r y . I n the o l d e r stands i t was not uncommon to f i n d s q u i r r e l nests i n r u s t i n f e c t e d t r e e s . At l o -c a t i o n 1 a nest occurred at the l e v e l of a canker, but a e c i a were never observed during the 5 years, although f r e s h chewing occurred each year. The main r e s u l t of the rodent-feeding was the-removal of the p y c n i a l zone, and the f u t u r e a e c i a l zone, which brought about an enormous r e d u c t i o n i n the volume of p o t e n t i a l aeciospores f o r the f o l l o w i n g season. Often cankers were prevented from producing any a e c i a f o r a number of years through the rodent a c t i v i t y . A secondary f a c t o r was t h a t the death of a diseased t r e e was o f t e n hastened, which f u r t h e r reduced the r T a b l e XIV. The p e r c e n t a g e i n c i d e n c e o f f r e s h r o d e n t chewing o f C r o n a r t i u m comandrae c a n k e r s a t s e l e c t e d l o c a t i o n s d u r i n g t h e y e a r s 1966 t o 1968. L o c a t i o n V i c a r y Honeymoon B a r i l M i s t R i b b o n Marmot Robb Saskatchewan R i v e r C r o s s i n g Creek Creek Creek Creek Creek Creek Road b u r n #1 #2 #3 1 H Year £ 1966 78 81 25 25 31 83 67 0 77 0 1967 . 55 90 26 13 68 74 32 17 80 9 1968 77 53 82 0 33 63 2 6 ' 83 100 1+6 - 107 -p o t e n t i a l of a canker to produce aeciospores. A l s o , a s s o c i a t e d w i t h the rodent chewing damage there was g e n e r a l l y copious r e s i n flow, which o f t e n contaminated the a e c i a l zone preventing aeciospore d i s p e r s a l . Dur-ing the w i n t e r - s p r i n g season of 1966-67 at k l o c a t i o n s , an average of 25$ (range f o r i n d i v i d u a l l o c a t i o n s 10 to 3*+$) of the canker bark was removed from a l l cankers showing any rodent damage, and i n many cases the bark not removed was no longer productive. S i m i l a r values f o r the 1967-68 w i n t e r - s p r i n g season, from cankers chewed at 17 l o c a t i o n s , showed th a t 30$ (range f o r i n d i v i d u a l l o c a t i o n s 7 to 73$) of the canker bark was removed, most being from the p o t e n t i a l aecia-bearing zone o f the canker. There were numerous cases where 70 to 100$ of the p o t e n t i a l a e cia-bearing bark on a canker was removed. Rodents tended to remove the i n f e c t e d bark nearest the center of the canker, the p o r t i o n on which the f i r s t a e c i a would develop, thus even i f some i n f e c t e d bark remained, a e c i a l s p o r u l a -t i o n was s t i l l delayed on these cankers. Often the few remaining a e c i a would not sporulate u n t i l two weeks a f t e r the main aeciospore s p o r u l a -t i o n p e r i o d . I t was common to f i n d rodent gnawing a l l round a branch stub which had served as the mode of entry of the r u s t i n t o the main stem: Response of the t r e e The main response of the t r e e to the canker was the pro d u c t i o n of r e s i n . The most n o t i c e a b l e r e s i n production occurred i n the p y c n i a l zone, although considerable amounts were a l s o produced i n the t i s s u e s of the a e c i a l zone. C h a r a c t e r i s t i c a l l y the r e s i n flowed down over the canker and the stem area below, causing most damage when o r i g i n a t i n g i n the upper p y c n i a l zone. The r e s i n o f t e n prevented f u r t h e r d i s p e r s a l of aeciospores during the season, and formed a cr u s t over the bark which may have - 108 -e f f e c t i v e l y prevented, a e c i a from pushing through the c r u s t i n f u t u r e years to disperse aeciospores. I t was not uncommon f o r the r e s i n flow to take on an orange-yellow c o l o r where p y c n i a l drops or aeciospores were i n c o r -porated i n t o the r e s i n . Most r e s i n flow occurred towards the end o f the main aeciospore s p o r u l a t i o n p e r i o d , c o n t i n u i n g u n t i l at l e a s t l a t e Septem-ber. Resin was probably produced because the r e s i n canal c e l l s were rup-tured by the a e c i a l zone