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Ecological studies of Hylobius radicis Buch., H. Pales (HBST.) and Pissodes approximatus Hopk. (Coleoptera:… Finnegan, Raymond Rene Joseph 1958

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©lie Pmtarsti|j of ^rtttsij (Eolomdbia Faculty of Graduate Studies  PROGRAMME OF THE  FINAL ORAL EXAMINATION FOR THE D E G R E E OF  DOCTOR OF PHILOSOPHY "t  RAYMOND JOSEPH FINNEGAN B.Sc.F. New Brunswick 1948 M.Sc.F. New Brunswick 1950 IN ROOM 187A BIOLOGICAL SCIENCES  BUILDING  Saturday, November 8, 1958 9:30 a.m. COMMITTEE IN C H A R G E DR. F. H. SOWARD, Chairman K. G R A H A M G. S. A L L E N I. McT. COWAN J. E. BIER P. A. LARKIN V. KRAJINA D E A N W. H . G A G E External Examiners of Thesis JOHN MacSWAIN (Univ. of California) JULIUS A. RUDINSKY (Oregon State College) W. G. WELLINGTON (Division of Forest Biology)  ECOLOGICAL STUDIES OF HYLOBIUS H. PALES  (HBST.)  A N D PISSODES  RAD1C1S  APPROXIMATUS  BUCH., HOPK.  (COLEOPTERA: CURCULIONIDAE) IN SOUTHERN ONTARIO. ABSTRACT Three native weevils have become increasingly important in recent years in stands of planted pines in southern Ontario. The pine root collar weevil, Hyldbius radicis finch., breeds in the root collar of healthy pines, killing over 90% of the trees in some plantations. The pales weevil, H. pales (Hbst.), and the northern pine weevil, Pissodes approximates Hopk., are important because the adults, feeding on the tender bark of twigs and small branches of healthy pines, kill the branches or even the whole tree. The life histories and bionomics of the three species were determined from natural populations in the field and colonies in the insectary. These studies were facilitated by a special technique devised for rearing the weevils permitting continuous observation's of larval and pupal development and periodic measurement of body size and larval feeding. Stand density is the chief factor regulating populations: of H. radicis, fostering high populations in the dense stands of plantations, and excluding the insect from sparser natural stands. Scots pine is evidently more susceptible than red pine to H. radicis where the two tree species grow together, but the presence of Scots pine increases the infestation in red pine. Availability of suitable breeding material in the form of numerous stumps left after cutting is the factor governing the number of H. pales and P. approximates. The implications for forestry consist of recommendations to avoid pure dense stands especially of exotic species, and to practice forest sanitation in cutting operations.  PUBLICATIONS  STEWART, K. E., R. J. FINNEGAN A N D C. S. KIRBY. Control of Fletcher scale, Lecanium fletcheri Ckll., on Japanese yew. Can. Dept. Agr., For. Biol. Div., Bi-Monthly Prog. Rept. 9 (2): 3. 1953. FINNEGAN, R. J. Weevils attacking pines in southern Ontario. Can. Dept. Agr., For. Biol. Div., Bi-Monthly Prog. Rept. 12(2): 3. 1956. FINNEGAN, R. J. Elm bark beetles in southern Ontario. Canad. Ent. 89 (6): 275-280. 1957. FINNEGAN, R. J. The pine weevil, Pissodes approximates Hopk., in southern Ontario. Canad. Ent. 90(6): 384-354. 1958.  Faculty of Graduate Studies  PROGRAMME OF THE  FINAL ORAL  EXAMINATION  FOR THE D E G R E E OF  DOCTOR OF PHILOSOPHY  RAYMOND JOSEPH FINNEGAN B.Sc.F. New Brunswick 1948 M.Sc.F. New Brunswick 1950 IN ROOM 187A BIOtOGICAL SCIENCES BUILDING Saturday, November 8, 1958 9:30 a.m. COMMITTEE IN C H A R G E DR. F. H. SOWARD, Chairman K. G R A H A M G. S. A L L E N I. McT. COWAN J. E . BIER P. A. LARKIN V. KRAJINA D E A N W. H. G A G E External Examiners of Thesis JOHN MacSWAIN (Univ. of California) JULIUS A. RUDINSKY (Oregon State College) W. G. WELLINGTON (Division of Forest Biology)  ECOLOGICAL STUDIES OF HYLOBWS H. PALES  (HBST.) A N D PISSODES  RADICIS  APPROXIMATUS  BUCH., HOPK.  (COLEOPTERA: CURCULIONIDAE) IN SOUTHERN ONTARIO. ABSTRACT Three native weevils have become increasingly important in recent years in stands of planted pines in southern Ontario. The pine root collar weevil, Hylobius radicis Buch., breeds in the root collar of healthy pines, killing over 90% of the trees in some plantations. The pales weevil, H. pales (Hbst.), and the northern pine weevil, Pissodes approximatus Hopk., are important because the adults, feeding on the tender bark of twigs and small branches of healthy pines, kill the branches or even- the whole tree. The life histories and bionomics of the three species were determined from natural populations in the field and colonies in the insectary. These studies were facilitated by a special technique devised for rearing the weevils permitting continuous observations of larval and pupal development and periodic measurement of body size and larval feeding. • Stand density is the chief factor regulating;.;populations; of H. radicis, fostering high populations in the dense stands of plantations, and excluding the insect, from sparser natural stands. Scots pine is evidently more susceptible than red pine to H. radicis where the two tree rspecies* grow together,. but the presence of Scots pine increases the infestation in red pine. Availability of suitable breeding material in the form of numerous stumps left after cutting is the factor governing the number of H. pales and P. approximatus. The implications for forestry consist of recommendations to avoid pure dense stands especially of exotic species, and to practice forest sanitation in cutting operations.  PUBLICATIONS  STEWART, K. E., R. J. FINNEGAN A N D C. S. KIRBY. Control of Fletcher scale, Lecanium fletcheri Ckll., on Japanese yew. Can. Dept. Agr., For. Biol. Div., Bi-Monthly Prog. Rept. 9 (2): 3. 1953. FINNEGAN. R. J. Weevils attacking pines in southern Ontario. Can. Dept. Agr., For. Biol. Div., Bi-Monthly Prog. Rept. 12(2): 3. 1956. FINNEGAN, R. J. " Elm bark beetles in southern Ontario. Canad. Ent. 89 (6): . 275-280. 1957. FINNEGAN, R. J. The  pine weevil, Pissodes approximates Hopk., in' southern  Ontario. Canad. Ent. 90(6): 384-354. 1958.  ECOLOGICAL STUDIES OF HYLOBIUS RADICIS BUCH., H. PALES (HBgT.) AND PISSODES APPROXIMATUS HOPK. (COLEOPTERA  : CURCULIONIDAE)  IN SOUTHERN ONTARIO.  lay  RAYMOND JOSEPH  FINNEGAN  B. Sc. ( F . ) 1948, U n i v e r s i t y o f New Brunswick. M. Sc. (P.) 1950, U n i v e r s i t y  o f New Brunswick.  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  i n t h e Department of Zoology  We a c c e p t t h i s t h e s i s a s conforming t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA September, 1958.  ABSTRACT  Three n a t i v e w e e v i l s have "become i n c r e a s i n g l y important i n r e c e n t y e a r s i n stands  of p l a n t e d pines i n southern  a r i o . The p i n e r o o t c o l l a r w e e v i l , H y l o b i u s  Ont-  r a d i c i s Buch.,  breeds i n the r o o t c o l l a r o f h e a l t h y pines;, k i l l i n g  over  SO<fo of the t r e e s i n some p l a n t a t i o n s . The p a l e s w e e v i l , H. pales. ( H o s t . ) , and  the n o r t h e r n p i n e w e e v i l ,  a-p-proximatus Hook.» a r e important on the t e n d e r b a r k of twigs pines  t  kill The  and  Pissodes  because the a d u l t s , f e e d i n g  s m a l l branches of h e a l t h y  the branches or even the whole t r e e .  l i f e h i s t o r i e s and bionomics of t h e t h r e e  species  were determined from n a t u r a l p o p u l a t i o n s i n the f i e l d  and  c o l o n i e s i n the i n s e c t a r y . These s t u d i e s were f a c i l i t a t e d by a s p e c i a l t e c h n i q u e p e r m i t t i n g continuous  d e v i s e d f o r r e a r i n g the observations  weevils  of l a r v a l and  pupal  development and p e r i o d i c measurment of body s i z e and  larval  feeding. Stand d e n s i t y i s the c h i e f f a c t o r r e g u l a t i n g p o p u l a t i o n s of H. r a d i c i s , f o s t e r i n g h i g h p o p u l a t i o n s i n t h e dense stands  of p l a n t a t i o n s , and  e x c l u d i n g the i n s e c t from  sparser  n a t u r a l s t a n d s . Scots p i n e i s e v i d e n t l y more s u s c e p t i b l e t h a n r e d p i n e t o H.  r a d i c i s where the two  t r e e s p e c i e s grow  t o g e t h e r , but the p r e s e n c e of Scots p i n e i n c r e a s e s the  infes-  iii  t a t i o n i n r e d p i n e . A v a i l a b i l i t y of s u i t a b l e b r e e d i n g i n the  form of numerous stumps l e f t a f t e r c u t t i n g i s  f a c t o r g o v e r n i n g the The  implications  avoid  number of H. p a l e s and  for forestry consist  P.  material the  approximatus.  of recommendations  pure dense s t a n d s e s p e c i a l l y of e x o t i c  to p r a c t i c e f o r e s t s a n i t a t i o n i n c u t t i n g  species,  operations.  and  to  In p r e s e n t i n g the  this thesis in partial fulfilment  requirements f o r an advanced degree at the  of  University  of B r i t i s h Columbia, I agree t h a t the  L i b r a r y s h a l l make  it  study.  f r e e l y available f o r reference  and  I  further  agree t h a t permission f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may  be granted by the  Department or by h i s r e p r e s e n t a t i v e .  Head o f  my  I t i s understood  that  copying or 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  gain  s h a l l not  Department  be allowed without my  of  The U n i v e r s i t y of B r i t i s h Vancouver 8, Canada.  Columbia  written  permission.  iv  CONTENTS Page 1  INTRODUCTION TAXONOMY  4 10  METHODS Study o f I n s e c t B i o l o g i e s  10  Measurment  15  of Damage  HYLOBIUS RADICIS BUCK  19  History  19  D e s c r i p t i o n of L i f e H i s t o r y Stages  21  D i s t r i b u t i o n and Hosts  29  Seasonal H i s t o r y  50  Habits  34  •  Limiting Factors  42  Effect  46  on t h e Tree  HYLOBJJJS PALES (HBST.)  56  History  57  D e s c r i p t i o n o f L i f e H i s t o r y Stages  59  D i s t r i b u t i o n and Hosts  64  Seasonal H i s t o r y  67  Habits  71  Limiting Factors  74  Effect  77  on t h e Tree  V  PISSODES APPROXIMATUS HOPE  78  History  .  ..  78 t . 1...  D e s c r i p t i o n o f L i f e H i s t o r y Stages  79  D i s t r i b u t i o n and Hosts  83  Seasonal H i s t o r y  84  Habits Limiting Factors Effect  i.  85  ...  91  t*... i  on t h e Tree'  94  DISCUSSION AND ^CONCLUSIONS .. ..  ;  :  BIBLIOGRAPHY  95 103  FIGURES F i g . 1. Method,;.of r e a r i n g p i n e w e e v i l s i n t h e i n s e c t a r y from t h e egg t o t h e a d u l t s t a g e showing, ( a ) p o u r i n g t h e sa'nd over t h e * i n n e r bark and s c r e e n ; ( b ) a s e c t i o n a l view of t h e rea'ring u n i t  12  F i g . 2. Larvae o f H y l o b i u s r a d i c i s i n r e a r i n g (a) F e e d i n g l a r v a , (b) Prepupa i n p u p a l - r cell  14  F i g . 3. Caged p i n e t r e e s used i n s t u d y i n g t h e bionomics o f H y l o b i u s r a d i c i s  17  F i g . 4. H y l o b i u s r a d i c i s . (a) Egg x 2 4 ; (b) Larva x 6 ; ( c ) Pupa i n e a r t h e n c e l l x 6 ; (d) A d u l t x6  22  F i g . 5. D o r s a l view (b) H. p a l e s , on t h e e l y t r a to t h e b a r r e d H. p a l e s ..  23  of (a) H y l o b i u s r a d i c i s and showing the* s c a t t e r e d spots'' o f H. r a d i c i s i n c o n t r a s t p a t t e r n on t h e e l y t r a o f .....  vi  Pig.  Pig.  Pig.  6.  ( a ) Hind t i b i a l uncus o f H y l o b i u s r a d i c i s males; (b) Hind t i b i a l uncus of H. -pales males; ( c ) Hind t i b i a l uncus °f H» r a d i c i s and H. p a l e s females and (d) Abdominal i m p r e s s i o n s found on H. r a d i c i s and H. p a l e s males. .. . D i s t r i b u t i o n of head c a p s u l e measurments of 84 H y l o b i u s r a d i c i s l a r v a e r e a r e d i n the i n s e c t a r y from t h e egg t o t h e adult.. The c r o s s - h a t c h e d a r e a s r e p r e s e n t t h e o v e r l a p between a d j a c e n t i n s t a r s  26  7.  8.  D i s t r i b u t i o n o f head c a p s u l e measurments of H y l o b i u s r a d i c i s , r e p r e s e n t i n g (a) 476 l a r v a e c o l l e c t e d i n the f i e l d V (b) 84 ' " l a r v a e r e a r e d i n t h e i n s e c t a r y . .........  27  J  Pig. Pig.  pig.  Pig.  pig.  28  9. S e a s o n a l h i s t o r y o f H y l o b i u s r a d i c i s i n s o u t h e r n O n t a r i o . ...  31  10. S e c t i o n through t h e r o o t c o l l a r o f a s i x - i n c h Scots p i n e showing t y p i c a l wounds caused by H y l o b i u s r a d i c i s l a r v a e . T h i s t r e e had been i n f e s t e d f o r a t l e a s t thirteen ye%rs.  35  11. H y l o b i u s r a d i c i s damage to. t h e r o o t c o l l a r of S c o t s p i n e , (a) Root c o l l a r of i n f e s t e d t r e e w i t h t h e p i t c h - i n f i l t r a t e d s o i l p a r t l y removed t o show a l a r v a i n the o u t e r bark; (b)stump o f i n f e s t e d t r e e with s o i l completely removed t o show s w e l l i n g a t t h e r o o t c o l l a r due t o l a r v a l damage; ( c ) Stump of i n f e s t e d t r e e wi'th b a r k removed from t h e r o o t c o l l a r t o show extent o f damage t o t h e wood.  36  12. D i s t r i b u t i o n o f H y l o b i u s r a d i c i s l a r v a e and pupae i n the s o i l around the r o o t c o l l a r o f i n f e s t e d S c o t s pines i . . . .  39  13. Emergence o f H y l o b i u s r a d i c i s a d u l t s from twenty t r e e s d u r i n g the summer o f 1955  40  vii  P i g . 14. H y l o b i u s r a d i c i s damage, ( a ) A h e a v i l y i n f e s t e d twenty-year-old Scots pine p l a n t a t i o n ; (b) Two i n f e s t e d t r e e s b r o k e n a t t h e r o o t c o l l a r and blown over by wind. P i g . 15. Growth curves o f 20 r e d p i n e s and 20 Scots p i n e s , h e a v i l y i n f e s t e d w i t h .-•- H y l o b i u s r a d i c i s , and 10 h e a l t h y white p i n e s growing i n a mixed s t a n d . The t r e e s were a l l 22 y e a r s o l d Pig.  16. H y l o b i u s r a d i c i s damage, showing a l i e r nate rows o f l i v i n g i n f e s t e d r e d p i n e s ••• and dead Scots p i n e s  P i g . 17.  Hylobius pales adult  R e l a t i o n s h i p between t h e head c a p s u l e s i z e o f prepupae and a d u l t s o f H y l o b i u s p a l e s . The r e g r e s s i o n l i n e Y = 0.413X + 0.889 has been f i t t e d t o t h e d a t a .  P i g . 20.  51  54 60  xlO  P i g . 18. D i s t r i b u t i o n o f head c a p s u l e measurments of 75 H y l o b i u s p a l e s l a r v a e r e a r e d i n t h e i n s e c t a r y from t h e egg t o t h e a d u l t . The b l a c k a r e a r e p r e s e n t s t h e measurments o f the f i f t h i n s t a r l a r v a e t h a t c o n t i n u e d development t o a s i x t h i n s t a r b e f o r e p u p a t ing. P i g . 19.  .48  62  65  Seasonal h i s t o r y o f H y l o b i u s p a l e s i n  southern Ontario  *  P i g . 21. P i s s o d e s apprdximatus • a d u l t  68 xl2.  80  P i g . 22.  D i s t r i b u t i o n o f head c a p s u l e measurments of P i s s o d e s approximatus l a r v a e . . .......... P i g . 23. Seasonal h i s t o r y o f p i s s o d e s a p p r o x i matus in., s o u t h e r n O n t a r i o .  81 84  P i g . 24. L a r v a of P i s s o d e s approximatus i n r e a r i n g . Note l a r v a l mines p a r a l l e l ' ' t o t h e g r a i n of the bark V... 88 P i g . 25. "Chip c o c o o n s o f P i s s o d e s approximatus showing, ( a ) one c e l l i n t a c t and ( b ) another opened t o r e v e a l t h e prepupa i n s i d e . Note t h e e x c e l s i o r - l i k e c o v e r i n g M  viii  ,  of the c e l l s  90  F i g . 26. Stem o f a t h r e e - i n c h r e d p i n e i n f e s t e d w i t h p i s s o d e s approximatus ( p u p a l s t a g e ) .  92  F i g . 27. F o u r - i n c h S c o t s p i n e stump i n f e s t e d w i t h P i s s o d e s approximatus a n d H y l o b i u s p a l e s ( p u p a l s t a g e ) . The l a c k of p u p a l c e l l s above ground l e v e l i s due t o comp e t i t i o n from b a r k b e e t l e s .  93  TABLES TABLE I  The d u r a t i o n o f t h e immature s t a g e s of H y l o b i u s r a d i c i s r e a r e d i n an u n heated i n s e c t a r y d u r i n g t h e summerseason.  33  TABLE II M o r t a l i t y o f immature H y l o b i u s r a d i c i s c a l c u l a t e d from p o p u l a t i o n s on 60 r e d p i n e s and 78 Scots p i n e s and expressed as a p e r c e n t o f t h e i n i t i a l egg p o p u l a tion.  46  TABLE III Growth r a t i o s f o r 20 Scots p i n e s and 20 r e d p i n e s h e a v i l y i n f e s t e d w i t h H y l o bius r a d i c i s  52  TABLE IV Comparison between observed head c a p s u l e widths o f H y l o b i u s p a l e s l a r v a e and those e s t i m a t e d by u s i n g Dyar's Rule  63  TABLE  V The d u r a t i o n o f t h e immature s t a g e s o f H y l o b i u s p a l e s r e a r e d i n a n unheated i n s e c t a r y d u r i n g t h e summer season  70  TABLE VI  Comparison between observed head capsule* widths o f P i s s o d e s approximatus l a r v a e by u s i n g Dyar's Rule and on t h e b a s i s o f a linear regression relationship.  82  TABLE VII The d u r a t i o n o f t h e immature s t a g e s - o f p i s s o d e s approximatus r e a r e d i n a n u n heated i n s e c t a r y d u r i n g t h e summer months.  86  ACKNOWLEDGEMENT S  I wish t o e x p r e s s my i n d e b t e d n e s s  t o D r . K. Graham,  P r o f e s s o r of P o r e s t Entomology, and D r . I . McTaggart Cowan, Head o f t h e Department o f z o o l o g y , U n i v e r s i t y o f B r i t i s h Columbia, f o r t h e i r guidance,  encouragement and a d v i c e d u r i n g  t h i s study. Much o f t h e f i e l d work was made p o s s i b l e o n l y by the f r e q u e n t a s s i s t a n c e and guidance  o f D r . R. M. B e l y e a ,  Officer-in-Charge, Porest Insect Laboratory, Sault Ste. Marie, Ont. P e r m i s s i o n t o u s e d a t a o b t a i n e d w h i l e i n t h e employ o f the F e d e r a l Government was g r a n t e d by D r . M. L . P r e b b l e , C h i e f , P o r e s t B i o l o g y D i v i s i o n . I w i s h t o thank D r s . R. M. B e l y e a and M. L . P r e b b l e f o r t h e i r c r i t i c i s m s The p h o t o g r a p h i c photographer,  of the manuscript.  work was done by Mr. D. C. Anderson, B i o -  P o r e s t I n s e c t L a b o r a t o r y , S a u l t S t e . M a r i e , Ont.  