UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The anthracnose disease of daphne mezereum caused by Marssonina daphnes (Desm et Rob.) Mag 1939

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
UBC_1939_A4_M3_A4.pdf
UBC_1939_A4_M3_A4.pdf [ 18.69MB ]
Metadata
JSON: 1.0105233.json
JSON-LD: 1.0105233+ld.json
RDF/XML (Pretty): 1.0105233.xml
RDF/JSON: 1.0105233+rdf.json
Turtle: 1.0105233+rdf-turtle.txt
N-Triples: 1.0105233+rdf-ntriples.txt
Citation
1.0105233.ris

Full Text

' THE ANTHRACNOSE DISEASE.' OT DAPHNE "MEZEREUM caused by Ma r s s on i n a daphnes (Desm. et Rob . ) Mag by lames Dav i d Menz i e s -o0o~ A T h e s i s s ubm i t t ed f o r the Degree o f MASTER OE SCIENCE I N AGRICULTURE i n t he Department of BOTANY -oOo- THE UNITERSITY OE BRITISH. COLUMBIA A p r i l , 1 9 5 9 I CONTENTS Acknowledgements I l l The Suscep t . . « 1 P l a n t s a f f e c t e d . . . 1 P a r t s a f f e c t e d . . 2 V a r i e t a l s u s c e p t i b i l i t y . . . . . . . . . . . . . 2 The D i s e a s e . . . . . . . . . . . . . . . . 4 Names . . . . . . . . . . . . . . . . . 4 H i s t o r y and range 4 Economic impor tance . . . . . . . . . . . 6 Symptomatology . . . . . . . . . . . . . . . . . . . . 6 M o r p h o l o g i c a l symptoms . . . . . . . . . . . . . 7 On the l e a v e s . . . . . . . . . . . . . . . 7 On the b lossoms 7 O n t he stems . . . . . . . . . . . . 8 On t he bud s c a l e s . . . . . . . . . . . . . 8 Gross symptoms • • 8 E t i o l o g y 9 Name, h i s t o r y and c l a s s i f i c a t i o n o f pathogene . . 9 Morpho logy o f pathogene 11 P a t h o g e n i c i t y . . . . . . . . . . . . . 12 L i f e h i s t o r y o f pathogene . . . . . . . . . . . . 13 The p r ima r y c y c l e s . . . . . . . . 13 The secondary c y c l e s . . . . . . . . . . . . 14 I I E t i o l o g y ( con t i nued ) P a t h o l o g i c a l h i s t o l o g y 17 C u l t u r a l s t u d i e s . . . . . . . 20 E p i p h y t o l o g y . . 2 2 C o n t r o l . . . . . . . . . . . . 2 4 E x c l u s i o n 2 4 E r a d i c a t i o n . . . . . . . . . . . . . . . . . . . 25 P r o t e c t i o n 25 1937 expe r imen t . . . . . . . . . . . . . . 25 1938 expe r imen t . . . . . . . . . . . . . . 28 Summary 51 B i b l i o g r a p h y . . . . . . 52 I l l u s t r a t i o n s 6 . . . . . . . . . . . . . . . . . . . 55 ACKNOWLEDGEMENTS I I I Du r i n g the t h r e e y e a r s t h a t t h i s work has been- i n p r o g r e s s I have r e c e i v e d v a l u a b l e a s s i s t a n c e and c o - o p e r a t i o n f o r wh i c h I w i s h t o thank those r e s p o n s i b l e . I am p a r t i c u l a r l y i n d eb t ed t o D r . F . D i c k s on o f the Department o f Bo tany , U n i v e r s i t y o f B r i t i s h C o l u m b i a , unde r whose d i r e c t i o n t h i s s t udy was made. D r . D i c k s on r e a d i l y gave v a l u a b l e a d v i c e and encouragement, a s s i s t e d i n the more d i f f i c u l t p a r t s o f t he work and d i d some o f the pho tog raphy . I a l s o w i s h t o thank D r . A . F . B a r s s o f the Department o f H o r t i c u l t u r e f o r a u t h o r i z i n g the use o f daphne p l a n t i n g s on the campus f o r s p r a y i n g expe r imen t s and f o r s u p p l y i n g t he s p r a y i n g equipment and 3abor f o r t h e se t e s t s . M r . J . W. Eastham, P r o v i n c i a l P l a n t P a t h o l o g i s t , s u p p l i e d v a l u a b l e da t a and was most generous i n a l l o w i n g me the use o f h i s e x c e l l e n t r e f e r e n c e l i b r a r y . I w i s h t o thank a l s o D r . "Wm. Newton, M r . H. F . O lds and M r . W a l t e r J one s , a l l o f t h e Domin ion Department o f A g r i c u l t u r e , and many o t h e r members o f the s t a f f s o f the U n i v e r s i t y and the Department o f A g r i c u l t u r e whose names a r e om i t t e d o n l y f o r b r e v i t y . The exchange o f i n f o r m a t i o n and da t a w i t h t he se men has a i d e d g r e a t l y i n the p r e p a r a t i o n o f t h i s p ape r . THE ANTHRACNOSE DISEASE OF DAPHNE MEZEREUM caused by Ma r s s on i n a daphnes (Desxn. e t Rob . ) Mag . The ha rdy o r namen ta l , Daphne mezereum, i s a f a m i l i a r bo rde r p l a n t i n t he s ou t he r n coa s t r e g i o n s o f B r i t i s h Co l umb i a . W e l l known f o r i t s p i n k o r w h i t e s p i k e s o f perfumed f l o w e r s , wh i c h appear i n J anua r y o r F eb r ua r y when few o t h e r p l a n t s a r e i n b loom, and f o r i t s b r i l l i a n t r e d b e r r i e s and waxy f o l i a g e d u r i n g t he summer, t h i s shrub i s becoming i n c r e a s i n g l y p o p u l a r i n pa r k s and p r i v a t e g a r den s . However, w i t h i n t he l a s t t h r e e y e a r s t he p r o p a g a t i o n o f t h i s shrub has been s e r i o u s l y t h r e a t e n e d by t he sudden o c cu r r ence o f an an th r a cnose o r l e a f - s p o t t i n g d i s e a s e , wh i c h p r i o r t o t h i s t ime had been unknown i n N o r t h A m e r i c a . T h i s d i s e a s e r e p e a t e d l y d e f o l i a t e s t he p l a n t s , s t u n t s o r c omp l e t e l y k i l l s t he b loom and u s u a l l y k i l l s young s e e d l i n g s . The work r e p o r t e d h e r e i n was unde r t a ken t o s tudy t h i s d i s e a s e under l o c a l c o n d i t i o n s and, i f p o s s i b l e , t o f i n d p r a c t i c a l c o n t r o l measu res . THE SUSCEPT P l a n t s a f f e c t e d . The d i s e a s e has been found o n l y on Daphne mezereum. Other s p e c i e s o f Daphne a r e a p p a r e n t l y immune. A t t empts t o i n f e c t a r t i f i c i a l l y D. cneorum and D. l a u r e o l a have been u n s u c c e s s f u l , and beds o f t he f o rme r , grow ing unde rnea th s e v e r e l y i n f e c t e d bushes o f D. mezereum, have rema ined c omp l e t e l y f r e e o f t he d i s e a s e d u r i n g t h r e e y e a r s o f o b s e r v a t i o n . The numerous o t h e r s p e c i e s o f daphne have not been t e s t e d s i n c e t hey a r e grown o n l y r a r e l y i n B r i t i s h Co l umb i a . There i s no r e f e r e n c e i n t he s c an t y l i t e r a t u r e on t h i s d i s e a s e t o i t s o c cu r r en ce on o t h e r s p e c i e s . . P a r t s a f f e c t e d . The most appa ren t i n j u r y caused by daphne an t h r a cno se i s t o t h e l e a v e s . The l e s i o n s a r e s m a l l but u s u a l l y v e r y numerous and c h a r a c t e r i s t i c a l l y l o c a t e d a l o n g the m i d - r i b , r e s u l t i n g i n d e f o l i a t i o n o f t he p l a n t . As many as t h r e e c r op s o f l e a v e s have been de s t r o yed i n one season , l e a v i n g t he p l a n t v e r y weak i n t he f a l l and s u b j e c t t o w i n t e r i n j u r y . S i n c e the daphne i s u sed as an o rnamen ta l shrub the u n s i g h t l y appearance o f the s p o t t e d l e a v e s , even w i t h o u t d e f o l i a t i o n , s e r i o u s l y r educe s i t s a t t r a c t i v e n e s s . F l owe r i n f e c t i o n ocou r s i n t he s p r i n g , c a u s i n g r educed and deformed b l oom. Stem i n f e c t i o n s have been obse r ved on t he c u r r e n t s e a s on ' s new growth bu t they r a r e l y k i l l t he s hoo t . S p i n d l y s u c k e r s , s t a r t i n g l a t e i n t he f a l l , have been k i l l e d back by l e s i o n s o f t h e a n t h r a c n o s e . M a t u r i n g buds become i n f e o t e d i n t he f a l l but a r e not k i l l e d . L e s i o n s a r e formed on t h e bud s c a l e s bu t t he fungus rema ins dormant u n t i l s p r i n g be fo re ' s p o r u l a t i n g . V a r i e t a l s u s c e p t i b i l i t y . A l t h o u g h t h e r e a r e s e v e r a l v a r i e t i e s o f Baphne mezereum r e co r ded by Kew Gardens , o n l y the p i n k f l o w e r e d fo rm and a wh i t e f l o w e r e d v a r i e t y , D. mezereum l a r . a l b a , a r e known i n B r i t i s h -Columbia. Of t he se two the p i n k fo rm i s much more commonly grown. Bo t h these v a r i e t i e s a r e ve r y s u s c e p t i b l e t o the d i s e a s e . O c c a s i o n a l l y a da rk p i n k f o rm i s f o u n d , w h i c h , a l t h o u g h by no means immune, i s c o n s i d e r a b l y more r e s i s t a n t t h an t h e common p i n k . Nurserymen r e p o r t t h a t when daphnes a r e r a i s e d f r o m seed a s m a l l pe r cen tage o f t h e p l a n t s w i l l be o f t he da rk f o rm . T h i s s t r a i n i s c h a r a c t e r i z e d by l a r g e r f l o w e r s wh i ch a r e a lmos t r e d i n c o l o u r . The dormant buds a r e o f a r e d d i s h t i n g e and the p e t i o l e s and m i d - r i b s o f t he l e a v e s a re a l s o r edde r t han t ho se o f t h e common p i n k f o rm . Ano the r p e c u l i a r daphne i s found on the campus and as y e t has no t been i d e n t i f i e d . I t i s s i m i l a r t o the mezereum except t h a t t he bloom i s p a l e r , t he b ranches t h i c k e r and more s p r e a d i n g and the l e a v e s i n more d e f i n i t e w h o r l s . T h i s daphne i s c omp l e t e l y immune t o a n t h r a c no s e , a c c o r d i n g t o f i e l d o b s e r v a t i o n s and l a b o r a t o r y t e s t s and , a l t h o u g h no t as showy as t he common p i n k mezereum, i t may be v a l u a b l e as a s u b s t i t u t e . E f f o r t s a r e b e i n g made t o de te rm ine t he v a r i e t y name o f t h i s t y p e . Because o f the s e v e r i t y o f the an th r a cnose on the p i n k fo rm o f daphne, nurserymen who p ropaga te t h i s s p e c i e s f rom seed wou ld be w e l l a d v i s e d t o s e l e c t the dark p i n k fo rm wh i ch i s e q u a l l y b e a u t i f u l but more d i s e a s e r e s i s t a n t . 