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The agricultural ecology of peachtree borer, (Synanthedon Exitiosa say) Edwards, Linda Lynne 1986

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THE AGRICULTURAL ECOLOGY OF PEACHTREE BORER, (SYNANTHEDON EXITIOSA SAY). By LINDA LYNNE EDWARDS B . S c , The U n i v e r s i t y of B r i t i s h Columbia, 1982 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF PLANT SCIENCE We a c c e p t t h i s t h e s i s as c o n f o r m i n g to the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1986 t£) L i n d a Lynne Edwards, 1986 7 8 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It i s understood that copying or pu b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date / 1/6 V/ 9 L >TT_ C I O /"7Q \ i i ABSTRACT The p e a c h t r e e b o r e r , Svnanthedon e x i t i o s a ( S a y ) , ( S e s i i d a e ) , was s t u d i e d t o determine f a c t o r s i n f l u e n c i n g i t s d i s t r i b u t i o n , and f o u r p o s s i b l e methods f o r i t s c o n t r o l i n Prunus o r c h a r d s i n the Okanagan V a l l e y , B.C. A s u r v e y f o r p e a c h t r e e b o r e r i n f e s t a t i o n was made by i n s p e c t i n g more than 7000 Prunus t r e e s i n 49 o r c h a r d s , and 34 c h o k e c h e r r y t r e e s , Prunus v i r g i n i a n a L., the n a t i v e h o s t , a t 9 s i t e s . S e v e n t y - f i v e per c e n t of the Prunus p l a n t i n g s c o n t a i n e d p e a c h t r e e b o r e r . I n f e s t a t i o n l e v e l s ranged from 0.9-83.3 % of the t r e e s per p l a n t i n g . Young t r e e s were l e a s t o f t e n a t t a c k e d . Peach was the most h e a v i l y a t t a c k e d s p e c i e s , prunes and a p r i c o t s were i n t e r m e d i a t e , and c h e r r y was the l e a s t a t t a c k e d . D i f f e r e n c e s i n bark t e x t u r e appeared t o be an i m p o r t a n t f a c t o r i n f l u e n c i n g o v i p o s i t i o n b e h a v i o u r and l a r v a l s u r v i v a l and e s t a b l i s h m e n t . Trees i n c l a y s o i l w i t h o u t v e g e t a t i o n around the t r u n k were more h e a v i l y i n f e s t e d than t r e e s i n loam o r i n c l a y w i t h v e g e t a t i o n . No p e a c h t r e e b o r e r s were found i n any of the c h o k e c h e r r y t r e e s examined nor i n any abandoned Prunus p l a n t i n g s . F e r t i l i z a t i o n and i r r i g a t i o n were imp o r t a n t i n d e t e r m i n i n g b o r e r s u r v i v a l and e s t a b l i shment. More than h a l f of the f o r t y growers s u r v e y e d d i d not know i f t h e i r o r c h a r d s were i n f e s t e d w i t h p e a c h t r e e b o r e r , a l t h o u g h a l l mature p l a n t i n g s where no c o n t r o l s were b e i n g c a r r i e d out c o n t a i n e d b o r e r s . i i i F our p o s s i b l e c o n t r o l methods were t e s t e d i n f i v e i n f e s t e d o r c h a r d s . Two methods, removal of b o r e r l a r v a e by hand and c o a t i n g the t r u n k w i t h r u b b e r l a t e x i n an attempt to p r e v e n t l a r v a l e n t r y , were i n e f f e c t i v e . Chemical c o n t r o l was more s u c c e s s f u l but 20 % of the t r e e s s p r a y e d once w i t h e n d o s u l f a n (Thiodan) a t the b e g i n n i n g of the p e r i o d of a d u l t emergence were s u c c e s s f u l l y a t t a c k e d d u r i n g the summer. T h i s was reduced to 7.8 % on t r e e s t h a t r e c e i v e d a second s p r a y 4 weeks l a t e r . An aluminum cone d e s i g n e d to p r o t e c t the b a s a l a r e a of the t r e e t r u n k t h a t i s most s u s c e p t i b l e t o b o r e r a t t a c k was c o m p l e t e l y s u c c e s s f u l i n p r e v e n t i n g i n f e s t a t i o n . These r e s u l t s are compared w i t h the r e s u l t s of growers' c o n t r o l programs. C o n v e n t i o n a l e n d o s u l f a n t r u n k s p r a y s are very e f f e c t i v e when p r o p e r l y a p p l i e d , but o n l y 5 of 40 growers were u s i n g them. The advantages and d i s a d v a n t a g e s of a l l methods of c o n t r o l are d i s c u s s e d and the importance of g r o wers' u n d e r s t a n d i n g the b i o l o g y of the i n s e c t and c o m p a t i b i l i t y of c o n t r o l methods w i t h i n the c o n t e x t of the t o t a l o r c h a r d o p e r a t i o n emphasized. i v ACKNOWLEDGEMENTS I am g r e a t l y i n d e b t e d t o my s u p e r v i s o r , Dr. Judy Myers, f o r h e r s u p p o r t , encouragement and a s s i s t a n c e t h r o u g h o u t . Roxanne Rousseau gave v a l u a b l e t e c h n i c a l a s s i s t a n c e i n the f i e l d t h a t was much a p p r e c i a t e d . I am g r a t e f u l t o the many growers who c o o p e r a t e d i n the s u r v e y and e x p e r i m e n t s , e s p e c i a l l y Gabe Coupal who suggested and a s s i s t e d i n c a r r y i n g out the l a t e x t r e a t m e n t s and Ron R u t t who h e l p e d i n d e s i g n i n g the guards. I a l s o thank John P r o c t o r and F r e d Banham f o r t h e i r a d v i c e and i n t e r e s t and C r i s Guppy f o r d o n a t i n g the pheromone used i n the p r o j e c t . Dr. Mark Winston r e a d an e a r l y d r a f t of t h i s t h e s i s and made a number of h e l p f u l s u g g e s t i o n s . Dr. B i l l W e l l i n g t o n was a c o n s t a n t source of a d v i c e and encouragement. My thanks a l s o to D r s . Myers, W e l l i n g t o n , Isman and Rune c k l e s f o r t h e i r guidance and a s s i s t a n c e as my s u p e r v i s o r y committee. V TABLE OF CONTENTS Page TITLE i ABSTRACT i i ACKNOWLEDGEMENTS i v TABLE OF CONTENTS v LIST OF TABLES v i LIST OF FIGURES v i i INTRODUCTION 1 CHAPTER I THE SURVEY: PEACHTREE BORER DISTRIBUTION AND THE ROLE OF ENVIRONMENTAL FACTORS 4 CHAPTER I I THE EXPERIMENT: EVALUATION OF FOUR CONTROL METHODS 30 CONCLUSIONS 57 REFERENCES .' 63 v i LIST OF TABLES Page Table I . R e l a t i o n s h i p between peach t r e e age and r a t e of p e a c h t r e e b o r e r i n f e s t a t i o n 8 Table I I . E f f e c t of t r e e s p e c i e s d i f f e r e n c e s w i t h i n o r c h a r d s on l e v e l s of i n f e s t a t i o n 11 Table I I I . E f f e c t of v a r i e t i e s on per ce n t of t r e e s i n f e s t e d by p e a c h t r e e b o r e r w i t h i n o r c h a r d s of t r e e s of the same age 12 Table IV. I n f l u e n c e of s o i l on t r e e s i n f e s t e d by pe a c h t r e e b o r e r 19 Table V. I n f l u e n c e of v e g e t a t i o n on t r e e s i n f e s t e d by pe a c h t r e e b o r e r 20 Table V I . I n f l u e n c e of s o i l and v e g e t a t i o n on per c e n t of t r e e s a t t a c k e d by p e a c h t r e e b o r e r 22 Table V I I . P e a c h t r e e b o r e r a t t a c k i n o r c h a r d s exposed t o d i f f e r e n t c o n t r o l p r o c e d u r e s ....26 Table V I I I . P e a c h t r e e b o r e r l a r v a l p o p u l a t i o n s : i n i t i a l assessment 34 Table IX. Summary of the number of t r e e s i n each t r e a t m e n t 41 Table X. Per c e n t a g e of l a r v a e missed by mechanical removal t r e a t m e n t (S.E.) 43 Table X I . P e r c e n t a g e s of t r e e s a t t a c k e d by p e a c h t r e e b o r e r i n 1984 f o l l o w i n g d i f f e r e n t c o n t r o l t r e a t m e n t s 44 Table X I I . Thiodan t r e a t e d t r e e s w i t h p e a c h t r e e b o r e r l a r v a e i n September 1984 45 Table X I I I . Number of t r e e s t r e a t e d w i t h m echanical removal and/or Thiodan s p r a y i n g had l a r v a e from 1983 p r e s e n t i n September 1984 47 Table XIV. P e r c e n t a g e s of c o n t r o l t r e e s a t t a c k e d by pe a c h t r e e b o r e r i n September 1984 46 v i i LIST OF FIGURES Page F i g u r e 1. Map of experiment s i t e s 33 F i g u r e 2. Guard 39 F i g u r e 3. P o s s i b l e gaps i n Thiodan p r o t e c t i o n 52 1 INTRODUCTION Svnanthedon e x i t i o s a Say, ( L e p i d o p t e r a t S e s i i d a e ) , a n a t i v e N o r t h American i n s e c t , became a s e r i o u s p e s t , "the p e a c h t r e e b o r e r " , f o l l o w i n g the i n t r o d u c t i o n of d o m e s t i c Prunus v a r i e t i e s to N o r t h America (Saunders 1871; Lyne 1913; S l i n g e r l a n d and Crosby 1915; Gould 1923; Boyce 1961; M e t c a l f and F l i n t 1962; Davidson & Lyon 1979; Yonce and G e n t r y 1982). The females of t h i s d i u r n a l , c l e a r - w i n g e d moth o v i p o s i t on or near Prunus t r e e s . The l a r v a e burrow under the bark of the t r u n k and f e e d on the cambium l a y e r f o r one or two y e a r s ( E s s i g 1938; Armstrong 1940; S m i t h 1952). Young t r e e s are o f t e n g i r d l e d and k i l l e d . O l d e r t r e e s are a f f e c t e d more i n d i r e c t l y . B o r e r a t t a c k can i n c r e a s e t h e i r s u s c e p t i b i l i t y t o w i n t e r i n j u r y , d i s e a s e s and o t h e r i n s e c t s (Gould 1923; M e t c a l f and F l i n t 1962; Agr. Handbook 1974; Heflebower 1984). I n a d d i t i o n , c a l l o u s i n g (the response to b o r e r i n j u r y ) draws h e a v i l y on the t r e e s ' energy r e s e r v e s and r e s u l t s i n poor growth ( W i l s o n e t a l . 