ECOLOGICAL STUDIES OP HYLOBIUS RADICIS BUCH., S. PALES (HBST.) AND PISSODES APPROXIMATUS (COLEOPTERA t CURCULIONIDAE) IN .SOUTHERN  HOPE.  ONTARIO.  INTRODUCTION  I n r e c e n t y e a r s , w e e v i l damage t o p i n e t r e e s grown i n county f o r e s t s and i n Christmas  t r e e p l a n t a t i o n s has  i n c r e a s e d remarkably i n southern O n t a r i o a s w e l l a s i n t h e eastern United States. Several species of weevils are i n v o l v e d , sometimes a t t a c k i n g i n d i v i d u a l l y , but m o s t l y i n a s s o c i a t i o n w i t h one a n o t h e r .  The complex i n c l u d e s t h e p i n e  r o o t c o l l a r w e e v i l , H y l o b i u s r a d i c i s Buch., t h e p a l e s w e e v i l , H. p a l e s ( H b s t . ) , the white p i n e w e e v i l , P i s s o d e s  strobi  ( P e c k ) , the n o r t h e r n p i n e w e e v i l , P. approximatus Hopk., and  t h e strawberry  Although  root weevil, Brachyrhinus  ovatus  (Lee).  t h e importance o f P. s t r o b i a s a f o r e s t p e s t has  been known f o r over a c e n t u r y i n N o r t h America, t h a t o f t h e o t h e r w e e v i l s i n the complex has not been f u l l y  appreciated  u n t i l more r e c e n t l y . Two o f them i n f a c t , have o n l y been d e s c r i b e d a s s p e c i e s s i n c e the t u r n o f the c e n t u r y  ( P . app-  roximatus and H. r a d i c i s ) • I t was the sudden r i s e from a n unknown e x i s t e n c e t o economic importance o f H. r a d i c i s i n southern  Ontario i n  2  1.954  t h a t l e d t o the p r e s e n t  i n v e s t i g a t i o n . A. b r i e f app-  r a i s a l of the i n f e s t a t i o n i n Simooe County e a r l y i n  1955  showed t h a t not  pro-  o n l y had H.  p o r t i o n s i n the a r e a , but complex (H. p a l e s and P. in  r a d i o i s r e a c h e d epidemic  t h a t two  other weevils of  approximatus) were a l s o p r e s e n t  s u f f i c i e n t numbers t o c o n t r i b u t e a p p r e c i a b l y t o  t o t a l damage of p i n e  the  the  stands.  The purpose of t h i s i n v e s t i g a t i o n has been t o extend the p r e s e n t knowledge of the i n t e r r e l a t i o n s h i p s between the t h r e e w e e v i l s and importance; and reproductive  t h e i r host p l a n t s ; of t h e i r  economic  of the e f f e c t of the environment on  potential.  H. p a l e s and P. approximatus b o t h breed decadent p i n e s and  cause l i t t l e  i n dead or  or no damage as l a r v a e .  a d u l t s , however, f e e d on the t e n d e r l i n g s and may  their  bark of c o n i f e r o u s  cause s e r i o u s damage where outbreaks  H. r a d i c i s ,  seed-  occur.  on the o t h e r hand, causes o n l y s l i g h t damage  by i t s a d u l t f e e d i n g . However, i t s h a b i t of a t t a c k i n g breeding  The  i n the r o o t c o l l a r of h e a l t h y p i n e s , o f t e n  the d e a t h of the t r e e , makes t h i s w e e v i l one  and  causing  of the more  s e r i o u s f o r e s t p e s t s i n e a s t e r n N o r t h America. A l t h o u g h the three w e e v i l s are n a t i v e t o N o r t h America, it  i s o n l y d u r i n g the l a s t f i f t y y e a r s t h a t they have been  c o n s i d e r e d a s important  f o r e s t p e s t s . T h i s change of  their  5  economic importance, a s a d i r e c t r e s u l t of i n c r e a s e b e r s , has  been due  l a r g e l y t o the a c t i o n s of man  i n nunri'  by making  a v a i l a b l e l a r g e q u a n t i t i e s of b r e e d i n g m a t e r i a l e i t h e r by c l e a r c u t t i n g or by p l a n t i n g pure s t a n d s of  pines.  TAXONOMY  The genus H y l o b i u s b e l o n g s t o t h e t r i b e  Hylobiini,  sub-family Curculioninae, family Curculionidae. I t contains about  50 s p e c i e s , f i v e o f which a r e n a t i v e t o N o r t h America;  H. -pales (Hbst.)„ H. p i n i c o l a  H. congener  ( D e l i a T o r r e ) (-confusus  Kby.),  ( C o u p e r ) , H. r a d i c i s Buch,, and H. w a r r e n i Wood.  Although these f i v e species a r e r e a d i l y separated i n t o two groups, t h e i n d i v i d u a l s w i t h i n each group a r e v e r y s i m i l a r and may be e a s i l y c o n f u s e d . H. p a l e s , H. congener^and dicis^  on t h e average, a r e s m a l l e r t h a n H. p i n i c o l a and H.  warreni> and d i f f e r i n g e n e r a l appearance shape it,  H. r a -  from them. The  o f the femora and t h e p r e s e n c e o r absence o f t e e t h on  a s i s i n d i c a t e d i n t h e f o l l o w i n g key, a r e a l s o important  d i s t i n g u i s h i n g c h a r a c t e r s o f the two groups. I n 1934 Buchanan (16) d e s c r i b e d H. r a d i c i s a s a new s p e c i e s and p r e s e n t e d a s y n o p t i c k e y f o r H. p a l e s , H. congener, and t h e new s p e c i e s H. r a d i c i s . These t h r e e w e e v i l s c o n s t i t u t e d a l l t h e N o r t h American s p e c i e s o f the genus H y l o b i u s known a t t h a t t i m e . R e c e n t l y , Wood (125) i n a r e view o f t h e N o r t h American a l l i e s  o f the E u r a s i a n s p e c i e s  H y l o b i u s p i c e u s (DeGeer), e l i m i n a t e d t h e genus Hypomolyx of Leconte by s e p a r a t i n g t h e s i n g l e h o l a r c t i c s p e c i e s i n t h e genus, Hypomolyx p i c e u s (DeGeer), i n t o two s e p a r a t e s p e c i e s  and t r a n s f e r r i n g them to the genus Hylobius under the names H. piceus (palaearctic) and H. p i n i c o l a ( n e a r c t i c ) . In the same paper he described a new North American species, H. warreni, which i s apparently c l o s e l y r e l a t e d to H. p i n i c o l a . He also presented a key separating the three species involved, i . e . H. -piceus, H. p i n i c o l a , and H. warreni. In view of the excellent work done on these weevils by Leeonte  (75), Buchanan (16) and Wood (125), the author p r e -  f e r s to present the f o l l o w i n g key synthesized from the work of the above taxonomists rather than attempt of an independent key:  the c o n s t r u c t i o n  ,  ,  Key to Species of North American Hylobius I. Femora club-shaped, strongly toothed  2  Femora feebly club-shaped, not toothed  4  2. Scutellum v i r t u a l l y glabrous; a n t e r i o r face of at l e a s t the hind femur almost always with a narrow, shallow, median groove i n about basal t h i r d ; inner edge of fore t i b i a of male with a f r i n g e of white h a i r , the length of some of the longer h a i r s equal to width of t i b i a . 5,8 to 9.0 mm.  Length congener (Delia Torre)  Scutellum normally covered by a dense coating  6  of seta-like scales; hind femur rarely with even a trace of a groove; male 3  without t i b i a l fringe as above 3 . Size smaller, 5 . 8 to 1 1 . 3 mm.; head normally with a spot or line of coarser setalike scales on vertex or on front; punctures immediately behind interocular puncture more or less strongly coalescent to form short, irregular rugae; hind t i b i a l uncus of male broad, parallel-sided, very broadly rounded at apex  pales (Hbst.)  Size larger, 9 . 4 t o 1 3 . 0 mm.; head without a line or spot of scales on front :<3f vertex; punctures behind interocular puncture generally separated by narrow intervals, or at most only feebly coalescent; hind t i b i a l uncus of male narrow, sides generally convergent to the sub-acute apex 4. Rostrum rather stout, less than 2.6 times as long as wide, noticeably wider d i s t a l l y ; apical umbones of the elytra obscure or entirely undefined; meta-  radicis Buch.  7  •thoracic wings s h o r t , not  extending  "beyond the p o s t e r i o r m a r g i n of  first  v i s i b l e abdominal sternum; male g e n i t a l i a w i t h apex of aedeagus b l u n t , a n t e r o d o r s a l m a r g i n of conspicuously  the  gonocoxites  b i s i n u a t e , and  lacking a  d a r k l y pigmented median a r e a w i t h i n the aedeagus  warreni  Rostrum s l e n d e r , more t h a n 2.9  t i m e s as  Wood  long  as wide, not w i d e r d i s t a l l y ; a p i c a l urnbones of e l y t r a prominent; wings l o n g e x t e n d i n g  metathoracic  w e l l beyond  elytral  apex; male g e n i t a l i a w i t h apex of aedeagus a c u t e l y p o i n t e d , the a n t e r o d o r s a l m a r g i n of the g o n o c o x i t e s  e v e n l y rounded;  and  a pigmented median t r i a n g u l a r or Y-shaped a r e a w i t h i n the aedeagus v i s i b l e from v e n t r a l aspects  The sub-family l a r g e and  genus P i s s o d e s  the  pinicola  belongs t o the t r i b e  (Couper)  pissodini,  Curculioninae, family Curculionidae. I t i s a cosmopolitan  America a l o n e  (71).  genus w i t h about 30 s p e c i e s i n N o r t h  S e v e r a l of the e a s t e r n N o r t h American  s p e c i e s a r e so s i m i l a r m o r p h o l o g i c a l l y ,  t h a t i t has  been  found  i m p o s s i b l e t o s e p a r a t e them on t h i s b a s i s . S i n c e t h e  s i m i l a r i t y between t h e s p e c i e s o f t e n extend  to their b i o -  nomics as w e l l , i t i s s u g g e s t i v e t h a t perhaps the group i s e x p e r i e n c i n g an a c t i v e p e r i o d o f e v o l u t i o n and t h a t s e v e r a l populations p o s s i b l y e x i s t , a t the s u b - s p e c i f i c  level.  From p e r s o n a l communications w i t h D r . G. K. Manna  1  2 and Dr. S. G. Smith  i t has been l e a r n e d t h a t a c l o s e i n t e r -  r e l a t i o n s h i p e x i s t s among w e e v i l s o f t h e genus P i s s o d e s . Manna has found t h a t P. s t r o b i  (peek), P. engelmanni Hopk.,  and P. s i t c h e n s i s Hopk. a l l p o s s e s s  34 chromosomes, w h i l e  p . a f f i n i s Rand., P. r a d i a t a e Hopk., and P. f a s c i a t u s Rand, a l l possess canadensis  30 chromosomes. P. approximatus Hopk. and p . Hopk. on the o t h e r hand, p o s s e s s from 30 t o 34  chromosomes, t h e r e b e i n g a more o r l e s s g r a d u a l change from 30 chromosomes i n w e e v i l s c o l l e c t e d i n s o u t h e r n O n t a r i o t o 32 chromosomes i n w e e v i l s c o l l e c t e d a l o n g t h e n o r t h of the Great Lakes, t o 34 chromosomes i n w e e v i l s i n c e n t r a l Manitoba. 'Science S e r v i c e P o s t d o c t o r a t e F e l l o w s h i p Forest Insect Laboratory, S a u l t S t e . M a r i e , Ont. Head* S e c t i o n o f C y t o l o g y and G e n e t i c s , Forest Insect Laboratory, S a u l t S t e . M a r i e , Ont.  Holder,  shore  collected  9  Marina  i s o f the o p i n i o n t h a t t h e r e i s no ground f o r  s e p a r a t i n g t h i s p o p u l a t i o n i n t o two s p e c i e s  (P. approximatus  i n t h e south and P. c a n a d e n s i s i n t h e n o r t h ) as done by Hopkins ( 7 1 ) .  I t has been l e a r n e d a t a l a t e date t h a t Manna and Smith have r e c e n t l y p u b l i s h e d t h e i r f i n d i n g s as d i s c u s s e d above. vide: MANNA, G. K. AND S. G. SMITH. 1958. A d a p t i v e chromosomal polymorphism and i n t e r - r e l a t i o n s h i p s , , among bark w e e v i l s o f the genus -Pissodes Germar. P r o c . I n t e r . Congr. G e n e t i c s , p.178.  METHODS  The  i n v e s t i g a t i o n s o f H. r a d i c i s , H. p a l e s , and P.  approximatus were c a r r i e d out i n Simcoe County i n s o u t h e r n O n t a r i o , d u r i n g t h e 1955, 1956, and 1957 growing s e a s o n s . Field  o b s e r v a t i o n s were made i n s e v e r a l w i d e l y  separated  p l a n t a t i o n s o f mixed e a s t e r n white p i n e , p i n u s  strobus L.,  r e d p i n e , P. r e s i n o s a A i t . , , j a c k p i n e , P. b a n k s i a n a Lamb., and  Scots p i n e , P. s y l v e s t r i s L., and i n n u r s e r y  beds a t Angus and M i d h u r s t , were conducted a t a f i e l d  Ont. The l a b o r a t o r y  seedling observations  s t a t i o n a t Angus, Ont. i n t h e  summer, and a t t h e U n i v e r s i t y o f B r i t i s h Columbia and t h e Porest the  Insect Laboratory  a t Sault Ste. Marie,  Ont. d u r i n g  winter.  Study o f I n s e c t B i o l o g i e s t I n i n v e s t i g a t i n g t h e s e a s o n a l h i s t o r y and h a b i t s o f the w e e v i l complex, i n s e c t p o p u l a t i o n s were kept under observation both i n n a t u r a l breeding m a t e r i a l i n the f i e l d and  i n cages i n t h e i n s e c t a r y . The w e e v i l s  reared i n the  i n s e c t a r y c o n s i s t e d o f t h e progeny o f twelve p a i r s (male and  female) o f young H. r a d i c i s ; twelve p a i r s o f young H.  pales.; and twelve p a i r s o f young p . a p p r o x i m a t u s . E a c h p a i r was kept s e p a r a t e l y i n g l a s s v i a l s and p e r m i t t e d and  t o feed  o v i p o s i t f o r two growing seasons on s e c t i o n s o f p i n e  11  branches ( f o u r i n c h e s l o n g and ^ i n c h i n d i a m e t e r ) , p l a c e d i n the v i a l s . S i n c e the females  sometimes dropped t h e i r eggs  away from the p i n e m a t e r i a l , the g l a s s v i a l s were p l a c e d w i t h t h e i r open ends down on a w i r e s c r e e n so t h a t the l o o s e eggs f e l l t h r o u g h the s c r e e n onto a watch g l a s s p l a c e d u n d e r n e a t h . F r e s h p i n e branches were added t o the v i a l s  daily,  w h i l e the branches o f the p r e v i o u s day were c a r e f u l l y p e e l e d and  examined f o r eggs. The  380  eggs d u r i n g the two  twelve H. r a d i c i s females  laid  summers, but o n l y 84 were r e a r e d t o  the a d u l t s t a g e . The H. p a l e s females  laid  556  eggs, o f which  73 were r e a r e d t o a d u l t s , and the twelve P approximatus females, l a i d  522  eggs, o f which 42 were r e a r e d t o a d u l t s .  A s p e c i a l t e c h n i q u e was  devised f o r r e a r i n g the w e e v i l s .  T h i s c o n s i s t e d o f r e a r i n g t h e i n s e c t from the egg t o the a d u l t stage under g l a s s , on f r e s h i n n e r bark o f S c o t s p i n e removed from the t r e e . The  newly hatched  l a r v a was p l a c e d i n  a. s m a l l groove made on the cambial s u r f a c e of the bark w h i c h was  t h e n p r e s s e d t i g h t l y a g a i n s t the bottom of a p e t r i  dish  by f i l l i n g the d i s h w i t h sand and a p p l y i n g p r e s s u r e on the c o v e r w i t h r u b b e r bands ( P i g . 1 ) . The d i s h was sand from  l i n e d w i t h a "Kleenex"  c o v e r of the p e t r i  t i s s u e so as t o p r e v e n t  e s c a p i n g between the two  the  d i s h e s and t o m a i n t a i n a  more u n i f o r m p r e s s u r e on the sand. The  bark was  prevented  from d r y i n g out by s q u i r t i n g about 1 c c . o f water each  day  12  F i g . 1. Method of r e a r i n g p i n e w e e v i l s i n the i n s e c t a r y from the egg t o the a d u l t  stage  showing, (a) p o u r i n g the sand over the i n n e r bark and s c r e e n ; rearing unit.  (b) a s e c t i o n a l view of the  13  between the edges of the p e t r i d i s h e s onto the  "Kleenex"  tissue. D u r i n g t h e p r e p u p a l s t a g e , the l a r v a e had a tendency t o bore through order to prevent  the bark and d i s a p p e a r i n t o the s a n d . I n t h i s , a c i r c u l a r p i e c e of galvanized wire  s c r e e n wags cut t o f i t s n u g l y i n s i d e the p e t r i d i s h and p l a c e d over the bark b e f o r e the sand was  added. The  screen  d i s c , a l t h o u g h p r e v e n t i n g t h e prepupa from, e n t e r i n g the sand, d i d not i n t e r f e r e w i t h the u n i f o r m p r e s s u r e the  of the sand  on  bark. T h i s r e a r i n g method p e r m i t t e d c o n t i n u o u s  observations  of l a r v a l and p u p a l development and the p e r i o d i c measurment of body s i z e and  e x t e n t of l a r v a l f e e d i n g ( P i g . 2). I t  p o s s i b l e t o keep the i n n e r bark g r e e n and contamination  f o r more t h a n two  sand and glassware,  was  f r e e from fungus  weeks by u s i n g  sterilized  and by k e e p i n g t o a minimum t h e  t h a t t h e cambial s u r f a c e of the i n n e r b a r k was  time  exposed t o  the a i r d u r i n g p r e p a r a t i o n s . I n r e a r i n g the w e e v i l s some l a r v a e were t r a n s f e r r e d t o f r e s h bark a f t e r each moult, w h i l e o t h e r s were t r a n s f e r r e d a f t e r two moults,  thus  per-  m i t t i n g more a c c u r a t e measurments o f the f e e d i n g damage by each i n s t a r . A f t e r the l a s t i n s t a r l a r v a e had  constructed  p u p a l chambers, t h e y were l e f t u n d i s t u r b e d u n t i l t h e a d u l t s were formed.  Pig.  2. Larvae  (a) F e e d i n g l a r v a ,  of H y l o b i u s r a d i c i s i n r e a r i n g , (b) Prepupa i n p u p a l  cell.  E i g h t y - f o u r H. r a d i c i s , 73 H. p a l e s and 42 P. ximatus were r e a r e d i n t h i s manner from  appro-  egg t o a d u l t . The  l a r v a e t h r i v e d on the i n n e r bark and t h e i r development corresponded the f i e l d .  v e r y c l o s e l y t o t h a t of f r e e p o p u l a t i o n s i n  A l t h o u g h m o r t a l i t y of r e a r e d l a r v a e was as h i g h  as 50fo d u r i n g the e a r l y s t a g e s of e x p e r i m e n t a t i o n ,  the t e c h -  nique was e v e n t u a l l y improved t o t h e p o i n t where l e s s 5f<> of t h e l a r v a e were  than  lost.  Most o f the d a t a on the s e a s o n a l h i s t o r y of H. p a l e s were o b t a i n e d from white p i n e t r e e s , the p r e f e r r e d h o s t , one  of which was f e l l e d and s e t up a s t r a p l o g s near i t s  stump every two weeks d u r i n g f i v e months o f the 1956 ing  grow-  season. The t r e e s , which were between 4 and 5 i n c h e s  i n diameter and formed p a r t o f a dense s t a n d , 3-foot  were cut i n  s e c t i o n s and p l a c e d h o r i z o n t a l l y on t h e ground. The  l o g s and r o o t s o f each t r e e were sampled and w e e v i l ment was r e c o r d e d  develop-  weekly u n t i l pupae began t o form u n d e r t h e  b a r k . A t t h i s time t h e stump and m a i n r o o t system were excavated  and p l a c e d i n outdoor s c r e e n cages. About 6 i n c h e s  of s o i l was kept over t h e stumps t o p r e v e n t d e s i c c a t i o n , p i n e b a r k f r e s h l y removed from t r e e s was used i n t h e cages as, t r a p s f o r the emerging a d u l t s which were c o l l e c t e d d a i l y . None o f t h e l o g s s e t up i n the f i e l d were s u c c e s s f u l l y i n f e s t e d by t h e w e e v i l , and t h e y were Ten  discarded.  