4. THE DISEASE Names. A l t h o u g h the c a u s a l fungus o f daphne a n t h r a c - nose was f i r s t d e s c r i b e d i n 1843 > t h e r e i s s t i l l v e r y l i t t l e l i t e r a t u r e on t he d i s e a s e i t s e l f . L aube r t (7) d e s c r i b e d the d i s e a s e f rom Germany i n 1931 but d i d no t g i v e i t a common name. The f i r s t p u b l i s h e d work i n E n g l i s h was by Green (4) i n 1935• He u sed the name "Daphne L ea f Spo t " t o d e s c r i b e the d i s e a s e . L o c a l names used by ga rdene r s and nurserymen i n c l u d e "Daphne B l i g h t " and " S c a b . " The name "Daphne An t h r a cno se " i s sugges ted as b e i n g t he mo s t . ' a c c u r a t e . The. l e s i o n s a r e n e c r o t i c and h y p o p l a s t i c and t h e r e f o r e , a c c o r d - i n g t o J e n k i n s ' (6) c l a s s i f i c a t i o n , t h e d i s e a s e shou ld be c a l l e d an a n t h r a c n o s e . T h i s name w i l l be used t h roughou t t h i s p ape r . • • H i s t o r y and Range. The d i s e a s e i s o f Eu ropean o r i g i n . The pathogene was f i r s t d e s c r i b e d by Desmaz ie re i n 1843, when i t was found on n a t i v e European D. mezereum ( S a c c . S y l l . Eung . I l l : 498). I n 191$ t he an th r a cno se was r e p o r t e d by Bubak and Kabat on w i l d daphnes i n the T y r o l (1). L aube r t (7) i n 1931 i n Germany d e s c r i b e d the d i s e a s e as v e r y i n j u r i o u s i n n u r s e r i e s and gave a s ho r t d e s c r i p t i o n o f symptoms and e t i o l o g y , Green (4) f ound the fungus on t he c u l t i v a t e d daphne i n Eng l and but r e p o r t e d t h a t i t was v e r y r a r e and c e r t a i n l y no t o f economic i m p o r t a n c e . The most r e c e n t r e p o r t s i n d i c a t e t h a t the t r o u b l e i s known i n F r a n c e , S w i t z e r l a n d , I t a l y , Denmark, A u s t r i a , L a t v i a , H o l l a n d , G rea t B r i t a i n and A u s t r a l i a , as w e l l as i n B r i t i s h Co lumb ia , Canada, (4), (3) and ( l l ) » A p p a r e n t l y t he d i s e a s e i n t h e s e European c o u n t r i e s i s o f m ino r impo r t ance s i n c e t h e r e i s p r a c t i c a l l y no l i t e r a t u r e a v a i l a b l e on t he s u b j e c t . • Daphne anthracnose- was f i r s t r e p o r t e d i n B r i t i s h Co lumbia i n June , 1936 , when spec imens were sen t t o M r . J . W, Eastham, P r o v i n c i a l P l a n t P a t h o l o g i s t , f r om L a y r i t z N u r s e r i e s , L i m i t e d , Vancouve r . M r . Eastham f o u n d - t h a t the d i s e a s e was seve re on the daphnes a t t h i s n u r s e r y and a l s o a t t h e i r n u r s e r y i n V i c t o r i a , About t he same t ime the d i s e a s e was n o t i c e d by D r . E . D i c k s o n , P r o f e s s o r o f Botany a t t he U n i v e r s i t y o f B r i t i s h Co lumb ia , on t he D. mezereum p l a n t s on the campus o f t h e U n i v e r s i t y . F u r t h e r i n v e s t i - g a t i o n s by the au t ho r d u r i n g the same summer showed t h a t a few p l a n t s i n p r i v a t e gardens were d i s e a s e d but g e n e r a l i n f e c t i o n had no t o c c u r r e d . The s t u d i e s were c on t i n ued the nex t summer when i t was f ound t h a t t he d i s e a s e had sp read t o gardens i n w i d e l y s epa r a t ed p a r t s o f the c i t y . I n t he summer o f 1938 d i s e a s e d p l a n t s were found i n a l l t he suburban n u r s e r i e s v i s i t e d . S e v e r a l nurserymen r e p o r t e d t h a t t h e i r e n t i r e p l a n t i n g s o f s e e d l i n g s t o c k had been k i l l e d by t h i s d i s e a s e i n s p i t e o f a t t emp ted c o n t r o l by s p r a y i n g . A number o f p l a n t i n g s i n p u b l i c p a r k s th roughou t t he c i t y have a l r e a d y been t a k e n ou t because o f t h e r avages o f the a n t h r a c n o s e . A t t he p r e s en t t ime the d i s e a s e has no t been r e p o r t e d anywhere e l s e i n North. A m e r i c a . I t has no t been p o s s i b l e t o de te rm ine when and how the d i s e a s e was i n t r o d u c e d i n t o B r i t i s h Co l umb i a . A check t h rough the f i l e s o f the P l a n t I n s p e c t i o n O f f i c e i n Vancouver showed t h a t , a l t h o u g h the L a y r i t z N u r s e r i e s had no t impo r t ed daphnes f rom any coun t r y where the d i s e a s e i s known f o r a t l e a s t two y e a r s p r i o r t o the ou t b r eak , t h i s p l a n t has i n the pa s t been impo r ted f rom H o l l a n d . I t i s q u i t e p o s s i b l e t h a t some o f t h i s s t o c k was d i s e a s e d , o r a t l e a s t c a r r i e d t he spo res o f t h e pa thogene . Economic impo r t an ce . The economic impor tance o f the daphne i n Canada i s no t v e r y g r e a t . The p l a n t i s c o n f i n e d t o m i l d , tempera te r e g i o n s where the w i n t e r s a r e open and the summers r e l a t i v e l y c o o l and humid , such as i n s ou t he r n B r i t i s h Co l umb i a . There a r e p r o b a b l y more daphnes grown here than i n any o t h e r p a r t o f Canada. I n t h i s a r e a t he daphne i s o f d e f i n i t e impor tance t o nurserymen and ga rdene r s and u n l e s s methods a r e found t o check t he damages o f a n t h r a c - nose , the use o f t h i s sh rub as an impo r t an t o rnamen ta l w i l l have t o be d i s c o n t i n u e d * STICPTOMADOLOG-Y. Symptoms o f t h e d i s e a s e a r e found on a lmos t a l l p a r t s o f t he p l a n t . The buds , b l o s soms , l e a v e s , b e r r i e s and young shoo t s a r e a l l a t t a c k e d by the a n t h r a c n o s e . The most d e s t r u c t i v e phase o f the d i s e a s e o c c u r s on t he 7. l e a v e s ( P l a t e I ) . The f i r s t symptoms o f i n f e c t i o n a r e m inu te da rk g reen o r b l a c k d o t s . These u s u a l l y appear on a r e a s o f the l e a v e s where f r e e wa t e r can a c cumu l a t e . The m i d - r i b o f a daphne l e a f i s sunken and i t i s i n t h i s t r o u g h t h a t most o f the l e s i o n s appea r . The T a c t t h a t the l e s i o n s a r e g e n e r a l l y c l u s t e r e d on t h e m i d - r i b a t t he base o f t h e l e a f b l a de and on the s h o r t p e t i o l e a c coun t s f o r the d e f o l i a t i n g a c t i o n o f t h i s d i s e a s e . W i t h i n a few days the spo t s e n l a r g e , f i n a l l y t o a d i ame te r o f 1 t o 2 mm., c o a l e s c e and t u r n dark g r e y o r p a l e brown i n c o l o u r . The marg i n s o f t h e se l e s i o n s a r e v e r y d e f i n i t e and t h e s u r f a c e i s s l i g h t l y r a i s e d . The g r e y , erumpent n a t u r e o f t he l e s i o n s a t t h i s s tage i s due t o the f o r m a t i o n o f a g l i s t e n i n g , waxy mass o f spo res ove r the s u r f a c e . The i n f e c t i o n s r ema in i n t h i s s tage u n t i l a r a i n o r heavy dew washes away the spore masses , l e a v i n g s h a l l o w , brown d e p r e s s i o n s wh i c h do n o t e n l a r g e bu t g e n e r a l l y p roduce a new c rop o f s p o r e s . L e s i o n s have been found on bo th s i d e s o f t h e l e a v e s bu t t he g r e a t e s t number o c cu r s on t h e upper s u r f a c e . B lossom i n f e c t i o n i s c h a r a c t e r i z e d by ma l fo rmed o r c o m p l e t e l y k i l l e d f l o w e r s ( P l a t e I T ) . U s u a l l y t he l e s i o n s o c cu r on t he c a l y x l o b e s c a u s i n g them t o c u r l and d i e . I f t he buds become i n f e c t e d b e f o r e t h e y open t hey become mummif ied and rema in t o sp read the d i s e a s e t o the young l e a v e s wh i c h appear a s soon as t he b l oom ing p e r i o d i s o v e r . The l e s i o n s on t he b e r r i e s a r e s i m i l a r t o