1983). C o n t r o l methods r a n g i n g from washes of m a t e r i a l s l i k e P a r i s g r een and l e a d a r s e n a t e , to s p r a y s of p a r a t h i o n and DDT have been used over the y e a r s w i t h v a r y i n g degrees of s u c c e s s ( S l i n g e r l a n d and Crosby 1915; Smith 1952; Madsen and B a i l e y 1959; Snapp 1962; Davidson & Lyon 1979). C u r r e n t l y , i n Canada and the U.S., two s p r a y s of the o r g a n o c h l o r i n e i n s e c t i c i d e , e n d o s u l f a n ( T h i o d a n ) , 3 to 4 2 weeks a p a r t , a re recommended ( e . g . Ge n t r y & Yonce 1982; P a c i f i c NW I n s e c t C o n t r o l Handbook 1984; B.C. Tree F r u i t 1984 P r o d u c t i o n Guide; O n t a r i o Tree F r u i t P r o d u c t i o n Guide 1984). However, a p r e l i m i n a r y s u r v e y a t the o u t s e t of t h i s s t u d y showed t h a t many o r c h a r d i s t s i n the N o r t h Okanagan V a l l e y i n B r i t i s h Columbia were not f o l l o w i n g t h i s recommendation even when t h e i r t r e e s were i n f e s t e d w i t h p e a c h t r e e b o r e r . Some were s t i l l u s i n g a very o l d t e c h n i q u e , removal of the b o r e r l a r v a e by hand from the t r u n k s of i n f e s t e d t r e e s (Saunders 1871; B r i t t a i n 1914). Many were d o i n g n o t h i n g t o c o n t r o l b o r e r . The o b j e c t i v e s of t h i s i n v e s t i g a t i o n were to determine 1) how widespr e a d p e a c h t r e e b o r e r i n f e s t a t i o n s were i n s t o n e - f r u i t p l a n t i n g s and i n a n a t i v e h o s t , Prunus  v i r g i n i a n a L., i n the Okanagan V a l l e y , 2) t o compare the n a t u r a l c o n d i t i o n s under which the i n s e c t o c c u r s w i t h those found i n o r c h a r d s , 3) to determine the e f f e c t of these d i f f e r e n t h a b i t a t s on p e a c h t r e e - b o r e r s u r v i v a l and d i s t r i b u t i o n . Growers were s u r v e y e d t o determine which c o n t r o l methods they used and why they made the c h o i c e s they d i d . I a l s o wanted to e v a l u a t e c o n t r o l measures a g a i n s t p e a c h t r e e b o r e r t h r o u g h f i e l d e x p e r i m e n t s , and to use i n f o r m a t i o n about the e c o l o g i c a l r e l a t i o n s h i p s t o improve the e f f e c t i v e n e s s of these methods o r to suggest new avenues f o r c o n t r o l . 3 C h a p t e r I r e p o r t s t h e r e s u l t s o f t h e s u r v e y I c a r r i e d o u t t o d e t e r m i n e t h e e x t e n t o f O k a n a g a n p e a c h t r e e - b o r e r i n f e s t a t i o n , a n d t o d e t e r m i n e p o s s i b l e r e l a t i o n s h i p s b e t w e e n 1) e n v i r o n m e n t a l f a c t o r s a n d management t e c h n i q u e s w i t h i n t h e d i f f e r e n t o r c h a r d s , a n d 2) l e v e l s o f b o r e r i n f e s t a t i o n t h e r e i n . The n a t i v e h o s t o f t h i s i n s e c t , P r u n u s v i r g i n i a n a L . , was a l s o s u r v e y e d a n d g r o w e r a w a r e n e s s o f t h e p r o b l e m a n d e f f e c t i v e n e s s o f t h e i r c o n t r o l p r o g r a m s was a s s e s s e d . C h a p t e r I I , c o n t a i n s t h e r e s u l t s o f e x p e r i m e n t s I c o n d u c t e d i n 5 i n f e s t e d o r c h a r d s t o e v a l u a t e t h e e f f e c t i v e n e s s o f f o u r me t hod s o f c o n t r o l l i n g o r p r e v e n t i n g b o r e r i n f e s t a t i o n . The se me t hod s i n c l u d e d e n d o s u l f a n s p r a y s , r e m o v a l o f b o r e r l a r v a e by h a n d , a n d c o v e r i n g t h e t r u n k w i t h e i t h e r a c o a t o f l i q u i d l a t e x o r a n a l u m i n u m c o n e . The a d v a n t a g e s a n d d i s a d v a n t a g e s o f e a c h me thod u n d e r o r c h a r d c o n d i t i o n s a r e d i s c u s s e d . 4 CHAPTER I THE SURVEY: PEACHTREE BORER DISTRIBUTION AND THE ROLE OF ENVIRONMENTAL FACTORS. 5 INTRODUCTION Pe a c h t r e e b o r e r was f r e q u e n t l y r e p o r t e d as a s e r i o u s p e s t of Prunus o r c h a r d s i n B r i t i s h Columbia i n the e a r l y 1900's (Lyne 1913; B r i t t a i n 1914, Ruhman 1923) and g u i d e s f o r growers (B.C. Tree F r u i t P r o d u c t i o n Guide 1984) s i n c e then have always c o n t a i n e d recommendations f o r c o n t r o l . D u r i n g my p r e l i m i n a r y i n q u i r i e s i n 1983, however, I found t h a t growers and a g r i c u l t u r a l e x t e n s i o n p e r s o n n e l d i d not know how wi d e s p r e a d the problem c u r r e n t l y was. There was a l s o no i n f o r m a t i o n on what f a c t o r s might determine B r i t i s h Columbia p o p u l a t i o n s of the i n s e c t . T h i s s t u d y was undertaken to a s s e s s the e x t e n t of pe a c h t r e e b o r e r i n f e s t a t i o n i n n a t i v e h o s t s and i n Prunus o r c h a r d s , and t o determine i f l e v e l s of b o r e r i n f e s t a t i o n were r e l a t e d t o e n v i r o n m e n t a l and management d i f f e r e n c e s i n d i f f e r e n t o r c h a r d s . Grower awareness of the problem, and the e f f e c t i v e n e s s of t h e i r c o n t r o l programs, when used, were a l s o a s s e s s e d . METHODS A t r e e - b y - t r e e s e a r c h f o r b o r e r i n f e s t a t i o n was c a r r i e d out on over 7000 t r e e s i n 49 d i f f e r e n t Prunus p l a n t i n g s i n the Okanagan V a l l e y of B r i t i s h Columbia i n 1984. I su r v e y e d e v e r y p l a n t i n g w i t h more th a n 20 Prunus t r e e s t h a t I c o u l d f i n d i n the Westbank a r e a (17 i n t o t a l ) . Four o r c h a r d s i n the South Okanagan were checked and 28 o t h e r s 6 were s e l e c t e d a r b i t r a r i l y w i t h i n the a r e a between Westbank and Oyama. F o r t y - t w o of the 49 p l a n t i n g s were commercial o r c h a r d s . The o t h e r s e i t h e r were used o n l y by the owner or were abandoned. T h i r t y - f o u r c h o k e c h e r r y t r e e s , Prunus  v i r q i n i a n a L., the o n l y n a t i v e h o s t of p e a c h t r e e b o r e r s i n the Okanagan (Lyon 1952) were a l s o checked i n 9 d i f f e r e n t l o c a t i o n s . The t r u n k of each t r e e was i n s p e c t e d from the f i r s t s c a f f o l d b ranch to 10-15 cm below the s o i l s u r f a c e f o r the c h a r a c t e r i s t i c r e d d i s h - b r o w n gum/frass m i x t u r e t h a t exudes from l a r v a l t u n n e l s . Based on the degree of wounding and s i z e of l a r v a e found, i t was p o s s i b l e t o d etermine i f the t r e e had been a t t a c k e d i n the c u r r e n t y e a r , the p a s t year or p r e v i o u s to t h a t . Approximate age and g e n e r a l c o n d i t i o n , s p e c i e s ( p r u n e , a p r i c o t , peach, n e c t a r i n e , c h e r r y ) and whenever p o s s i b l e , v a r i e t y ( e . g . Red Haven, F a i r Haven), of the t r e e s was r e c o r d e d . O r c h a r d and c h o k e c h e r r y s i t e c o n d i t i o n s , e s p e c i a l l y m o i s t u r e l e v e l s and i r r i g a t i o n p r a c t i c e s , v e g e t a t i o n c o n t r o l , and s o i l t y p e s were a l s o r e c o r d e d . RESULTS AND DISCUSSION More than 3/4 of the o r c h a r d s (38 of 4 9 ) , had t r e e s w i t h p e a c h t r e e b o r e r l a r v a e . L e v e l of a t t a c k per o r c h a r d ranged from 0.9 t o 83.3 %. The number of b o r e r s per a t t a c k e d t r e e v a r i e d from 1 to 25. " T o t a l o r c h a r d " e v a l u a t i o n or c omparison i s not u s e f u l however, because a l l but 3 of the o r c h a r d s had more than one v a r i e t y , s p e c i e s or age of 7 Prunus and the e x t e n t and s e v e r i t y of a t t a c k v a r y w i t h these f a c t o r s . F o r example, w i t h i n an o r c h a r d , over h a l f of one age group o r s p e c i e s may be a t t a c k e d w h i l e none of a n o t h e r a r e . E n v i r o n m e n t a l c o n d i t i o n s and management p r a c t i c e s t h a t might a f f e c t b o r e r p o p u l a t i o n s a l s o v a r i e d from one o r c h a r d t o a n o t h e r . The e f f e c t of these d i f f e r e n t f a c t o r s i s c o n s i d e r e d below. 1. The Tree: i ) Tree Age Trees l e s s t h a n 5 y e a r s o l d had the lo w e s t r a t e of i n f e s t a t i o n ( T a b l e I ) . T h i s was a l s o t r u e i n o r c h a r d s where younger t r e e s were i n t e r p l a n t e d w i t h o l d e r t r e e s of the same v a r i e t y and under the same e n v i r o n m e n t a l and management c o n d i t i o n s . However, when young t r e e s were a t t a c k e d , the damage was much more s e r i o u s than i n o l d e r t r e e s . I n 11 of the 24 o r c h a r d s w i t h peach t r e e s 4 y e a r s o l d o r l e s s , young t r e e s g i r d l e d by as few as one p e a c h t r e e b o r e r l a r v a had been k i l l e d . Trees i n the 5-10 year range were the most f r e q u e n t l y and heav-ily a t t a c k e d . Trees o l d e r t h a n 10 y e a r s were i n f e s t e d a t about t w i c e the fr e q u e n c y of young t r e e s but o n l y h a l f as much as those i n the middle age ranges (Table I ) . Young t r e e s , e s p e c i a l l y i n new and/or i s o l a t e d b l o c k s , may have escaped a t t a c k because t h e y have not y e t been d i s c o v e r e d by b o r e r s . A d u l t females appear to be poor d i s p e r s e r s . In 1984, I mo n i t o r e d a t t a c k l e v e l s i n f o u r 8 TABLE I : NUMBER OF PEACH ORCHARDS AND TREES WITH PEACHTREE BORER RELATIVE TO TREE AGE. ORCHARDS TREES Tree T o t a l With T o t a l W ith P e r c e n t Age B o r e r B o r e r 1-4 YRS. 24 16 2575 224 8.7 5-10 YRS. 22 20 2406 760 31.6 11 YRS.