S c o t s p i n e t r e e s were used i n a s i m i l a r f a s h i o n  t o study t h e s e a s o n a l h i s t o r y and h a b i t s of P„approximatus. The  f e e d i n g h a b i t s o f H. -pales were s t u d i e d on n a t u r a l  regeneration  i n the s t u d y p l a n t a t i o n s and on p o t t e d  d i s t r i b u t e d i n a g r i d p a t t e r n i n a two-acre a r e a the p r e v i o u s  plants  cut over  f a l l i n which t h e stumps were i n f e s t e d w i t h  H. p a l e s . E q u a l numbers ( s i x of each s p e c i e s ) of f o u r - y e a r old  white p i n e , r e d p i n e , A u s t r i a n p i n e , P. n i g r a Am.,  and  S c o t s p i n e p l a n t s were s e t o u t . The f e e d i n g damage were obs e r v e d and tagged a t weekly i n t e r v a l s .  Measurment of Damages The  e f f e c t o f r a d i c i s damage on p i n e  growth was  studied  16  by comparing height and radial growth increments of infested and non-infested twenty-year-old trees, and by controled infestations on caged ten-year-old trees. To f a c i l i t a t e accurate determination of the effect of weevil attack on the tree, 40 healthy Scots pines averaging about ten years of age, were transplanted i n October of 1955 to a heavily i n fested area. These trees were grown at the Midhurst  Nursery  as ornamental stock and had been pruned yearly for over f i v e years so that although the diameter of the stem at ground level was between two and three inches, they did not exceed four feet i n height. In May 1956, 24 of the trees were selected randomly and enclosed individually i n screen cages measuring four feet square by five feet i n height (Pig. 3 ) . In early June, 1956 the caged trees and the s o i l within each cage was sprayed thoroughly with ethylene dichloride, a fumigant, i n order to k i l l any weevils present. After the poisonous effects of the insecticide had dissipated (about two weeks),, the 24 caged trees were randomly divided into three groups of eight trees and infested with two mated pairs of young adult weevils (four insects) to each tree as follows; group one on June 19, 1956; group two on July 17, 1956; and group three on May 23, 1957. One tree from each group of infested trees and two from the checks were removed monthly during the 1956 and 1957 growing seasons and examined  17  F i g . 3. Caged p i n e t r e e s used of H y l o b i u s  i n s t u d y i n g the bionomics  radicis.  f o r damage and w e e v i l p o p u l a t i o n a t the r o o t The  effect  o f H. r a d i c i s on the growth o f p i n e s was  i n v e s t i g a t e d d u r i n g the summer of 1955. of 20-year-old  I n a mixed s t a n d  white, r e d , and Scots p i n e s h e a v i l y i n f e s t e d  w i t h the w e e v i l s i n c e 1950, and  collar.  10 white p i n e s , 20 r e d p i n e s ,  20 Scots p i n e s were c u t and t h e i r annual h e i g h t and  r a d i a l increments  measured f o r the p e r i o d 1945  to  1955.  Since o n l y the white p i n e s i n the stand were not i n f e s t e d  18  w i t h t h e w e e v i l , t h e i r measurements were u s e d a s a n i n d i c a t i o n of  normal growth o v e r t h e t e n y e a r p e r i o d c o n s i d e r e d and a s  a check on t h e growth o f t h e two o t h e r h e a v i l y i n f e s t e d s p e c i e s . The t r e e s were a l l c u t i n June and e a r l y J u l y a t a time "before Hhe new a d u l t s emerged so t h a t a n a c c u r a t e count  o f t h e w e e v i l p o p u l a t i o n on each t r e e c o u l d be made. From s e c t i o n s ( d i s c s ) c u t a t t h e r o o t c o l l a r s o f t e n  h e a v i l y i n f e s t e d Scots p i n e s and t e n r e d p i n e s t h a t had r e c e n t l y been k i l l e d by H. radicis« i t was p o s s i b l e t o determine t h e f i r s t  y e a r each t r e e was a t t a c k e d and, r o u g h l y ,  the p r o g r e s s made by t h e w e e v i l s u n t i l t h e d e a t h o f t h e t r e e . D u r i n g t h e 1955,  1956,  and 1957  growing seasons,  78  Scots, p i n e s and 60 r e d p i n e s i n f e s t e d w i t h H i r a d i c i s were examined i n o r d e r t o determine  t h e extent o f damage, t h e  number and d i s t r i b u t i o n o f t h e d i f f e r e n t s t a g e s i n t h e v i c i n i t y o f t h e r o o t c o l l a r , and t o determine  t h e cause and  e x t e n t o f m o r t a l i t y w i t h i n each s t a g e as t h e season gressed.  pro-  19  HYLOBIUS RADICIS BUCH.  H y l o b i u s r a d i c i s Buchanan (16) (30, 31,  BIOLOGY: F e l t 40,  41,  32, 33, 34,  42, 43,  Glasgow (60,  45,  61),  and Bromley (49»  47),  37 ( p a l e s ) , York (126  plumb (90, 91, 50,  Leod ( 7 8 ) , S c h a f f n e r  51),  39,  (pales)),  92), F e l t  Maxwell and Mac-  (104, 105,  106, 1 0 8 ) ,  S c h a f f n e r and Mc I n t y r e (109),  Craighead  (20),  (120),  Shenefelt  Prentice Warren  (94),  (111),  ISallace  1/lktson (123), F i n n e g a n  (52),  (121).  History: H. r a d i c i s was d e s c r i b e d i n 1934 owing s e v e r a l r e p o r t s by F e l t York (126)  (30,  d e s c r i b i n g a new type  31,  by Buchanan (16) 32, 33, 34,  foll-  37) and  o f w e e v i l damage on S c o t s  p i n e , r e d p i n e , and p i t c h p i n e , P. r i g i d a M i l l . , i n t h e S t a t e of New York, which t h e y b e l i e v e d was caused by the p a l e s w e e v i l . From 1934  t o 1942,  s e v e r a l s h o r t r e p o r t s on t h e h o s t s ,  d i s t r i b u t i o n and damage caused by H. r a d i c i s were made by Felt  (37,  (60,  6 1 ) , Maxwell and MacLeod (78),  Schaffner Intyre  41, 43,  47),  F e l t and Bromley (49,  (104, 105, 106,  (109)  Plumb (89,  1 0 8 ) . I n 1944,  50,  51), Glasgow  91, 9 2 ) , and  S c h a f f n e r and Mc-  d i s c u s s e d t h e l i f e h i s t o r y , h a b i t s , economic  20  importance, and c o n t r o l o f t h e s p e c i e s i n t h e New E n g l a n d S t a t e s , s t a t i n g t h a t t h e w e e v i l was a s e r i o u s p e s t  of Scots  p i n e , A u s t r i a n p i n e , and i t s v a r i e t y C o r s i c a n p i n e . They a l s o noted t h a t heavy i n f e s t a t i o n s were observed o n l y where t h e t r e e s were growing i n l i g h t  sandy s o i l s as r e p o r t e d  by P e l t and Bromley ( 4 9 ) . S c h a f f n e r and M c l n t y r e  earlier  stated  f u r t h e r t h a t i n f e s t a t i o n s were a l s o observed i n j a c k p i n e , Mugho pine» P. mugho T u r r a . , p i t c h p i n e , r e d p i n e , and e a s t e r n w h i t e p i n e , but t h a t s e r i o u s i n j u r y occured  t o these  o n l y where t h e y were growing near i n f e s t e d Scots p i n e s . I n 1950 S h e n e f e l t chemical  (111) p r e s e n t e d  species  or A u s t r i a n  a p a p e r on t h e  c o n t r o l o f the w e e v i l i n Wisconsin.  I n Canada, t h e f i r s t  r e c o r d o f H . r a d i c i s was made by  i a l l a e j e (120) i n 1954, who r e p o r t e d up t o 25$ m o r t a l i t y i n S c o t s and r e d p i n e p l a n t a t i o n s i n f e s t e d by the w e e v i l i n southern  O n t a r i o . The f o l l o w i n g y e a r  a morphological  1/latson (123) p r e s e n t e d  d e s c r i p t i o n o f the f u l l  grown l a r v a o f t h e  w e e v i l , and P r e n t i c e (94) r e p o r t e d damage t o r e d p i n e and j a c k p i n e i n Manitoba, t h a t l a t e r p r o v e d t o be a n i n f e s t a t i o n of t h i s s p e c i e s . I n 1956 Pinnegan (52) d i s c u s s e d  briefly  the damage caused by H . r a d i c i s i n a s s o c i a t i o n w i t h H j . p a l e s and P. approximatus i n s o u t h e r n  O n t a r i o . The o r i g i n o f t h e  w e e v i l i n M a n i t o b a was b r i e f l y d i s c u s s e d by l/parren (121) i n 1956.  21  D e s c r i p t i o n of L i f e H i s t o r y Stages; ADULT:  The adult H. r a d i c i s i s robust, measuring from  9.4 to 13.0 mm. i n length and from 3.7 to 5.2 mm. i n width (Fig.  4,, d ) . The weevil i s dark brown and i s marked i r r e g u -  l a r l y on the thorax and e l y t r a with spots of cream coloured, s c a l e - l i k e h a i r s . The beak i s stout and about as long as the prothorax, with the antennae attached s l i g h t l y i n front of the middle. I t resembles c l o s e l y H. p a l e s , and although Buchanan (16) gives a considerable l i s t of minute d i f f e r e n c e s between the two species, he summarises these as f o l l o w s : "aside from the narrower male uncus, the characters of r a d i c i s that appear to be d i s t i n c t i v e , i n comparison with p a l e s , are the l a r g e r s i z e , the lack of s c a l y spot on forehead and the spotted, rather than barred e l y t r a . " Since a l l of these characters intergrade, i t i s very d i f f i c u l t to separate a large percentage of the weevil population. In the f i e l d , the best macroscopic characters that can be used to separate the two species with some degree of accuracy, i s the l a r g e r body s i z e and spotted e l y t r a of H. r a d i c i s as contrasted with the smaller body s i z e and barred e l y t r a of H. pales ( f i g . 5). The male H. r a d i c i s i s about 1.5 mm., shorter than the female. I t a l s o d i f f e r s from the female i n three main charact e r s ; f i r s t , the uncus of the hind t i b i a i s stouter and d i s t i n c t l y f l a t t e n e d i n the male, while that of the female  F i g . 4. H y l o b i u s r a d i c i s . (e) Pupa i n e a r t h e n c e l l  (a) Egg  x24;  x6; (d) A d u l t  (b) L a r v a  x6.  x6  23  Fig.  5. D o r s a l view of (a) H y l o b i u s  •pales, showing the s c a t t e r e d s p o t s in  contrast  to the  barred  pattern  r a d i c i s and  on the e l y t r a on the  elytra  (b) H.  of H. of H.  radicis pales.  24  is  conical  ( F i g . 6 a, c ) ; second, the f i r s t  and second a b -  dominal s t e r n i t e s , o f t h e male a r e more o r l e s s  concave  a l o n g the median l i n e , w h i l e i n t h e female t h e y a r e convex (Fig.  6 d ) ; t h i r d , i n the male the m i d d l e p a r t o f t h e f i f t h  abdominal s t e r n i t e e x h i b i t s a c i r c u l a r i m p r e s s i o n d i s t i n g u i s h i n g i t from the l a t e r a l p a r t s EGGs  (Fig. 6 d).  The egg i s e l l i p s o i d a l and measures 1.92 ± 0.10  i n l e n g t h and 1.15  ± 0.05 mm.  i n diameter ( F i g . 4 a ) .  mm.  It i s  opaque and d u l l creamy white i n c o l o u r . LARVA*  The l a r v a i s t y p i c a l l y c u r c u l i o n i d i n form ( F i g .  4 b ) . Ihen f u l l y grown i t i s about 15 nun. i n l e n g t h w i t h a l e g l e s s white body, dark-brown head and b l a c k m a n d i b l e s . The w i d t h o f t h e head c a p s u l e s o f t h e 84 l a r v a e  reared  i n t h e i n s e c t a r y were measured a f t e r each moult from t h e egg to  the pupa. F i g . 7 i l l u s t r a t e s t h e d i s t r i b u t i o n o f t h e s e  measurments s e p a r a t e d by sex, as t h e y developed t h r o u g h each i n s t a r . Seven l a r v a e ( a l l f e m a l e s ) pupated a f t e r a minimum of  five instars;  45 (23"males- and: 22. f e m a l e s ) r e q u i r e d s i x  i n s t a r s ; and t h e r e m a i n i n g 52 (23 males and 9 f e m a l e s ) , seven i n s t a r s b e f o r e p u p a t i n g . A l t h o u g h t h e r e i s a l a r g e o v e r l a p between t h e s i z e o f head c a p s u l e s o f males and f e m a l e s i n each i n s t a r , t h e mean v a l u e f o r the females i s c o n s i s t e n t l y l a r g e r t h a n t h a t o f  F i g . 6 . (a) H i n d t i b i a l uncus of H y l o b i u s  radicis  males; (b) H i n d t i b i a l uncus o f H. p a l e s males; H i n d t i b i a l uncus of H. r a d i c i s and H. p a l e s and  (d) Abdominal i m p r e s s i o n s found  H. p a l e s m a l e s .  (c)  females  on H. r a d i c i s  and  27  100  1.50 HEAD  7.  Fig. Hylobius  CAPSULE  WIDTH  IN  2.50  MM.  D i s t r i b u t i o n of head c a p s u l e measurmehts of 8 4  r a d i c i s l a r v a e r e a r e d i n the i n s e c t a r y from  egg t o the a d u l t . The  cross-hatched  o v e r l a p between a d j a c e n t  the a d u l t and  areas  represent  i n s t a r s . This trend  continues of  population.  While the head c a p s u l e measurments of the  six  the  accounts f o r the l a r g e r average s i z e  the females i n the a d u l t  larvae f a l l  the  instars.  the males i n c o r r e s p o n d i n g to  2.00  into a distinct  reared  c l a s s f o r each of the  first  i n s t a r s , the measurments of 4 7 6 l a r v a e c o l l e c t e d i n the  f i e l d d u r i n g two  growing seasons g i v e l i t t l e  or no  indication  28  1.50  2.00  HEAD CAPSULE  WIDTH IN MM.  P i g . 8. D i s t r i b u t i o n o f head c a p s u l e measurments o f Hylobius r a d i c i s , representing i n the f i e l d ;  (b) 84 l a r v a e  ( a ) 476 l a r v a e  collected  reared i n the i n s e c t a r y .  of t h e number o f i n s t a r s p r e s e n t . The d i s t r i b u t i o n o f t h e s e measurments i s shown i n p i g . 8. The d i f f i c u l t y i n f i n d i n g t h e f i r s t and second i n s t a r l a r v a e  experienced i n the bark  i s l a r g e l y r e s p o n s i b l e f o r the s m a l l number of t h e s e  indi-  v i d u a l s i n the sample, w h i l e the r e l a t i v e l y l a r g e r p r e p u p a l stage i s r e s p o n s i b l e f o r the l a r g e number of prepupae l e c t e d . The  col-  l a c k o f r e s o l u t i o n of head c a p s u l e measurments  of l a r v a e c o l l e c t e d i n the f i e l d i n t o c l a s s e s a c c o r d i n g t o i n s t a r s i s t o be expected where such a l a r g e number of i n s t a r s i s p r e s e n t . The  i n f l u e n c e o f the environment on  growth of the w e e v i l s , p a r t i c u l a r l y those t h a t  the  overwinter  i n the l a r v a l s t a g e , i s g r e a t , and i t i s o n l y under  rigidly  controlled rearing conditions that s u f f i c i e n t l y uniform l a r v a l development occurs t o r e v e a l the b a s i c growth p a t t e r n ,  PUPAs  The pupa i s c o m p l e t e l y white when f i r s t  ( P i g , 4 c ) . The  formed  eyes and mandibles t u r n b l a c k about  the  e i g h t or n i n t h day, and the rostrum, p r o t h o r a x , and l e g s darken t o medium brown about two weeks a f t e r p u p a t i o n .  D i s t r i b u t i o n and S i n c e 1934,  Hosts? H. r a d i c i s has been r e p o r t e d i n M i n n e s o t a ,  Wisconsin, P e n n s y l v a n i a , M a s s a c h u s e t t s ,  Connecticut,  New  York, and V i r g i n i a i n the U n i t e d S t a t e s , and i n M a n i t o b a and  O n t a r i o i n Canada (16, 32,  69,  94,  109,  O n t a r i o the w e e v i l has been found throughout and i n two  HI,  120).  In  Simcoe County  other widely separated areas - Sault Ste. Marie  30  and Petawawa. S c h a f f n e r and M c l n t y r e  (109) r e p o r t t h e f o l l o w i n g  t r e e s as host p l a n t s ? Pinus s y l v e s t r i s L. " nigra Am. " banksiana Lamb. mugho T u r r a . rigida M i l l . resinosa A i t . strobus L. In southern  Scots p i n e . Austrian pine. Jack p i n e . Mugho p i n e . Pitch pine. Red p i n e . E a s t e r n white p i n e .  O n t a r i o , i t was found  i n f e s t i n g Scots  pine,  r e d p i n e , A u s t r i a n p i n e , Mugho p i n e , and jack- p i n e , but was never found  on white p i n e . T r e e s o f a l l ages w i t h a r o o t  c o l l a r i n excess Seasonal  o f 1-^- i n c h e s may be a t t a c k e d .  History?  In southern  O n t a r i o , H. r a d i c i s o v e r w i n t e r s  i n the  l a r v a l , p u p a l , and a d u l t s t a g e s . Young o v e r w i n t e r e d  adults  o v i p o s i t from e a r l y May u n t i l September, and t h e n u s u a l l y overwinter  a g a i n t o l a y eggs d u r i n g a second season ( P i g . 9)»  A few o f t h e l a r v a e a r i s i n g from eggs l a i d i n e a r l y May complete t h e i r development i n time t o pupate i n September and  overwinter  as a d u l t s . Prom a t o t a l o f 84 eggs r e a r e d i n  the i n s e c t a r y , 11 developed the end o f September), w h i l e  t o a d u l t s i n one season ( b e f o r e t h e remainder o v e r w i n t e r e d as  l a r v a e t o pupate i n l a t e June and e a r l y J u l y o f t h e next  31  STAGE WIN. MAY ADULT EGG LARVA  1  JUNE|JULY AUG. SEPT. OCT.  s  - "~ 1B  -  1"  PUPA ADULT  •  —  I  n 9.  — I  HIII HI;  Pig.  m  n  ADULT  LARVA  JUNE JULY AUG. SEPT. OCT. WIN.  P  PUPA  EGG  m  1 WIN. MAY  '  11  :  1  1  ^.„„:„':„,.,:.:':!:J:^,.:.  ft  Seasonal h i s t o r y of Hylobius r a d i c i s i n southern  Ontario.  y e a r . S c h a f f n e r and M c l n t y r e  ( 1 0 9 ) r e p o r t a two-year  c y c l e f o r the s p e c i e s i n t h e New England  life  S t a t e s , but do  not mention t h e p o s s i b i l i t y o f p a r t o f t h e p o p u l a t i o n h a v i n g a one-year The 1955,  life  cycle.  