t hose on t he 8 . l e a v e s but a r e s m a l l e r i n s i z e , se ldom becoming l a r g e r t h an 1 mm. i n d i ame t e r . A no rma l b e r r y i s b r i g h t r e d i n c o l o u r and about 1 cm. i n d i a m e t e r . S e v e r e l y i n f e c t e d b e r r i e s do not c o l o u r as c o m p l e t e l y and a r e s m a l l e r i n s i z e . P remature b e r r y d rop i s a phase o f t he d i s e a s e due more t o a weakened c o n d i t i o n o f the p l a n t t han t o p e d i c l e i n f e c t i o n s . Stem i n f e c t i o n s on t h e c u r r e n t s e a s o n ' s g rowth a r e o c c a s i o n a l l y f o u n d . They a r e erumpent, o l i v e g reen i n c o l o u r and somewhat e l onga t ed v e r t i c a l l y . Such l e s i o n s a r e neve r more t han 2 mm. i n d i a m e t e r . These i n f e c t i o n s do no t k i l l t h e t w i g and a r e c o n s i d e r e d un impo r t an t compared t o o t h e r phases o f t h e d i s e a s e . The l e s i o n s on t h e dormant bud s c a l e s a r e q u i t e c h a r a c t e r i s t i c ( P l a t e I I I ) . They v a r y i n s i z e f r om l e s s t h an 1 mm. i n d i ame te r t o e l o nga t ed l e s i o n s 1 cm. i n l e n g t h . The ma rg i n s o f t hese s po t s a r e c l e a r l y d e f i n e d and r i n g e d by a w h i t e , papery f r i n g e o f t he b roken c u t i c l e and e p i - d e r m i s . The c e n t e r o f t h e se l e s i o n s i s c o a l - b l a o k , s t r oma- l i k e and d i s t i n c t l y - erumpent . Bud s c a l e i n f e c t i o n o c c u r s i n t h e l a t e summer as t he buds a r e m a t u r i n g and the b l a c k l e s i o n s can be found a t any t ime d u r i n g the w i n t e r b e f o r e t he buds open and the s c a l e s f a l l . Gross symptoms on a s e v e r e l y i n f e c t e d p l a n t r e semb le seve re f r o s t i n j u r y . The t e n d e r young l e a v e s w i l t and t u r n y e l l o w b e f o r e d r o p p i n g , w h i l e t he o l d e r l e a v e s show dead o r f l a c c i d p o r t i o n s where t he l e s i o n s have been most numerous. L a t e r on i n the season , d e f o l i a t i o n i s t h e most common g e n e r a l symptom. S e v e r e l y i n f e c t e d p l a n t s , a f t e r l o s i n g one c rop o f l e a v e s , u s u a l l y do no t produce a f u l l new se t b e f o r e t he l e a v e s a r e k i l l e d o f f a g a i n . As a r e s u l t such p l a n t s have o n l y a w h o r l o f new l e a v e s a t the t i p s o f the- stems as c o n t r a s t e d to t he u s u a l heavy f o l i a t i o n o f a h e a l t h y p l a n t . The p l a n t s t hu s p r e s en t a g e n e r a l r agged , s t r a g g l y appea rance . ETIOLOGY Name, H i s t o r y and C l a s s i f i c a t i o n o f t he Pa thogene . The c a u s a l o rgan i sm o f t h e daphne an th r a cnose i s Ma r s s on i n a daphnes (Desm. e t Rob . ) Mag . , an i m p e r f e c t fungus o f the f a m i l y Me l a n con i a c e ae . The e a r l i e s t r e c o r d o f t h i s fungus da te s f rom 1843 when Desmaz le re d e s c r i b e d the fungus by t he name o f S e p t o r i a daphnes Desm. e t Rob . ( S a c c . S y l l , F ung . I l l : 498). L a t e r Oudeman (Mat . Myc . N e e r l . I I , p . 28) d e s - c r i b e d a fungus wh i c h he named G l eo spo r i um Daphne Oudem. The pathogene was t r a n s f e r r e d by Sacca rdo t o t he genus M a r s s o n i a ( s p e l l e d M a r s o n i a by Sacca rdo) wh i c h had been e r e c t e d by F i s c h e r (Raben. F . E u r . n.1857) i n 1957 ( S a c c . I l l : 769). I n 1923 Magnus ( S e c . V . H6*hn, 1923) changed the t i t l e o f the genus t o Ma r s s on i n a because t he p r e v i o u s name had been p r e o c cup i e d by a phanerogamic genus . The r e - f o r e a t the p r e s e n t t ime the a c c e p t e d name o f the fungus i s Ma r s s on i n a daphnes (Desm. e t Rob . ) Mag. An a p p a r e n t l y d i f f e r e n t f ungus , G l eo spo r i um meze r e l Gke. was d e s c r i b e d 1 0 . f r om Eng l and by Cooke i n I89O ( G r e v i l l e a 1 9 : p . 8 , 1 8 ? 0 ) , d i f f e r i n g f rom M. daphnes i n h a y i n g n o n - s e p t a t e s p o r e s . Cor respondence between the a u t h o r and D r . B i s b y o f Kew Gardens r e s u l t e d i n a r e - e x a m i n a t i o n o f Cooke ' s o r i g i n a l m a t e r i a l , i n 1 9 3 7 , wh i c h showed t h a t , t o quote D r . B i s b y , "G l eo spo r i um meze r e i Cooke i s i d e n t i c a l w i t h Ma r s s on i n a daphnes (Desm. e t Rob . ) S a c c . . . . . M. daphnes i s t h e o l d e r name and i t wou ld be a good t h i n g t o r e l e g a t e t he i m p e r f e c t l y d e s c r i b e d G. me ze r e i t o synonymy." A p p a r e n t l y t he c o n f u s i o n r e s u l t e d f rom t he f a c t t h a t immature spo res o f t h e fungus a r e n o n - s e p t a t e and a p p r o x i m a t e l y 1 5 X 6 u i n s i z e , wh i c h i s a G l eospo r i um c h a r a c t e r , but mature spo res a r e m o s t l y 1 - s e p t a t e and more u s u a l l y 2 0 u l o n g , w h i c h c h a r a c t e r s p l a c e the fungus i n the genus M a r s s o n i n a . Connors i n the Canad ian P l a n t D i s e a s e Su r vey , 1 9 3 7 , r e p o r t e d the ou tb reak o f the d i s e a s e i n B r i t i s h Co lumb ia and i d e n t i - f i e d the fungus as G. m e z e r e i Cke. L a t e r , i n p r i v a t e co r respondence the i d e n t i f i c a t i o n was changed t o M. daphnes . Grove ( 5 ) i n 1 9 3 7 , i n h i s monograph o f B r i t i s h Stem and Lea f F u n g i , l i s t e d G. me ze r e i as " p r o b a b l y a young s t a t e o f M. daphnes , " a l t h o u g h he d i d no t examine Cooke ' s m a t e r i a l . Many s p e c i e s o f Ma r s s on i n a have been found t o be t h e i m p e r f e c t s t a ge s o f b o t h D i s comyce te s and Py renomyce tes , but t h e r e i s s t i l l no p e r f e c t s t age o f E . daphnes known. A t t emp t s t o l o c a t e a p e r f e c t s t age were made d u r i n g t h e s t u d y . F a l l e n l e a v e s were examined p e r i o d i c a l l y d u r i n g the w i n t e r , as were the b e r r i e s . Bud s c a l e l e s i o n s were examined a t a l l s t ages and t w i g l e s i o n s s t u d i e d whenever t h e y were f o u n d . On none o f t h e se s t r u c t u r e s was t h e r e any i n d i c a t i o n o f a p e r f e c t s t a g e . The f a l l e n p a r t s o f t h e p l a n t s a lways decayed i n t he f i e l d l o n g b e f o r e b l oom ing t i m e , p r e c l u d i n g t he p o s s i b i l i t y o f a p e r f e c t s t age f o r m i n g on them i n " t h e s p r i n g . I t i s p o s s i b l e t h a t m l e s s humid c l i m a t e s t he l e a v e s , b e r r i e s and bloom wou ld p e r s i s t on the ground u n t i l s p r i n g . Morpho logy o f Pa thogene . The f r u i t i n g body o f M.daphnes cove r s t he who le o f the s u r f a c e o f t he i n d i v i d u a l l e s i o n . I t i s o f t he t y p i c a l a c e r v u l u s t y pe and i s formed i n the ep i de rma l l a y e r o f the p l a n t t i s s u e ( P l a t e I V , F i g . 1 )« The spores a r e produced i n a g e l a t i n o u s m a t r i x on v e r y s h o r t , s imp l e c o n i d i o p h o r e s . They a r e obova t e , s l i g h t l y bent t o one s i d e , h y a l i n e and w i t h numerous g u t t u l a t i o n s ( P l a t e V I , F i g . J ) . A b a s a l septum i s formed i n mature s p o r e s , mak ing two unequa l c e l l s , t he l a r g e r a p i c a l c e l l u s u a l l y b e i n g the one t o p roduce a ge rm- tube . Measurements on 100 spo res f rom n a t u r a l l e s i o n s on daphne l e a v e s showed t h a t t h e ave rage s i z e o f the spo res i s 8 X 20 u , w i t h a range i n w i d t h f rom 7 t o 9 u and i n l e n g t h f rom 18 t o 21 u . The myce l i um i s c omp l e t e l y i n t r a - c e l l u l a r and v e r y c h a r a c t e r i s t i c i n shape, b e i n g a l t e r n a t e l y s w o l l e n and c o n s t r i c t e d , b r a n c h i n g and t o r t u o u s ( P l a t e jy , F i g . 2 )« T h i s p e c u l i a r t ype o f myce l i um i s found i n a l l t he t i s s u e s a t t a c k e d and i n c u l t u r e . 