+ 20 14 999 173 17.3 9 o r c h a r d s on 210 t r e e s which had not p r e v i o u s l y been a t t a c k e d and on 624 which had been i n f e s t e d s i n c e a t l e a s t 1983. Of the t r e e s p r e v i o u s l y a t t a c k e d , 66 % were a t t a c k e d a g a i n . T h i r t e e n per c e n t of the u n a t t a c k e d t r e e s were, by September, 1984. In o r c h a r d s w i t h low b o r e r p o p u l a t i o n s , the t r e e s t h a t a l r e a d y had b o r e r s were a t l e a s t 7 times more l i k e l y t o be a t t a c k e d a g a i n , t h a n were p r e v i o u s l y u n a t t a c k e d t r e e s of the same age. Even i n h e a v i l y i n f e s t e d o r c h a r d s , r e a t t a c k was t w i c e as l i k e l y as new a t t a c k . The female moths are h e a v y - b o d i e d , weak f l i e r s and u s u a l l y l a y most of t h e i r eggs on the t r e e from which they emerge or on i m m e d i a t e l y a d j a c e n t ones (Snapp and Thomson 1943; S m i t h 1952; B a r r y and N i e l s e n 1984). I o b s e r v e d t h a t they f r e q u e n t l y walk r a t h e r than f l y . The a t t r a c t i v e n e s s of p r e v i o u s l y a t t a c k e d t r e e s to b o r e r females has a l s o been observed by o t h e r s ( B l a k e s l e s s 1914; Armstrong 1940; S m i t h and H a r r i s 1952; Madsen and B a i l e y 1959). T h i s i s a t l e a s t p a r t l y due to the gum/frass m i x t u r e from p r e v i o u s b o r e r wounds and from cocoons b e i n g an o v i p o s i t i o n s t i m u l a n t ( G e n t r y and W e l l s 1982). Younger t r e e s may a l s o be l e s s a t t r a c t i v e t o o v i p o s i t i n g females and/or have a lower r a t e of l a r v a l e s t a b l i s h m e n t because of bark t e x t u r e . The females p r e f e r t o o v i p o s i t i n c r a c k s i n the bark or o l d wounds ( B e c k e r 1917; E s s i g 1938; S m i t h 1952; M e t c a l f & F l i n t 1862; B a r r y and N e i l s e n 1984; p e r s o n a l o b s e r v a t i o n s ) . Young t r e e s have smoother bark than o l d e r t r e e s and u s u a l l y fewer or no wounds. Newly 10 h a t c h e d l a r v a e t h a t can imme d i a t e l y seek s h e l t e r i n a f i s s u r e of some k i n d have a much b e t t e r chance of a v o i d i n g p r e d a t i o n ( B u t l e r 1932; Davidson and Lyon 1979) and d e a t h from d e s i c c a t i o n ( S m i t h 1965; a l s o see next s e c t i o n ) . Trees o l d e r than 10 y e a r s have a lower r a t e of i n f e s t a t i o n than those i n the 5-10 year range ( x a = 72.1 p<0.001). Bark t h i c k n e s s and i n a c c e s s i b i l i t y of the cambium l a y e r i n c r e a s e w i t h age. I t may a l s o be t h a t those t r e e s t h a t s u r v i v e have o t h e r as yet u n i d e n t i f i e d r e s i s t a n c e f a c t o r s . i i ) S p e c i e s and V a r i e t y I compared f r e q u e n c i e s of a t t a c k on d i f f e r e n t Prunus s p e c i e s of comparable age growing i n the same o r c h a r d s ( T a b l e I I ) . Only 1 of 146 c h e r r y t r e e s , Prunus avium, i n 11 o r c h a r d s w i t h o t h e r i n f e s t e d Prunus s p e c i e s had b o r e r l a r v a e . Peaches, Prunus p e r s i c a . had the h i g h e s t r a t e of i n f e s t a t i o n , 3 t o 4 ti m e s t h a t of p r u n e s , Prunus d o m e s t i c a , and a p r i c o t s , Prunus a r m e n i a c a . and about t w i c e as much as n e c t a r i n e s , Prunus p e r s i c a . Prunes were the l e a s t a t t a c k e d , a f t e r c h e r r i e s . A p r i c o t s and n e c t a r i n e s f e l l between peaches and prunes (Table I I ) . V a r i e t i e s of peaches t h a t were of the same age w i t h i n the same o r c h a r d were compared (Table I I I ) . I n 4 of the 8 o r c h a r d s , t h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n r a t e of a t t a c k among v a r i e t i e s : o r c h a r d # 1 (x = 5.0, p< 0.1), o r c h a r d # 4 (x^=0.2, p< 0.5 ( E l b e r t a s vs F a i r Haven) and 11 TABLE I I : EFFECT OF TREE SPECIES DIFFERENCES WITHIN ORCHARDS ON LEVELS OF INFESTATION. SPECIES ORCHARDS TREES TREES % TREES ATTACKED ATTACKED Peaches & Prunes * 14 Peaches 1495 464 31.0 Prunes 358 32 8.9 * Peaches & A p r i c o t s 14 Peaches 1567 369 23.6 A p r i c o t s 483 36 7.5 ** Peaches & N e c t a r i n e s 8 Peaches 576 99 17.2 N e c t a r i n e s 206 20 9.7 *** Prunes & A p r i c o t s 9 Prunes 210 28 13.3 A p r i c o t s 158 30 19.0 *** Prunes & N e c t a r i n e s 3 Prunes 100 9 9.0 N e c t a r i n e s 8 2 25.0 *** A p r i c o t s & N e c t a r i n e s 3 A p r i c o t s 36 7 19.4 N e c t a r i n e s 48 7 14.6 Chi square t e s t : * degree of a t t a c k between s p e c i e s s i g n i f i c a n t l y d i f f e r e n t a t P<0.005 ** degree of a t t a c k between s p e c i e s s i g n i f i c a n t l y d i f f e r e n t a t P<0.010 *** no s i g n i f i c a n t d i f f e r e n c e s , P<0.750 t o P<0.10 12 TABLE I I I : EFFECT OF VARIETIES ON TREES INFESTED WITH PEACHTREE BORER WITHIN ORCHARDS OF TREES THE SAME AGE. ORCHARD AGE NUMBER TREES ATTACKED/TOTAL TREES V a r i e t y 1 V a r i e t y 2 V a r i e t y 3 V a r i e t y 4 8 11 + 11 + 1 1 + 11 + < 5 < 5 5-10 5-10 5-10 V: 1/10 (10.0 %) E:3/6 (50.0 %) FH:5/35 (14.3 %> E:3/3 (100 %) FH:3/8 (37.5 %) 1 ER:6/25 (24.0 %) ER:10/14 (71.4 %) ER:76/95 (80.0 %) i V:46/48 (95.8 %) ER:4/40 (10.0 %) ER:4/20 (20.0 %> V:3/26 (11.5 %) FH:7/9 (77.8 %) GH:1/4 (25.0 %) H:23/300 (7.7 %) RH:198/279 (71.0 %) FH:50/123 (40.7 %) E:4/20 (20.0 %) ER:11/101 (10.9 %) RH:65/246 (26.4 %) GH:4/8 (25.0 %) FH:7/20 (35.0%) V: V e t e r a n ER: E a r l y Red Haven RH: Red Haven GH: Glow Haven E: E l b e r t a H: H a r b r i t e FH: F a i r Haven * v a r i e t a l i n f e s t a t i o n r a t e s i g n i f i c a n t l y h i g h e r , P<0.005 ( c h i square t e s t ) than o t h e r v a r i e t i e s i n o r c h a r d . See t e x t f o r d e t a i l 13 i x =0.1, p< 0.5 ( F a i r Havens vs Glow H a v e n s ) ) , o r c h a r d # 2 (x * = 1.5, p< 0.1), o r c h a r d # 3 (x*= 0.3, p< 0.5), and o r c h a r d # 6 (x*= 0.0, p< 0.975). In o r c h a r d # 8, V e t e r a n was i n f e s t e d a t a s i g n i f i c a n t l y h i g h e r r a t e of the 3 o t h e r v a r i e t i e s t h e r e ( x*= 9.7, p< 0.005) but t h e r e was no s i g n i f i c a n t l y d i f f e r e n t r a t e of a t t a c k among the o t h e r t h r e e v a r i e t i e s . In o r c h a r d # 5, E a r l y Red Haven was more f r e q u e n t l y a t t a c k e d than H a r b r i t e ( x*= 7.2, p< 0.005). In o r c h a r d # 7, F a i r Haven was more f r e q u e n t l y a t t a c k e d t h a n x Red Haven ( x = 5.3, p< 0.025) and the E a r l y Red Haven was s i g n i f i c a n t l y more a t t a c k e d than e i t h e r of the o t h e r 2 v a r i e t i e s ( x a = 41.2, p< 0.005). These r e s u l t s c o n f i r m the e a r l i e r o b s e r v a t i o n s of o t h e r s t u d i e s . E s s i g (1938) obse r v e d t h a t , w h i l e a l l Prunus s p e c i e s were a t t a c k e d by p e a c h t r e e b o r e r , peaches were p r e f e r r e d and a p r i c o t s , e s p e c i a l l y on t h e i r own r o o t s t o c k s , were the most r e s i s t a n t . In O n t a r i o , Weaver and Boyce (19 6 5 ) , o b s e r v e d an i n f e s t a t i o n range from 8 - 81 % on 23 v a r i e t i e s of peaches. S i n c e damage and r a t e of a t t a c k were reduced on many of the l e s s w i n t e r — h a r d y v a r i e t i e s , t hey s u g g e s t e d t h a t such v a r i e t i e s d i d not have enough l i v e t i s s u e t o s u p p o r t b o r e r s . However, these a u t h o r s a l s o noted a number of hardy v a r i e t i e s w i t h low r a t e s of a t t a c k . C h a p l i n and S c h n e i d e r (1975) demonstrated t h a t d i f f e r e n t r o o t s t o c k s c o u l d be a s s o c i a t e d w i t h r a t e s of a t t a c k r a n g i n g from 10% to 69%. Red Haven budded onto S i b e r i a n C 14 r o o t s t o c k always had the h i g h e s t r a t e of i n f e s t a t i o n and the g r e a t e s t amount of i n j u r y whereas Red Haven on R u t e r s Red L e a f had the l o w e s t i n f e s t a t i o n r a t e and the l e a s t i n j u r y . S i n c e the more s u s c e p t i b l e S i b e r i a n C r o o t s t o c k induces w i n t e r h a r d i n e s s , C h a p l i n and S c h n e i d e r ' s r e s u l t s suggest t h a t " t o l e r a n c e " r a t h e r than " w i n t e r h a r d i n e s s " u n d e r l i e s any r e s i s t a n c e of peach s t o c k t o b o r e r i n f e s t a t i o n . Bark t e x t u r e ( i . e . , the degree of c r a c k i n g ) , which i s g e n e t i c a l l y i n f l u e n c e d by b o t h the s c i o n and the r o o t s t o c k , v a r i e s among Prunus s p e c i e s and v a r i e t i e s . As n o t e d p r e v i o u s l y , t e x t u r e c o u l d be i m p o r t a n t i n d e t e r m i n i n g the h o s t ' s a t t r a c t i v e n e s s t o o v i p o s i t i n g females and i t s s u i t a b i l i t y as a s h e l t e r f o r newly emerged l a r v a . I n h e r e n t d i f f e r e n c e s i n b u l k d e n s i t i e s of wood, d i g e s t i b i l i t y and the presence of t a n n i n s and o t h e r secondary compounds c o u l d a l s o p l a y a r o l e i n d e t e r m i n i n g the r a t e s of s u c c e s s f u l a t t a c k on d i f f e r e n t k i n d s of Prunus. i i i ) P h y s i o l o g i c a l C o n d i t i o n of the Tree Bark c r a c k s can r e s u l t from i n j u r y , most commonly t h a t caused by c o l d . W i n t e r h a r d i n e s s i s under g e n e t i c c o n t r o l but i s g r e a t l y i n f l u e n c e d by the p h y s i o l o g i c a l c o n d i t i o n of the t r e e and w i n t e r damage ( e.g. bark c r a c k i n g , i n c r e a s e d s u s c e p t i b i l i t y of dormant f l o w e r buds to damage) o c c u r s l e a s t on m o d e rately v i g o r o u s t r e e s t h a t grew w e l l the 15 p r e v i o u s season and were not weakened by b o r e r s , d i s e a s e o r nematodes ( A g r i c u l t u r e R esearch S e r v i c e 1984). Becker (1917) r e p o r t e d f l u c t u a t i o n s i n the numbers of i n s e c t s t h a t matured each year from the same t r e e s and sug g e s t e d ( w i t h o u t e l a b o r a t i n g ) t h a t t h i s was "due t o changes i n the c o n d i t i o n s of the t r e e s " . Smith (1952) l i n k e d lower r a t e s of l a r v a l e s t a b l i s h m e n t w i t h t r e e s of low v i g o r . In e x p e r i m e n t s he conducted w i t h l e s s e r p e a c h t r e e b o r e r , t r e e s t h a t r e c e i v e d h i g h r a t e s of n i t r o g e n and c l e a n c u l t i v a t i