earliest  egg found i n the f i e l d was on May 2 ,  w h i l e i n t h e i n s e c t a r y o v i p o s i t i o n took p l a c e as  e a r l y as m i d - A p r i l i n 1 9 5 8 . The number o f eggs l a i d  varies  g r e a t l y between f e m a l e s . Whereas some females l a y o n l y a  32  few eggs,, others may lay as many as 40 i n one season. In the insectary, the average number of eggs l a i d per female was. 17.5 during the f i r s t season and 14.2 during the second season. None of the reared females survived a third winter. During the peak of the egg-laying period (early July) an > active female may lay up to four eggs i n one day, but the average was, found to be s l i g h t l y less than one per day per female. Prom a total of 256 eggs incubated i n the insectary 74» or 29$, did not hatch. Table I shows the average duration of each of the instars for five-, six-, and seven-instar larvae, as well as for the egg and pupal stages, of weevils reared i n an unheated insectary during the summer months. It should be noted, however, that i n the f i e l d the larvae overwinter i n a l l but the f i r s t two instars and the period of these overwintering instars are thereby much prolonged. Owing to the lengthy oviposition period, the larval population consists of a mixture of different sized larvae throughout the year. The rate of development of overwintered larvae i s modified i n nature, however, to produce a concentration of prepupae i n late June. This means that larvae overwintering i n an advanced state of development (sixth and seventh instar), by delaying their time of pupation, permit the younger individuals to catch up i n their development, with the result  33  that  t h e o v e r w i n t e r e d l a r v a l p o p u l a t i o n pupates over a s h o r t  p e r i o d i n e a r l y J u l y . D u r i n g t h e l a t t e r p a r t o f the summer,  TABLE I The d u r a t i o n o f t h e immature s t a g e s of Hylobius. r a d i c i s r e a r e d i n a n unheated i n s e c t a r y d u r i n g t h e summer season ' Time (days)  Stage Egg  :  14.5 ± 1.2  j  8.6 ± 1.0  1st  instar  2nd  instar  •  8.3 ±  3rd  instar  :  9.5 ± 1.3  4th  instar  : 11.8 ± 1.5  5th i n s t a r 5th  (Prepupa) '. 27.5  6.2  ! 17.0 ± 4.0  instar  6th i n s t a r  ±  1.9  (Prepupa)  I  31.0 ± 6 . 8  6th  instar  \ 24.1 ± 4.4  7th  instar  (Prepupa) : 28.2 ± 5.1  Pupa  : 19.8  ± 4.6  i n August and September, a few pupae c a n be found, but t h e s e have a r i s e n from eggs l a i d  e a r l y i n the spring  y e a r and n o t from o v e r w i n t e r e d l a r v a e .  o f t h e same  The e a r l i e s t pupa  found, i n t h e f i e l d was on June 20, 1957. Habits? The  a d u l t s u s u a l l y overwinter i n c r e v i c e s i n the outer  b a r k o f t h e stem o f l i v i n g p i n e  t r e e s , a t o r s l i g h t l y below  ground l e v e l , but a s m a l l number o v e r w i n t e r i n t h e d u f f a t the base o f t h e t r e e s . I n s o u t h e r n O n t a r i o ,  the overwintered  a d u l t s become a c t i v e d u r i n g t h e l a t t e r p a r t  o f A p r i l and  apparently  spend most o f t h e i r l i v e s i n and around t h e r o o t  c o l l a r o f t h e host  t r e e , m a t i n g and o v i p o s i t i n g from  May t o mid-September. The eggs a r e o f t e n l a i d as f a r as. two i n c h e s placed  i n the s o i l  from t h e t r e e , but u s u a l l y t h e y a r e  i n f e e d i n g wounds made by t h e a d u l t s i n t h e i n n e r  bark of the root  collar.  T/1/hen t h e eggs h a t c h , t h e young l a r v a e a r e v e r y and  begin searching  laid  early  f o r food  active  i m m e d i a t e l y . I f t h e eggs a r e  c l o s e t o t h e cambium o f t h e t r e e , t h e l a r v a e  experience  no d i f f i c u l t y i n e s t a b l i s h i n g t h e m s e l v e s . When a t r e e i s first  attacked,  t h e young l a r v a e f e e d m o s t l y i n t h e i n n e r  bark, a l t h o u g h the s u r f a c e  o f the wood i s a l s o  s c a r r e d . The f e e d i n g i s c o n f i n e d  slightly  t o i s o l a t e d a r e a s around  the r o o t c o l l a r t h a t u s u a l l y become e l l i p t i c a l i n shape w i t h the l o n g a x i s r u n n i n g p a r a l l e l t o t h e g r a i n o f t h e wood. They i n c r e a s e  i n s i z e as t h e l a r v a e develop and i n l a r g e  t r e e s a r e u s u a l l y r e - i n f e s t e d by t h e l a r v a e  of succeeding  F i g . 10. S e c t i o n through the r o o t c o l l a r o f a s i x - i n c h Scots pine  showing t y p i c a l wounds caused by H y l o b i u s  radicis  l a r v a e . T h i s t r e e had been i n f e s t e d f o r a t l e a s t t h i r t e e n years.  generations.  Thus the t r u n k  a t the r o o t c o l l a r becomes  f l u t e d , s i n c e the undamaged cambium grows beyond the i n j u r y on e i t h e r s i d e o f the wound  ( F i g . 1 0 ) . E v e n t u a l l y , as the  i n f e s t a t i o n i n c r e a s e s , the t r e e becomes c o m p l e t e l y  girdled  36  Fig.  11. H y l o b i u s r a d i c i s  Scots p i n e , (a) Root c o l l a r infiltrated  damage "to t h e r o o t c o l l a r of of i n f e s t e d tree with the p i t c h -  s o i l p a r t l y removed t o show a l a r v a i n t h e o u t e r  bark; (b) Stump o f i n f e s t e d t r e e w i t h s o i l  completely  removed  t o show s w e l l i n g a t the r o o t c o l l a r due t o l a r v a l damage; ( c ) Stump o f i n f e s t e d t r e e w i t h bark removed from the r o o t c o l l a r t o show the extent o f damage t o t h e wood.  and  death f o l l o w s  vigorous, copius  ( P i g . 11  o ) . I f the t r e e i s h e a l t h y  i t responds t o the l a r v a l damage by p r o d u c i n g  q u a n t i t i e s of r e s i n o u s  so t h a t l a r g e p o c k e t s of gum apparently  and  sap a t the s i t e of the  injury  a r e formed. Advanced l a r v a e  are  w e l l adapted t o l i v i n g i n t h i s environment, f o r  t h e y a r e o f t e n found c o m p l e t e l y immersed i n the s t i c k y substance.  I t apparently  the sap p r e s s u r e  becomes n e c e s s a r y , however, t o r e l i e v e  p e r i o d i c a l l y , and  by d i g g i n g c i r c u i t o u s t u n n e l s the  larvae accomplish  s e v e r a l inches  this  i n length  s o i l , thus l e a d i n g some of the sap away from the  a r e a . Consequently, i n a h e a v i l y i n f e s t e d t r e e the  into  injured  soil  s u r r o u n d i n g the r o o t c o l l a r soon becomes soaked w i t h r e s i n for  a distance  of up  t o two  or' t h r e e  inches  (Pig.  11 a ) . TSBien the l a r v a e a r e f u l l y  final  journey i n t o the s o i l up  and  there  t o two  from t h e  tree  grown they make a inches  from the  tree  c o n s t r u c t p u p a l c e l l s i n which t h e y pupate ( P i g .  4 c ) . O c c a s i o n a l l y the outer b a r k . P i g . 12 pupae found i n the  c e l l i s constructed  i n the  gum-soaked  shows the d i s t r i b u t i o n of l a r v a e s o i l s u r r o u n d i n g the r o o t c o l l a r s  and of  i n f e s t e d t r e e s . The  p u p a l c e l l i s u s u a l l y made w i t h i t s  long axis v e r t i c a l ,  or s l i g h t l y i n c l i n e d t o the  Its  vertical.  depth v a r i e s from s o i l l e v e l t o about t e n i n c h e s  the s u r f a c e . The  l a r v a c o v e r s the i n s i d e of the c e l l  below with  a c e m e n t - l i k e substance ( p o s s i b l y r e s i n from the t r e e ) ,  F i g . 12.  D i s t r i b u t i o n of H y l o b i u s r a d i c i s l a r v a e  pupae i n the Scots p i n e s .  s o i l around the  root  c o l l a r of  infested  and  10  n.,, n  XL  a  AUG.  TIME OF YEAR  Pig.  13. Emergence o f H y l o b i u s r a d i c i s a d u l t s from twenty  t r e e s d u r i n g the summer of  1955.  which b i n d s the g r a i n s of sand i n t o a hard  shell-like  s t r u c t u r e . I t then remains i n a c t i v e f o r about one week before pupating. The newly formed c a l l o w a d u l t s remain i n a c t i v e i n t h e i r p u p a l c e l l s from one t o two weeks b e f o r e emerging from the s o i l .  I n June,  1955>  twenty h e a v i l y  infested  stumps from three t o f o u r i n c h e s i n d i a m e t e r were dug up, each w i t h a one-foot b a l l  o f e a r t h around the r o o t  collar,  and p l a c e d i n cages f o r emergence o b s e r v a t i o n s . F r e s h bark was p l a c e d i n each cage weekly d u r i n g the emergence p e r i o d to  a t t r a c t the w e e v i l s as t h e y emerged from the s o i l  and  d a i l y c o l l e c t i o n s were made from the b a r k . F i g . 13 shows  41  the emergence p a t t e r n of the 96 which were males and The  50  weevils  c o l l e c t e d - 46  of  females.  young a d u l t s b e g i n f e e d i n g almost immediately a f t e r  emerging from the s o i l . They f e e d on the i n n e r bark o f t r u n k i n the v i c i n i t y of the r o o t c o l l a r and at  n i g h t , on the t e n d e r b a r k of twigs and  the  occasionally,  s m a l l branches o f  h e a l t h y t r e e s . However, the a d u l t p o p u l a t i o n i n the  field  i s never s u f f i c i e n t l y l a r g e t o cause s e r i o u s f e e d i n g damage. The  f e e d i n g damage i s q u i t e c o n s p i c u o u s on b r a n c h e s , a p p e a r -  ing  as s m a l l open p i t s about  coalesce  t o form l a r g e r wound a r e a s ,  r a t e of spread ing  i n diameter that  of the w e e v i l  i s not  often  i n a n a t u r a l stand,  the  r a p i d s i n c e a d u l t s emerg-  from the r o o t c o l l a r o f a l i v i n g t r e e u s u a l l y remain t o  continue  and  i n c r e a s e the i n f e s t a t i o n on t h a t p a r t i c u l a r  t r e e . However, i n i n f e s t e d p i n e p l a n t a t i o n s , where heavy c u t s a r e made p e r i o d i c a l l y , the w e e v i l s  emerging from a stump  or dead t r e e must of n e c e s s i t y f i n d new  l i v i n g material  which t o f e e d and  o v i p o s i t , producing  a more r a p i d  of the w e e v i l t h a n i s o t h e r w i s e e x p e r i e n c e d .  spread  This fact  e s t a b l i s h e d by s e t t i n g out b a r k t r a p s from e a r l y May mid-September i n b o t h a h e a v i l y i n f e s t e d Scots p i n e and  i n a r e c e n t l y cut-over  had  been l e f t  on  was  until stand  a r e a where the i n f e s t e d stumps  i n the ground. No w e e v i l s  bark t r a p s i n the i n f e s t e d s t a n d  were found on  the  - i n d i c a t i n g a l a c k of  42  m i g r a t i o n - w h i l e a l a r g e number was c o l l e c t e d from t h e b a r k t r a p s p l a c e d i n t h e stump a r e a . L i m i t i n g Factors? I n s o u t h e r n O n t a r i o , H. r a d i c i s i s found  i n epidemic  numbers o n l y i n a r e a s where e x o t i c p i n e s ( m o s t l y S c o t s and A u s t r i a n p i n e s ) , a r e grown e x t e n s i v e l y . The w e e v i l  will  a t t a c k open-grown S c o t s p i n e as h e a v i l y as S c o t s p i n e grown i n a dense s t a n d . However i t was n e v e r found  on n a t i v e p i n e s ,  even i n dense s t a n d s , i s o l a t e d from e x o t i c p i n e s . Where a stand of pure r e d o r j a c k p i n e grows a d j a c e n t t o a n i n f e s t e d stand o f Scots p i n e , o n l y t h e m a r g i n a l r e d and j a c k p i n e s become i n f e s t e d . I n mixed stands  o f n a t i v e and e x o t i c s p e c i e s  on t h e o t h e r hand, a l l t h e t r e e s a r e s u s c e p t i b l e t o i n f e s tation. While s t a n d c o m p o s i t i o n and d e n s i t y a r e a p p a r e n t l y c r i t i c a l f a c t o r s l i m i t i n g w e e v i l p o p u l a t i o n p e r t r e e on n a t i v e p i n e s , t h e y do not seem t o be important  to w e e v i l  d e n s i t i e s on e x o t i c s p e c i e s . T h i s i s , p r o b a b l y due t o p h y s i o l o g i c a l d i f f e r e n c e s i n t h e two groups of p i n e s . Throughout t h e y e a r t h e w e e v i l p o p u l a t i o n on S c o t s p i n e was almost  50f h i g h e r t h a n on r e d p i n e o f s i m i l a r 0  size,  even where i n f e s t a t i o n s were heavy and t h e two s p e c i e s grew i n c l o s e p r o x i m i t y t o each o t h e r . F i e l d  o b s e r v a t i o n s showed  43  t h a t a d u l t females  o v i p o s i t i n g on r e d p i n e l a i d as. .many eggs  as those o v i p o s i t i n g on S c o t s p i n e , hut t h a t the  coefficient  of d e s t r u c t i o n f o r the immature s t a g e s d i f f e r e d f o r p o p u l a t i o n s b r e e d i n g on t h e s e two  hosts» I n b o t h p i n e s the g r e a t e s t  m o r t a l i t y o c c u r r e d i n t h e egg s t a g e and d u r i n g the ment of the newly hatched  establish-  l a r v a e . I n the i n s e c t a r y i t was  found t h a t about 30$ of the eggs l a i d d i d not h a t c h . A p a r t from t h i s i n i t i a l l o s s , a l a r g e number of eggs a r e s u b j e c t e d t o p o s s i b l e p r e d a t i o n by m i t e s and since approximately  other s o i l  scavengers,  25$ a r e d e p o s i t e d i n the s o i l as f a r as  t h r e e i n c h e s from the t r e e . I t was  not p o s s i b l e t o  determine  a c c u r a t e l y the extent o f t h i s h a z a r d , but l a r v a l counts first-instar  l a r v a e i n the s o i l around the r o o t c o l l a r  of of  i n f e s t e d t r e e s kept i n cages i n d i c a t e d t h a t i n b o t h r e d p i n e and Scots, p i n e about 20$  of the v i a b l e eggs were d e s t r o y e d  b e f o r e t h e y h a t c h e d . The v i a b l e eggs l a i d i n n i c h e s i n t h e i n n e r bark of the r o o t c o l l a r , on the o t h e r hand, a r e w e l l p r o t e c t e d by p l a n t t i s s u e s and  j u i c e s and s u f f e r l i t t l e  or  no m o r t a l i t y from p r e d a t i o n . The to  newly h a t c h e d  f o u r days without  l a r v a e a r e a c t i v e and may  live  up  e a t i n g . T h e r e f o r e , l a r v a e emerging  from eggs l a i d i n the s o i l a r e u s u a l l y a b l e t o r e a c h  living  t i s s u e of the near-by r o o t c o l l a r b e f o r e s t a r v i n g . I t i s w h i l e a t t e m p t i n g t o e s t a b l i s h i t s e l f i n the cambium of t h e  44  l i v i n g t r e e t h a t the l a r v a l p o p u l a t i o n m o r t a l i t y . The  flow  of sap  suffers i t s greatest  from the f r e s h l y wounded r o o t  c o l l a r i s v e r y pronounced and  i n S c o t s p i n e k i l l s up  of the young l a r v a e , w h i l e i n r e d p i n e as much as 75$ larvae are k i l l e d at t h i s  60$  to of  the  time.  Once the l a r v a e have succeeded i n e s t a b l i s h i n g thems e l v e s i n the l i v i n g t i s s u e s of the r o o t c o l l a r , t h e y we3Ll p r o t e c t e d  from the  environment, s i n c e t h e y a r e  are  almost  always c o m p l e t e l y surrounded by l a r g e q u a n t i t i e s of s t i c k y r e s i n which a c t s as an e x c e l l e n t p r o t e c t i o n a g a i n s t and p a r a s i t e s . The  predators  l a r v a l stage i s p r a c t i c a l l y f r e e from  p a r a s i t e a t t a c k . D u r i n g the whole s t u d y p e r i o d  only  two  l a r v a e c o l l e c t e d i n the f i e l d were found t o be p a r a s i t i z e d . Three p a r a s i t e s emerged from these two t i f i e d as C o e l o i d e s  l a r v a e and  sp_.  The pupa i s w e l l p r o t e c t e d c e l l w a l l , a l t h o u g h h a r d and t o m o i s t u r e , however, and  i n the p u p a l chamber.  c e m e n t - l i k e , i s not  inches  i t was  4.42  inches  the  of  i n the Angus a r e a as compared w i t h an average of  a check was and  impervious  cause the d e a t h of  o c c u p a n t s . D u r i n g the month of J u l y , 1956,  2.77  The  when p r o l o n g e d p r e c i p i t a t i o n o c c u r s  d u r i n g the p u p a l p e r i o d , f l o o d i n g may  rain f e l l  were i d e n -  f o r the p r e v i o u s made on the  45  y e a r s . The  f o l l o w i n g week  c o n d i t i o n of the pupae i n " the  found t h a t about 15$  d i e d from drowning.  soil  v  \V>  The  small, p u p a l p o p u l a t i o n t h a t e n t e r s h i b e r n a t i o n i n  the f a l l s u f f e r s heavy m o r t a l i t y due t o low temperatures. I n November, 1 9 5 7 , about 85$ chambers, w h i l e had  o f t h e pupae were dead i n t h e i r  i n A p r i l of the f o l l o w i n g spring m o r t a l i t y  r i s e n t o over 9 5 $ . The  a d u l t s spend n e a r l y t h e i r whole l i v e s i n t h e d u f f  surrounding  the root c o l l a r of pines  on which they f e e d and  o v i p o s i t . I n t h i s environment t h e y a r e r e l a t i v e l y f r e e from the e f f e c t  o f c l i m a t e and a t t a c k by p r e d a t o r s . Death i n t h i s  stage occurs m o s t l y d u r i n g t h e o v e r w i n t e r i n g  p e r i o d . Out o f  an i n i t i a l p o p u l a t i o n o f 67 young a d u l t s r e a r e d from pupae d u r i n g t h e summer o f 1955, w i n t e r and 41,  o r 61$,  were overwintered ing  s i x inches  H»  o r 16$,  died during the f i r s t  d u r i n g t h e second w i n t e r . These a d u l t s  i n a n unheated i n s e c t a r y i n cages  of s t e r i l i z e d  contain-  sawdust.  D u r i n g t h e summer o f 1956  a f t e r a d u l t emergence from  i n f e s t e d stumps kept i n cages had c e a s e d , t h e s o i l  surrounding  the stumps wqs examined f o r a d u l t s t h a t had f a i l e d t o emerge from, t h e i r p u p a l chambers. I t was found t h a t 21$ o f t h e new adults, had d i e d i n t h e i r c e l l s and were i n f e s t e d w i t h a g r e e n e x t e r n a l fungus and a white i n t e r n a l f u n g u s . The g r e e n fungus was i d e n t i f i e d as a s a p r o p h y t i c B e n i c i l l i u m s p . but e f f o r t s t o grow t h e white fungus on e i t h e r a r t i f i c i a l media or l i v i n g i n s e c t s i n t h e l a b o r a t o r y f a i l e d and i d e n t i f i c a t i o n  ^  was not p o s s i b l e . The m o r t a l i t y o f t h e immature s t a g e s o f H. r a d i c i s is  summarized i n T a b l e I I f o r b o t h r e d and S c o t s p i n e s .  TABLE I I M o r t a l i t y o f immature H y l o b i u s r a d i c i s , c a l c u l a t e d from p o p u l a t i o n s on 60 r e d p i n e s and 78 Scots p i n e s and expressed as a p e r c e n t o f the i n i t i a l egg p o p u l a t i o n . Host  red  pine  Scots  Mortality  ;  "  I  Egg  :  1 »  (percent)  '' [  Larva  Pupa  41.8  \  45.0  \  2.0  43.2  i\  35.4  1  2.8  *  E f f e c t on t h e Tree? H. r a d i c i s w i l l a t t a c k h e a l t h y t r e e s from l i - i n c h e s i n diameter a t stump h e i g h t (6 i n c h e s above ground), t o mature t r e e s measuring as much as two f e e t i n diameter a t b r e a a t h e i g h t . S c o t s p i n e s measuring l e s s t h a n 4" dbh. a r e n o r m a l l y k i l l e d a f t e r t h r e e or f o u r y e a r s o f heavy  infesta-  t i o n , w h i l e r e d and j a c k p i n e s c a n w i t h s t a n d t h e a t t a c k f o r one  o r two years l o n g e r . P i n e s t h a t a r e l a r g e r t h a n 4" dbh.  when f i r s t  a t t a c k e d a r e seldom c o m p l e t e l y g i r d l e d ,  t h e i r r o o t c o l l a r s may be s e r i o u s l y weakened.  