1 2 . P a t h o g e n i c i t y . Two a t t emp t s t o i n f e c t h e a l t h y daphne p l a n t s i n ' t h e g reen-house w i t h M. daphnes f rom s i n g l e spo re c u l t u r e s were u n s u c c e s s f u l . T h i s may have heen due t o i n c o r r e c t h u m i d i t y r e l a t i o n s , hut s i n c e t ime and f a c i l i t i e s were no t a v a i l a b l e to c o r r e c t t h i s e r r o r , t h e g reen-house t e s t s were abandoned i n f a v o u r o f ; e x c i s e d l e a f c u l t u r e s . The method o f c u l t u r i n g t he daphne l e a v e s was a m o d i f i c a t i o n o f t h a t u s ed by C l i n t o n and McGormick ( 2 ) . The l e a v e s were suspended ove r a c u l t u r e s o l u t i o n i n P e t r i d i s h e s o r t r a y s , on f l o a t i n g waxed -pape r . The l e a f p e t i o l e s p r o j e c t e d i n t o the s o l u t i o n t h r ough s m a l l s l i p s i n t he paper ( P l a t e X I ) . T h i s method was found v e r y s a t i s f a c t o r y s i n c e i t h e l d t he l e a v e s f r e e f rom t he s o l u t i o n and y e t t he p e t i o l e s were a lways Immersed. The l e a v e s were h e l d s e c u r e l y i n the paper and c ou l d be t r a n s f e r r e d , a tom i zed o r photographed w i t h e a s e . A l t h o u g h a two p e r c en t su c ro se s o l u t i o n was used i n e a r l y t r i a l s , i t was found t h a t pure wa t e r k ep t t h e l e a v e s i n good h e a l t h f o r a t l e a s t s i x weeks„ S i n c e c on t am i na t i o n s were e l i m i n a t e d by u s i n g wa t e r and s i n c e two weeks were s u f f i c i e n t f o r t he p a t h o g e n i c i t y s t u d i e s , t h i s medium was used i n a l l subsequent c u l t u r e s . I t was found ne c e s s a r y t o keep the c o ve r s on t he P e t r i p l a t e s i n o r d e r t o m a i n t a i n a s u f f i c i e n t l y h i g h h u m i d i t y . S a t i s f a c t o r y l i g h t i n g was o b t a i n e d f rom n o r t h windows and a l l c u l t u r e s were k ep t i n the l a b o r a t o r y a t room t empe r a t u r e . I n o c u l a t i o n s on e x c i s e d l e a v e s r e a d i l y gave i n f e c t i o n s 1 3 . a f t e r an i n c u b a t i o n p e r i o d o f t e n d a y s . P a t h o g e n i c i t y was demonst ra ted i n one i n s t a n c e where spo r e s f rom a mono - spo r i c c u l t u r e o f M. daphnes gave t y p i c a l i n f e c t i o n s on the e x c i s e d l e a v e s . Subsequent r e - i s o l a t i o n s f rom t h e s e an th r a cno se l e s i o n s y i e l d e d c u l t u r e s i n d i s t i n g u i s h a b l e f rom the o r i g i n a l i s o l a t i o n s . No d i f f i c u l t y was e xpe r i e n c ed i n c a u s i n g i n f e c t i o n by a t o m i z i n g spo re s f rom d i s e a s e d l e a v e s on t o t he l e a v e s i n c u l t u r e . L i f e H i s t o r y o f the Pa thogene . To unde r s t and t he l i f e c y c l e s o f the daphne an th r a cnose pathogene i t i s n e c e s s a r y to know the s e a s ona l deve lopment o f t he daphne p l a n t . Under l o c a l c o n d i t i o n s t he daphne has a v e r y s h o r t p e r i o d o f dormancy. U s u a l l y the f l o w e r s appear i n J anua r y o r F e b r u a r y , b e f o r e the open ing o f the l e a v e s . The b loom i s c l u s t e r e d a l o ng the p r e v i o u s s e a s o n ' s g rowth , f o r m i n g a dense s p i k e o f f l o w e r s . The b l oom ing p e r i o d i s r e l a t i v e l y p r o l o n g e d , l a s t i n g f rom a month to s i x weeks . G e n e r a l l y i n l a t e March the new l e a v e s appea r , m o s t l y f rom l e a f buds among t he dead o r d y i n g f l o w e r s . By t he end o f A p r i l t he p l a n t i s i n f u l l l e a f and rema ins so u n t i l l a t e i n t h e w i n t e r . The b r i g h t s c a r l e t b e r r i e s r i p e n i n the l a t e summer and , on h e a l t h y p l a n t s , p e r s i s t w e l l i n t o t h e w i n t e r . The buds on the c u r r e n t s e a s on ' s growth e n t e r a shor t - dormant p e r i o d i n t he f a l l p r i o r t o t h e n e x t s e a s o n ' s deve lopment . The p r ima r y c y c l e s . The l i f e h i s t o r y o f M. daphnes c o n s i s t s o f a s e r i e s o f c y c l e s , none o f wh i c h c o n t a i n s a 14 . p e r f e c t s t age o f t he fungus ( P l a t e I X ) . The p r ima r y c y c l e t a k e s p l a c e on the b l o s soms . The i nocu l um i s s u p p l i e d by the s p o r u l a t i o n o f o v e r w i n t e r e d l e s i o n s on the bud s c a l e s . Because the f l o w e r s a r e c l u s t e r e d c l o s e t o g e t h e r on t he s tem, the t r a n s f e r o f i no cu l um i s e a s i l y e f f e c t e d by s p l a s h i n g r a i n o r even a heavy dew, t he dense s p i k e a l s o m a i n t a i n i n g a f a v o u r a b l e h i g h h u m i d i t y f o r spore g e r m i n a t i o n . Because t he f r u i t i n g b od i e s a r e t y p i c a l a c e r v u l i wa t e r i s e s s e n t i a l f o r spore d i s s e m i n a t i o n as a s o l v e n t f o r the g e l a t i n o u s m a t r i x i n w h i c h the spores a r e embedded. I n f e c t i o n s o c c u r b o t h on the p e t a l - l i k e c a l y x l o b e s and on the c a l y x t u b e . The r e s u l t i n g l e s i o n s p roduce spo res b e f o r e t he b lossoms d r o p . T h i s i s t he end o f the p r ima r y c y c l e ; t h e r e i s no s ap r ogene s i s as f a r as i s known, the f a l l e n b loom p l a y i n g no f u r t h e r p a r t i n t he l i f e h i s t o r y . The secondary c y c l e s . The f i r s t l e a f i n f e c t i o n c y c l e s commence w i t h the t r a n s f e r o f i nocu l um f rom the d i s e a s e d b lossoms t o t he young l e a v e s . The bud s c a l e s may supp l y some i nocu l um f o r t hese c y c l e s but u s u a l l y t h e y have dropped b e f o r e the l e a v e s open . Because o f the c l o s e a s s o c i a t i o n between the b lossoms and the w h o r l s o f young l e a v e s i t i s h a r d l y p o s s i b l e f o r the l e a v e s to escape i n o c u l a t i o n f rom the d i s e a s e d b l oom. I t has been no t ed t h a t , as the l e a v e s open, the f l o w e r s drop and a r e h e l d i n t he who r l s o f l e a v e s i n t he same manner t h a t the l o o sened bud s c a l e s a r e h e l d by the b l o s s oms . R a i n and dew a r e 15. ne c e s s a r y bo th f o r d i s s e m i n a t i o n and g e r m i n a t i o n . The p o i n t s o f s e v e r e s t i n f e c t i o n on t h e l e a v e s a r e i n v a r i a b l y where f r e e m o i s t u r e can accumulate . , F a l l e n d e b r i s and bloom on t h e l e a f s u r f a c e s r e t a i n the m o i s t u r e ; t h e m i d - r i b t r o u g h , bent-down edges and l e a f t i p s h o l d drops o f wa t e r ; a f i l m o f wa t e r w i l l s t a y where two l e a v e s come i n c o n t a c t . These a r e a s a r e a lways t he most s e v e r e l y a f f e c t e d . There i s no r e l a t i o n between t he s tomata and t he l o c a t i o n o f i n f e c t i o n s s i n c e mos t , bu t no t a l l , o f t h e l e s i o n s a r e on the uppe r s u r f a c e o f t h e l e a f s w h i l e a l l o f t he s tomata a r e on t h e l owe r s u r f a c e . The r e l a t i v e i n f r e q u e n c y o f the u n d e r - l e a f i n f e c t i o n s i s p r o b a b l y due t o t he absence o f f r e e wa te r on t he l owe r s u r f a c e and t o the g r e a t e r d i f f i c u l t y o f i n o c u l a t i o n . The i n c u b a t i o n p e r i o d has been f ound t o be t e n days w i t h a r t i f i c i a l i n o c u l a t i o n s on e x c i s e d l e a v e s . I n t he f i e l d new i n f e c t i o n s a r e q u i t e e v i d e n t w i t h i n two weeks o f a r a i n y p e r i o d . A t t h i s t i m e waxy, s p o r u l a t i n g p u s t u l e s a r e p r e s e n t , t h e spo re s f rom wh i ch c o n s t i t u t e the i nocu l um f o r the r e pea t ed summer c y c l e s . The l e a f c y c l e s c o n t i n u e i n t o l a t e summer, as l o n g as new l e a v e s c on t i nue t o appea r . There i s a s t r i k i n g r e l a t i o n between wea the r c o n d i t i o n s and t he se c y c l e s . Du r i n g a d r y s p e l l , new, u n i n f e c t e d l e a v e s a r e p roduced and rema in h e a l t h y u n t i l a f t e r a r a i n . Then a new g e n e r a l i n f e c t i o n appea r s , f o l l o w e d by a n o t h e r d e f o l i a t i o n . O the r , l e s s o b v i o u s , seconda ry c y c l e s appear d u r i n g t he 16. summer on the shoo t s and on t he r i p e n i n g b e r r i e s . As i n t he o t h e r c y c l e s t h e r e i s a c l o s e a s s o c i a t i o n between the sou r ce o f i no cu l um and t he s u s c e p t i b l e t i s s u e * The c y c l e on t he shoo t s a p p a r e n t l y c a r r i e s t he d i s e a s e o v e r w i n t e r , , and , a c c o r d i n g t o Green (4 ) , t h e se l e s i o n s s p o r u l a t e i n t h e s p r i n g . Because o f the much g r e a t e r p r e v a l e n c e o f h u d - s c a l e i n f e c t i o n , t h e r o l e o f t w i g l e s i o n s i n i n i t i a t i n g t he p r ima r y f l o w e r i n f e c t i o n c y c l e s i s r e l a t i v e l y u n i m p o r t a n t . The b e r r i e s a r e i n f e c t e d i n l a t e summer f rom the d i s e a s e d l e a v e s . Some o f t h e se d i s e a s e d b e r r i e