o n had h i g h e r r a t e s of a t t a c k than those w i t h h i g h n i t r o g e n and a r y e c o v e r c r o p . Trees g i v e n s m a l l amounts of n i t r o g e n w i t h o u t a c o v e r c r o p had the t h i r d h i g h e s t r a t e of i n f e s t a t i o n and those w i t h low r a t e s of I f , as i t a p p e a r s , l e s s v i g o r o u s t r e e s are not as s u s c e p t i b l e t o p e a c h t r e e b o r e r a t t a c k , then the p h y s i o l o g i c a l c o n d i t i o n of i n t e r p l a n t e d young t r e e s may p l a y a r o l e i n t h e i r lower r a t e s of i n f e s t a t i o n . They are i n c o m p e t i t i o n w i t h much l a r g e r t r e e s and are o f t e n n u t r i e n t s t r e s s e d . I r r i g a t i o n r a t e s s e t f o r the o l d e r t r e e s a l s o are g e n e r a l l y i n s u f f i c i e n t f o r the younger ones. 2. The Environment: i ) I r r i g a t i o n E f f e c t s Of the 49 o r c h a r d s s u r v e y e d , 11 were f r e e of p e a c h t r e e b o r e r i n f e s t a t i o n . Seven of the 11 o r c h a r d s w i t h o u t p e a c h t r e e b o r e r were e i t h e r u n i r r i g a t e d o r ve r y r a r e l y 16 i r r i g a t e d . Two of these s i t e s (a t o t a l of 53 t r e e s ) were t o t a l l y abandoned. I had obser v e d a h i g h i n f e s t a t i o n of b o r e r 6 y e a r s p r e v i o u s l y , when one of these s i t e s was b e i n g i r r i g a t e d . The o t h e r had many t r e e s w i t h o l d wounds around the base t y p i c a l of p r e v i o u s p e a c h t r e e b o r e r l a r v a l damage. F i v e o t h e r o r c h a r d s ( 306 t r e e s ) of the 7 t h a t were o n l y watered i n f r e q u e n t l y , a l s o had no b o r e r . In two o r c h a r d s a d j a c e n t t o each o t h e r , 10 % of 320 peach and n e c t a r i n e t r e e s i n the s i t e watered l e s s than h a l f as much as 340 t r e e s i m m e d i a t e l y a d j a c e n t , were a t t a c k e d w h i l e 40 % of the l a t t e r c o n t a i n e d a c t i v e b o r e r p o p u l a t i o n s . The b l o c k w i t h the lower r a t e of i n f e s t a t i o n was a l s o more n u t r i e n t s t r e s s e d . No f e r t i l i z e r s had been a p p l i e d f o r s e v e r a l y e a r s and the t r e e s e x h i b i t e d e x t e n s i v e l e a f y e l l o w i n g and were s m a l l e r than t r e e s of comparable age and s p e c i e s i n the o t h e r p l a n t i n g . I n a n o t h e r p l a n t i n g of 60 peaches of the same age and v a r i e t y , h a l f of the t r e e s were w e l l watered and h a l f were n o t . Almost 80 % of the t r e e s i n the w e l l - w a t e r e d s e c t i o n were h e a v i l y a t t a c k e d . Only 10 % i n the h a l f e s t i m a t e d by the o r c h a r d i s t t o r e c e i v e h a l f as much water, had b o r e r l a r v a e . Most of the o r c h a r d s w i t h h e a v i e r b o r e r i n f e s t a t i o n s were watered once a week f o r about 12 hours i n n o n - r a i n y p e r i o d s . I a l s o examined 34 c h o k e c h e r r y t r e e s , Prunus v i r g i n i a n a L., i n n i n e d i f f e r e n t l o c a t i o n s i n the su r v e y a r e a . None of the n a t i v e h o s t s , i n c l u d i n g 6 t r e e s 17 b o r d e r i n g i n f e s t e d o r c h a r d s , had l i v e b o r e r s , a l t h o u g h some had o l d wounds a t the base. While the type of l o c a t i o n v a r i e d ( r o a d s i d e s , a c r e e k d e l t a , r a v i n e s ) , a l l were much d r i e r t h a n a l l but the most n e g l e c t e d o r c h a r d s . The humid m i c r o - c l i m a t e c r e a t e d i n we 1 1 - i r r i g a t e d o r c h a r d s may g r e a t l y enhance l a r v a l e s t a b l i s h m e n t , f e e d i n g , p u p a t i o n , and a d u l t emergence. The c o n t r a s t i n g d e p r e s s a n t e f f e c t of a d r y c l i m a t e or d r y p e r i o d s of weather on p e a c h t r e e b o r e r p o p u l a t i o n s has been noted b e f o r e (Snapp and Thompson 1943; Madsen and B a i l e y 1959). Sm i t h (1965) found t h a t h i g h h u m i d i t y was v e r y i m p o r t a n t f o r e a r l y i n s t a r s u r v i v a l i n the l a b o r a t o r y . He a l s o n o t e d t h a t d e s i c c a t i o n i n the f i e l d c o u l d r e s u l t i n l a r v a l m o r t a l i t i e s as h i g h as 99.5 per c e n t . I found t h a t e a r l y i n s t a r s exposed to s u n l i g h t c o u l d d i e i n 10 minutes whereas, i n shade or i n moist s o i l , o r when they c o u l d r e a c h wounds o r c r a c k s , they s u r v i v e d . E s s i g (1938) observed t h a t l a r v a e e n t e r e d t r e e s more r e a d i l y i f the bark was damp. Gen t r y e t a l . ( 1 9 7 8 ) r e p o r t e d t h a t wet s p r i n g s and summers hastened a d u l t emergence. Sm i t h (1965) observed t h a t p e a c h t r e e b o r e r s d i d not t h r i v e i n abandoned o r c h a r d s but d i d not s p e c u l a t e on why t h i s was so. Madsen and B a i l e y ( 1 9 5 9 ) , who found C a l i f o r n i a p e a c h t r e e b o r e r p o p u l a t i o n s to be much h i g h e r on a p r i c o t s than peaches, s u g g e s t e d t h i s d i f f e r e n c e o c c u r r e d because the i n s e c t was more of a p e s t i n the c o a s t a l a r e a s 18 where a p r i c o t s were the dominant Prunus s p e c i e s . In the d r i e r i n t e r i o r , where peaches were the dominant stone f r u i t c r o p , b o r e r s were not such a s e r i o u s problem. I r r i g a t i o n or the l a c k of i t a l s o a f f e c t s the t r e e ' s p h y s i o l o g i c a l c o n d i t i o n . D r o u g h t - s t r e s s e d t r e e s may be l e s s l i k e l y t o be a t t a c k e d or a b l e t o s u p p o r t b o r e r l a r v a e than w e l l - w a t e r e d specimens. i i ) S o i l Type and V e g e t a t i o n C o n t r o l Method The s o i l i n the o r c h a r d s s u r v e y e d was e i t h e r c l a y o r a sandy loam . O v e r a l l , t r e e s i n c l a y s o i l had a 3. s i g n i f i c a n t l y h i g h e r r a t e of a t t a c k than those i n loam (x = 33.3, p< 0.001) (T a b l e I V ) . There were 3 main types of v e g e t a t i o n c o n t r o l p r a c t i s e d i n the su r v e y e d o r c h a r d s . Some growers (24) e i t h e r d i d n o t h i n g , o r o n l y mowed the g r a s s around t h e i r t r e e s . O thers (13) used an h e r b i c i d e t o k i l l a l l v e g e t a t i o n i n the row, and a l s o mowed between the rows. A few (5) kept t h e i r o r c h a r d s f r e e of a l l v e g e t a t i o n by u s i n g an h e r b i c i d e w i t h i n the rows and mechanical c u l t i v a t i o n between them. As can be seen from Table V, those k e e p i n g the a r e a around the base of the t r e e f r e e of v e g e t a t i o n had a h i g h e r o v e r - a l l r a t e of b o r e r a t t a c k than those t h a t l e t g r a s s and x o t h e r p l a n t s grow up around the base of the t r e e s (x = 50.8, p> 0.005). 19 TABLE IV: INFLUENCE OF SOIL ON TREES INFESTED BY PEACHTREE BORER. AREA CLAY SANDY LOAM Orchards Trees A t t a c k e d Orchards Trees A t t a c k e Westbank 14 1998 572 2 436 113 X = 0.82, P<0.250 Lakeview 0 0 0 4 500 77 Oyama 4 580 51 2 208 40 X a= 226.5, P<0.001 W i n f i e l d - 5 473 25 O l i v e r - 2 70 Kelowna 3 1070 228 O v e r a l l 21 3648 851 15 1687 264 X a= 33.3, P<0.001 20 TABLE 5: INFLUENCE OF VEGETATION ON TREES INFESTED BY PEACHTREE BORER. AREA CLEAN CULTIVATION VEGETATION Orchards Trees A t t a c k e d Orchards Trees A t t a c k e d Westbank 7 Lakeview 1 1013 462 7 989 X* = 38.0, P<0.005 60 0 3 440 256 77 Oyama 279 47 509 44 W i n f i e l d 1 256 14 172 1 1 Kelowna 870 204 200 24 Lakeview 1 60 0 440 77 0 1 i v e r 70 15 O v e r a l l 16 2557 706 17 X = 50.8, P<0.005 2310 412 S i g n i f i c a n c e o n l y where noted <p<0.250). 21 In an o r c h a r d s u r v e y e d i n e a r l y J u l y , 1984, some of the t r e e s had the v e g e t a t i o n c l e a r e d away from the base of t r e e s and some had n o t . I obser v e d t h a t the former c o n t a i n e d many cocoons and l a r v a e w h i l e the l a t t e r c o n t a i n e d l a r v a e o n l y . The s o i l around the base of the t r e e s w i t h no v e g e t a t i o n was exposed to the sun and w h i l e the temperature d i f f e r e n c e between t h a t and the s o i l around the base of the o t h e r t r e e s w i t h g r a s s a t the base was not measured, i t was a p p r e c i a b l y warmer, p o s s i b l y as much as 5 C ( A t k i n s o n & White 1980). I a l s o l o o k e d a t the combined e f f e c t s of s o i l type and v e g e t a t i o n management (T a b l e V I ) . Trees i n c l a y s o i l , where the a r e a around the t r e e was kept c l e a r of a l l v e g e t a t i o n , had h i g h e r r a t e s of b o r e r a t t a c k t h a n those i n c l a y s o i l w i t h p l a n t growth around the base of the t r e e (x* = 180.7, p<0.005) or t r e e s i n loam w i t h e i t h e r k i n d of v e g e t a t i o n management (x = 4.9, p< 0.025). C l a y s o i l r e t a i n s water l o n g e r than sandy loam and thus may c o n t r i b u t e t o the mo i s t m i c r o c l i m a t e t h a t i s more f a v o u r a b l e t o l a r v a l s u r v i v a l . When c l a y d r i e s , however, i t forms a hard c r u s t which might hamper emerging a d u l t s . 