although  SIGNS AND SYMPTOMSs  The f i r s t  e x t e r n a l symptom o f t h e  t r e e t o w e e v i l a t t a c k c o n s i s t s o f sap e s c a p i n g  from t h e  wounded r o o t c o l l a r i n t o the s u r r o u n d i n g s o i l ,  producing  a compactLlayer o f p i t c h - i n f i l t r a t e d s o i l o f t e n two o r t h r e e inches  i n thickness  over the whole damaged a r e a  Under the r e s i n - s o a k e d  ( P i g ; 11 a ) .  s o i l t h e o u t e r b a r k o f t h e stem i s  u s u a l l y w e l l preserved,  although o f t e n separated  from t h e  sound wood by a s much a s one i n c h o f gummy semi-hardened r e s i n mixed w i t h l a r v a l f r a s s . I t i s i n t h i s l a y e r t h a t most of t h e l a r v a l p o p u l a t i o n  i s found; I n a h e a v i l y i n f e s t e d  t r e e , removal o f t h e o u t e r b a r k and t h e gummy r e s i n around the r o o t  c o l l a r r e v e a l s a g r e a t l y reduced stem w i t h o n l y a  s m a l l amount o f cambium b r i d g i n g the damaged a r e a The  t r e e may remain a l i v e and v i g o r o u s  under t h e s e  ( P i g . 11 c ) conditions  f o r s e v e r a l y e a r s . The l a r g e q u a n t i t y o f sap c o v e r i n g t h e wound c r e a t e s a moist s e p t i c c o n d i t i o n f a v o u r a b l e  t o the  p l a n t ; However, t r e e s t h a t a r e open-grown o r a t t h e edge o f s t a n d s a r e v e r y s u s c e p t i b l e t o windthrow and snowbreak and u s u a l l y l e a n h e a v i l y i n the d i r e c t i o n o f the p r e v a i l i n g winds ( P i g . 1 4 ) . A l t h o u g h windthrow has not y e t o c c u r r e d s i v e l y i n dense s t a n d s i n s o u t h e r n O n t a r i o , a b l e t h a t should  exten-  i t i s conceiv-  e x c e p t i o n a l l y s t r o n g winds o c c u r , t h i s  type  of damage would be commonplace, f o r t r e e s measuring 6" dbh. h e a v i l y i n f e s t e d w i t h H. r a d i c i s f o r f i v e t o t e n y e a r s c a n u s u a l l y be pushed over by two men without g r e a t  difficulty.  F i g . 1 4 . H y l o b i u s r a d i c i s damage, (a) A h e a v i l y i n f e s t e d twenty-year-old  Scots p i n e p l a n t a t i o n ;  (b) Two  infested  broken a t the r o o t c o l l a r and blown over by wind.  trees  49  When t h e t r e e i s c o m p l e t e l y g i r d l e d , t h e r e i s a r e l a t i v e l y s h o r t p e r i o d d u r i n g which t h e c o l o u r o f t h e f o l i a g e changes from green t o a p a l e y e l l o w f o l l o w e d by a r e d and t h e n brown c o l o u r a t i o n ; EFFECT ON GROWTHS  The e f f e c t o f H. r a d i c i s damage on t h e  growth o f p i n e s was s t u d i e d by measuring t h e annual and r a d i a l increments  of twenty-year-old  height  S c o t s , r e d , and  white p i n e s f o r t h e p e r i o d 1945 t o 1955» An average o f 10.1 and 9»7 immature w e e v i l s were found  on t h e S c o t s and r e d  p i n e s r e s p e c t i v e l y , showing t h a t t h e t r e e s were h e a v i l y a t t a c k e d , but none o f t h e white p i n e s were i n f e s t e d . Twenty S c o t s and 20 r e d p i n e s , h e a v i l y i n f e s t e d s i n c e 1950, and 10 n o n - i n f e s t e d white p i n e s were measured. F i g . 15 shows the average growth o f these t r e e s , b o t h i n h e i g h t and r a d i a l l y . When t h e growth curves o f t h e Soots and r e d p i n e s a r e examined i n d i v i d u a l l y , t h e r e i s no i n d i c a t i o n o f a r e d u c t i o n i n growth from 1950 t o 1955» except f o r the h e i g h t of Scots p i n e which drops s l i g h t l y . The apparent  increment  l a c k of  e f f e c t on these two p i n e s by w e e v i l a t t a c k was f u r t h e r emphas i z e d by t h e normal l e n g t h and c o l o u r o f t h e i r n e e d l e s and the g e n e r a l h e a l t h y appearance o f t h e crowns. B l a i s (4) s t a t e s t h a t t h e f i r s t y e a r o f growth s i o n o f balsam f i r and white s p r u c e , P i c e a g l a u c a  suppres-  (Moench)  Voss, h e a v i l y d e f o l i a t e d by t h e spruce budworm, C h o r i s t o n e u r a  F i g . 15. Growth curves o f 20 reel p i n e s and 20  Scots  p i n e s , h e a v i l y i n f e s t e d w i t h H y l o b i u s r a d i c i s , and h e a l t h y white p i n e s growing i n a mixed s t a n d . The were a l l 22 y e a r s o l d .  10 trees  DATE  (YEARS)  f u m i f erarta Clem.,, s e v e r a l y e a r s i n s u c c e s s i o n , can be  indi-  c a t e d by growth r a t i o s o b t a i n e d by d i v i d i n g the average a n n u a l increment o f the a f f e c t e d s p e c i e s by t h e average annual growth increment of n o n - i n f e s t e d s p e c i e s growing i n the same a r e a ^ He  considers, the apparent f i r s t  s u p r e s s i o n t o be the one t h a t o f any  y e a r o f growth  showing a growth r a t i o l e s s  of the p r e c e e d i n g  of d e c l i n i n g r a t i o s . Table  y e a r s , f o l l o w e d by a  than  series  I I I shows the a n n u a l growth r a t i o s  TABLE I I I Growth r a t i o s f o r 20 Scots p i n e s and i n f e s t e d with Hylobius r a d i c i s . Scots  20 r e d p i n e s h e a v i l y  pine  Red  pine'  Year  1945  [  [?  '  :  1  1946 1947 1948  Radial ' . growth  |  1  ,  5  5  1.07  1.26  .  t  1949  [  1.85  1950  ;  1.54  1951  |  1.17  :  |  1.44  ';  \  1  '  1.89  '  \  1.50  !  ,  5  2  ' '  0.80  1952  Height growth  1.62  i  Radial growth 0.75  '',  0.95  1.04  '  0.85  '  1.25  0.98 1.64 1.64  |  1.56  0.92  \  0.92  '  0.80  [  0.65  |  0.75  1954  '  0.70  ',  0.95  1.08  1 , 3 5  1.10  1955  Height growth  !  1.35 [  1.16 0.86  '  0.71 1.06  53"-  f o r the Scots and red pines obtained i n t h i s manner. I t can be seen fnom the r a t i o s that there i s an apparent reduction i n the growth of the two i n f e s t e d species from 1951 to then B l a i s  1  1955.  c r i t e r i o n i s a p p l i e d to the data i n Table I I I ,  the f i r s t year of suppression f o r Scots pine i s apparently 1951 f o r height growth and 1952  f o r r a d i a l growth, This i s  true also f o r red pine i f the small r a t i o s f o r height growth i n 1946 and r a d i a l growth i n 1945 are ignored. The growth r a t i o s f o r the year 1954 a l l show s l i g h t increases suggesting a recovery of the a f f e c t e d species from weevil attack during that year. I t should be kept i n mind, however, that B l a i s * a n a l y s i s of the e f f e c t of C. fumiferana on the growth of balsam f i r and white spruce might not be a p p l i c a b l e to the e f f e c t of H. r a d i c i s on pines. The marked d i f f e r e n c e s that e x i s t s between the two types; of damages could be  reflected  i n the growth of the respective hosts. The trees studied by B l a i s had suffered almost complete d e f o l i a t i o n f o r s e v e r a l consecutive years before dying, while the pines attacked by H. r a d i c i s maintained healthy crowns throughout the period of observation. Prom sections ( d i s c s ) cut at the root c o l l a r s of i n fested pines, i t was. found that Scots pines attacked at the age of four or f i v e years were k i l l e d about three or four years l a t e r , while trees attacked when 10 to 15 years of  F i g . 16. H y l o b i u s r a d i c i s damage, showing a l t e r n a t e rows of l i v i n g i n f e s t e d r e d p i n e s and dead Scots p i n e s .  age  d i e d a f t e r s i x t o e i g h t y e a r s of i n f e s t a t i o n .  In general  red p i n e s remained a l i v e about t h r e e y e a r s l o n g e r than  Scots  p i n e s i n the same a r e a . I n stands where S c o t s p i n e s and r e d p i n e s a r e p l a n t e d i n a l t e r n a t e rows t h i s i s v e r y  stricking,  f o r the e a r l y death of the S c o t s p i n e c r e a t e s a c o n t r a s t w i t h the a p p a r e n t l y h e a l t h y r e d p i n e s as shown i n F i g . 16  56  HYLOBIUS PALES (HBST.)  C u r c u l i o p a l e s Herbst  (66).  H y l o b i u s p a l e s Boheman (6, 7 ) , Leconte  (75, 7 6 ) ,  Provancher  ( 9 6 ) , H a r r i n g t o n (62, 63), B l a t e h l e y and Leng ( 5 ) . a s s i m i l i s Roelofs (99). p i s s o d e s m a c e l l u s Germar ( 5 8 ) , Leconte BIOLOGY: H a r r i s  (64,  65),  Dodge ( 2 3 ) , Smith  (75).  P i t c h ( 5 3 ) , Le Baron ( 7 4 ) , (112), P a c k a r d  (79, 80,  81),  Thomas (119), Saunders (100, 101), Hopkins (70), P e l t 37,  (27, 28, 29,  38, 44,  Brues  (15),  46,  30,  47), Hinds  31, 32,  33,  34, (17),  (68), C a r t e r  P e i r s o n (82, 83, 84, 85, 86,  87),  B r i t t o n ( 1 2 ) , Wells (124), Anon ( 1 ) , B r i t t o n and Zappe ( 1 4 ) , C r a i g h e a d (21, 2 2 ) , K n u l l  (19, 2 0 ) , D i e t r i c h  ( 7 2 ) , York (126), Glasgow (60,  61), S c h a f f n e r (103, 107), P e l t and (49), F r i e n d  (54), Lyle  Bromley  ( 7 7 ) , Robinson  98), S a v l e y (102), Bourne ( 8 ) , P r i c o C o n k l i n ( 1 8 ) , Eddy (26), and Chamberlin  (95),  H e t r i c k (67),  Friend  ( 5 7 ) , B e a l and M c C l i n t i c k ( 2 ) ,  Bess ( 3 ) , S e n t e l l (110), H o l t (69), Speers  (97,  ( 2 5 ) , Speers  (lt-4, 115),  E b e l and  Thatcher  (118).  57  History; H. pales was described i n 1797 by Herbst  (66)  and placed  i n the genus C u r c u l i o . In 1834, Boheman (6) t r a n s f e r r e d i t to the genus Hylobius which had r e c e n t l y been described by Germar (58). During the century that followed Herbst's desc r i p t i o n , the weevil was not considered to be of economic importance and was mentioned only b r i e f l y by Pelt (27), P i t c h (53), Harris (64, 65), Packard (79, 80, 81), and Thomas (119). It was not u n t i l Carter (17) i n 1916 and Peirson (82) i n 1921 pointed out i t s role i n l i m i t i n g white pine regeneration i n cut-over areas by feeding on the tender bark of seedlings, that the importance of the insect was f u l l y r e a l i z e d . Carter (17) reported that H. pales was a very important  factor i n  l i m i t i n g the reproduction of c o n i f e r s i n and around cut-over areas of white pine i n the Harvard Porest at Petersham, Mass. He stated that due to the feeding of pales adults, as much as 70$ of the young regeneration had been k i l l e d during the f i r s t two years f o l l o w i n g c l e a r c u t t i n g of white pine. He concluded that i t was unwise to plant cut-over pine lands during the f i r s t two seasons a f t e r c u t t i n g operations, because the weevil population remained high i n the area f o r at l e a s t that length of time. He warned f u r t h e r , that i n p l a n t i n g pasture land with c o n i f e r s large pines i n the area should not be cut before the p l a n t i n g because the seedlings i n the  58  vicinity  of the stumps would he s u b j e c t e d t o heavy f e e d i n g  by the w e e v i l and t h e r e s u l t i n g l o s s would produce open a r e a s i n the p l a n t a t i o n . He m a i n t a i n e d  t h a t H. p a l e s damage t o  c o n i f e r r e g e n e r a t i o n would l i k e l y be h e a v i e r i n a r e a s where the shelterwood  method o f c u t t i n g was  used, s i n c e t h e  final  c u t t i n g a f t e r the r e g e n e r a t i o n had become e s t a b l i s h e d would produce b r e e d i n g m a t e r i a l f o r a l a r g e p o p u l a t i o n o f w e e v i l s . He  s t a t e d t h a t i n j u r y t o p i n e r e p r o d u c t i o n c o u l d a l s o be  p e c t e d where s t r i p  c u t t i n g was  the s t r i p s p r o g r e s s e d damage was  ex-  p r a c t i c e d , e s p e c i a l l y where  from leeward  almost i n v a r i a b l y found  t o windward, s i n c e w e e v i l as f a r as 100  y a r d s from  the edge o f t h e o l d s t a n d . peirson»s (82) paper i n 1921 and  presented  the l i f e  history  c o n t r o l o f H. p a l e s f o r the S t a t e of M a s s a c h u s s e t s .  d i s c u s s e d a t some l e n g t h the h i s t o r y , d i s t r i b u t i o n and plants,, s e a s o n a l h i s t o r y , h a b i t s , and  (1020» S e n t e l l (110), and  Wells  (3),  (124)  have p o i n t e d  out the c o n t i n u e d importance of t h e w e e v i l a s a f o r e s t and have shown t h a t i t i s found  host  c o n t r o l of the w e e v i l ;  More r e c e n t p a p e r s by B e a l and M c C l i n t i c k ( 2 ) , Bess Savely  He  pest  over most o f the United^  S t a t e s e a s t of the M i s s i s s i p p i and  n o r t h of F l o r i d a ,  and  from Nova S c o t i a t o Manitoba i n Canada; I n r e p o r t i n g t h e i r o b s e r v a t i o n s on H. p a l e s i n j u r y t o white p i n e p l a n t i n g s i n Few. England i n 1942,  F r i e n d and  Chamberlin (57) s t a t e d t h a t  59  i n a d d i t i o n to the s i z e and density of the young t r e e s , the number of stumps present and the proximity  of the trees to  them i s important, and that the amount of damage i n an area i s dependent to some extent on the presence or absence of new  areas i n the v i c i n i t y a t t r a c t i v e to the weevil. I f  new  areas did not materialize!,~ the adults u s u a l l y remained i n f  the o r i g i n a l area to hibernate f o l l o w i n g spring. In 1957,  and cause f u r t h e r damage the  Ebel and Speers (25)  discussed  the population l e v e l s of pine weevils i n North Carolina during the growing season f o l l o w i n g c u t t i n g , and stated that nearly 90$ of the specimens c o l l e c t e d were H. pales. They concluded that the use of traps to determine weevil abundance i n the f i e l d was promising and deserved f u r t h e r study. Speers (114, 115) dips and  a l s o discussed  controls f o r the weevil with  sprays.  D e s c r i p t i o n of L i f e H i s t o r y Stages; ADULT $ to 11.3 17)% and  The adult H. pales i s robust, measuring from nim. i n length and from 2.1  i n width ( P i g .  c l o s e l y resembles H. r a d i c i s . The prothorax and  e l y t r a are u s u a l l y conspicuously coloured  to 4.5 mm.  5.8  marked with spots of cream  s c a l e - l i k e h a i r s . In most i n d i v i d u a l s the  elytral  spots are arranged i n two d e f i n i t e groups or bars which divide the e l y t r a i n t o three sub-equal p a r t s . The  composite  bars are oblique to the median l i n e of the body and can a l s o  b P i g . 17. Hylobius pales adult  xlO.  be seen from the sides (Pigs. 5 h, 17). The strength of the bars vary g r e a t l y , some i n d i v i d u a l s e x h i b i t i n g no d e f i n i t e pattern. The spots on the e l y t r a of H. r a d i c i s , on the hand, are never displayed i n bars ( P i g .  other  5a).  As stated previously, no d i f f i c u l t y i s experienced i n  61  s e p a r a t i n g t h e males., o f t h e two s p e c i e s by t h e shape o f t h e h i n d t i b i a l uncus ( P i g . 6 a , b ) . The f e m a l e s , however, a r e v e r y s i m i l a r and u n l e s s and  t h e e l y t r a l markings, average  amount o f s c a l e s p r e s e n t  size,  on t h e f r o n t o f t h e head a r e  t y p i c a l f o r each s p e c i e s , i t i s not p o s s i b l e t o s e p a r a t e them w i t h c e r t a i n t y . The t h r e e secondary s e x c h a r a c t e r s c r i b e d f o r H. r a d i c i s a l s o a p p l y t o H. p a l e s EGG?  des-  (Pig. 6).  The egg i s e l l i p s o i d a l and measures 1.10 ± 0^07  i n l e n g t h and 0.68 ± 0.04 mm.  mm.  i n d i a m e t e r . I t i s opaque and  d u l l creamy white i n c o l o u r . I t i s o n l y i n t h i s s t a g e t h a t H. pales, and H. r a d i c i s c a n be c o m p l e t e l y  separated,  since  the eggs o f H. r a d i c i s a r e almost t w i c e as l a r g e as those of H. p a l e s . LARVA$  The l a r v a i s t y p i c a l l y c u r c u l i o n i d i n form and  when f u l l y grown measures about 12. mm.  i n l e n g t h . I t has a  l e g l e s s white body, dark brown head, and b l a c k m a n d i b l e s . At present  i t i s impossible  t o separate,  morphologically,  the l a r v a e o f H. p a l e s from those o f H. r a d i c i s , except f o r the f i r s t  i n s t a r H, p a l e s l a r v a e , which a r e s m a l l e r t h a n t h e  s m a l l e s t H. r a d i c i s l a r v a e , and t h e l a r g e s t H. r a d i c i s (seventh  larvae  i n s t a r ) which a r e l a r g e r t h a n t h e maximum s i z e  a t t a i n e d by H. pales, l a r v a e ^ Out  o f 73 l a r v a e r e a r e d  i n t h e i n s e c t a r y from egg t o  ui  30 -  :.50 HEAD CAPSULE  WIDTH IN MM.  P i g . 18. D i s t r i b u t i o n of head c a p s u l e measurments of 73 H y l o b i u s p a l e s l a r v a e r e a r e d i n the i n s e c t a r y from the egg t o t h e a d u l t . The b l a c k a r e a r e p r e s e n t s t h e measurments o f the f i f t h i n s t a r l a r v a e t h a t c o n t i n u e d development t o a s i x t h i n s t a r before pupating.  a d u l t , 33 were males and 40 were f e m a l e s . P i g . 18 i l l u s t r a t e the d i s t r i b u t i o n o f measurments of head c a p s u l e widths of these l a r v a e s e p a r a t e d by s e x as t h e y developed  through  each i n s t a r . I t can be seen from t h e graph t h a t most of the l a r v a e pupated a f t e r f i v e i n s t a r s , but t h a t 16 males and 18  63  females r e q u i r e d s i x i n s t a r s b e f o r e p u p a t i n g . Simple of  c a l c u l a t i o n s comparing t h e r a t i o o f t h e means  the head c a p s u l e widths  o f s u c c e s s i v e i n s t a r s show t h a t  t h i s r a t i o i s r e l a t i v e l y constant f o r the f i r s t of  five  instars  b o t h males and females, but t h a t between t h e f i f t h and  s i x t h i n s t a r s i t i n c r e a s e s c o n s i d e r a b l y ( T a b l e I V ) . Thus  TABLE IV Comparison between observed head c a p s u l e widths o f H y l o b i u s p a l e s l a r v a e and those e s t i m a t e d by u s i n g Dyar's Rule  Sex  : Instar-  Observed measurments  \ \  | widths [ r a t i o s | ; t  :.. Male  | i  I II III !  0.94  IV -  1.37  ;  1.82  i  2.18  :  0.51  II ]  0.75  ! !  Y  VI I  Female <  III IV  ! 1  [  V ! VI  ;  0.72 : . 0.73 ; 0.69  '.  0.76  ;  0.83  !  0.68  0.68 '  1.06 1.52 2.00 2.43  j  0.71  Rule)  0.68 0.94 1.31  ;  l.8l  1  2.51  ;  0.72  \  1.01  !  