cracking and d r y i n g out, and through pressure produced on the r e s i n canal c e l l s by the increased amount of i n t e r c e l l u l a r r u s t mycelium. Further r e s i n flow occurred through the i n s e c t and rodent-damage, e s p e c i a l l y that of the l a t t e r , and helped s u b s t a n t i a l l y to pro-duce a crust- of d r i e d r e s i n over much of the canker. Often r e s i n flow extended f o r s e v e r a l f e e t below cankers o c c u r r i n g higher upon t r e e s . R e s in production o f t e n occurred annually on a c t i v e cankers. TableXV r e -cords the incidence of f r e s h r e s i n o s i s on cankers i n the years I966 to 1968 at v a r i o u s l o c a t i o n s . Most of those cankers not r e c o r d i n g f r e s h r e s i n o s i s were i n a c t i v e cankers, although some cankers showing no a c t i v e p y c n i a l or a e c i a l s p o r u l a t i o n zones or the presence of T u b e r c u l i n a or other f u n g i , s t i l l produced some surface r e s i n . f l o w presumably i n r e s -ponse to the extension of the rust- mycelium around the p e r i p h e r y of the canker,.- Resin production was more extensive i n a s s o c i a t i o n w i t h Tuber-c u l i n a than w i t h the r u s t alone. I n the three main years of observation only 37 cankers (7.9$) were observed that d i d not show evidence of some r e s i n o s i s during t h e i r h i s t o r y . The m a j o r i t y of these occurred on very young trees ( l l ) , or on t r e e s that were observed f o r only one or two years before dying (20). P r a c t i c a l l y every t r e e w i t h an i n a c t i v e canker showed evidence of some p e r i o d of r e s i n o s i s , and o f t e n the v a s t m a j o r i t y of the - 109 -canker and area below was covered i n d r i e d r e s i n . The r e s i n o f t e n im-pregnated l a r g e areas of the bark and outer sapwood. Table XV. The incidence- of f r e s h r e s i n o s i s on Cronartium comandrae cankers on lodgepole pine and the number of cankers obser-ved at a number of l o c a t i o n s i n southwest A l b e r t a during the years 1966 to 1968. Year Wo. of l o -cations -" observed No. of cankers observed No. of cankers w i t h f r e s h r e s i n Per cent of cankers w i t h f r e s h r e s i n 1966 20 356 237 . 66 .6 1967 22 398 282 71.1 1968 22 320 212 66.2 D i s c u s s i o n T u b e r c u l i n a maxima i s reported to be a hyperparasite o f r u s t s , i n c l u d i n g those of the Cronartium (Peridermium) group (Hedgcock 1935; Hubert 1935a; Mielke 1933; Tubeuf 1901, 19lk; Weir and Hubert 1917). However, present observations, and the study of Wicker on C_. r i b i c o l a i n Idaho (Leaphart and Wicker 1968) i n d i c a t e that T. maxima i s not a tru e hyperparasite o f the r u s t , but i s p a r a s i t i c on the r u s t canker area where the mycelium invades the bark t i s s u e . This i s i n agreement w i t h the e a r l y work of Lechmere (1914) who found t h a t T. maxima d i d not att a c k or destroy the r u s t mycelium. A l l e a r l i e r r e p o r t s are i n agreement t h a t the cankered bark dies a f t e r i n v a s i o n by T. maxima and tha t i t g r e a t l y reduces or-• e n t i r e l y ' i n h i b i t s the production of aeciospores where i t occurs. T. maxima was described by Rostrup (1890) as a t t a c k i n g C. r i b i c o l a ( P u c c i n i a  klebahni) on Pinus strobus i n Europe, and was f i r s t r eported on C. comandrae - 110 -on P. ponderosa and P. c o n t o r t a "by Weir and Hubert (1917) from Montana. Tuberculina was not found on t h i s group of r u s t s i n A l b e r t a u n t i l 1964 (Powell and Morf 1965), but has been known since I926 on C.' r i b i c o l a i n B r i t i s h Columbia (Mielke 1933). I n 1964, T u b e r c u l i n a was found at 11 l o c a t i o n s on C_. comandrae on P. c o n t o r t a and one on P. s y l v e s t r i s between Robb and Beaver Mines, A l b e r t a . Since that time T u b e r c u l i n a has been found at a f u r t h e r 11 l o c a t i o n s i n A l b e