s sp read the fungus t o l a t e - a p p e a r i n g l e a v e s , and t he c y c l e ends w i t h the f a l l and decay o f t h e f r u i t . The f i n a l c y c l e o f t h e season t a k e s p l a c e on the buds formed i n t he a x i l s o f the l e a v e s . . I n t h i s oase t he p r o x i m i t y o f i no cu l um t o s u s c e p t i b l e t i s s u e i s most s t r i k i n g l y i l l u s t - r a t e d . Any r a i n f a l l i n g on t h e d i s e a s e d l e a v e s i s d r a i n e d down the m i d - r i b and ba thes t he a x i l l a r y bud w i t h a s u spen s i on o f s p o r e s . I n t h i s c y c l e the i n o c u l a t i o n i s so su re t h a t t h e r e i s p r a c t i c a l l y one hundred p e r c en t b u d - s c a l e i n f e c t i o n i n the f a l l . The c on s t an t c l o s e p r o x i m i t y o f t he i n f e c t i o n c o u r t s t o t h e sou r ce o f i nocu lum i n a l l o f t he c y c l e s l a r g e l y e x p l a i n s the d e v a s t a t i n g n a t u r e o f g e n e r a l i n f e c t i o n s f o l l o w i n g a p e r i o d o f r a i n . The h a b i t o f g rowth r e s u l t i n g i n t h i s c o n d i t i o n i s i l l u s t r a t e d by P l a t e X . The b u d - s c a l e l e s i o n s deve l op i n t o b l a c k , erumpent, s t r o m a - l i k e , o v e r - w i n t e r i n g b od i e s wh i c h do no t s p o r u l a t e u n t i l b l o s s om i ng 17. t ime i n t he s p r i n g ( P l a t e I U , F i g s . 1 and 2 ) . Spore p r o d u c t i o n a t t h a t t ime s u p p l i e s the i no cu l um f o r the s t a r t o f the p r i m a r y c y c l e a g a i n . P a t h o l o g i c a l H i s t o l o g y . H i s t o l o g i c a l s t u d i e s on the r e l a t i o n between pathogene and su s cep t were made on n a t u r a l l y i n f e c t e d m a t e r i a l excep t t h a t some o f the s t ages i n p e n e t r a t i o n were o b t a i n e d f rom a r t i f i c i a l i n o c u l a t i o n s on e x c i s e d l e a v e s . A m o d i f i c a t i o n o f t h e l a c t o - p h e n o l method (9) of c l e a r - i n g and s t a i n i n g l e a v e s and o t h e r m a t e r i a l was used w i t h good r e s u l t s . ' P o r t i o n s of l e a v e s o r p e t a l s , b a r k of young t w i g s and b e r r y s k i n s were t r e a t e d by t he f o l l o w i n g method: the f r e s h m a t e r i a l was b o i l e d i n a b s o l u t e a l c o h o l f o r f i v e m i nu t e s t o remove t h e c h l o r o p h y l l and o t h e r p igments and t o f i x the t i s s u e , The t i s s u e was then t r a n s f e r r e d t o ho t l a c t o - p h e n o l f o r c l e a r i n g . I t was f ound t h a t when t h e l a c t o - p h e n o l was h e l d a t a s l ow b o i l f o r a few m inu te s and „ t h en r a p i d l y c o o l e d t h e r e was l e s s danger o f a i r bubb l e s i n t he t i s s u e . A few d rops o f c o t t o n - b l u e s t a i n were added t o t he l a c t o - p h e n o l , t h e c o n c e n t r a t i o n b e i n g de te rm ined by e x p e r i m e n t a t i o n and v a r y i n g w i t h t h e t i s s u e b e i n g t r e a t e d . The c l e a r e d and s t a i n e d m a t e r i a l was mounted on m i c r o s cope s l i d e s i n l a c t o - p h e n o l o r g l y c e r i n j e l l y ( 8 ) . I n mak ing s l i d e s o f l e a v e s and p e t a l s t h e ep i d e rm i s was sometimes s t r i p p e d o f f a f t e r c l e a r i n g and s t a i n i n g . S i n c e t he e a r l y s t ages of i n f e c t i o n a r e c o n f i n e d t o the ep i de rma l l a y e r , 18 , t h i s t e c hn i q ue gave a c l e a r e r s l i d e . By t h i s method the p l a n t c e l l s were l e f t t r a n s p a r e n t and the fungus t i s s u e was s t a i n e d a dark b l u e , r e s u l t i n g i n v e r y c l e a r d i f f e r e n t i a t i o n . I t was p o s s i b l e t o f o l l o w the cou r se o f myce l i um down i n t o the spongy m e s o p h y l l and even t o s tudy i n f e c t i o n s i n t he l owe r ep i d e rma l c e l l s t h r ough t he r e s t o f the l e a f . The spores a p p a r e n t l y become f i r m l y a t t a c h e d t o the s u r f a c e o f the l e a f by t he s e c r e t i o n o f some adhes i v e sub- s t a n c e . E x am i n a t i o n o f spo res by t he I n d i a - i n k method (8) showed t h a t t h e r e i s no t h i c k g e l a t i n o u s enve l ope a round the s p o r e s . S t a i n e d spo res on the s u r f a c e o f l e a f m a t e r i a l were a lways su r rounded by a d i f f u s e d s t a i n e d a r e a wh i c h wou ld i n d i c a t e a fungus s e c r e t i o n . TJngerminated spo re s on l e a f m a t e r i a l t r e a t e d by t he c l e a r i n g method d e s c r i b e d above were no t d i s l o d g e d i n t he r a t h e r s t r enuous p r o c e s s . Ge rm i n a t i o n t a k e s p l a c e f rom e i t h e r t he l a r g e o r the s m a l l c e l l o f the s po r e , but u s u a l l y f rom the l a r g e r . The germ-tube a lways o r i g i n a t e s f rom the s i d e o f the spore wh ioh i s i n c on t a c t w i t h t he p l a n t s u r f a c e . A f i n e p e n e t r a t i o n tube i s formed immed i a t e l y under t he spore and p e n e t r a t e s d i r e c t l y t h r ough the c u t i c l e and ep i d e rma l c e l l w a l l . The f a c t t h a t t h e r e i s no h o r i z o n t a l g rowth o f a s u p e r f i c i a l germ-tube i s s t r i k i n g l y i l l u s t r a t e d by the f a c t t h a t spo res have been seen l odged d i r e c t l y on a s t oma t a l open ing and y e t t he hyphae p e n e t r a t e d i r e c t l y i n t o t h e guard c e l l r a t h e r than t h r ough the s t oma t a l o p e n i n g . Soon a f t e r e n t e r i n g the 19. ep i d e rma l c e l l the hypha forms a s m a l l bu l bous v e s i c l e ( P l a t e 7 1 , F i g . 1)From t h i s o rgan the t y p i c a l s w o l l e n hypha1 bod i e s r a d i a t e t o the p e r i p h e r y of, the c e l l ( P l a t e vT, F i g . 4 ) . Ad j a c en t c e l l s a r e p e n e t r a t e d o n l y when the i n v aded c e l l i s p r a c t i c a l l y f i l l e d w i t h hyphae . The fungus sp reads v e r y s l o w l y and mature s i n g l e i n f e c t i o n s a r e se ldom more t h an t e n ep i d e rma l c e l l s w ide ( P l a t e I V , F i g . l ) . The p a l i s a d e l a y e r i s g e n e r a l l y p e n e t r a t e d and many o f t he se c e l l s have been found c o m p l e t e l y f i l l e d w i t h fungous t i s s u e . The spongy me sophy l l i s v e r y r a r e l y a t t a c k e d f r om i n f e c t i o n s on the upper- s u r f a c e and no case has been seen where an i n f e c t i o n has p e n e t r a t e d c o m p l e t e l y t h r ough the l e a f . When the i n f e c t i o n s o c cu r ove r the m i d - r i b the xy l em e lements become c o m p l e t e l y f i l l e d w i t h hyphae wh i ch wou ld e x p l a i n the d e f o l i a t i n g a c t i o n o f t h i s d i s e a s e . As the l e s i o n s mature t he e p i d e rma l c e l l s a r e r u p t u r e d by the p r e s s u r e o f the fungous growth and the s ' p o r u l a t i n g l a y e r i s exposed ( P l a t e YS I V ) . The immature spo res a r e fo rmed , b e f o r e t he c u t i c l e i s r u p t u r e d , on s h o r t c o n i d i o p h o r e s . When the c u t i c l e b r e a k s the g e l a t i n o u s m a t r i x e x t r u d e s , as shown i n P l a t e I , F i g . 2. I t has been no t ed t h a t the c e l l w a l l s o f i n vaded t i s s u e s a r e c o n s i d e r a b l y t h i c k e r t h an t ho se o f h e a l t h y t i s s u e s . T h i s r e sponse on t he p a r t o f the p l a n t may be somewhat r e s p o n s i b l e f o r the r e s t r i c t e d n a t u r e o f t h e l e s i o n s . H i s t o l o g i c a l e x am i na t i o n o f dormant b u d - s c a l e l e s i o n s show t h a t the b l a c k , e r umpen t s u r f a c e i s s c l e r o t i a l i n n a t u r e , 20. ( P l a t e .VII , F i g s . 