1.42  0.69  •  0.76 '  !  0.82  •  (Dyar's  1  !  !  Calculated widths  I !  2.00 2.81  64  the mean o f t h e s i x t h i n s t a r i s c l o s e r t o the mean o f t h e fifth  i n s t a r , f o r each sex, t h a n i s i n d i c a t e d  by Dyar's R u l e .  The  cause o f t h e i n c r e a s e i n t h e r a t i o becomes e v i d e n t when  the  l a r v a e o f the s i x t h i n s t a r a r e t r a c e d back t o t h e i r  proper p o s i t i o n s  i n the f i f t h  i n s t a r * The shaded a r e a s under  the  f i f t h i n s t a r i n P i g . 18 r e p r e s e n t s t h e s e l a r v a e and t h e y  are  s e e n t o be t h e s m a l l e r i n d i v i d u a l s  means t h a t  of that  instar.  This  the s i x t h i n s t a r l a r v a e a r e not r e p r e s e n t a t i v e  of t h e f i f t h  i n s t a r i n head c a p s u l e w i d t h and c o n s e q u e n t l y  have a mean w i d t h l e s s t h a n i s p r e d i c t e d by Dyar's It  i s of further  i n t e r e s t that  is  closely related  rule.  since the s i z e of the adult  t o t h e s i z e o f t h e prepupa, as shown i n  P i g . 19, t h e s m a l l e r u s u a l l y  l e s s vigorous larvae,  by con-  t i n u i n g t h e i r development t o a s i x t h i n s t a r b e f o r e p u p a t i n g , ultimately  produce t h e l a r g e r a d u l t s i n t h e w e e v i l p o p u l a -  tion.  PUPA? but  The pupa i s c o m p l e t e l y white when f i r s t  formed,  t h e eyes and mandibles t u r n b l a c k and t h e rostrum, p r o -  t h o r a x , and l e g s darken t o medium brown b e f o r e changing t o the  adult.  D i s t r i b u t i o n and Hosts? P e i r s o n (82) s t a t e d  that  t h e d i s t r i b u t i o n o f H. p a l e s  1.4  1.5  1.6  I.V  1.8  1.9  2.0  2.1  2.2  2.3  2.4  2.5  2.6  2.7  SIZE OF PREPUPA HEAD CAPSULE IN MM.  P i g . 1 9 . R e l a t i o n s h i p between t h e head c a p s u l e s i z e o f prepupae and a d u l t s o f H y l o b i u s p a l e s . The r e g r e s s i o n l i n e Y = 0.413X +  0.889  has been f i t t e d  t o the d a t a .  was g e n e r a l throughout the e a s t e r n h a l f o f t h e U n i t e d  States  and  this  i n southeastern  Canada. He p o i n t e d  out t h a t s i n c e  range was g r e a t e r t h a n the range o f the w e e v i l ' s  favorite  f o o d p l a n t , white p i n e , o t h e r t r e e s must n e c e s s a r i l y be used as f o o d and b r e e d i n g m a t e r i a l . T h i s was l a t e r shown to be t r u e by s e v e r a l workers (2, 21, 25, 9 7 , 102, 110) who r e p o r t e d the w e e v i l f e e d i n g on s o u t h e r n p i n e s and  o t h e r c o n i f e r s i n n o r t h e r n F l o r i d a , Alabama, and D u r i n g the p a s t  Mississippi  50 y e a r s the f o l l o w i n g t r e e s have been  r e p o r t e d as a d u l t f o o d p l a n t s (2, 17,  57,  Pinus "  s t r o b u s L. rigida M i l l . resinosa A i t . ponderosa Laws. " s y l v e s t r i s L. " taeda L . » echinata M i l l . " palustris Mill. " virginiana M i l l . " mugho T u r r a . cembroides Zucc, L a r i x l a r i c i n a (Du R o i ) K. Koch » decidua M i l l . P i c e a rubens S a r g . " a b i e s (L.) K a r s t . A b i e s balsamea (L.) M i l l . Tsuga canadensis. ( L . ) C a r r . Pseudotsuga m e n z i e s i i ( M i r b e l ) Franco J u n i p e r u s communis L. " v i r g i n i a n a L. Cupressus a r i z o n i e a Green. Cedrus deodara (Roxb.) Loud. Betula. p o p u l i f o l i a Marsh. F r a x i n u s americana L .  124) s  E a s t e r n white p i n e . Pitch pine. Red p i n e . Ponderosa p i n e . Scots p i n e . Loblolly pine. Shortleaf pine. Longleaf pine. Virginia pine. Mugho p i n e . Cembra-pine• Tamarack. European l a r c h . Red s p r u c e . Norway s p r u c e . Balsam f i r . E a s t e r n hemlock. Douglas f i r . Dwarf j u n i p e r . Red j u n i p e r . Arizona cypress. Deodar c e d a r . Wire b i r c h . White a s h .  M  M  However, C a r t e r (17), P e i r s o n ( 8 2 ) , and  82,  F r i e n d and Cham-  b e r l i n (57) agree t h a t w h i t e p i n e i s the p r e f e r r e d f o o d p l a n t . In southern  O n t a r i o the w e e v i l has been found  feeding  on white p i n e , r e d pine, j a c k p i n e , A u s t r i a n p i n e , S c o t s and  tamarack. A l t h o u g h  f e e d i n g o c c u r s on the branches of  l a r g e t r e e s , the t r e e s s u f f e r l i t t l e have reached  pine  or no damage a f t e r  a h e i g h t of about t e n f e e t .  they  67  I t has not been c l e a r l y s t a t e d , however, i n what p l a n t s the w e e v i l b r e e d s . S e v e r a l a u t h o r s r e f e r t o p i n e s and  spruces  as s u i t a b l e b r e e d i n g m a t e r i a l ( 5 »  57,  white p i n e , p i t c h p i n e , ponderosa  p i n e , mugho p i n e , and  82, 124), but o n l y  cembra p i n e have been named s p e c i f i c a l l y as p r o b a b l e h o s t s of the immature s t a g e s (2, 5»  57,  82). In southern Ontario,  H. pales, a d u l t s . w e r e r e a r e d from stumps , of r e d p i n e y j a c k p i n e , and S c o t s p i n e , as w e l l a s - f r o m white p i n e . White p i n e stumps, however, were found t o support almost twice,,as many weevils, as the r e d , j a c k , or S c o t s p i n e stumps of ...similar size. Seasonal History? A c c o r d i n g t o P e i r s o n ( 8 2 ) , H. p a l e s a d u l t s emerge.from h i b e r n a t i o n about mid-May i n M a s s a c h u s e t t s and f e e d u n t i l about mid-June, a t which time t h e y m i g r a t e t o an a r e a where t h e r e i s s u i t a b l e b r e e d i n g m a t e r i a l . He i n d i c a t e d t h a t o v i p o s i t i o n b e g i n s about J u l y 1, t h a t the r e s u l t i n g pupate about  larvae  September 1 t o emerge as a d u l t s about  I , and t h a t t h e y f e e d f o r twp  October  or t h r e e weeks b e f o r e e n t e r i n g  h i b e r n a t i o n , thus c o m p l e t i n g one g e n e r a t i o n p e r y e a r . A l t h o u g h P e i r s o n does not e l a b o r a t e the p o i n t , he c o n c l u d e d , on t h e b a s i s of l a r v a e h a v i n g been found as l a t e as October 8, some i n d i v i d u a l s u n d o u b t e d l y p a s s the w i n t e r i n the  that  larval  or p u p a l s t a g e i n stumps or l o g s . B e a l and M c C l i n t i c k  (2)  68  Pig.  20.  Seasonal h i s t o r y of H y l o b i u s p a l e s i n  southern  Ontario.  questioned and  P e i r s o n ' s d e s c r i p t i o n of the s e a s o n a l  s t a t e d t h a t i n N o r t h C a r o l i n a t h e r e i s "one  g e n e r a t i o n and a p a r t i a l second o v e r l a p p i n g annually". In southern both the a d u l t and 70$  complete  generation  O n t a r i o , H. p a l e s o v e r w i n t e r s  l a r v a l stages  ( P i g . 20).  of the summer l a r v a e pupate and  late-August  history,  in  Approximately  emerge as a d u l t s from  t o mid-October t o o v e r w i n t e r a f t e r a s h o r t  i n g p e r i o d . The  remaining  30$  overwinter  i n the l a r v a l  feedstage.  69  Head c a p s u l e measurments o f 27 o v e r w i n t e r i n g l a r v a e l a t e i n November i n d i c a t e d t h a t t h e y  overwinter  f i f t h and s i x t h i n s t a r s . These l a r v a e c o n t i n u e  collected  only i n the development  d u r i n g t h e f o l l o w i n g s p r i n g and emerge as. a d u l t s from about mid-June t o August 1 . Only a few eggs a r e l a i d by t h e s e e a r l y a d u l t s d u r i n g t h e c u r r e n t summer. I n t h e f a l l t h e e a r l y a d u l t s merge w i t h t h e main a d u l t p o p u l a t i o n t o o v e r winter  i n t h e s o i l , u s u a l l y a t t h e base o f young p l a n t s on  which t h e y were f e e d i n g . The o v e r w i n t e r e d  a d u l t s emerge from  h i b e r n a t i o n i n l a t e A p r i l and e a r l y May and f e e d f o r about two months b e f o r e  o v i p o s i t i n g . The f i r s t  i n s e c t a r y i n 1958  was on June 12;  egg l a i d  the general o v i p o s i t i o n  p e r i o d l a s t e d u n t i l t h e end o f J u l y , a l t h o u g h laid  i n the  one female  t h r e e v i a b l e eggs on August 30 a f t e r b e i n g i n a c t i v e f o r  over f o u r weeks. Rearing  experiments showed t h a t a d u l t w e e v i l s a r e l o n g -  l i v e d ; about 35$  o v e r w i n t e r i n g t w i c e , t h e females o v i p o s i t i n g  d u r i n g two s u c c e s s i v e growing s e a s o n s . The females l a y about 30 eggs, o r 60$ o f t h e i r t o t a l quota, d u r i n g t h e summer f o l l o w i n g the f i r s t 18,  o r 40$,  d u r i n g t h e second summer.  I n 1957 on J u l y 6.  o v e r w i n t e r i n g p e r i o d as a d u l t s , and about  the f i r s t  summer l a r v a was found i n t h e f i e l d  The l a r v a l p e r i o d l a s t s f o r about 47 days,  f o l l o w e d by a p u p a l p e r i o d o f about 22 days. T a b l e  V shows  the  average d u r a t i o n o f each o f t h e i n s t a r s f o r b o t h f i v e -  and s i x - i n s t a r l a r v a e , a s w e l l a s f o r the egg and p u p a l s t a g e s , o f w e e v i l s r e a r e d i n a n unheated i n s e c t a r y d u r i n g the  summer months. I n s o u t h e r n O n t a r i o t h e f i r s t pupa t o \  appear i n t h e f i e l d  i n 1957 was on August 26. The newly  formed a d u l t s remain i n t h e i r p u p a l c e l l s about two weeks b e f o r e emerging through t h e b a r k and s o i l . The peak o f a d u l t emergence i s about t h e l a s t week o f September. TABLE V The d u r a t i o n o f t h e immature s t a g e s of H y l o b i u s -pales r e a r e d i n a n u n heated i n s e c t a r y d u r i n g t h e summer season Stage  Time (days)  !  9.9 ±  Egg 1st  instar  1.3  j  5.3  2nd i n s t a r  j•  5.0 ± 0.8  3rd  instar  j\  5.1 ± 0.7  4th  instar  s\  6.5 * 1.0  5th i n s t a r  ± 0.8  (Prepupa) s• 20.8 ± 2.2 i .9.3 i  5th  instar  6th  i n s t a r (Prepupa) j\ 2 1 . 3 ± 2.8  Pupa  , 21.8 ±  1.4  1.3  Habits$ The  adults overwinter  i n the d u f f and  s o i l a t the f o o t  of the s m a l l t r e e or s e e d l i n g on which i t was are o f t e n gregarious i n s m a l l groups  f e e d i n g . They  a t t h i s time of year and may  found  u s u a l l y under s u c h o b j e c t s as wood c h i p s ,  s m a l l r o c k s , or the r o o t s o f t r e e s . I n s o u t h e r n t h e y become a c t i v e i n e a r l y May from the s o i l and  continue  Ontario,  a t which time t h e y  emerge  t h e i r f e e d i n g a t n i g h t on  t e n d e r b a r k of s e e d l i n g s and  the  s m a l l b r a n c h e s of l a r g e r t r e e s  throughout the growing s e a s o n and overwinter  be  t h e n e n t e r the s o i l  to  again.  During  th©  egg l a y i n g season, the females e n t e r  s o i l o v e r l y i n g the r o o t s of f r e s h stumps and  oviposit i n  n i c h e s chewed i n the i n n e r bark of the r o o t s and of the stump below ground l e v e l . The e r r a t i c a l l y , sometimes l a y i n g two  the  the p a r t  female l a y s h e r  or t h r e e i n one  eggs  day,  f o l l o w e d by s e v e r a l days of i n a c t i v i t y , d u r i n g which time it  feeds  deposited together The  on h e a l t h y p i n e s above ground^ The s i n g l y , but  sometimes two  eggs a r e u s u a l l y  or'three are  i n s i n g l e n i c h e s chewed by the  placed  female.  newly h a t c h e d l a r v a e f e e d i n " the cambial  area  of  the r o o t s or stump, s c a r r i n g the wood more d e e p l y t h a n the i n n e r b a r k . The  t u n n e l s do not form a d e f i n i t e p a t t e r n i n  the l o w e r part, of the stump, but wander without  respect  to  72  •the g r a i n o f t h e wood. I n t h e r o o t s , however, t h e t u n n e l s always r u n w i t h t h e g r a i n , y/hen t h e l a r v a e r e a c h  maturity  they c o n s t r u c t " c h i p cocoons" i n t h e wood about V  i  n  depth  and p a r a l l e l t o t h e g r a i n . These c e l l s may be found i n t h e p a r t o f t h e stump l y i n g below ground l e v e l and throughout the r o o t system where t h e r o o t s a r e more t h a n i " i n d i a m e t e r . About 70$ o f t h e l a r v a e pupate i n t h e r o o t s a t a d i s t a n c e g r e a t e r t h a n one f o o t from t h e stump. A' few o f t h e p u p a l a r e made c o m p l e t e l y  w i t h i n t h e wood. When t h e p u p a l  complete t h e l a r v a e n c l o s e s entrance  cells  cell i s  i t s e l f w i t h i n i t by s e a l i n g t h e  w i t h l o n g e x c e l s i o r - l i k e c h i p s o f wood  obtained  w h i l e d i g g i n g t h e c e l l . A s h o r t p r e p u p a l p e r i o d o f about t h r e e days f o l l o w s , d u r i n g which t h e prepupa i s i n a c t i v e . A l t h o u g h P e i r s o n (82) and S a v e l y  (102)  s t a t e t h a t H.  p a l e s breeds i n p i n e l o g s a s w e l l as i n stumps, B e a l and M c C l i n t i c k (2) c l a i m t h a t t h i s i s not t h e case i n N o r t h C a r o l i n a , but t h a t i t breeds o n l y i n t h e r o o t s and stumps of d y i n g t r e e s . I n s o u t h e r n a t t r a c t e d t o the underside  O n t a r i o , t h e a d u l t w e e v i l s were o f f r e s h l y c u t p i n e l o g s , but  o n l y a few eggs were l a i d and none o f t h e r e s u l t i n g l a r v a e developed t o m a t u r i t y . T h i s i s p r o b a b l y low m o i s t u r e content  p a r t l y due t o t h e  o f t h e l o g s d u r i n g d r y p e r i o d s , and  p a r t l y t o c o m p e t i t i o n from immature s t a g e s and  o f p . approximatus  I p s r j i n i ( S a y ) , a b a r k b e e t l e t h a t a t t a c k s f r e s h l y cut.  73  p i n e l o g s i n l a r g e numbers. I n t h e t e n study t r e e s c u t i n 1956, about 80$ o f t h e H. p a l e s l a r v a e developed i n the r o o t s of the stump, w h i l e t h e r e m a i n i n g  20$ developed i n t h e p a r t  of t h e stump below t h e r o o t c o l l a r , i n and around t h e c r o t c h e s of t h e main r o o t s . Bark t r a p s and p o t t e d s e e d l i n g s s e t up i n the f i e l d  showed t h a t o v e r w i n t e r e d  adults, f e e d and s e a r c h  for  b r e e d i n g m a t e r i a l u n t i l about the t h i r d week i n June,  and  t h e n devote most o f t h e i r time t o egg l a y i n g i n dead o r  d y i n g stumps. The f e e d i n g damage i s l i g h t d u r i n g J u l y and August, but becomes heavy a g a i n i n mid-September when t h e new. a d u l t s b e g i n emerging. There a r e , t h e r e f o r e , two f e e d i n g periods p e r year,  one i n t h e s p r i n g and one i n t h e f a l l .  Following a c u t t i n g operation there are three f e e d i n g periods on s u r r o u n d i n g  regeneration before  the weevil  s u b s i d e s , a s r e p o r t e d by P e i r s o n (82)?  population  the f i r s t  i s i n the  s p r i n g f o l l o w i n g t h e c u t t i n g , by a d u l t s a t t r a c t e d t o t h e f r e s h l y cut stumps from t h e s u r r o u n d i n g in  the f a l l  a r e a ; t h e second i s  o f t h e same y e a r a f t e r t h e new a d u l t s have  emerged from t h e stumps; and t h e t h i r d i s i n t h e f o l l o w i n g s p r i n g by t h e l a r g e a d u l t p o p u l a t i o n t h a t o v e r w i n t e r e d i n the  area. P e i r s o n (82) s t a t e s t h a t t h e r e i s a mass f l i g h t  period  about mid-June from c u t - o v e r a r e a s , p a r t i c u l a r l y i n the t h i r d y e a r of i n f e s t a t i o n . T h i s h a b i t has n o t been noted i n s o u t h -  74  em  O n t a r i o . I t s h o u l d be remembered, however, t h a t P e i r s o n  was r e f e r r i n g t o w e e v i l p o p u l a t i o n s a s s o c i a t e d w i t h  lumbering  o p e r a t i o n s , so t h a t when t h e a v a i l a b l e b r e e d i n g m a t e r i a l was used up, the a d u l t w e e v i l s had t o move,,of n e c e s s i t y , t o a new a r e a f o r b r e e d i n g p u r p o s e s .  I n s o u t h e r n O n t a r i o , on t h e  o t h e r hand, t h e w e e v i l i s a s s o c i a t e d m o s t l y w i t h  Christmas  t r e e p l a n t a t i o n s , where s e l e c t i v e c u t t i n g i s p r a c t i s e d and a continuous  supply of breeding m a t e r i a l i s a v a i l a b l e t o the  w e e v i l . Under these c o n d i t i o n s i t i s not n e c e s s a r y f o r mass m i g r a t i o n t o take p l a c e . Limiting Factors? In a p i n e stand where white p i n e , r e d p i n e , and S c o t s p i n e grow i n a p p r o x i m a t e l y  e q u a l numbers, white p i n e stumps  were p r e f e r r e d over r e d and Scots p i n e stumps,as f e e d i n g and b r e e d i n g m a t e r i a l . Throughout the season about 5 5 $ of t h e a d u l t w e e v i l p o p u l a t i o n found  i n t h e s o i l was on white  pine  stumps, w h i l e 2 9 $ and 16$ were on r e d and S c o t s p i n e stumps r e s p e c t i v e l y . A p p a r e n t l y t h e l a y i n g h a b i t s o f t h e females a r e not a l t e r e d by t h e h o s t , f o r t h e number o f young l a r v a e found i n the stumps were always i n p r o p o r t i o n t o t h e number of l a y i n g females  i r r e s p e c t i v e of the h o s t .  S i n c e t h e eggs a r e l a i d  i n n i c h e s i n t h e i n n e r bark o f  the stumps and r o o t s , they a r e w e l l p r o t e c t e d from  environ-  75  mental hazards.  The  i n i t i a l l o s s o f 23$  of the eggs due  to  f a i l u r e t o h a t c h i s the o n l y f a c t o r s e r i o u s l y a f f e c t i n g egg  the  population. I n a r e a s where the w e e v i l p o p u l a t i o n i s heavy, c o m p e t i -  t i o n f o r f o o d i n the l a r v a l stage becomes s e r i o u s and cause the death of 70$  or more of the young l a r v a l  Dendroctonus v a l e n s Lee., p i n e t r e e s and p l e t e l y exclude  may  population.  