r t a , and one l o c a t i o n i n Kootenay N a t i o n a l Park, B r i t i s h Columbia, on P. contorta, the l a t t e r • r e c o r d being the f i r s t on C. comandrae i n that Province. S e v e r a l T u b e r c u l i n a c o l l e c -t i o n s were a l s o made on C. comandrae on P. banksiana from one l o c a t i o n on the Mackenzie Highway, 110 miles south of Rae, Northwest T e r r i t o r i e s (Baranyay 1968), but Tu b e r c u l i n a has not been recorded on t h i s pine host i n A l b e r t a , Saskatchewan or Manitoba. P o w e l l and Morf (1965) reported the occurrence, of Tu b e r c u l i n a on Peridermium s t a l a c t i f o r m e i n A l b e r t a , but not on C. r i b i c o l a or P. h a r k n e s s i i . However i n 1965 T u b e r c u l i n a was found on P. h a r k n e s s i i on P. co n t o r t a (CFB 6895) i n Kootenay N a t i o n a l Park, B r i t i s h Columbia, the f i r s t r e c o r d on t h i s r u s t i n western Canada. In 1966 T u b e r c u l i n a was c o l l e c t e d on C_. comptoniae on P. c o n t o r t a x P. banksiana h y b r i d (CFB 7736), 40 miles north of Nahanni Butte, Northwest T e r r i t o r i e s , which was r e c e n t l y reported by Baranyay (1968). Tu b e r c u l i n a was p r e v i o u s l y only known on t h i s r u s t host from B r i t i s h Columbia (Mielke 1933). I t s occurrence on C. comandrae and other Cronartium (Peridermium) spp. i n western North American i s probably more widespread than the c o l -l e c t i o n s i n d i c a t e . On C. r i b i c o l a and C. comptoniae, T. maxima i s r e -ported to sporulate most abundantly on the p y c n i a l zones o f the canker (Hubert 1935a,b; Mielke 1933; Wicker, p e r s o n a l communication 1968), but on C_. comandrae i t r a r e l y sporulates on the p y c n i a l zone but abundantly - I l l -on the a e c i a l zone. I t was found i n the present study t h a t only current season p y c n i a l and a e c i a l zones appear to be s u s c e p t i b l e to T. maxima:, no f r e s h i n f e c t i o n occurred on i n a c t i v e cankers. I n o c u l a t i o n t e s t s , r e -ported by Wicker and Kimmey (1967) s i m i l a r l y showed th a t n o n f r u i t i n g cankers were not s u s c e p t i b l e to i n f e c t i o n , p roving that i n f e c t i o n e n t r y was only gained through s p o r u l a t i n g p y c n i a or a e c i a . Wicker and Wells (1968) reported t h a t T. maxima was able to overwinter as spores, sporo-dochia, or i n the m y c e l i a l stage w i t h i n the pine cortex. Some spore v i a b i l i t y was r e t a i n e d a f t e r 19 months storage at -31°C. T. maxima was always found i n d i r e c t a s s o c i a t i o n w i t h the r u s t , and from the evidence th a t s m a l l areas remained u n i n f e c t e d and were able to s p o r u l a t e , i t -appeared that T. maxima d i d not extend to or beyond the l i m i t of the r u s t mycelium i n the i n f e c t e d bark and t h e r e f o r e d i d not give complete b i o l o g i -c a l c o n t r o l of the r u s t . A number of people i n Europe and America have used T. maxima as a c o n t r o l of C. r i b i c o l a w i t h l i m i t e d or no success (Hubert 1935a,b; Mielke 1933, Quick and Lamoureaux 1967, Tubeuf 1914, 1917, 1930). Mielke (1933) and Hubert (1935a,b) were of the o p i n i o n that i t s p o s s i b i l i t i e s as a c o n t r o l agent were remote, but the more r e -cent work of Quick and Lamoureaux (1967), Wicker and Wells (1968) and Wicker (personal communication 1968) i n d i c a t e d greater p o t e n t i a l . T. maxima was c e r t a i n l y able to cause marked r e d u c t i o n i n aeciospore pro-d u c t i o n (Lechmere 191k; Spaulding 1929, Tubeuf 1 9 l 4 ; and the present study). Leaphart and Wicker (1968) reported a marked increase i n the percentage of C. r i b i c o l a cankers p a r a s i t i z e d by T. maxima. Ranges of incidence at the s t a r t were 37 to 80%, but by 1966 were 83 to 100%, a l -though some may not have been i n o c u l a t e d n a t u r a l l y . I n the present