1 and 2 ) . T h i s s t r u c t u r e i s composed a lmos t e n t i r e l y o f da rk c o l o u r e d c l o s e l y k n o t t e d myce l i um . I n t he s p r i n g the s u r f a c e o f t he l e s i o n becomes a s p o r u l a t i o n l a y e r . C u l t u r a l S t u d i e s . M. daphnes was o b t a i n e d i n pure mono - spo r i c c u l t u r e by t h e f o l l o w i n g method: a d i l u t e s u spen s i on o f spo res f rom f r e s h l e a f l e s i o n s was s t r e a k e d on t o t h i n , c l e a r e d aga r i n P e t r i p l a t e s . I s o l a t e d spo re s were l o c a t e d w i t h a b i n o c u l a r m i c r o s cope and marked by r i n g s o f I n d i a - i n k on the under s u r f a c e o f the p l a t e . A f t e r the spo res had ge rm ina ted t h ey were p i c k e d out w i t h a v e r y f i n e - p o i n t e d p l a t i n u m need l e and t r a n s f e r r e d t o t e s t - t u b e s l a n t s o f p o t a t o - d e x t r o s e a g a r . A l t h o u g h t he fungus grew v e r y s l o w l y on t h i s a g a r , s u f f i c i e n t s i n g l e - s p o r e c u l t u r e s were o b t a i n e d f o r the c u l t u r a l s tud i e s . , A s e r i e s o f d i f f e r e n t med ia were used to de te rm ine the most s a t i s f a c t o r y one f o r g rowth o f the f ungu s . Tab l e I shows the med ia used and t h e growth r e sponses o b t a i n e d a f t e r t h r e e weeks a t a p p r o x i m a t e l y 22 degrees C. The " D i f c o " aga r s used a r e commerc i a l p r e p a r a t i o n s and were made a c c o r d i n g t o the d i r e c t i o n s on the c o n t a i n e r s . Coon*s aga r was made f rom the f o rmu l a g i v e n i n R a w l i n f s " P h y t o p a t h o l o g i c a l Methods" ( ? ) . The daphne t w i g aga r was made by s t e e p i n g $0 grams o f d r i e d daphne t w i g s i n 500 c c ' s . o f wa te r by b o i l i n g f o r o n e - h a l f h o u r . The e x t r a c t was f i l t e r e d and added t o 500 c c T s . o f ho t 4 p e r c en t aga r , s t r a i n e d , t ubed and a u t o c l a v e d . The b e s t g rowth was o b t a i n e d on daphne t w i g aga r 21. but even t h a t medium gave v e r y s l ow g r ow th . P rune aga r was a lmos t a s good, and , s i n c e t he daphne m a t e r i a l c o u l d no t be e a s i l y o b t a i n e d , most o f t he r o u t i n e c u l t u r i n g was done on the prune a g a r . More d e t a i l e d s t u d i e s o f c u l t u r a l c h a r a c t e r - i s t i c s were abandoned because t he s low growth o f t h e o rgan i sm wou ld n o t a l l o w f o r q u a n t i t a t i v e measurements o f g rowth r e s p o n s e s . T ab l e I , The r e a c t i o n o f M. daphnes t o v a r i o u s med i a . Medium. D i f co Prune Agar pH 5,1 Average d i ame te r ! growth i n 5 weeks , on 4 c o l o n i e s . 9.75 9.37 8.25 8.57 F i n a l Average• 8.95 mm. " Corn Mea l Agar 5.5 9.75 9-55 6.25 4.75 7.55 " " P o t a t o - d e x t r o s e Agar 5 . 4 7.00 8.00 6.22 •_ 7.21 " " M a l t E x t r a c t Aga r 5.0 6.00 •5.57" 4.87 5.00 5.51 " " Bean Pod Agar 5.0 5.00 6.57; 5.00 5.00 5.54- " " L ima Bean Aga r 5.5 1.00 2.00 1.00 1.50 1.57 " Coon ' s S y n t h e t i c Agar 5.1 n i l n i l n i l n i l n i l " Daphne Twig Aga r 5-5 9.00 9-50 9.50 9.57 9.54 A t y p i c a l c o l on y on daphne t w i g aga r i s compressed, erumpent, w i t h a s l i g h t l y c o n v o l u t e d s u r f a c e and a c l e a r l y d e f i n e d m a r g i n . I t i s a lmos t b l a c k i n c o l o u r w i t h a nar row brown m a r g i n . The s u r f a c e o f mature c o l o n i e s becomes cove red w i t h the waxy, w h i t e spore masses . A c h a r a c t e r i s t i c brown s t a i n permeates the agar s u r r o und i n g the c o l o n y , f a d i n g out about 1 cm. f rom t he m a r g i n . 22 . The spo re s ge rm ina te s l o w l y i n d i s t i l l e d w a t e r . Tab l e I I shows the r e s u l t s o b t a i n e d f rom a g e r m i n a t i o n s e r i e s i n Van Tiegham c e l l s a t v a r i o u s t empe ra tu r e s and u s i n g d i s t i l l e d w a t e r . Complete d a t a on t he e f f e c t o f n u t r i e n t , pH and t empera tu re were no t o b t a i n e d . The optimum tempe ra tu re f o r Tab l e I I . The e f f e c t o f t empe ra tu re on spore g e r m i n a t i o n . Temperature i n degrees C. % Ge rm i na t i o n a f t e r 24 hours© % Ge rm i na t i o n a f t e r 48 h o u r s 0 . . ' • • 2.3 10 3.0 7 • 6 . 24.2 32.5 20 5 2 . 4 75.0 ( e s t i m . ) 25 0 0 spore g e r m i n a t i o n l i e s between 20 and 25 degrees C. o r a p p r o x i m a t e l y 70 degrees E. Ve r y s l i g h t g e r m i n a t i o n o c cu r s i f t he t empe ra tu re i s be low 15 degrees C. A t 25 degrees C. and above the spo res were k i l l e d b e f o r e any s i g n o f germ- i n a t i o n appea r ed . T h i s i n f o r m a t i o n cannot be c o m p l e t e l y c o r r e l a t e d w i t h t he t empe ra tu re r e l a t i o n s o f the d i s e a s e i n t he f i e l d bu t does h e l p t o e x p l a i n why e p i p h y t o t i c s o f t he an th r a cnose a r e a s s o c i a t e d w i t h ho t summer wea t he r . EPIPHYTOLOGY Weather c o n d i t i o n s a p p a r e n t l y p l a y a v e r y impo r t an t p a r t i n i n f l u e n c i n g t he s e v e r i t y o f t h e a t t a c k s o f daphne a n t h r a c n o s e . The u n u s u a l l y l o n g p e r i o d o f appa ren t h e a l t h 23. shown by t h e p l a n t s between b l o s som i n f e c t i o n and g e n e r a l l e a f i n f e c t i o n seems t o be due t o u n f a v o u r a b l e wea the r con - d i t i o n s f o r the d i s e a s e d u r i n g t h a t t i m e . There i s c e r t a i n l y abundant i n o cu l um p r e s en t on t he dead o r d y i n g b loom to i n f e c t t he young l e a v e s wh i ch a r e a p p a r e n t l y v e r y s u s c e p t i b l e as shown by the seve re a t t a c k s o f d i s e a s e on l a t e - a p p e a r i n g l e a v e s i n t he summer. Weather c h a r t s o f t he Vancouver d i s t r i c t have been c o n s u l t e d i n an e f f o r t t o c o r r e l a t e t empe ra t u r e and h u m i d i t y c o n d i t i o n s w i t h an t h r a cno se e p i p h y t o t i c s . The da te o f f i r s t g e n e r a l l e a f i n f e c t i o n was no t ed d u r i n g 1937 and 1938 and s i n c e t he i n c u b a t i o n p e r i o d i s a p p r o x i m a t e l y t e n days , the wea the r c o n d i t i o n s t e n days p r i o r t o t h i s da te were s t u d i e d . I n 1937 f i r s t g e n e r a l l e a f i n f e c t i o n was n o t i c e d on May 2 9 . From the wea the r c h a r t s i t was f ound t h a t on May 17 and 18 t he mean d a i l y t empe ra tu re was 35 degrees F , , accompan ied by l i g h t p r e c i p i t a t i o n . P r i o r t o t h a t da te t h e t empe ra tu re had a t t a i n e d t h i s h e i g h t on two o c c a s i o n s , but w i t h o u t r a i n . T h e r e f o r e t he se two days were the f i r s t d u r i n g the y e a r when h u m i d i t y was h i g h and t empera tu re 55 degrees o r h i g h e r . I n 1938 l e a f i n f e o t i o n f i r s t became g e n e r a l about May 1 5 . That y e a r the f i r s t two days d u r i n g wh i ch r a i n accompanied a t empe ra tu re o ve r 55 degrees F . were May 7 and 8 , wh i c h was one week p r i o r t o t h e f i r s t e p i p h y t o t i c . As i n 1937 such t empe ra tu re s had been reached e a r l i e r i n the 24 . season,, but no t accompanied by r a i n f a l l . A l t h ough two y e a r s ' e v i dence cannot be c o n s i d e r e d c o n c l u s i v e , t he f a c t s a r e wo r t h r e p o r t i n g i n e x p l a i n i n g t he i n c i d e n c e o f the d i s e a s e i n t he summer. Whether o r no t i t i s t r u e t h a t t empe ra tu re s above 55 degrees F . , accompanied b y ' r a i n , a r e n e c e s s a r y f o r i n f e c t i o n w i l l have t o be shown by o b s e r v a t i o n s i n f u t u r e s e a son s . One s u b s t a n t i a t i n g f a c t i s o b t a i n e d f rom t he spore g e r m i n a t i o n t e s t s . A t 59 degrees F . t h e r e was J2 p e r c en t g e r m i n a t i o n i n 48 hou r s bu t o n l y 7-5 p e r c en t a t 50 degrees F . , under optimum c o n d i t i o n s o f h u m i d i t y and w i t h a c on s t a n t t empe r a t u r e . CONTROL E x c l u s i o n . E x c l u s i o n a r y measures wou ld be o f d e f i n i t e v a l u e i n p r e v e n t i n g t he sp read o f daphne an t h r a cno se t o new a r e a s . Long d i s t a n c e sp read o f the d i s e a s e i s a lmos t e n t i r e l y e f f e c t e d by movement o f d i s e a s e d s t o c k and p r obab l y was t h e method o f i n t r o d u c i n g t he d i s e a s e t o s ou t he r n B r i t i s h Co l umb i a . A t p r e s e n t the a d j a c e n t s t a t e o f Wash ing ton impo r t s c o n s i d e r a b l e numbers o f daphnes each y e a r f rom B. C. S i n c e t h e r e has been no r e p o r t o f daphne an th r a cnose i n t h a t s t a t e , and s i n c e i t i s h a r d l y l i k e l y t h a t i n f e c t e d p l a n t s w i l l no t be sen t t h e r e e v e n t u a l l y u n l e s s oheoked, i t wou ld be i n t he i n t e r e s t s o f daphne growers i n Wash ing ton t o ban impo r t s o f daphnes f rom i n - f e c t e d a r e a s . A l t h o u g h t h e r e i s s t i l l t he danger o f n a t u r a l sp read o f t he d i s e a s e down the c o a s t , e x c l u s i o n a r y measures 25. wou ld g r e a t l y reduce t he danger o f t h e d i s e a s e becoming e s t a b l i s h e d . E r a d i c a t i o n . Daphne an th r a cnose appears t o be o f such an i n f e c t i o u s n a t u r e t h a t t h e r e i s l i t t l e hope o f b e i n g a b