22 TABLE V I : SOIL TYPES AND VEGETATION MANAGEMENT EFFECTS ON INFESTATION RATES SOIL/VEGETATION CONTROL METHOD ORCHARDS 7 9 NUMBER OF TREES 746 1000 ATTACKED 163 177 Loam/clean Loam/vegetat i o n X = 4.9, P<0.025 C l a y / c l e a n C l a y / v e g e t a t i on 11 8 1612 2610 583 413 = 180.7, P<0.005 23 C l a y i s a l s o s l o w e r t o warm i n the s p r i n g than loams or sandy s o i l s . S i n c e o n l y a l i m i t e d number of comparisons among o r c h a r d s w i t h d i f f e r e n t s o i l t y p e s i n the same a r e a were p o s s i b l e , however, no s t r i k i n g o r c o n s i s t e n t t r e n d emerged and t h e r e may s t i l l be u n i d e n t i f i e d f a c t o r s t h a t are r e s p o n s i b l e f o r the a p p arent s o i l - r e l a t e d d i f f e r e n c e s i n b o r e r a t t a c k . V e g e t a t i o n a f f e c t s s o i l t e m p e r a t u r e , k e e p i n g i t lower than t h a t of exposed s o i l i n the s p r i n g and warmer i n the f a l l . T h i s d i f f e r e n c e can be as much as 5-6 C ( A t k i n s o n and White 1980). D u r i n g most of the growing p e r i o d , the temperature of bare s o i l i s h i g h e r than t h a t c o v e r e d by v e g e t a t i o n . B o r e r s i n o r c h a r d s w i t h o u t v e g e t a t i o n around the base of the t r e e s and w i t h sandy loam s o i l s might b e g i n f e e d i n g e a r l i e r i n the growing s e a s o n , and might pupate and emerge e a r l i e r t han those i n o r c h a r d s w i t h v e g e t a t i o n and c l a y s o i l s . S o i l type and degree of v e g e t a t i o n c o n t r o l c l e a r l y a f f e c t the p h y s i o l o g i c a l c o n d i t i o n of the t r e e s and t h e r e f o r e the s u c c e s s of the b o r e r s . As Smith (1963) d e m o n s t r a t e d , v e g e t a t i o n around the base of the t r e e s can d e c r e a s e the r a t e of a t t a c k by b o r e r s . But ground c o v e r can a c t i n a number of ways. C o m p e t i t i o n from such v e g e t a t i o n may reduce the t r e e ' s v i g o r and, as n o t e d e a r l i e r , l e s s v i g o r o u s t r e e s tend to have lower and l e s s damaging r a t e s of i n f e s t a t i o n . F u r t h e r m o r e , such c o v e r , t h r ough i t s i n f l u e n c e on the b a s a l m i c r o c l i m a t e , can 24 d i r e c t l y a f f e c t the r a t e of development and thus the s u r v i a l of the b o r e r l a r v a e . And when c o v e r i s p a r t i c u l a r l y dense and t a n g l e d as w i t h heavy growth of hedge bindweed, C o n v o l v u l u s a r v e n s i s , o r w i l d r o s e , Rosa  nutkana P r e s l . , i t may s i m p l y p r e v e n t a d u l t s from r e a c h i n g the t r e e t o o v i p o s i t . 25 3. The Growers: Of 40 growers i n t e r v i e w e d c o n c e r n i n g 46 o r c h a r d s ( 3 had more than one b l o c k ) , 21 d i d not know whether t h e i r t r e e s had p e a c h t r e e b o r e r and 19 were not t a k i n g any c o n t r o l measures. Two of t h i s group of 21 were d o i n g r o u t i n e c a l e n d a r c h e m i c a l s p r a y i n g as a p r e v e n t a t i v e measure. The o r c h a r d s i n which no c o n t r o l s were used had i n f e s t a t i o n s r a n g i n g from 0.9 t o 83.3 % of the t r e e s . T h i r t e e n of the above 21 growers c o u l d r e c o g n i z e p e a c h t r e e b o r e r damage because they had d e a l t w i t h i t i n the p a s t . E i g h t , a l l r e l a t i v e l y new o r c h a r d i s t s , were not f a m i l i a r w i t h the type of damage the i n s e c t does. S i x t e e n o t h e r o r c h a r d i s t s ( o f the 40) knew t h e i r p l a n t i n g s had p e a c h t r e e b o r e r , c o n s i d e r e d i t t o be an economic problem and were a t t e m p t i n g t o c o n t r o l i t . In 5 o t h e r b l o c k s , the o r c h a r d i s t s knew b o r e r was p r e s e n t but were not t a k i n g any a c t i o n a g a i n s t i t . In 2 of these s i t u a t i o n s , the growers had j u s t r e a l i z e d the e x t e n t of the problem but had not yet d e c i d e d what t o do. The o t h e r 3 b l o c k s a l l belonged t o the same owner who knew b o r e r s were p r e s e n t but was w i l l i n g t o a c c e p t the l o s s e s i n c u r r e d . A l t h o u g h a few o r c h a r d i s t s r e c o g n i z e d the a d u l t moths as something they had seen b e f o r e , none knew them f o r what they were. 26 TABLE V I I : PEACHTREE BORER ATTACK IN ORCHARDS EXPOSED TO DIFFERENT CONTROL PROCEDURES. TYPE OF CONTROL ATTACKED ORCHARDS TREES X % TREES Th iodan 5 1010 2.5 Se v i n 1 42 17.5 DDT 1 94 0.0 Thiodan & M e c h a n i c a l Removal 4 884 12.3 Cygon, D i a z i n o n & Mech. Removal 1 30 0.0 M e c h a n i c a l Removal Only 5 1751 44.5 Wood Ashes 1 199 5.6 No C o n t r o l s * 26 3502 25. 1 * Abandoned o r c h a r d s e x c l u d e d . 27 C o n t r o l s Used and T h e i r E f f e c t i v e n e s s Table V I I i l l u s t r a t e s the d i v e r s i t y of c o n t r o l methods b e i n g used by the growers and t h e i r e f f e c t i v e n e s s . While c h e m i c a l c o n t r o l s were the most e f f e c t i v e , o n l y 12 growers were u s i n g them. Seven r e l i e d on them s o l e l y and 5 o t h e r s used them i n c o n j u n c t i o n w i t h mechanical removal of l a r v a e . Thiodan was used i n 9 o r c h a r d s and DDT, Cygon and S e v i n i n the o t h e r s . Four of these o r c h a r d s c u r r e n t l y had no b o r e r s a l t h o u g h a l l had i n the p a s t . The c h e m i c a l s , when c o r r e c t l y used, gave good c o n t r o l (0-3.1 % i n f e s t a t i o n ) . The r e l a t i v e i n e f f e c t i v e n e s s of combined c h e m i c a l and mech a n i c a l c o n t r o l was p r o b a b l y a matter of poor t i m i n g . Growers u s i n g both t r e a t m e n t s u s u a l l y a p p l i e d o n l y the f i r s t Thiodan s p r a y and then c a r r i e d out mechanical c o n t r o l l a t e f a l l o r e a r l y s p r i n g . As w i l l be seen i n Chapter I I , t h i s c o m b i n a t i o n i s not e f f e c t i v e . Ten growers were t r y i n g t o c o n t r o l the b o r e r by removing l a r v a e by hand. F i v e r e l i e d o n l y on t h i s method and 5 o t h e r s were u s i n g i t i n c o n j u n c t i o n w i t h c h e m i c a l methods. M e c h a n i c a l c o n t r o l a l o n e was not e f f e c t i v e ( T a b l e V I I ) . Almost h a l f of the t r e e s i n these o r c h a r d s were a t t a c k e d even though the method had been used f o r s e v e r a l y e a r s . T h i s h i g h r a t e was p a r t l y because a l l the o r c h a r d s i n t h i s group were i n the most s u s c e p t i b l e age range (5-10 y e a r s o l d ) . The o r c h a r d i s t who s c a t t e r e d wood ashes around the base of a l l h i s t r e e s had a low r a t e of a t t a c k (6.9 % ) . 29 methods of p e s t c o n t r o l . The acute t o x i c i t y of Thiodan ( o r a l LD 50 18, dermal LD 50 74) i s c o n s i d e r e d to be a h e a l t h t h r e a t by some. But many growers are a l s o not aware t h a t the l a r v a e can l i v e i n the t r u n k up to 2 y e a r s ( E s s i g 1938; Armstrong 1940; Smith 1965) and s p r a y i n g programs have sometimes been abandoned because the growers thought the s p r a y s were i n e f f e c t i v e because b o r e r s were s t i l l i n the t r e e s the year f o l l o w i n g t r e a t m e n t . 28 However most of h i s t r e e s were a l s o o l d e r t h a n 15 y e a r s and t h e r e f o r e l e s s l i k e l y t o be a t t a c k e d . Lack of awareness of or i n some c a s e s , l a c k of c o n c e r n about p e a c h t r e e b o r e r can be a t t r i b u t e d t o a number of f a c t o r s . P e s t s t h a t cause i n d i r e c t damage are o f t e n u n d e r - e s t i m a t e d and t h e r e i s no sense of urgency about t h e i r c o n t r o l . The type of v e g e t a t i o n management o r c h a r d i s t s use a l s o a f f e c t s t h e i r awareness or p e r c e p t i o n of the problem. F or example, whereas 17 of 26 growers w i t h g r a s s o r o t h e r v e g e t a t i o n around t h e i r t r e e s were not aware of t h e i r b o r e r i n f e s t a t i o n s , o n l y 6 of the 19 who used h e r b i c i d e s or c u l t i v a t i o n d i d not know they had b o r e r s . The growers* p e r c e p t i o n of the problem i s compounded by the b i o l o g y of p e a c h t r e e b o r e r and c o n t r o l methods which are not w e l l s u i t e d t o an i n s e c t w i t h such asynchronous development and v e r y l o n g emergence p e r i o d . The l a t t e r r e q u i r e s c o n t i n u a l o r r e p e a t e d a p p l i c a t i o n of p r o t e c t i v e measures f o r p e r i o d of 3 t o 6 months (see Chapter I I ) . U n f o r t u n a t e l y , the most e f f e c t i v e form of c o n t r o l ( Thiodan t r u n k s p r a y s ) i s l a b o r - i n t e n s i v e and i s most u r g e n t l y r e q u i r e d d u r i n g a p e r i o d when h a r v e s t i s u s u a l l y underway and when a c c e s s to the t r u n k i s d i f f i c u l t . And a l t h o u g h the l a b o r i o u s removal of l a r v a e by hand can be done d u r i n g the o f f - s e a s o n , i t i s not e f f e c t i v e ( C h apter I I ) . Changing a t t i t u d e s towards c h e m i c a l s p r a y s a l s o p l a y a p a r t i n the growers* view of the s i t u a t i o n . F i f t e e n of the 40 growers i n t e r v i e w e d d i s l i k e d s p r a y i n g . Two were u s i n g o n l y o r g a n i c 30 CHAPTER I I THE EXPERIMENTS: EVALUATION OF CONTROL METHODS 31 INTRODUCTION The most w i d e l y recommended c o n t r o l f o r p e a c h t r e e b o r e r i s t r u n k s p r a y s t w i c e per season w i t h e n d o s u l f a n ( T h i o d a n , manufactured by H o e c h s t ) , ( Ge n t r y 1981; Banham 1982; B.C. Tree F r u i t P r o d u c t i o n Guide 1984; O n t a r i o Tree F r u i t P r o d u c t i o n Guide 1984; P a c i f i c NW. I n s e c t C o n t r o l Handbook 1984). However, a p r e l i m i n a r y s u r v e y i n 1983 showed t h a t many o r c h a r d i s t s i n the N o r t h Okanagan V a l l e y i n B.C. were not f o l l o w i n g t h i s recommendation, even when t h e i r t r e e s were i n f e s t e d w i t h p e a c h t r e e b o r e r . Some who were u s i n g i t r e p o r t e d mixed r e s u l t s . Other growers were k i l l i n g the b o r e r l a r v a e i n the t r u n k of the t r e e w i t h a k n i f e or w i r e . Many were d o i n g n o t h i n g . In t h i s c h a p t e r , I e v a l u a t e the e f f e c t i v e n e s s of the above methods f o r c o n t r o l l i n g or p r e v e n t i n g b o r e r i n f e s t a t i o n , and a s s e s s t h e i r r e s p e c t i v e advantages and d i s a d v a n t a g e s under o r c h a r d c o n d i t i o n s . A l s o , I t e s t two types of p r o t e c t i v e b a r r i e r s based on o b s e r v a t i o n s of the b e h a v i o u r of t h i s i n s e c t : a l i q u i d l a t e x p a i n t e d on the tr u n k of the t r e e , and an aluminum s h i e l d wrapped around the base. These were d e s i g n e d t o p r e v e n t a d u l t o v i p o s i t i o n and l a r v a l e s t a b l i s h m e n t . 