study, - 112 -average annual incidence of 13 to 24$vas recorded f o r a l l l o c a t i o n s . The high l e v e l o f incidence, plus the f a c t that i t was r a r e l y present on the same canker f o r more than one or two years and th a t i t u s u a l l y i n a c t i v a t e d the canker, i n d i c a t e s that Tuberculina was p l a y i n g an important r o l e i n c o n t r o l l i n g C. comandrae and presumably other Cronartium r u s t s . A Cladosporium sp. has not been reported as an ass o c i a t e d fungus of Cronartium stem, r u s t s , although Keener (1964) found Cladosporium spp. on the a e c i a l s o r i of the cone r u s t Cronartium conigenum Hedge. & Hunt.. He als o s t a t e d that Cladosporium a e c i d i i c o l a Thum was the most f r e q u e n t l y encountered fungus on a l l types of r u s t s o r i , and reported s e v e r a l cases on r u s t s i n Worth America (Keener 1954, 1956, 1964). Cladosporium exoasci Lindau, C. e x o b a s i d i i Jaap. (C. cl a d o s p o r i o i d e s Thum), and C. hemileiae Steyaert were a l s o reported to be hyperparasites on other p a r a s i t i c f u n g i (de V r i e s 1952). According to Dr. E l l i s (see above, page 83) Cladosporium tax. sp. 1. does not f i t any of the d e s c r i p t i o n s f o r Cladosporium spp. asso c i a t e d w i t h r u s t s . Cladosporium tax. sp. 1 was f a i r l y widespread as i n a d d i t i o n to the l o c a t i o n s reported above, i t was found on C. comandrae on P. banksiana (CFB 7447), 60 m i l e s northeast of F o r t Providence, W.W.T., and i s qui t e common (9 CFB c o l l e c t i o n s ) on P. h a r k n e s s i i g a l l s , on P. con t o r t a i n A l b e r t a and the Wational Parks i n B r i t i s h Columbia. Dr. Sutton (personal communication 1966) a l s o reported i t on C. comandrae and P. h a r k n e s s i i on P. banksiana i n the Saskatchewan and Manitoba area. Some evidence was gained that Cladosporium tax. sp. 1 might be p a r a s i t i c on C. comandrae aeciospores. de V r i e s (1952) doubted whether a l l of the described r u s t a s s o c i a t e d Cladosporium species were a c t u a l l y "hyperpara-s i t e s " as he was unable to detect connections between Cladosporium hyphae - 113 -and uredospores of Melampsora l a r i c i - e p i t e a Kleb. on S a l i x sp., the s o r i of which were covered by C. c l a d o s p o r i o i d e s , but the r e p o r t o f Steyaert (1930) f o r C_. hemileiae on Hemil e i a v a s t a t r i x Berk. & Br. i s convincing. Keener (1964) was of the o p i n i o n that species such as Cladosporium ap-p a r e n t l y lacked the c a p a c i t y to destroy r u s t spores and probably only impeded spore dissemination. Smith (1905) reported t h a t a species of Cladosporium on Asparagus r u s t i n C a l i f o r n i a , which he b e l i e v e d to be C. herbarum Link, was able to destroy r u s t spores and i l l u s t r a t e d a Clados-porium germinating from a dead r u s t spore. C. herbarum was observed l e s s f r e q u e n t l y i n the present study from spore c o l l e c t i o n s and may be p l a y i n g a r o l e i n reducing the v i a b i l i t y of aeciospores, along w i t h C_. tax. sp. 1. C. herbarum was r e c e n t l y i s o l a t e d from d e t e r i o r a t i n g t e l i a l g a l l s of of Gymnosporangium juvenescens Kern ( E s l y n i 9 6 0 ) . Cladosporium spp. are common among the primary f u n g a l c o l o n i z e r s on p l a n t m a t e r i a l (Greene 1952; Leben .1965). A number of people have i n d i c a t e d t h a t there i s a succession of f u n g a l c o l o n i z e r s on p l a n t m a t e r i a l s (Hudson 1962; Last 1955), and tha t Cladosporium o f t e n overruns the other c o l o n i z e r s , e s p e c i a l l y under h i g b humidity c o n d i t i o n s . When i n s e c t cages were maintained on cankers i n the present study, o f t e n causing a higher humidity l e v e l , Cladosporium, when present, r a p i d l y . c o v e r e d the whole canker. Of the other m i c r o f l o r a l species i s o l a t e d i n the present