l e t o e r a d i c a t e the d i s e a s e i n d i s t r i c t s where i t i s now e s t a b l i s h e d . The a r ea i n v o l v e d i n B r i t i s h Co lumbia i s s t i l l s m a l l bu t the su s cep t p l a n t s a r e so w i d e l y s c a t t e r e d t h a t i t wou ld be p r a c t i c a l l y i m p o s s i b l e t o a t t empt c o n t r o l by d e s t r o y i n g t he d i s e a s e d bu she s . Mo reove r , t he d i s e a s e i s so e a s i l y sp read t h a t eve ry i n f e c t e d bush i n t he w h o l e ' a r e a wou ld have t o be l o c a t e d and de s t r o yed t o e f f e c t complete e r a d i c a t i o n . I n a r e a s where the d i s e a s e i s no t y e t f i r m l y e s t a b l i s h e d , * r o g u i n g out i n f e c t e d p l a n t s i s recommended. P r o t e c t i o n . The p r ima r y p rob lem o f c o n t r o l l i n g the d i s e a s e where i t i s a l r e a d y w i d e sp r e ad i s one o f p r o t e c t i n g t he p l a n t s f rom i n f e c t i o n by s p r a y i n g . C o n t r o l by the use o f f u n g i c i d e s i s made d i f f i c u l t by the extreme and summer- l o n g s u s c e p t i b i l i t y o f a lmos t a l l p a r t s o f t he p l a n t s . However, s p r a y i n g expe r imen t s have been made d u r i n g the l a s t two summers i n an e f f o r t t o c o n t r o l o r r educe the damages o f t he l e a f i n f e c t i o n s . 1937 e xpe r imen t . I n 1937 t he a u t ho r expe r imen ted on f i f t y mature p l a n t s on t he U n i v e r s i t y campus. F i v e o f t he bushes were l e f t unsp rayed as checks and the rema inder were d i v i d e d i n t o t h r e e equa l g r oup s . E v e r y p l a n t was c l a s s i f i e d as t o s i z e , v i g o u r and l o c a t i o n and the p l a n t s i n 26. each t e s t were as n e a r l y as p o s s i b l e e qua l i n a l l r e s p e c t s . The sp ray m a t e r i a l s used were Lime S u l p h u r , i n the fo rm o f a commerc i a l p r e p a r a t i o n known as M i c r o s u l , p roduced by the Lunava l e P r o d u c t s L i m i t e d , L a n c a s t e r , . E n g l a n d ; Burgundy M i x t u r e i n the fo rm o f M i c r o n i z e d Burgundy, p roduced by t he same company; and home-made Bordeaux M i x t u r e . The concen - t r a t i o n s u sed we re : M i c r o s u l 8 l b s . pe r 100 g a l s . M i c r o n i z e d Burgundy . 4 l b s . pe r 100 g a l s . Bordeaux M i x t u r e . 4 - 4 - 40 A sp r eade r and s t i c k e r known as L e t h a l a t e W e t t i n g F l u i d , made by t he Lunava l e P r o d u c t s L i m i t e d , was found t o be s a t i s f a c t o r y . Good cove rage was o b t a i n e d u s i n g 2 l b s . o f L e t h a l a t e pe r 100 g a l l o n s o f s p r a y , a h i g h c o n c e n t r a t i o n n e c e s s a r y because o f the v e r y waxy na tu re ' o f t h e l e a v e s . On ly h a l f t h i s amount o f sp reade r was used w i t h M i c r o n i z e d Burgundy wh i c h i s s o l d w i t h t he sp reade r added . Three sp r a y s o f each m a t e r i a l were a p p l i e d i n the most t ho rough manner p o s s i b l e . The da te s o f a p p l i c a t i o n were A p r i l 8, June 4 and J u l y 1 3 . A t t h e end o f t h i s program the exper iment had t o be d i s c o n t i n u e d ; t h e r e f o r e the r e s u l t s were t a k e n on t h e amount o f c o n t r o l e f f e c t e d up t o t h a t t i m e . By t he end o f May the check p l a n t s showed g e n e r a l i n f e c t i o n and were c o m p l e t e l y d e f o l i a t e d a t the c o n c l u s i o n o f t he e xpe r imen t . The Lime S u l p h u r sp r ay gave v e r y poor c o n t r o l , the •27. d e f o l i a t i o n b e i n g a lmos t as seve re as on the c h e c k s . The M i c r o n i z e d Burgundy gave f a i r c o n t r o l . A l t h o u g h t h e r e was moderate i n f e c t i o n , t h e d e f o l i a t i o n was much l e s s seve re t h an on the c h e c k s . The Bordeaux M i x t u r e gave the be s t c o n t r o l . A t the t ime o f t he l a s t s p r ay t h e r e were v e r y few l e s i o n s on t he l e a v e s , t h e r e had been p r a c t i c a l l y no d e f o l i a t i o n and t h e p l a n t s were much more h e a l t h y t h an the r e s t o f t h e p l o t . I n s p i t e o f t he good c o n t r o l w i t h Bordeaux , t h e s e p l a n t s became i n f e c t e d l a t e r i n t he summer, and by t he end o f Augus t a l l t he p l a n t s had been d e f o l i a t e d . An i n t e r e s t i n g a f t e r - e f f e c t o f t h i s s p r a y i n g program was no ted a t b l oom ing t ime t h e nex t s p r i n g . Wh i l e c l a s s - i f y i n g the p l a n t s f o r v i g o u r i t was obse rved t h a t p l a n t s wh i c h had been sp rayed w i t h d i f f e r e n t s p r a y s showed marked d i f f e r e n c e s i n e a r l i n e s s and amount o f b loom. The r e s u l t s a r e shown i n Tab le I I I . Tab l e I I I . The e f f e c t o f s p r a y t r e a tmen t s on f o l l o w i n g y e a r ' s b l oom. Treatment used Time o f B l oom ing Amount o f Bloom 1937 L a t e Medium E a r l y Good Medium S l i g h t Bordeaux 100% 0 0 80 20 0 Burgundy 66 34 0 73- :0 . 27 Lime Su l phu r - 1 3 4 0 47 26 20 54 Che ok 0 60 40 0 20 80 I t w i l l be seen t h a t t he b e t t e r the s p r a y c o n t r o l the l a t e r and more p r o f u s e was the b loom produced i n the s p r i n g . A 28* l o g i c a l e x p l a n a t i o n o f t h i s wou ld he t h a t the Bordeaux sp r ay , and , t o a l e s s e r e x t e n t , t h e o t h e r s , by d e l a y i n g d e f o l i a t i o n p r e ven t ed the p l a n t s f rom becoming dormant as e a r l y as the c he c k s , but a t t h e same t ime gave them more v i g o u r . On the o t h e r hand the b a d l y d e f o l i a t e d cheeks became dormant e a r l i e r i n ' t h e f a l l and bloomed e a r l i e r i n t he s p r i n g . The d i s e a s e , however, l e f t t he p l a n t s i n a weakened c o n d i t i o n , r e f l e c t e d i n poor b l oom. 1938 e xpe r imen t . The same p l o t o f p l a n t s was sp rayed i n 1938 u s i n g o n l y t he M i c r o n i z e d Bu r gundy . ' Bordeaux was d i s c o n t i n u e d because , a l t h o u g h i t gave the b e s t c o n t r o l i n t he p r e v i o u s y e a r , the u n s i g h t l y r e s i d u e made i t q u i t e u n s u i t a b l e as a sp ray f o r an o rnamen ta l p l a n t . I t seemed p o s s i b l e t h a t t he Burgundy m igh t g i v e s a t i s f a c t o r y c o n t r o l i f t h e a p p l i c a t i o n s were more f r e q u e n t and the s p r a y i n g c on t i n ued l a t e r i n t he summer. Sp ray s were a p p l i e d on t h e f o l l o w i n g d a t e s : A p r i l 18, May 4 , May 201 June 9, J u l y 15 and Augus t 1. On the f i r s t s p r a y i n g t he c o n c e n t r a t i o n o f M i c r o n i z e d Burgundy was 1 l b . i n 8 g a l l o n s o f w a t e r , wh i c h i s much h i g h e r t han the recommended s t r e n g t h , but a c o n c e n t r a t i o n wh i c h gave s a t i s - f a c t o r y c o n t r o l o f r u s t on a n t i r r h i n u m s a t S a a n i c h t o n , w i t h o u t sp ray I n j u r y . T h i s s t r e n g t h d i d , however, s e r i o u s l y i n j u r e t he daphnes and the sp r ay had t o be d i l u t e d i n subsequent a p p l i c a t i o n s t o 1 l b . i n 40 g a l l o n s b e f o r e t he i n j u r y was e l i m i n a t e d . The s p r a y i n j u r y spo t s on the l e a v e s 29. were v e r y s i m i l a r i n appearance t o t he l e s i o n s o f t he a n t h r a cno s e , mak ing o b s e r v a t i o n s on c o n t r o l d i f f i c u l t . The p l a n t s so i n j u r e d were g r e a t l y reduced i n v i t a l i t y , and a l t h o u g h the subsequent sp r ay s d i d n o t cause b u r n i n g , the p l a n t s were i n poor c o n d i t i o n f o r the d u r a t i o n o f t h e summer, The p l a n t s were d i v i d e d as b e f o r e i n t o t h r e e g r oup s . The f i r s t group r e c e i v e d a l l t he s p r a y s ; t he second group was no t sp rayed on A p r i l 18 ; and the t h i r d group was no t sp rayed on A p r i l 18 no r May 4, A l t h o u g h the i n t e r v a l s between sp ray s were no t r e g u l a r , an e f f o r t was made t o a p p l y t he s p r a y s b e f o r e t h r e a t e n e d r a i n i n o r d e r to g i v e t he b e s t p r o t e c t i o n p o s s i b l e , T ab l e I V . R e s u l t s o f s p r a y i n g expe r imen t - 1938. Amount o f Observed Observed Observed Observed D i s ea se A p r i l 15 &ay 12 May 25 J u l y 5 #1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 No D i s e a s e 15 15 15 15 15 13 13 3 6 4 Very S l i g h t 2 2 3 5 3 1 S l i g h t 6 4 5 7 3 1 Moderate 3 3 1 8 6 Severe 13 15 6 14 15 E x p l a n a t i o n s - t he f i g u r e s r e f e r t o the number o f p l a n t s out o f 15 . The f i g u r e s on the 5 check p l a n t s were m u l t i p l i e d by 3 t o be comparab le . # These numbers r e f e r t o t he sp ray t r e a t m e n t , t h u s : jfl - a l l 6 sp rays a p p l i e d . 