a b a r k b e e t l e t h a t a t t a c k s weak  f r e s h l y cut stumps, may  a t times almost com-  the H. p a l e s p o p u l a t i o n from stumps. While  the l a r v a e a r e a c t i v e l y f e e d i n g t h e y a r e r e l a t i v e l y f r e e from a t t a c k by m i t e s . However, d u r i n g the p r e p u p a l i f m i t e s a r e s u c c e s s f u l i n e n t e r i n g the p u p a l may  inflict  period,  chamber,  a s u f f i c i e n t number of wounds t o k i l l  the  they pre-  pupa. About 2$ of the prepupae a r e k i l l e d i n t h i s manner. It  i s o n l y w i t h d i f f i c u l t y t h a t m i t e s can e n t e r the  pupal  c e l l s , f o r w h i l e the e x c e l s i o r - l i k e o u t e r l a y e r o f the cocoon" i s e a s i l y p e n e t r a t e d , c l o s e l y packed wood dust Braeonid  a second i n n e r l a y e r of  i s p r a c t i c a l l y impenetrable.  p a r a s i t e p l a y s a minor r o l e i n c o n t r o l l i n g  w e e v i l . The  r a t i o between t h i s p a r a s i t e and  emerging from stumps kept i n cages, was M o r t a l i t y i n the a d u l t stage was second o v e r w i n t e r i n g p e r i o d . About  36$  adult  about 1 %  "chip fine A  the  weevils 200.  heaviest during  the  of the young a d u l t  p o p u l a t i o n emerging i n the f a l l d i e d d u r i n g the f i r s t  winter  and about 45$  d u r i n g the second w i n t e r . The  remainder d i e d  d u r i n g the second growing season. None of the a d u l t s r e a r e d i n the i n s e c t a r y s u r v i v e d t o e n t e r a t h i r d p e r i o d of h i b e r nation. The most important  l i m i t i n g f a c t o r of H. p a l e s i s t h e  q u a n t i t y of a v a i l a b l e b r e e d i n g m a t e r i a l i n the f i e l d .  Until  r e c e n t y e a r s , damage t o p i n e s caused by the w e e v i l has been as e x t e n s i v e i n s o u t h e r n  not  Ontario as r e p o r t e d i n the  United States. This i s probably  due  t o the f a c t t h a t t h e r e  had been no l a r g e - s c a l e c u t t i n g o p e r a t i o n s of p i n e s i n the a r e a f o r some time, thus p r e v e n t i n g a b u i l d u p of the p o p u l a t i o n . S i n c e 1945, has  expanded g r e a t l y and  seven-, and  however, the Christmas  tree industry  l a r g e c u t t i n g o p e r a t i o n s of s i x - ,  e i g h t - y e a r - o l d t r e e s have been made d u r i n g  p a s t few y e a r s . The  stumps of these t r e e s , l e f t  t h a t i t now  the  occurs i n epidemic numbers i n Simcoe  'County and Durham County and  g e n e r a l l y i n the a r e a west of  a l i n e drawn through P o r t Severn and the damage i s h e a v i e s t , up  t o 40$  Trenton.  (52).  I n a r e a s where  o f the branches of  t o t e n - y e a r - o l d p i n e s have been k i l l e d the whole s t a n d  the  i n the  ground t o r o t , were h e a v i l y i n f e s t e d by H. p a l e s w i t h result  weevil  five-  or d i s c o l o u r e d over  77  E f f e c t on t h e Tree? H. p a l e s a d u l t s w i l l f e e d on t h e t e n d e r hark o f t w i g s and s m a l l branches o f p i n e s from t h e s e e d l i n g s t a g e up t o mature t r e e s . Tyhere t h e w e e v i l p o p u l a t i o n i s h i g h t h i s may result  i n t h e death o f s e e d l i n g s and young t r e e s up t o t e n  y e a r s of age, and o f i n d i v i d u a l branches on l a r g e r  trees.  The damage i s o f p a r t i c u l a r importance t o C h r i s t m a s t r e e growers, f o r the market v a l u e o f t r e e s i s g r e a t l y lowered by t h e p r e s e n c e o f damaged o r dead b r a n c h e s . SIGNS AND SYMPTOMS?  The f e e d i n g damage o f H. p a l e s i s  v e r y s i m i l a r t o t h a t o f H. r a d i c i s . The a d u l t s chew - s m a l l p i t s about  i n d i a m e t e r t h r o u g h t h e bark t o t h e wood.  Where h i g h p o p u l a t i o n s exist;-..the p i t s a r e so numerous t h a t t h e y j o i n t o g e t h e r t o form l a r g e r wound a r e a s t h a t  eventually  g i r d l e the stem o r b r a n c h . O f t e n t i m e s t h e bark o f s e e d l i n g s is  c o m p l e t e l y removed. F r e s h damage may be i d e n t i f i e d  readily,  but sap exuding from the wounds soon f i l l s up t h e s m a l l p i t s and upon s o l i d i f y i n g , h i d e s them by c o v e r i n g the branches w i t h r e s i n . G i r d l e d branches and t r e e s c a n be s p o t t e d a t a d i s t a n c e by t h e i r brown c o l o u r .  easily  78  PISSODES APPROXIMATES HOPK.  P i s s o d e s approximatus Hopkins ( 7 1 ) . BIOLOGY: B r i t t o n (10, 11, 1 3 ) ,  Wells (124), Anon  ( 1 ) , B o v i n g ( 9 ) , Plummer and P i l l s b u r y ( 9 3 ) , K n u l l (72, 7 3 ) , P e i r s o n  (88, 89), E a s t e r l i n g  (24), P e l t (35, 36, 48), Plumb (90, 91), Schaffner  (103), P e l t and Bromley (49, 50),  Stewart (116), P r i e n d  (55, 56), Bess ( 3 ) .  History? P. approximatus was d e s c r i b e d  i n 1911  by Hopkins ( 7 1 ) ,  who s t a t e d t h a t i t b r e d i n the t h i c k bark o f t h e t r e e , sometimes c a u s i n g  s e r i o u s damage t o t h e s a p l i n g s t a g e .  B o v i n g (9) d i s c u s s e d  I n 1929,  the taxonomic d i f f e r e n c e s between t h e  mature l a r v a e of p . ^approximatus and P. s t r o b i . Plummer and 1  pillsbury  (93) r e p o r t e d  the two w e e v i l s  t h a t a l t h o u g h the b r e e d i n g h a b i t s ' of  d i f f e r e d t h e i r seasonal  h i s t o r i e s were  s i m i l a r , , and suggested t h a t t h e y might p r o v e t o be one  very species  s i n c e they had been s u c c e s s f u l i n r e a r i n g P. s t r o b i e x p e r i mentally  i n the t r u n k s of weakened t r e e s . That t h e y a r e  i n d e e d d i f f e r e n t s p e c i e s i s shown by the d i f f e r e n c e i n t h e i r chromosome numbers ( S . G. Smith, unpub.,) and the absence from P, s t r o b i of the chromosomal polymorphism r e p o r t e d i n  79  (113).  P. approximatus  The  importance of p . approximatus as  a secondary p e s t i n a r e a s where p i n e s have been weakened by d e f o l i a t o r s , bark b e e t l e s , or by t r a n s p l a n t i n g , has p o i n t e d out by E a s t e r l i n g ( 2 4 ) , P e l t and  Stewart  (36),  been  Schaffner  (116).  There i s at p r e s e n t  o n l y scant i n f o r m a t i o n a v a i l a b l e  on the bionomics of t h i s w e e v i l , and  i t s present  status i n  the n o r t h e a s t e r n U n i t e d S t a t e s i s not c l e a r , a l t h o u g h (69)  Holt  has r e p o r t e d t h a t i t i s becoming an i n c r e a s i n g l y s e r i o u s  p e s t i n c o n i f e r o u s p l a n t a t i o n s i n the S t a t e of D e s c r i p t i o n of L i f e H i s t o r y ADULT: c u l i o n i d and  The a d u l t P. approximatus i s a t y p i c a l c l o s e l y resembles P.  from 2 to 3 mm.  i n width.  The  than l o n g e r the males. The  brown, d a r k e n i n g The p r o t h o r a x , white and  Pennsylvania.  Stages;  strobi  i n l e n g t h and  females a r e , on the  average,  newly emerged a d u l t i s medium  t o almost b l a c k a f t e r h a v i n g  e l y t r a , and  cur-  ( p i g . 21). I t v a r i e s  c o n s i d e r a b l y i n s i z e , b e i n g from 5 t o 8 mm.  1 mm.  (102),  overwintered.  l e g s a r e marked w i t h t u f t s  of  reddish-brown s c a l e s grouped t o form s e v e r a l s m a l l  spots on the p r o t h o r a x  and u s u a l l y two  the e l y t r a . The  snout  the p r o t h o r a x ,  curved  i r r e g u l a r bands a c r o s s  i s s l e n d e r and  about as l o n g  as  w i t h the antennae a t t a c h e d about mid-way a l o n g  i t s l e n g t h . Hopkins (71)  s e p a r a t e s P. approximatus from p .  F i g . 21. P i s s o d e s adult  s t r o b i by the  approximatus  xl2.  "average l a r g e s i z e , e l o n g a t e  body, the  of the e l y t r a more d i s t i n c t l y narrowed p o s t e r i o r l y . i s longer,  the spots  of the  the p o s t e r i o r ones r a r e l y EGG:  The  l e n g t h and  egg  0.50  e l y t r a are uniformly  0.03  mm.  The  beak  smaller,  connected".  i s ovoid and measures 0.80 t  sides  i n d i a m e t e r . The  ± 0.04  mm.  shape of  in the  2 <  o a. UJ  m  •30  .46  .63  .79  .96  1.12  1.29  1.45  HEAD CAPSULE WIDTHS IN MM.  Pig,  22. D i s t r i b u t i o n of head c a p s u l e measurments o f  p i s s o d e s approximatus l a r v a e .  egg v a r i e s c o n s i d e r a b l y , some b e i n g almost  s p h e r o i d . The  volume o f t h e egg, however, i s r e l a t i v e l y c o n s t a n t . When first laid  i t i s almost  c o l o u r l e s s w i t h a smooth g l i s t e n i n g  chorion, LARVA.: fully  The l a r v a i s t y p i c a l l y c u r c u l i o n i d i n form, When grown i t i s about 12 mm,  i n length with a l i g h t  brown  head and a white body. The 42 w e e v i l s r e a r e d from eggs i n  •the i n s e c t a r y a l l passed t h r o u g h f o u r l a r v a l i n s t a r s . F i g . 22 i l l u s t r a t e s the d i s t r i b u t i o n o f measurments o f head c a p s u l e  TABLE YI Comparison between observed head c a p s u l e widths o f p i s s o d e s approximatus l a r v a e by u s i n g Dyar's Rule and on the b a s i s of a l i n e a r r e g r e s s i o n r e l a t i o n s h i p Instar  i  Dyar' s Rule  Observed width  s CalcuCalcu- $ P e r cent \ >, l a t e d lated : error ! width width j • •  I II  J!  !  III IV  iI #> m  0.354  ' Linear regression  :  •  0.512  *  0.534 ?  -4.3  \;  0.568  0.755  • • •  0.805 i  -6.6  :  0.852  1.215  +0.2  !t  1.135  $ * * *  I  P e r cent error  p;285  • •  1.218  *  +19.5 # 0*  •  -10.9 -12.9  »  * #  • •  +  w i d t h of r e a r e d l a r v a e a s t h e y d e v e l o p e d t h r o u g h each from the egg t o the p u p a l s t a g e . A. f i e l d the  las.t i n s t a r by measuring the head  pupae c o l l e c t e d i n the f i e l d  6.8  instar  check was made on  c a p s u l e s o f 112 p r e -  from c h i p cocoons. The  p o l y g o n i n P i g . 22 r e p r e s e n t s t h e s e measurments and  hatched indicates  good agreement w i t h measurments of the r e a r e d m a t e r i a l . T a b l e VI shows a comparison between the observed head c a p s u l e widths and t h o s e e s t i m a t e d u s i n g Dyar's Rule and on the b a s i s of  a l i n e a r r e g r e s s i o n r e l a t i o n s h i p . I t i s e v i d e n t t h a t the  i n c r e a s e i n w i d t h from  one  i n s t a r t o the next f o l l o w s Dyar's  Rule more c l o s e l y t h a n the l i n e a r r e g r e s s i o n suggested Ghent (59) PUPA?  for certain  sawflies.  The pupa i s c o m p l e t e l y white when f i r s t  but the mandibles,  by  formed,  eyes, rostrum, p r o t h o r a x , and l e g s become  medium brown b e f o r e a d u l t emergence.  D i s t r i b u t i o n and  Hosts?  I n h i s o r i g i n a l d e s c r i p t i o n , Hopkins (71) r e p o r t e d the f o l l o w i n g p i n e s as h o s t p l a n t s ? Pinus strobus L. " rigida M i l l . " banksiana Lamb. " echinata M i l l . " resinosa/JLit. " virginiana M i l l . " pungens Lamb.  E a s t e r n white p i n e . Pitch pine. Jack p i n e . Shortleaf pine. Red p i n e . Virginia pine. T a b l e mountain p i n e ,  It. has s i n c e been r e p o r t e d b r e e d i n g i n Mugho p i n e (48)  and  S c o t s p i n e (90, 116). Hopkins r e c o r d e d i t s d i s t r i b u t i o n as Wisconsin, M i c h i g a n , P e n n s y l v a n i a , New Massachusetts,  Virginia,  i n the U n i t e d S t a t e s , and 1911,  York, Mew  Hampshire,  West V i r g i n i a , and North C a r o l i n a s o u t h e r n O n t a r i o i n Canada. S i n c e  P. approximatus has a l s o been r e c o r d e d i n C o n n e c t i c u t  (10) and Ohio ( 2 4 ) . I n O n t a r i o , the a u t h o r has w e e v i l a t w i d e l y s c a t t e r e d p o i n t s throughout  collected  the  southern  the  STAGE  WIN.  MAY  JUNE  JULY  ^>^< ADULT  EGG  lip  LARVA  IP  PUPA  AUG.  SEPT.  OCT.  WIN.  MAY  JUNE  JULY  HP  AUG.  SEPT.  OCT.  WIN.  1  • m  ADULT  wk EGG  LARVA  PUPA  ADULT  IIP  wk  B  wk  III  lip « lip  IP  1 i i —™  •  P i g . 23. Seasonal h i s t o r y o f p i s s o d e s a p p r o ximatus i n s o u t h e r n O n t a r i o .  p a r t o f the p r o v i n c e .  Seasonal H i s t o r y ? I n s o u t h e r n O n t a r i o , P. approximatus o v e r w i n t e r s i n the l a r v a l , p u p a l , and a d u l t s t a g e s . T h i s , t o g e t h e r w i t h the f a c t t h a t t h e r e i s a l o n g o v i p o s i t i o n p e r i o d , l e a d s t o a complicated seasonal h i s t o r y with generations of both  85  one and two y e a r s d u r a t i o n ( F i g . 2 3 ) . The m a j o r i t y o f t h e p o p u l a t i o n o v e r w i n t e r s i n t h e a d u l t s t a g e . The  remainder  o v e r w i n t e r s i n t h e l a r v a l and p u p a l s t a g e s t o emerge as a d u l t s i n l a t e June and J u l y o f t h e f o l l o w i n g y e a r and o v e r w i n t e r once a g a i n . The o v e r w i n t e r i n g a d u l t p o p u l a t i o n t h u s c o n s i s t s o f the progeny of t h e p r e v i o u s w i n t e r ^ s ing  a d u l t s , p l u s a d u l t s developed  overwinter-  d u r i n g t h e p r e v i o u s summer  from o v e r w i n t e r e d l a r v a e and pupae. I n t h e s p r i n g , o v e r w i n t e r e d a d u l t s from t h e s e two s o u r c e s a r e i n d i s t i n g u i s h a b l e . The f i r s t egg was found  i n the f i e l d  d u r i n g t h e 1956  growing season on. May 26, w h i l e i n t h e i n s e c t a r y t h e f i r s t egg was l a i d of  on June 13. Most o f t h e females  laytheir  quota  eggs b e f o r e t h e end o f t h e f i r s t week o f J u l y and t h e n  die.  The a d u l t p o p u l a t i o n i n t h e f i e l d ,  r a p i d l y e a r l y i n J u l y , but a few females until  early  therefore, declines continue  laying  September.  The developmental  p e r i o d o f t h e 42 w e e v i l s r e a r e d from  egg t o a d u l t i n 1956, was about 60 days. T a b l e V I I shows t h e average  d u r a t i o n o f t h e egg s t a g e , t h e f o u r l a r v a l  instars,  and t h e p u p a l stage o f i n s e c t s r e a r e d i n a n unheated  insectary  d u r i n g t h e summer months.  Habits? The a d u l t w e e v i l s o v e r w i n t e r i n t h e d u f f and t o p s o i l  86  o v e r l y i n g t h e r o o t s and under s c a l e s and i n c r e v i c e s o f t h e rough o u t e r hark of p i n e t r e e s . They emerge i n e a r l y May and f e e d f o r about t h r e e weeks on t h e i n n e r b a r k of p i n e and  on the stem o f s e e d l i n g s and s m a l l t r e e s . The  branches  underside  of l o w - l y i n g branches i n c o n t a c t w i t h t h e l i t t e r a r e p a r t i c u l a r l y a t t r a c t i v e as f e e d i n g  sites.  TABLE V I I The d u r a t i o n o f the immature s t a g e s of P i s s o d e s approximatus r e a r e d i n a n unheated i n s e c t a r y d u r i n g the summer months Stage  Time (days)  J  • •  Egg  #  1st  instar  2nd  instar  3rd  instar  4th  instar  «-0  8.6 + 1.6 3.6 + 0.5 3.9  + 0.8  %  4.9 + 0.9  %  24.0 + 6.1 14.8 + 0.7  Pupa «*  During  the l a t t e r h a l f of May, t h e r e i s a mass f l i g h t  p e r i o d when the w e e v i l s  search f o r s u i t a b l e breeding m a t e r i a l .  M a t i n g takes p l a c e a t t h i s time and o v i p o s i t i o n b e g i n s  about  l a t e May, Dead or d y i n g t r e e s of a l l age c l a s s e s from one-  87  and t w o - y e a r - o l d s e e d l i n g s t o mature t r e e s may  be a t t a c k e d  from the r o o t s up t o branches as s m a l l as •§-" i n d i a m e t e r . In  s e e d l i n g s , where the b a r k i s t o o t h i i t t o accommodate  mature l a r v a e , t h e l a r v a e bore t o the c e n t e r of the stem, where t h e y  pupate.  The eggs may  be l a i d  throughout  the t r u n k and  large  branches, but the rougher bark a t the b r a n c h nodes seems t o be p r e f e r r e d . I n the i n s e c t a r y , 12 females l a i d a n of  49 eggs each, w i t h one l a y i n g 102. The  average  eggs a r e deposited,  i n pockets; chewed i n the i n n e r bark by the f e m a l e s . They a r e normally l a i d groups  i n d i v i d u a l l y i n the p o c k e t s , but  of f o u r or f i v e eggs may  be found t o g e t h e r .  The newly hatched l a r v a e a r e v e r y s m a l l , about  1 mm.  frequently  i n l e n g t h . Immediately  measuring  upon h a t c h i n g t h e y b e g i n s  f e e d i n g i n the c a m b i a l l a y e r . They n o r m a l l y mine i n e i t h e r d i r e c t i o n a l o n g the g r a i n o f t h e wood u n l e s s i n t e r r u p t e d o b s t a c l e s , i n which case t h e y e i t h e r change d i r e c t i o n 180  o  by  through  * or work around the o b s t a c l e and c o n t i n u e w i t h the g r a i n  of the wood ( P i g . 2 4 ) . y«4ien the l a r v a e a t t a i n m a t u r i t y , t h e y c o n s t r u c t c h i p cocoons  t y p i c a l of the genus P i s s o d e s i n t h e  o u t e r s u r f a c e of the wood ( P i g . 2 5 ) . P u p a l development t a k e s p l a c e i n these chambers and r e q u i r e s t h r e e or f o u r days. Newly formed  a d u l t s remain i n the p u p a l chambers about  days b e f o r e chewing t h e i r way  t o t h e o u t s i d e , when t h e  five cuticle  88  Pig.  24. L a r v a of p i s s o d e s  roximatus i n r e a r i n g . Note mines p a r a l l e l  app-  larval  t o the g r a i n of the  bark.  soon hardens and darkens t o a medium brown. The f i r s t  adult  emerged i n cages i n 1 9 5 6 on J u l y 2 6 f o l l o w e d by a s u s t a i n e d h i g h emergence from about August 1 5 t o September r a t i o of emerging a d u l t s was  1 0 . The sex  a p p r o x i m a t e l y 1 j 1 . The  new  a d u l t s feed from the time of emergence u n t i l the onset of c o l d weather, but the females do not mate or o v i p o s i t the  until  f o l l o w i n g summer. Logs i n f e s t e d i n June, 1 9 5 6 , produced an average of  2 1 6 a d u l t s p e r square f o o t  of bark, w h i l e l o g s i n f e s t e d i n  Pig.  25. "Chip cocoons" of p i s s o d e s approximatus  showing, (a) one c e l l i n t a c t and (b) a n o t h e r t o r e v e a l the prepupa i n s i d e . Note t h e c o v e r i n g o f the  cells.  