study a few, or species of the same genus, have been reported as p l a y i n g a pos-s i b l e r o l e i n reducing the e f f e c t of other p l a n t pathogens. Wollenweber (1934) described Fusarium b a c t r i d i o i d e s which was found to p a r a s i t i z e the cone b l i s t e r r u s t , Cronartium conigenum. Goodding was al s o able to demon-s t r a t e the a b i l i t y of F. b a c t r i d i o i d e s to at t a c k C. r i b i c o l a , P. (C.) - 114 -h a r k n e s s i i and P. (C.) filamentosum from s u c c e s s f u l i n o c u l a t i o n s i n Oregon and Idaho (Goodding, i n Wollenweber 1934). Goodding (1932) a l s o b r i e f l y discussed another Fusarium sp. which occurred on C. r i b i c o l a cankers i n -dependent o f the a e c i a and was as s o c i a t e d w i t h a H e c t r i a sp. There are a number of r e p o r t s of the secondary f u n g i a s s o c i a t e d w i t h C. r i b i c o l a can-kers (Bingham 1942; Goodding 1932; Rhoads 1920; S n e l l 1929a,b; Spaulding 1922, 1929; S t o u f f e r 1932) which are not p a r a s i t i c on the r u s t . Rhoads (1920), Spaulding (1922) and Hubert (1935b), b e l i e v e d t h a t the secondary f u n g i a c c e l e r a t e d the g i r d l i n g of the r u s t and hastened the death of the canker t i s s u e s . Posey and Gravatt ( c i t e d i n Spaulding 1929) reported t h a t 15$ of the r u s t i n f e c t e d t r e e s recovered through the a c t i o n of the secondary f u n g i i n k i l l i n g the i n f e c t e d pine bark, and through suppres-s i o n of lower branches before the r u s t spread to the stem. Bingham (1942) and Bingham and E h r l i c h (1943) b e l i e v e d t h a t the secondary f u n g i reduce the a e c i a l s p o r u l a t i o n of the r u s t . A l s o t h a t one of these, a Dasyscypha sp., once e s t a b l i s h e d k i l l e d the bark much more r a p i d l y than C. r i b i c o l a (Bingham and E h r l i c h 1943). Among the secondary f u n g i reported by others . on C. r i b i c o l a and i d e n t i f i e d i n the present study were L a c h n e l l u l a (Dasyscypha) spp. (Bingham 1942; Bingham and E h r l i c h : . l 9 4 3 ; Goodding 1932; S n e l l 1929a,b; S t i l l i n g e r 1929), Tympanis spp. (Bingham 1942; Hubert 1931), Phoma sp. ( S n e l l 1929a) and Phomopsis sp. (Goodding 1932). Keener (1964) considered t h a t V e r t i c i l l i u m along w i t h D a r l u c a and Tuberculina were species capable of de s t r o y i n g r u s t spores. C a s t e l l a n i and G r a n i t i (1949) reported a V e r t i c i l l i u m t h a t was p a r a s i t i c on Cronartium  asclepiadeum aeciospores causing them to become h y a l i n e . Sukapure and Thirumalachar (1966) have reported a Cephalosporium p a r a s i t i c on the u r e d i a - 115 -of three r u s t s i n I n d i a . Greene (1952) r e p o r t s a Coniothyrium sp. on the t e l i a of P u c c i n i a anemones-virginianae Schw. i n Wisconsin, and a Phoma sp. on Taphrina m i r a b i l i s (Atk.) Giesenhag. Myren (1964) i s o l a t e d various imperfect f u n g i from a l l of the Cronartium fusiforme cankers c o l -l e c t e d from three l o c a t i o n s . T h i r t y per cent of the 132 cankers a l s o y i e l d e d b l u e - s t a i n f u n g i , and 13%-basidiomycetes. He thought t h a t the associated i n s e c t g a l l e r i e s served as i n f e c t i o n courts f o r v a r i o u s wood-i n h a b i t i n g f u n g i . Microorganisms have al s o been reported a s s o c i a t e d w i t h Hypoxylon pruinatum (Klotzsch) Cke. cankers. B i e r and Rowat (1962a) r e -ported P u l l u l a r i a sp. and Epicoccum nigrum to be common, and Wood and French (1965) added species of A l t e r n a r i a , Chaetomium, Cytospora and b a c t e r i a . S e v e r a l of these f u n g i i n h i b i t e d growth of Hypoxylon i n dual c u l t u r e , and prevented canker formation ( B i e r and Rowat 1962a, b, 1963). B i e r (1963) l a t e r reported that healthy bark-water suspensions c o n t a i n i n g f u n g i and b a c t e r i a c o n t r o l l e d a