32 MATERIALS AND METHODS Exp e r i m e n t s were conducted i n one o r c h a r d d u r i n g 1983 and 1984 and i n f o u r o t h e r s d u r i n g 1984. Three of the o r c h a r d s were i n the Westbank a r e a , one i n E a s t Kelowna and one i n Oyama, B r i t i s h Columbia ( F i g u r e 1 ) . The t r u n k s of 1195 peach t r e e s i n the f i v e o r c h a r d s were examined a t l e a s t t w i c e d u r i n g the s t u d y . They were checked from the f i r s t s c a f f o l d b ranch ( u s u a l l y 30 t o 60 cm above ground l e v e l ) to 10-15 cm below the s o i l s u r f a c e f o r the c h a r a c t e r i s t i c r e d d i s h - b r o w n , gum-frass m i x t u r e t h a t i n d i c a t e s the presence of l i v e b o r e r l a r v a e . At the i n i t i a l assessment, 9.6 % t o 70.2 % of the t r e e s i n the o r c h a r d s were a t t a c k e d and the average number of b o r e r s per t r e e ranged from 1.2 t o 4.8 i n the 5 o r c h a r d s ( T a b l e V I I I ) . S i n c e the d i s t r i b u t i o n of b o r e r s appeared to be non-random w i t h some t y p e s of t r e e s b e i n g a t t a c k e d more f r e q u e n t l y than o t h e r s (see Chapter I ) , I used o n l y c u r r e n t l y i n f e s t e d t r e e s f o r t e s t i n g c o n t r o l methods. I removed a l l the b o r e r s I c o u l d f i n d b e f o r e a d u l t moths began l a y i n g eggs, and t h e r e a f t e r a l l b o r e r s >1.5 cm i n l e n g t h were removed u n t i l m i d - J u l y . P a s t r e c o r d s f o r the a r e a (Banham, p e r s o n a l communication) showed t h a t no o v i p o s i t i o n o c c u r r e d b e f o r e l a t e June. O b s e r v a t i o n s of l a r v a l growth r a t e s by o t h e r s 33 F i g u r e 1. Map o f atudy a r e a i n t h e Okanagan V a l l e y o f B r i t i s h Columbia. L e t t e r s r e f e r t o e x p e r i m e n t a l o r c h a r d s f o r which d a t a a r e p r e s e n t e d i n t h e t e x t . S u rveys were c a r r i e d out between Oyama and O l i v e r . 34 TABLE V I I I : PEACHTREE BORER LARVAL POPULATIONS: INITIAL ASSESSMENT. ORCHARD % TREES WITH BORER X # LARVAE/TREE A 9.6 1.2 B 11.8 2.0 C 36.1 2.7 D 41.9 4.3 E 70.2 4.8 The number of l a r v a e p e r t r e e i s c a l c u l a t e d from a t t a c k e d t r e e s o n l y and i s p o s i t i v e l y c o r r e l a t e d w i t h the l e v e l of i n f e s t a t i o n i n each o r c h a r d (r=0.93, p< 0.01). 35 r e s e a r c h e r s (Lyne 1913; Armstrong 1940; Smith 1965) i n d i c a t e d t h a t any l a r v a l a r g e r than 1.5 cm b e f o r e mid-August was from an egg l a i d the p r e v i o u s y e a r . A l l i n f e s t e d t r e e s were a s s i g n e d a number, and i n d i v i d u a l s were randomly s e l e c t e d f o r each t r e a t m e n t ( T a b l e I X ) . Both a t t a c k e d and u n a t t a c k e d t r e e s i n f o u r of the o r c h a r d s were used as c o n t r o l s and the former p r o v i d e d a source of p e a c h t r e e b o r e r s f o r 1984. In the f i f t h o r c h a r d ( D ) , mechanical c o n t r o l was c a r r i e d out and guards put on a l l of the t r e e s . There were i n f e s t e d t r e e s i n the immediate v i c i n i t y , however, and cocoons c o l l e c t e d e l sewhere were p l a c e d i n the o r c h a r d s e v e r a l t i m e s over the summer of 1984 t o ensure presence of the i n s e c t s i n t h i s o r c h a r d . Wing t r a p s (Zoecon) c o n t a i n i n g p e a c h t r e e b o r e r female sex a t t r a c t a n t were m a i n t a i n e d i n a l l of the o r c h a r d s from e a r l y June u n t i l l a t e September to m o n i t o r a d u l t b o r e r emergence . M e c h a n i c a l Removal K i l l i n g b o r e r l a r v a e by hand has been w i d e l y p r a c t i c e d as a method f o r c o n t r o l of p e a c h t r e e b o r e r f o r a t l e a s t 100 y e a r s (Saunders 1871; S l i n g e r l a n d and Crosby 1915; Boyce 1961). The t r u n k of each t r e e i s examined and when the gum/frass m i x t u r e i s found e x u d i n g from a burrow, i t i s s c r a p e d away and the burrow probed w i t h a k n i f e o r w i r e , 36 or the wood i s c u t away, u n t i l the l a r v a i s l o c a t e d and k i l l e d . I wanted t o determine the e f f e c t i v n e s s of t h i s method f o r c o n t r o l l i n g b o r e r s i n t r e e s i n f e s t e d from p r e v i o u s y e a r s and t o see i f t r e e s so t r e a t e d would be prone t o f u r t h e r a t t a c k . I a l s o compared the e f f e c t i v e n e s s of s i n g l e and double t r e a t m e n t s d u r i n g one season. The f i r s t removal was c a r r i e d out on 212 i n f e s t e d t r e e s i n the f i v e o r c h a r d s by e a r l y J u l y 1984. F i f t e e n t o 33 days a f t e r the i n i t i a l assessment, I checked each t r e e and r e c o r d e d how many s t i l l c o n t a i n e d a c t i v e b o r e r s and a g a i n a t t e m p t e d to e l i m i n a t e a l l b o r e r s i n these t r e e s . The s u c c e s s of the second c o n t r o l attempt was e v a l u a t e d i n September 1984. Thiodan Spray Program P e s t c o n t r o l g u i d e s ( i . e . B.C. Tree F r u i t P r o d u c t i o n Guide 1984; P a c i f i c NW. I n s e c t C o n t r o l Handbook 1984), recommend t h a t p e a c h t r e e b o r e r be c o n t r o l l e d w i t h a t r u n k s p r a y of Thiodan (50% WP, 150 g per 100 L w a t e r ) , from ground l e v e l t o the f i r s t s c a f f o l d b r a n c h e s . T h i s i s t o be done i n e a r l y t o m i d - J u l y and r e p e a t e d 3- 4 weeks l a t e r . Use of pheromone t r a p s t o time the s p r a y s i s a l s o recommended by some ( G e n t r y e t a l . 1978; Banham 1982). I t e s t e d e f f e c t i v e n e s s of one and two s p r a y s i n p r e v e n t i n g l a r v a l e s t a b l i s h m e n t i n 1984, and the e f f e c t of Thiodan s p r a y i n g on l a r v a e a l r e a d y i n the t r e e . I n 4 37 o r c h a r d s , the t r u n k s of 64 t r e e s were s p r a y e d w i t h Thiodan between J u l y 4 and J u l y 9. Catches of a d u l t males i n Zoecon wing t r a p s ( w i t h s p r e a d e r s t o s e p a r a t e the top and bottom by 1.5 cm, and r u b b e r s e p t a l o a d e d w i t h female sex a t t r a c t a n t ) , and o b s e r v a t i o n s of emergence ti m e s from cocoons were used to time the s p r a y s ( B a r r y e t a l . 1978; Yonce & Pate 1979; Banhan 1982). T h i r t y - n i n e of the o r i g i n a l group of t r e e s were s p r a y e d a g a i n 4 weeks l a t e r . L arvae were removed m e c h a n i c a l l y from 44 of the 64 t r e e s b e f o r e s p r a y i n g . P r o t e c t i v e Guard Most b o r e r eggs are l a i d a t the base of the t r u n k , but some are d e p o s i t e d on the upper t r u n k , on l e a v e s , lower l i m b s , and on e a r t h and v e g e t a t i o n around the base of the t r e e ( B e c k e r 1917; Smith and Avens 1954; Davidson & Lyon 1979; p e r s o n a l o b s e r v a t i o n s ) . The e s t a b l i s h m e n t of l a r v a e i n t r u n k s more than 15 cm above ground l e v e l has a l s o been r e p o r t e d ( E s s i g 1938; S m i t h and Avens 1954; Madsen and B a i l e y 1959; M e t c a l f and F l i n t 1962; Watson p e r s o n a l c o m m u n i c a t i o n ) . However, i n my s u r v e y of over 7000 Prunus t r e e s i n the Okanagan V a l l e y , I found t h a t o n l y those l a r v a e a t the base of t r u n k s or below ground l e v e l s u r v i v e d the w i n t e r . S i n c e l a r v a l f e e d i n g done above ground i n the f a l l i s m a i n l y i n the bark and i s m i n i m a l , the base i s the o n l y p o t e n t i a l l y v u l n e r a b l e a r e a of the t r e e i n the N o r t h Okanagan. I f 38 o v i p o s i t i o n t h e r e c o u l d be p r e v e n t e d and l a r v a e from eggs l a i d e l sewhere c o u l d be kept from r e a c h i n g t h a t a r e a ( E s s i g 1938; Davidson and Lyon 1979), e s t a b l i s h m e n t of damaging p e a c h t r e e b o r e r l a r v a e s h o u l d be p r e v e n t e d . To t e s t t h i s p o s s i b i l i t y , I d e s i g n e d a cone-shaped guard t h a t extended 18 cm from the base of the t r u n k and upward about 30 cm ( F i g u r e 2 ) . The c o l l a r was t i g h t enough to p r e v e n t b o r e r l a r v a e from c r a w l i n g i n , but f l e x i b l e enough to accommodate growth of the t r e e over the season. I t was made from aluminum h e l d around the t r e e by s e l f - l o c k i n g s c rews, w i t h f i b e r g l a s s i n s u l a t i o n under the c o l l a r to a l l o w f o r t r e e growth. G r a f t i n g tape c l o s e d the t o p . These guards were p l a c e d around 28 t r e e s i n o r c h a r d D, m i d - J u l y , 1983, and on 46 more ( a t o t a l of 74) i n o r c h a r d s A,B,C & E between 1 June 1984 and 10 J u l y 1984. In o r c h a r d s A, B, and C the guards were i n p l a c e b e f o r e a d u l t s began emerging. T h i s was not the