2 - - f i r s t sp ray o m i t t e d , 3 - second sp r ay o m i t t e d . 4 - check - u n sp r a yed . 30. Prom Tab l e I V i t w i l l be seen t h a t even the whole s i x s p r a y s gave o n l y p a r t i a l c o n t r o l . T h i s f a c t was obv i ou s by the f i r s t o f J u l y and the two sp r a y s f o l l o w i n g t h a t da te were o f v e r y l i t t l e u s e . The p r o b a b i l i t y o f nurserymen o r ga rdene r s b e i n g w i l l i n g t o a pp l y more t han s i x sp r ay s i s remote ; t h e r e f o r e the o n l y c o n c l u s i o n i s t h a t summer s p r a y i n g w i t h Burgundy M i x t u r e i s no t a p r a c t i c a l c o n t r o l f o r the d i s e a s e . I n v i ew o f the r e s u l t s o b t a i n ed d u r i n g the p r e v i o u s y e a r w i t h Bordeaux , p r o b a b l y t h i s sp ray wou ld be more e f f e c t i v e t han Burgundy M i x t u r e . Under c e r t a i n c o n d i t i o n s , such as i n s e e d l i n g p l o t s and i n n u r s e r i e s , Bordeaux c o u l d be used t o save the p l a n t s even i f i t d e s t r o y ed the o rnamenta l v a l u e . There i s a s t r o n g p o s s i b i l i t y t h a t t he d i s e a s e can bes t be a t t a c k e d i n t he f a l l a t the t ime the b u d - s c a l e l e s i o n s form.- A s t r o n g dormant o r p re -do rmant s p r a y m igh t c o n t r o l o r reduce t he o v e r - w i n t e r i n g l e s i o n s . One p r i v a t e grower r e p o r t e d t h a t he c o n t r o l l e d the an th r a cnose by d i p p i n g young i n f e c t e d p l a n t s , d u r i n g November, i n a l y e s o l u t i o n , 1 o z . i n 10 g a l l o n s o f s o l u t i o n . A l t h ough t h e r e were no check p l a n t s i n h i s e xpe r imen t , the r e p o r t i s a u t h e n t i c and may i n d i c a t e t he v a l u e o f a dormant sp ray o r d i p . I t i s hoped t h a t t h i s work can be supp lemented i n the near f u t u r e . Prom t he se expe r imen t s t he o n l y recommendat ions t h a t can be made a r e t o u se a s t r o n g dormant sp ray j u s t a f t e r the no rma l l e a f drop i n the f a l l , f o l l o w e d i f n e c e s s a r y by 31. summer sp r ay s v / i t h Bordeaux M i x t u r e . These summer sp rays s hou l d .commence- e a r l y i n May and c on t i n u e d u r i n g the summer, so spaced t h a t t he p l a n t i s c o m p l e t e l y cove red w i t h sp ray a t t he c r i t i c a l p e r i o d s o f r a i n . SOTMARY The an th r a cno se o f t he o rnamenta l s h r ub . Daphne mezereum a d i s e a s e o f Eu ropean o r i g i n and p r e v i o u s l y unknown i n No r t h A m e r i c a , has appeared and r ea ched s e r i o u s p r o p o r t i o n s i n s ou the rn B r i t i s h Co l umb i a . The d i s e a s e i s a l e a f s p o t t i n g t y p e , the most s e r i o u s phase o f wh i ch i s d e f o l i a t i o n , . accompanied by b lossom b l i g h t and premature b e r r y d r op . T h i s t r o u b l e has become so seve re t h a t young n u r s e r y p l a n t - i n g s have been c o m p l e t e l y k i l l e d and o l d e r p l a n t s g r e a t l y weakened, w i t h a g e n e r a l l o s s i n o rnamen ta l v a l u e . The c a u s a l agent i s the M e l a n c o n i a c i o u s fungus Ma r s s on i n a daphnes (Desm. e t Rob . ) Mag. The fungus G l eo spo r i um meze r e i C ke , , p r e v i o u s l y b e l i e v e d t o be r e s p o n s i b l e f o r ano the r l e a f d i s e a s e o f daphne, has been p roved t o be a synonym o f M. daphnes . P a t h o l o g i c a l h i s t o l o g y has been s t u d i e d i n d e t a i l . The fungus o v e r - w i n t e r s on t he s c a l e s o f t he dormant buds i n the fo rm o f s t r o m a - l i k e l e s i o n s , wh i ch s p o r u l a t e d u r i n g b lossom t ime i n t he s p r i n g . E p i p h y t o t i c s o c cu r when h i g h summer t empe ra t u r e s a r e a s s o c i a t e d w i t h r a i n . Summer s p r a y i n g has no t proved, to be an e f f e c t i v e c o n t r o l , but hope i s h e l d f o r t h e use o f a s t r o n g dormant sp ray f o l l o w e d by summer s p r a y i n g w i t h Bordeaux M i x t u r e . 32, BIBLIOGRAPHY Bubak, F. Bin Beitrag zur P i l z f l o r a vor T i r o l und I s t r i e n . Ann. Mycol. XII: 205-220, 1914. Clinton, G, P. and Florence A. McCormick. Rust infection of leaves i n P e t r i dishes. B u l l , Conn, Agric. Exp. Sta. 260: 475-510, 1924. Connors, I . L. Sixteenth annual report of the-Canadian Plant Disease Survey. Can. Dept. Agric. 1936. Green, D. E. A leaf spot of Daphne mezereum. Royal Hort. S o c . J.. 60: I56-8, 1935. Grove, 11. B. B r i t i s h Stem and Leaf Fungi. Vol. 2. Cambridge University Press. 1937• Jenkins, A. E. Application of the terms "Anthracnose" and "Scab" to plant diseases caused by Sphacelona and Gleosporium. Phytopaith 23' 389-395, 1935. Laubert, R. A very injurious disease of Daphne mezereum (German t i t l e ) . Der Blumen - und Pflanzen- bau: 46: 138, 1931. Lee, A* B. The Micrometrists Vade Mecum. Ninth edition. P. Blakiston's Son and Co., Philadelphia, 1924. R a w l i n s , T, E . P h y t o p a t h o l o g i c a l and B o t a n i c a l • Research Methods. John Wiley and Sons, I n c . , London® 1933, Sac ca r do , P-^-. S y l l o g e Fungorum. Vo/. /-zs <?v</ S t even son , J. A . F o r e i g n P l a n t D i s e a s e s . U . S . D . A . , Wash.- 1 9 2 6 0 - 0 O 0 - PLATE I . F i g . 1 . Leaves o f Daphne mezereum i n f e c t e d by M a r s s o n i n a daphnes . From e x c i s e d l e a f c u l t u r e . I 1 , F i g . 2. I n f e c t e d daphne l e a f show ing waxy spo re masses on l e s i o n s . X 8 . F i g . J>. The same $ show ing k i l l i n g o f m i d - r i b . Pho tog raphs by D r . D i c k s o n .  PLATE I I . Blossom teds o f D. mezereum. % 6 . The t o p thre e ' buds a r e h e a l t h y , the bottom t h r show t h e l e s i o n s o f a n t h r a c n o s e . PLATE I I PLATE U T . ' Daphne anthracnose on the bud s c a l e s . E i g . l . Overwintering l e s i o n s . F i g . 2, New lesions on f o l d e d l e a v e s . PLATS I I I F i g . 2 , PLATE I V . - F i g . 1 . F i g . 2 . Semi-diagrammatic drawing of a c e r v u l u s o f M. daphnes , i n c r o s s section. Camera l u c i d a drawing of young i n f e c t i o n showing ra d i a t i n g hyphal bodies. PLATE I Y PLATE V. F i g . 1. P ho t om i c r og r aph o f cross section of a c e r v u l u s of Mv daphnes . X 5 0 0 . F i g . 2. Photomicrograph from cleared l e a f preparation showing radiating h y p h a l b o d i e s at edge of l e s i o n . X jjOQ. PLATE Y Pig. 2. PLATE VT . Morphology o f M, daphnes. F i g s . 1, 2, 4 and 5» camera l u c i d a d r aw ings o f stages i n penetration o f the fungus i n t o t he epidermal c e l l s o f t he daphne l e a f . . 'Fig. 3 . Spo re s o f M. daphnes g r e a t l y e n l a r g e d . The a c t u a l s i z e o f s p o r e s i s 8 x 20 u . P L A T E VI PLATE Y H . Pho t om i c r og r aph s o f bud-scale l e s i o n s . F i g . 1 . Free-hand section o f a single l e s i o n , showing c e l l s packed with mycelium and i l l u s - t r a t i n g the s t r o m a t i c nature o f the l e s i o n . X 100. F i g . 2. Portion o f same l e s i o n X 500® PLATE VII P i g . 2. PLATE V I I I . Figs. 1 and--2. -Phot omioro graphs --of- young petal infections showing h y p h a l b o d i e s in epidermal c e l l s . X 500® P L A T E V I I I F i g . 1 . F i g . 2 . PLATE I X . Diagram showing the various c y c l e s of M. daphne on D. mezereum. PLATE IX PLATE IX. DIAGRAMMATIC YEARLY CYCLE of Marssonina daphnes on Daphne mezereum. s c a l e l e s i o n s . PLATE X . A s p r a y o f daphne bloom, i l l u s t r a t i n g t he dense c l u s t e r s o f f l o w e r s i n c l o s e p r o x i m i t y to t he new l e a f w h o r l s . Cop i e s f r om N u t t h a l l ' s " B e a u t i f u l F l o w e r i n g S h r u b s . " PLATE X %^K^~A •WBSEBBB SSL PLATE XI. Photographs o f e x c i s e d l e a f c u l t u r e s , showing the method used t o support t he l e a v e s . P i g . 1 . A P e t r i dish c u l t u r e . E i g . 2 o A t r a y c u l t u r e , show ing m inu te l e s i o n s o f M. daphnes r e s u l t i n g f r om a r t i f i c i a l inoculation. Pho tog raphed by D r . D i c k s o n . P L A T E X I F i g . 2.

Cite

Citation Scheme:

    

Usage Statistics

Country Views Downloads
United States 5 1
China 2 36
Japan 2 0
City Views Downloads
Buffalo 3 0
Beijing 2 0
Tokyo 2 0
Providence 1 0
Ashburn 1 0

{[{ mDataHeader[type] }]} {[{ month[type] }]} {[{ tData[type] }]}

Share

Share to:

Comment

Related Items