opened  excelsior-like  90  ,91  e a r l y September produced o n l y 51 a d u l t s p e r square f o o t . I t must be remembered, however, t h a t the r e l a t i v e p e r c e n t a g e of  each stage o v e r w i n t e r i n g depends t o a l a r g e extent  on  the  time of the y e a r the b r e e d i n g m a t e r i a l becomes a v a i l a b l e t o the w e e v i l s . I n s o u t h e r n O n t a r i o , where l a r g e p o p u l a t i o n s the w e e v i l a r e u s u a l l y a s s o c i a t e d w i t h Christmas  tree  cutt-  i n g s , the stumps of t r e e s cut i n the f a l l a r e invaded l a t e May  and  e a r l y June the f o l l o w i n g y e a r , and  i n a l a r g e emergence of a d u l t s i n August and  this  of  in results  September,  B r e e d i n g m a t e r i a l a v a i l a b l e l a t e r i n the summer i s r e l a t i v e l y l i m i t e d , r e s u l t i n g i n o n l y a few  overwintering larvae  and  pupae?.  L i m i t i n g Factors? S i n c e P. approximatus i s a secondary i n s e c t of  incapable  a t t a c k i n g h e a l t h y p i n e s s u c c e s s f u l l y , the main f a c t o r  l i m i t i n g i t s p o p u l a t i o n d e n s i t y i s the a v a i l a b i l i t y of  suit-  a b l e b r e e d i n g m a t e r i a l . Under n a t u r a l c o n d i t i o n s t h i s , f a c t o r keeps the w e e v i l p o p u l a t i o n low. grown i n pure stands and left  i n the f i e l d  I n a r e a s where p i n e s  are  the stumps of h a r v e s t e d t r e e s a r e  t o r o t , however, p o p u l a t i o n s r a p i d l y  build  up t o epidemic p r o p o r t i o n s . S e v e r a l o t h e r f a c t o r s of l e s s e r importance operate c o n t r o l l i n g the p o p u l a t i o n of p . approximatus . D u r i n g  the  in  92  P i g . 26. Stem of a red p i n e  i n f e s t e d with  approximatus ( p u p a l  1956  growing season up  three-inch Pissodes  stage).  t o 3 5 $ of the l a r v a l p o p u l a t i o n  k i l l e d by a v i p i o n i d e c t o - p a r a s i t e b e l o n g i n g Coeloides.  Sap  suckers  and  a b l e importance. They are of l a r v a e , pupae, and  to the  woodpeckers are a l s o of  was  genus consider-  capable of d e v o u r i n g l a r g e numbers  a d u l t s from under the bark, p a r t i -  c u l a r l y i n t r e e s where the stem i s h e a v i l y i n f e s t e d t h r o u g h out i t s l e n g t h ( P i g .  2 6 ) .  In  I 9 5 6  the downy woodpecker,  F i g . 27. F o u r - i n c h Scots p i n e stump i n f e s t e d w i t h p i s s o d e s approximatus and p a l e s ( p u p a l s t a g e ) . The above ground l e v e l i s due  l a c k of p u p a l to  Hylobius cells  competition  from bark b e e t l e s .  Dendrocopus pubescens medianus (Swainson), 90$  d e s t r o y e d up  to  of the w e e v i l p o p u l a t i o n i n i n d i v i d u a l t r e e s by com-  p l e t e l y s t r i p p i n g the bark from the stem and l a r g e branches i n s e a r c h of f o o d . Weevil p o p u l a t i o n s i n stumps, however, were found t o be p r a c t i c a l l y f r e e from a t t a c k by b i r d s ( F i g . 27); t h e y a r e n e v e r t h e l e s s s u b j e c t t o s e r i o u s c o m p e t i t i o n from two pini  bark b e e t l e s , Dendroctonus v a l e n s L e c . and  ( S a y ) , and H.  pales.  Ips  94  Effect  on t h e Tree? A l t h o u g h P. approximatus n o r m a l l y breeds i n dead o r  d y i n g p i n e m a t e r i a l , i t c a n s u c c e s s f u l l y a t t a c k s e e d l i n g s ., and weak t r e e s f o r b r e e d i n g purposes, d i e . T h i s type  causing the p l a n t s to  o f damage was p a r t i c u l a r l y n o t i c e a b l e i n  seedlings of A u s t r i a n pine i n the Midhurst  Nursery,  where  about 9fo were k i l l e d by t h e w e e v i l i n 1956. R e c e n t l y t r a n s p l a n t e d f i v e - t o t e n - y e a r - o l d ornamental s t o c k was a l s o h e a v i l y a t t a c k e d i n t h e Angus a r e a i n 1956 and 1958. SIGNS AND SYMPTOMS? roximatus a n  ^  F r e s h f e e d i n g wounds made by P. app-  a r e somewhat d i f f e r e n t from those made by H. r a d i c i s  S» p a l e s . Ihereas t h e H y l o b i u s a d u l t s chew i r r e g u l a r  p i t s i n b o t h the o u t e r and i n n e r bark, p . approximatus l e a v e s the o u t e r bark i n t a c t except  f o r small punctures  through  which i t i n s e r t s i t s beak and chews out l a r g e r a r e a s o f t h e i n n e r b a r k . This, makes t h e f e e d i n g damage o f P. approximatus l e s s n o t i c e a b l e when i t i s f r e s h , but when t h e b a r k on t h e i n j u r e d twigs become weathered t h e o u t e r b a r k f l a k e s o f f and t h e f e e d i n g damage resembles t h a t o f t h e o t h e r s p e c i e s .  95  DISCUSSION AND  CONCLUSIONS  At the time when the p r e s e n t taken, a v a i l a b l e i n f o r m a t i o n on H. P. approximatus was the New  based m a i n l y  i n v e s t i g a t i o n s were u n d e r r a d i c i s , H, p a l e s ,  and  on o b s e r v a t i o n s made i n  E n g l a n d S t a t e s , M i n n e s o t a , and  W i s c o n s i n and a p p l i e d  t o problems somewhat d i f f e r e n t from those  i n southern  Ontario,  I t became apparent a t t h a t time t h a t c o n d i t i o n s brought about p r i m a r i l y by the Christmas  tree i n d u s t r y during the  previous  t e n y e a r s were i d e a l f o r the b u i l d u p of l a r g e w e e v i l t i o n s and t h a t t h i s p r e s e n t e d  popula-  a serious threat to p l a n t a t i o n  grown p i n e s , whether p l a n t e d as Christmas  t r e e s or i n county  forests. I n the p r e s e n t work t h e p r e v i o u s i n f o r m a t i o n  existing  on the t h r e e w e e v i l s has been brought t o g e t h e r and i n t e r p r e t e d i n the l i g h t ecology  of o b s e r v a t i o n s made i n s o u t h e r n  Ontario,  The  of the w e e v i l complex has been i n v e s t i g a t e d t o the  e x t e n t t h a t the bionomics and understood,  and  cause of outbreaks  are w e l l  the main l i m i t i n g f a c t o r s of the w e e v i l /  p o p u l a t i o n s , a r e known. With t h i s newly a c q u i r e d knowledge, i t i s p o s s i b l e t o a p p r a i s e the w e e v i l problem i n s o u t h e r n not p o s s i b l e p r e v i o u s l y , and  O n t a r i o i n a manner  t o draw c e r t a i n  conclusions  and make recommendations on p r a c t i c a l methods of growing  •  p i n e s i n pure stands r e l a t i v e l y f r e e from w e e v i l a t t a c k . B a s i c a l l y , t h e w e e v i l problem i n s o u t h e r n O n t a r i o i s of a s i l v i c u l t u r a l n a t u r e . The t h r e e w e e v i l s a r e n a t i v e s p e c i e s and a r e not known t o occur i n l a r g e numbers where p i n e s a r e grown i n pure s t a n d s  except  o r where l a r g e c u t t i n g  o p e r a t i o n o f p i n e s have t a k e n p l a c e . H. r a d i c i s d i f f e r s i n h a b i t s from H. p a l e s and P. approximatus m a i n l y i n t h a t i t a t t a c k s and breeds i n h e a l t h y p i n e s , w h i l e the l a t t e r two s p e c i e s breeds o n l y i n dead o r decadent p i n e m a t e r i a l . S i n c e H. r a d i c i s occurs i n epidemic  number o n l y i n puref stands  where e x o t i c p i n e s such as S c o t s , A u s t r i a n , o r mugho a r e p r e s e n t i n l a r g e numbers, one method o f c o p i n g w i t h the weev i l i s t o a v o i d the p l a n t i n g o f p i n e s i n such m i x t u r e s . i s not always d e s i r a b l e , however, f o r i n s o u t h e r n  Ontario  Scots p i n e has a g r e a t e r market v a l u e as a C h r i s t m a s than any o t h e r s p e c i e s and i s c o n s e q u e n t l y  This  tree  grown e x t e n s i v e l y  i n pure s t a n d s . I n such a r e a s i t may be n e c e s s a r y t o c o n t r o l H. r a d i c i s by means o t h e r than s i l v i c u l t u r a l . I t was  found  i n the p r e s e n t s t u d i e s t h a t the a p p l i c a t i o n o f b i o l o g i c a l c o n t r o l s would not be p r a c t i c a l , s i n c e a l l s t a g e s o f t h e w e e v i l a r e w e l l p r o t e c t e d from p r e d a t o r s , p a r a s i t e s , and f u n g i . Stewart  (117) r e p o r t s t h a t he o b t a i n e d 100$ c o n t r o l  of H. r a d i c i s i n f e s t i n g S c o t s p i n e i n s o u t h e r n O n t a r i o , by a p p l y i n g a d i e l d r i n s p r a y a t t h e b a s e o f t h e t r e e s . He has  97  a l s o communicated d i r e c t l y w i t h t h e a u t h o r t h a t one a p p l i c a t i o n o f t h i s i n s e c t i c i d e i s e f f e c t i v e i n p r o t e c t i n g the t r e e s from r e - i n f e s t a t i o n f o r a p e r i o d  o f up t o t h r e e  y e a r s . The  main o b j e c t i o n t o t h e c h e m i c a l c o n t r o l suggested by Stewart i s t h a t l a r g e q u a n t i t i e s o f water a r e needed f o r t h e s p r a y . S i n c e most p i n e p l a n t a t i o n s a r e l o c a t e d on h i g h ,  well-drained,  sandy s o i l s , the water problem i s o f paramount importance and u s u a l l y ..prohibits the u s e o f the recommended c o n t r o l . Therefore, Ontario  a p r a c t i c a l c o n t r o l f o r H. r a d i c i s i n s o u t h e r n  has n o t y e t been a c h i e v e d . T h i s i s t r u e  i n county f o r e s t s where p i n e s a r e p l a n t e d for  i n t h i s instance  particularly  t o grow t o m a t u r i t y ,  i t i s possible that several a p p l i c a t i o n  of i n s e c t i c i d e would be needed d u r i n g t h e l i f e  of the t r e e  t o p r e v e n t r e - i n f e s t a t i o n . However, when c o n s i d e r i n g  pines  grown f o r the Christmas t r e e market i t i s p o s s i b l e t h a t one a p p l i c a t i o n o f i n s e c t i c i d e would s u f f i c e . H. r a d i c i s not  a t t a c k t r e e s l e s s t h a n 1-fe- i n c h e s  height  (6 i n c h e s  i n d i a m e t e r a t stump  above ground), and a t r e e o f t h i s s i z e  ( u s u a l l y f o u r o r f i v e y e a r s o l d ) needs o n l y t h r e e years p r o t e c t i o n before Since Ontario  will  or four  c u t t i n g f o r market.  t h e a r e a i n f e s t e d by H. r a d i c i s i n s o u t h e r n  i s s t i l l a c t i v e l y expanding, i t was not p o s s i b l e t o  determine the f a c t o r s l i m i t i n g i t s d i s t r i b u t i o n . However, it  iwould'iseem  t h a t the s o i l e x e r t s  some i n f l u e n c e on the  98  i n s e c t , f o r a l l known i n f e s t a t i o n s i n the a r e a a r e to l i g h t  confined  sandy s o i l s of low f e r t i l i t y . T h i s i s i n agreement  with reports by,Schaffner  and M c l n t y r e  (109)  i n the  United  S t a t e s . P r e l i m i n a r y work done on the s o i l i n the Angus a r e a d u r i n g 1958  i n d i c a t e s t h a t t e x t u r e i s not  the o n l y f a c t o r  i n v o l v e d , f o r the w e e v i l i s c o n s p i c u o u s l y absent a r e a s where the s o i l i s l i g h t and  from  certain  sandy, a l t h o u g h heavy i n -  f e s t a t i o n s abound i n the immediate v i c i n i t y . I t i s p o s s i b l e t h a t a combination t e n t , and  o f f a c t o r s such as t e x t u r e , m o i s t u r e  con-  s o i l r e a c t i o n are a c t i n g together i n l i m i t i n g  the  d i s t r i b u t i o n o:g the w e e v i l . H. p a l e s and p . approximatus both breed decadent p i n e m a t e r i a l and  i n dead or  attack healthy t r e e s only  as  a d u l t s f o r f e e d i n g p u r p o s e s . T h e r e f o r e , a l a r g e amount of breeding m a t e r i a l i s necessary to  f o r the w e e v i l t o i n c r e a s e  epidemic numbers. I n n a t u r a l stands where the w e e v i l  occurs  i n s m a l l numbers, the f e e d i n g damage i s n e g l i g i b l e and u s u a l l y not n o t i c e d . I t i s the l a c k of a sound s a n i t a t i o n program i n Christmas  t r e e p l a n t a t i o n s and  county f o r e s t s t h a t  brought about the p r e s e n t problem i n s o u t h e r n The  c u t t i n g methods u s e d by Christmas  has  Ontario.  t r e e growers  poses s e r i o u s problems t o a sound s a n i t a t i o n program. Normally p i n e s a r e cut as Christmas  t r e e s between the  of s i x and nine y e a r s i n t h r e e s u c c e s s i v e y e a r s . The  ages first  99  year a l i g h t  cut i s made of the more advanced t r e e s .  The  second y e a r a heavy cut i s made of most of the merchantable trees followed  by a clean-up out i n the t h i r d y e a r . U s u a l l y  the a r e a i s r e p l a n t e d  d u r i n g the f o u r t h y e a r by p l o w i n g a  f u r r o w between the rows of stumps t o r e c e i v e the new T h i s means t h a t f o r t h r e e f r e s h stumps are  left  by H. p a l e s and P.  consecutive  plants.  y e a r s l a r g e numbers of  i n the ground t o r o t and  be  infested  approximatus. Under t h i s c u t t i n g system  the Christmas t r e e grower i s h e s i t a n t t o p u l l stumps a f t e r the f i r s t  and  second cut f o r f e a r of damaging the  remaining  t r e e s . Furthermore, many p l a n t a t i o n s a r e l o c a t e d on  land  covered w i t h l a r g e b o u l d e r s over which a t r a c t o r c o u l d be  not  operated. I n view of the f a c t t h a t Christmas t r e e growers a r e  h e s i t a n t i n p u l l i n g stumps a f t e r each cut f o r p r a c t i c a l w e l l as f i n a n c i a l r e a s o n s , an a l t e r n a t i v e s o l u t i o n t o  as  the  s a n i t a t i o n problem i s d e s i r a b l e . I t i s p o s s i b l e t h a t i n f e s t a t i o n s would be p r e v e n t e d i f the stumps and cut d u r i n g the f i r s t  and  trees  second y e a r a r e kept a l i v e by  the bottom whorl of l a r g e branches on the p u l l i n g a l l the  roots of  leaving  stumps, and .then  stumps a f t e r the t h i r d c u t w i t h a  bulldozer  or t r a c t o r . I n c o n s i d e r i n g c h e m i c a l c o n t r o l s of H. p a l e s and approximatus  t  i t i s conceivable  t h a t an i n s e c t i c i d a l  P.  spray  100  a p p l i e d -to the p a r t of the stump above ground l e v e l , would kill  the g r e a t e r p a r t of the P.  approximatus p o p u l a t i o n  when i t emerges as a d u l t s . However, s i n c e over 60$  of H.  pupate i n the r o o t s a t a d i s t a n c e i n excess of one  f o o t from  the stump and necessary  pales  emerge d i r e c t l y t h r o u g h the s o i l , i t would  t o s p r a y the s o i l  be  o v e r l y i n g the r o o t s as w e l l as  the stumps t o c o n t r o l t h i s s p e c i e s . I n a Christmas t r e e p l a n t a t i o n t h i s would mean s p r a y i n g the whole ground once f o r every crop grown, f o r the r o o t system of a d j a c e n t lap to a considerable The  l a r g e q u a n t i t y of water and  considered  i n s e c t i c i d e needed f o r and  o n l y as an emergency measure where a  crop w i l l be l o s t  over-  extent.  t h i s c o n t r o l makes i t u n s u i t a b l e f o r g e n e r a l use be  trees  should  valuable  i f s u b j e c t e d t o one more f e e d i n g s e a s o n .  S p r a y i n g the f o l i a g e of t r e e s t o p r o t e c t the branches from a d u l t f e e d i n g i s even more i m p r a c t i c a l , f o r an a p p l i c a t i o n of i n s e c t i c i d e would have t o be a p p l i e d every y e a r t o a l l the t r e e s i n the s t a n d . T h i s would mean about e i g h t a p p l i c a t i o n s p e r crop and would c r e a t e an expense t h a t the growers c o u l d not  bear. P l a n t a t i o n grown p i n e  i s s u b j e c t t o a t t a c k by a number  of d e s t r u c t i v e i n s e c t s . The  w e e v i l complex d i s c u s s e d i n t h i s  t h e s i s i s , perhaps, the most r e c e n t such problem t o economic importance i n s o u t h e r n  attain  Ontario. Since i n s e c t s u s u a l l y  101  become p r o b l e m a t i c wherever p l a n t s a r e grown i n c o n c e n t r a t e d numbers as a c r o p , i t o f t e n becomes n e c e s s a r y  either to  for-  mulate s u i t a b l e d i r e c t c o n t r o l s f o r the p e s t s , or t o d e s i s t the p l a n t i n g of pure s t a n d s . S i l v i c u l t u r a l c o n t r o l s are u s u a l l y more d e s i r a b l e t h a n d i r e c t c o n t r o l s , f o r t h e y tend t o prevent  i n s e c t outbreaks,  while d i r e c t  c o n t r o l s are g e n e r a l l y  a p p l i e d o n l y a f t e r the i n s e c t s have reached t i o n s . There a r e reasons  epidemic  propor-  to b e l i e v e that s i l v i c u l t u r a l  con-  t r o l s c o u l d be used s u c c e s s f u l l y a g a i n s t the w e e v i l s d i s c u s s e d h e r e . I n the Christmas  t r e e i n d u s t r y , the p u b l i c demand f o r  a s p e c i f i c s p e c i e s of p i n e or o t h e r c o n i f e r i s c r e a t e d l a r g e l y by the grower. I n the M a r i t i m e P r o v i n c e s the p r a c t i c e i s t o grow balsam f i r ;  i n s o u t h e r n O n t a r i o Scots p i n e ; and i n  n o r t h e r n O n t a r i o s p r u c e s . S t r a n g e l y enough most o f these t r e e s a r e s o l d t o a common d i s t a n t market i n the U n i t e d S t a t e s . I t i s the b e l i e f of the a u t h o r t h a t i t would be p r o f i t a b l e f o r growers t o operate  c o - o p e r a t i v e l y , p l a n t i n g a crop of mixed  c o n i f e r s i n s t e a d of o n l y one the ravages  s p e c i e s . T h i s would l i m i t g r e a t l y  of s e v e r a l i n s e c t p e s t s t h a t have become i n c r e a s -  i n g l y important  i n p l a n t a t i o n s d u r i n g the p a s t f i f t y  years,  by r e d u c i n g the d e n s i t y of t h e i r f a v o r i t e f o o d or b r e e d i n g material. The w e e v i l problem on p i n e s i n s o u t h e r n O n t a r i o e x i s t s , and the Christmas  still  tree industry i s seriously threa-  102  tened i n s e v e r a l a r e a s . There i s a need f o r f u r t h e r e c o l o g i c a l i n v e s t i g a t i o n s t o determine f a c t o r s as s o i l ,  climate,  the importance  of such  s t a n d c o m p o s i t i o n , and management  as they a f f e c t w e e v i l d e n s i t y and the Christmas t r e e  industry.  103  BIBLIOGRAPHY  (1)  ANON.  1927.  The  r e l a t i o n of i n s e c t s t o s l a s h d i s p o s a l .  TJ. S. Dept. Agr., (2)  BEAL, J . A.,  AND  C i r c . 411.  12. 1943.  K. B. McCLINTICK.  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