case i n o r c h a r d E, so the t r u n k of each even-numbered t r e e s e l e c t e d f o r a guard (10 of 20) was s p r a y e d w i t h D i a z i n o n when the guard was i n s t a l l e d t o k i l l any l a r v a e h a t c h i n g from eggs t h a t might a l r e a d y be on the t r u n k . In each i n s t a n c e , 1982/83 l a r v a e were removed. Guards were a l s o p l a c e d around 10 i n f e s t e d t r e e s t o which a d d i t i o n a l mature l a r v a e and cocoons were added. T h i s was done t o see whether i n s e c t s under the guards c o u l d complete t h e i r c y c l e , mate, and l a y eggs. 39 g r a f t i n g t a p e s e l f - l o c k i n g s c r a w l F i g u r e 2. P r o t e c t i v e guard made of t h i n aluminum s h e e t i n g to prevent o v i p o s i t i o n peachtree borer on the base o£ t r e e t r u n k s . Radius a t ground l e v e l i s 38 cm and height i s 30 cm. 40 Napthalene f l a k e s were p l a c e d under guards on 9 a d d i t i o n a l i n f e s t e d t r e e s i n an attempt to k i l l l a r v a e w i t h o u t mechanical r e m o v a l . The f l a k e s were a l s o poured i n a r i n g about 4 cm out from the base of 10 o t h e r t r e e s and c o v e r e d w i t h s o i l . L a t e x C o a t i n g L a t e x was t e s t e d as a n o t h e r p o s s i b l e means of p r o t e c t i n g the a r e a of the t r e e s u s c e p t i b l e to b o r e r s . Larvae were removed by hand from 11 t r e e s i n o r c h a r d C, i n June 1984. While s o i l was s t i l l p u l l e d away from the base, the t r u n k was p a i n t e d up t o the f i r s t s c a f f o l d branches w i t h a t h i c k l a y e r of l i q u i d l a t e x < F a r n w e l l ' s Tree Doc), n o r m a l l y used to c o v e r g r a f t i n g and p r u n i n g wounds. A l l t r e e s i n a l l t r e a t m e n t s p l u s the 210 c o n t r o l s w i t h a c t i v e b o r e r s and the 624 u n a t t a c k e d t r e e s were examined a g a i n from mid to l a t e September 1984. Ease of a p p l i c a t i o n , c o m p a t a b i 1 i t y w i t h o t h e r o r c h a r d o p e r a t i o n s , o p e r a t o r s a f e t y , c o s t , growers' p e r c e p t i o n s , and p o s s i b l e s i d e e f f e c t s of a l l the methods were e v a l u a t e d t h r o u g h 1983 and 1984. 41 TABLE IX: SUMMARY OF THE NUMBER OF TREES IN EACH TREATMENT. TREATMENT ORCHARD A B C D E TOTAL M e c h a n i c a l Removal 25 15 93 19 60 212 Guards 8 5 13 28 20 74 Thiodan 9 5 10 0 40 64 Late x 0 0 1 1 0 0 1 1 C o n t r o l s w i t h b o r e r s 1 1 13 49 0 137 210 w i t h o u t b o r e r s 309 92 131 0 92 624 T o t a l s 362 130 307 47 349 1 195 42 RESULTS M e c h a n i c a l Removal Three weeks a f t e r the f i r s t m e chanical removal i n J u l y 1984, a p p r o x i m a t e l y h a l f of a l l t r e a t e d t r e e s were found to s t i l l c o n t a i n 1983 l a r v a e . T h i s d e c r e a s e d t o 28.8 % a f t e r a second t r e a t m e n t ( T a b l e X ) . The l e v e l of r e - a t t a c k i n 1984 on t r e e s from which l a r v a e had p r e v i o u s l y been removed was much h i g h e r than was new a t t a c k on p r e v i o u s l y u n a t t a c k e d t r e e s ( T a b l e X I ) . In h e a v i l y a t t a c k e d o r c h a r d s (C & E ) , the r e a t t a c k r a t e on t r e e s i n the mechanical removal t r e a t m e n t was about the same as t h a t of a t t a c k e d c o n t r o l t r e e s from which l a r v a e had not been removed. In o r c h a r d s w i t h low b o r e r d e n s i t y ( A & B ) , r e - a t t a c k of t r e e s from which l a r v a e had been removed was much lower than of u n t r e a t e d c o n t r o l t r e e s ( T a b l e X I ) . Thiodan Twenty per c e n t of the t r e e s s p r a y e d once and 7.8 % of t r e e s s p r a y e d t w i c e , were s u c c e s s f u l l y a t t a c k e d by p e a c h t r e e b o r e r i n 1984 ( T a b l e X I I ) . The e f f e c t of Thiodan on l a r v a e i n the t r e e s from p r e v i o u s y e a r s i s not c l e a r . In two of the o r c h a r d s (B & C ) , the c o m b i n a t i o n of mechanical removal and Thiodan s p r a y d i d not reduce the number of l a r v a e from 1983 below t h a t of t r e e s r e c e i v i n g j u s t m e c h a n i c a l c o n t r o l ( T a b l e X I ) . 43 TABLE X: PERCENTAGE OF LARVAE MISSED BY MECHANICAL REMOVAL TREATMENT (S.E.) ORCHARD PERCENTAGE OF TREES WITH LARVAE AFTER TREATMENTS # 1 # 2 A 28.0 22.0 B 40.0 13.3 C 59.8 42.1 D 57.9 36.8 E 56.7 30.0 X 48.5 X 28.8 (13.9) (13.7) TABLE X I : PERCENTAGES OF TREES ATTACKED BY PEACHTREE BORER IN 1984 FOLLOWING DIFFERENT CONTROL TREATMENTS. TREATMENT ORCHARD A B C D E M e c h a n i c a l Removal 12.5 20.0 64.4 0.0 65 .0 Guards 0.0 0.0 0.0 0.0 0.0 Thiodan 0.0 0.0 30.0 N/A 10.0 L a t e x N/A N/A 90. 1 N/A N/A C o n t r o l s u n a t t a c k e d 06/1984 3.9 2.2 26.7 N/A 42. 4 a t t a c k e d 06/1984 27. 3 46.2 53. 1 N/A 69.3 These f i g u r e s a re f o r and up to 6 cm above 1984 ground l a r v a e e s t a b l i s h e d l e v e 1 . a t the base 45 TABLE X I I : THIODAN TREATED TREES WITH PEACHTREE BORER LARVAE IN SEPTEMBER 1984. ORCHARD # TREES # TREES WITH % TREES WITH 1983 1984 1983 & 1984 1984 LARVAE LARVAE LARVAE LARVAE One Spray C 5 1 E T+M * 10 1 T-M 10 4 T o t a l 25 6 Two Sprays A 9 1 B 5 1 C 5 1 E T+M 10 4 T-M 10 6 T o t a l 39 13 0 2 40 1 1 20 0 1 10 1 4 20 1 ** 0 11 0 0 0 0 1 20 1 0 10 0 0 0 2 1 7.8 * Thiodan p l u s mechanical c o n t r o l & Thiodan w i t h o u t m e c h a n i c a l c o n t r o l . ** L a r v a was > 15 cm above ground l e v e l and u n l i k e l y t o s u r v i v e the w i n t e r . 46 In o r c h a r d A, however, t r e e s r e c e i v i n g b oth mechanical removal and Thiodan had h a l f as many 1983 l a r v a e i n the autumn as t r e e s t r e a t e d o n l y w i t h the m echanical r e m o v a l . In o r c h a r d E, the t r e e s t h a t r e c e i v e d b o t h m e c h a n i c a l removal and Thiodan had s i g n i f i c a n t l y fewer l a r v a e from 1983 i n the autumn than the t r e e s o n l y s p r a y e d w i t h Thiodan. In t h i s o r c h a r d , however, the percentage of t r e e s w i t h 1983 l a r v a e a f t e r Thiodan t r e a t m e n t a l o n e was s t i l l l o w e r than t h a t i n u n t r e a t e d , p r e v i o u s l y a t t a c k e d t r e e s ( T a b l e s X I I I and X I V ) . Guards There was no 1984 l a r v a under any of the 74 g uards. Larvae found under 7 of the guards were a l l 2.5-3 cm l o n g and were t h e r e f o r e c a r r y - o v e r s from 1983 (Lyne 1913; Armstong, 1940). New l a r v a e found above 18 of the guards had not managed t o get underneath t o r e a c h the base where they c o u l d s u r v i v e the w i n t e r . Even though a d u l t s had begun t o emerge i n o r c h a r d E p r i o r t o i n s t a l l a t i o n of the g u a r d s , they a p p a r e n t l y d i d not o v i p o s i t on the e x p e r i m e n t a l t r e e s , or e l s e emerging l a r v a e f a i l e d t o e s t a b l i s h under the newly i n s t a l l e d g u a r d s . None of the D i a z i n o n - s p r a y e d t r e e s had 1983 l a r v a e i n the autumn whereas 4 of the 10 unsprayed t r e e s w i t h guards had. 47 TABLE X I I I : NUMBER OF TREES TREATED WITH MECHANICAL REMOVAL AND/OR THIODAN SPRAYING THAT HAD LARVAE FROM 1983 PRESENT IN SEPTEMBER 1984. ORCHARD TREES WITH LARVAE AFTER MECH . REMOVAL THIODAN + MECH. REMOVAL THIODAN % N % N % N A 25 2/8 11 1/9 -B 20 1 /5 20 1 /5 -C 56 33/59 50 5/10 E 65 13/20 30 6/20 55 11/20 48 TABLE XIV: PERCENTAGES OF CONTROL TREES ATTACKED BY PEACHTREE BORER IN SEPTEMBER 1984 ORCHARD PREVIOUSLY UNATTACKED CONTROLS PREVIOUSLY ATTACKED CONTROLS 1984 Larvae Onl y 1983 Larvae Only 1984 Larvae Only 1983 & 1984 Larvae T o t a l A t t a c k e d A 4.5 54.5 0.0 27.3 81.8 B 4.4 38.5 7.7 38.5 84.6 C 30.5 30.6 0.0 57. 1 87.8 E 42. 4 19.0 5.8 63.5 88.3 49 D i a z i n o n has a fumigant e f f e c t t h a t would have been i n t e n s i f i e d under the guard. Some of the l a r v a e and cocoons t h a t were i n t e n t i o n a l l y c o v e r e d by guards s u c c e s s f u l l y pupated and emerged as a d u l t s . Empty pupal c a s e s and dead a d u l t b o r e r s , but no new l a r v a e , were found under the cones a t the end of September, so mating and o v i p o s i t i o n d i d not o c c u r . However, l a r v a e from the p r e v i o u s y e a r , which had not completed t h e i r c y c l e , c o n t i n u e d t o feed under the cones, w h i l e t h e i r c o u n t e r p a r t s i n t r e e s w i t h o u t guards had stopped f o r the season. Napthalene f l a k e s around the base of t r e e s and under guards k i l l e d l a r v a e i n the t r e e s i n about t h r e e weeks. However, many of the t r e e s had a p h y t o t o x i c r e a c t i o n t o the n a p t h a l e n e , i n d i c a t e d by gumming of the tr u n k and y e l l o w i n g of the l e a v e s . Three l a t e r d i e d . The f l a k e s c o v e r e d w i t h s o i l had no e f f e c t on the t r e e s or the l a r v a e i n them. La t e x C o a t i n g In September 1984, 10 of the 11 t r e e s i n t h i s t r e a t m e n t had a c t i v e l a r v a e . Three of these t r e e s c o n t a i n e d l a r v a e from the 1983 g e n e r a t i o n t h a t had escaped the me c h a n i c a l c o n t r o l measures i n June, p l u s l a r v a e from 1984 eggs. The o t h e r seven had o n l y 1984 l a r v a e . T h i s was the h i g h e s t r a t e of e s t a b l i s h m e n t of 1984 l a r v a e on e i t h e r t r e a t m e n t o r c o n t r o l t r e e s ( T a b l e s XI and X I V ) . 50 DISCUSSION Thiodan s p r a y s gave 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 new p e a c h t r e e b o r e r i n f e s t a t i o n , and the p r o t e c t i v e guard was even more e f f e c t i v e . N e i t h e r of these methods was r e t r o a c t i v e , however, and damage from b o r e r s a l r e a d y i n the t r e e s c o u l d c o n t i n u e f o r a n o t h e r y e a r . Removal of l a r v a e by hand was o n l y p a r t i a l l y s u c c e s s f u l i n c o n t r o l l i n g the p a s t season's i n f e s t a t i o n , and d i d not p r e v e n t new a t t a c k s . The t r e e s p a i n t e d w i t h l a t e x had the h i g h e s t l e v e l of l a r v a l a t t a c k or s u r v i v a l of any i n v o l v e d i n these e x p e r i m e n t s . While Thiodan can be v e r y e f f e c t i v e i n r e d u c i n g p e a c h t r e e b o r e r p o p u l a t i o n s to low numbers and even e l i m i n a t i n g them from o r c h a r d s some season s , c o n t r o l i s e r r a t i c because of the l o n g and v a r i a b l e emergence time of the i n s e c t (Bobb 1949; M a r t i n 1953; K i n g and M o r r i s 1954; MacCreary 1954; Snapp 1958; Madsen and B a i l e y 1959; M e t c a l f & F l i n t 1962; G e n t r y e t a l . 1978; Davidson and Lyon 1979). A f t e r a l a t e , c o l d s p r i n g i n 1984, I o b s e r v e d and t r a p p e d a d u l t b o r e r s o c c a s i o n a l l y by mid-June and f r e q u e n t l y by the end of the month. In c o n t r a s t , warm, wet s p r i n g s cause emergence t o b e g i n e a r l i e r ( S n a p p and Thomson 1943; Madsen and B a i l e y 1959; S m i t h 1965; G e n t r y e t a l . 1978). Emergence and o v i p o s i t i o n c o n t i n u e d u n t i l l a t e September i n 1983 and 1984 i n the Okanagan r e g i o n . In O n t a r i o , emergence and 51 o v i p o s i t i o n have been r e p o r t e d to e x t e n d over a t l e a s t 3 months (Boyce 1961). I n C a l i f o r n i a , a d u l t s o c c u r from e a r l y May t h rough September (Madsen and B a i l e y 1959), and i n the s o u t h e r n U.S., t h e i r a c t i v i t y can e x t e n d over 5-6 months (Snapp and Thomson 1943; W y l i e 1956; Yonce and Pate 1979). A p p l y i n g Thiodan i n e a r l y t o m i d - J u l y and a g a i n 4 weeks l a t e r , c o u l d l e a v e the t r e e s u n p r o t e c t e d t h rough two d i f f e r e n t p e r i o d s . The f i r s t emerging a d u l t s i n l a t e J u n e - e a r l y J u l y c o u l d mate and s u c c e s s f u l l y o v i p o s i t b e f o r e the f i r s t s p r a y ( B e c k e r 1917; S m i t h 1965; B a r r y and N i e l s e n 1984). S i n c e egg i n c u b a t i o n can be as s h o r t as ten days (Armstrong 1940; M e t c a l f and F l i n t 1962; Smith 1965), l a r v a e from eggs l a i d i n June or even e a r l y i n J u l y c o u l d be s a f e l y e s t a b l i s h e d i n the t r e e b e f o r e a m i d - J u l y s p r a y . T h i s f i r s t gap i n p r o t e c t i o n c o u l d be a v o i d e d by the use of pheromone t r a p s t o m o n i t o r emergence t i m e s . Another window f o r a t t a c k o c c u r s i n the f a l l . S i n c e the r e s i d u a l p e r i o d of Thiodan i s 3-4 weeks, the t r e e s would not be p r o t e c t e d t h roughout most of September. See F i g u r e 3. In p r a c t i c e , the second s p r a y i s o f t e n missed or i s done l a t e l e a v i n g the t r e e s u n p r o t e c t e d d u r i n g the peak p e r i o d of b o r e r emergence and o v i p o s i t i o n . S i n c e t h i s p e r i o d u s u a l l y c o i n c i d e s w i t h the peach h a r v e s t i n the Okanagan, o r c h a r d i s t s f i n d i t d i f f i c u l t t o f i t t h i s l a b o r - i n t e n s i v e t a s k i n t o an a l r e a d y busy s c h e d u l e . Moreover, the h e a v i l y l a d e n branches of the t r e e s make a c c e s s t o the t r u n k 52 P O S S I B L E G A P S IN THIODAN P R O T E C T I O N a d u l t e m e r g e n c e p a t t e r n I i 1 1 1 J u n e t J u l y 1 A u g 1 S e p t 1 O c t 1 T h i o d a n S p r a y P r o t e c t i o n P e r i o d ! J u l y 1 s p r a y o n l y J u l y 1 & A u g u s t 15 s p r a y s J u l y 1 & A u g u s t 1 s p r a y s J u l y 7 & A u g u s t 7 s p r a y s F i g u r e 3. Schematic drawing of t y p i c a l p a t t e r n of a d u l t peachtree borer emergence i n the Okanagan V a l l e y i n B r i t i s h Columbia. The d u r a t i o n of i n f l u e n c e of sprays a p p l i e d at d i f f e r e n t times i s shown to i n d i c a t e gaps when t r e e s are unprotected with d i f f e r e n t spray regimes. 5 3 v e r y d i f f i c u l t . I n the s o u t h e a s t e r n U.S., where most of the p e a c h t r e e b o r e r f l i g h t o c c u r s a f t e r the f r u i t i s p i c k e d , a p p l i c a t i o n of a s p r a y t o p r o t e c t the t r e e s d u r i n g the p e r i o d of h e a v i e s t a t t a c k does not c o n f l i c t w i t h the p e r i o d of h a r v e s t i n g and d i f f i c u l t a c c e s s ( G e n t r y & Yonce 1982) . In a r e a s w i t h c o l d w i n t e r s , such as the N o r t h Okanagan, i t may not be n e c e s s a r y t o sp r a y as h i g h as the lower s c a f f o l d b r a n c h e s . S p r a y i n g o n l y the lower t r u n k would be as e f f e c t i v e , i s l e s s e x p e n s i v e , and would make the second s p r a y e a s i e r t o c a r r y o u t . I n o r c h a r d s where i n f e s t a t i o n s are l o c a l i z e d , s p o t s p r a y i n g may be a l l t h a t i s n e c e s s a r y . U n l i k e Thiodan s p r a y i n g , m echanical removal i s n o n - t o x i c , does not r e q u i r e the p r e c i s e t i m i n g of c h e m i c a l t r e a t m e n t s , and can be done i n the o f f - s e a s o n . T h i s , and the p s y c h o l o g i c a l s a t i s f a c t i o n d e r i v e d from d e s t r o y i n g the pe s t p r o b a b l y account f o r the p o p u l a r i t y of t h i s method. In h e a v i l y i n f e s t e d t r e e s , however, where l a r v a e of a l l s i z e s make c r i s s - c r o s s i n g t u n n e l s and cause gum t o ooze everywhere, i t i s o f t e n i m p o s s i b l e t o determine how many b o r e r s a re a c t u a l l y p r e s e n t so c o n s e q u e n t l y some, p a r t i c u l a r l y the s m a l l e r i n s t a r s , may be o v e r l o o k e d . S i g n s of b o r e r s are a l s o o f t e n o v e r l o o k e d i f the t r e e s are checked too e a r l y i n the s p r i n g b e f o r e heavy f e e d i n g produces d e t e c t a b l e gum, or too l a t e i n the autumn, a f t e r gum p r o d u c t i o n has ceased. There are o t h e r s e r i o u s 54 draw-backs to t h i s method. By the time the b o r e r s can be d e t e c t e d , most of the damage has a l r e a d y been done. In a d d i t i o n , the c u t t i n g and p r o b i n g r e q u i r e d to l o c a t e the l a r v a e can d i r e c t l y harm the t r e e . M e c h a n i c a l removal of b o r e r l a r v a e i s o n l y u s e f u l when i t i s f o l l o w e d by Thiodan s p r a y i n g o r guard cones. A l o n e , i t s c a r c e l y r e d u c e s the r a t e of i n c r e a s e i n p e a c h t r e e b o r e r p o p u l a t i o n s . The guard cones are c a p a b l e of g i v i n g p r o t e c t i o n throughout the y e a r . I n s t a l l i n g them i s l a b o r - i n t e n s i v e b u t , once i n p l a c e , they may r e q u i r e no f u r t h e r a t t e n t i o n f o r a number of y e a r s e x c e p t f o r a y e a r l y adjustment f o r growth of the t r e e . They s h o u l d be put on b e f o r e e g g - l a y i n g b e g i n s (from e a r l y s p r i n g u n t i l a p p r o x i m a t e l y the end of J u n e ) . I f t r e e s are p l a n t e d i n the autumn, guards s h o u l d a l s o be i n s t a l l e d t h e n . S i n c e s p r i n g and f a l l a r e p e r i o d s when o t h e r o r c h a r d o p e r a t i o n s are l e s s demanding, t h e r e i s a l s o time a v a i l a b l e f o r i n s t a l l a t i o n . The guards are most s u i t a b l e f o r young o r c h a r d s . I f they are p l a c e d on b o r e r - f r e e n u r s e r y s t o c k a t p l a n t i n g , they s h o u l d not o n l y s a f e g u a r d young t r e e s from b o r e r but would a l s o a c t as a mouse gu a r d , p r o v i d e s u p p o r t a g a i n s t wind damage, and p r e v e n t weed growth i n the immediate a r e a . Cost f o r m a t e r i a l s , about 50 c e n t s per t r e e , i s c e r t a i n l y comparable t o 4-5 y e a r s of s p r a y i n g Thiodan t w i c e a y e a r . Such guards cannot be f i t t e d around t r e e s w i t h t w i s t e d t r u n k s or ones t r a i n e d a t an a n g l e . I t i s a l s o d i f f i c u l t 55 t o put them on o l d e r t r e e s w i t h l a r g e t r u n k s . A guard t h a t does not f i t p r o p e r l y i s worse than none because any l a r v a e t h a t get i n s i d e are th e n p r o t e c t e d from p r e d a t o r s and d e s i c c a t i o n . In a r e a s where c a n k e r (Phvthophora cactorum) might be a problem, i t would be a d v i s a b l e t o p a i n t the tr u n k w i t h f i x e d copper b e f o r e p u t t i n g the guard around i t . Recommendations f o r u s i n g t h i s c o n t r o l method and f o r c h e m i c a l s p r a y i n g must i n c l u d e warnings f o r o r c h a r d i s t s about the a b i l i t y of b o r e r l a r v a e t o feed i n the t r e e f o r more than one season. Armstrong (1940) found i n O n t a r i o t h a t as many as 60% of the l a r v a e s t a y e d i n the t r e e s f o r 2 y e a r s . Many growers who have used s p r a y s have c o n c l u d e d t h a t the c h e m i c a l was i n e f f e c t i v e because b o r e r s were s t i l l p r e s e n t the year a f t e r s p r a y i n g . R e c u r r e n t i n f e s t a t i o n f o l l o w i n g poor t i m i n g of the s p r a y s , or a l o n g emergence and o v i p o s i t i o n p e r i o d r e s u l t i n g i n i n f e s t a t i o n a l s o have c o n v i n c e d some o r c h a r d i s t s t h a t s p r a y s are not e f f e c t i v e . A s i m i l a r a t t i t u d e c o u l d d e v e l o p i f guards were c a r e l e s s l y i n s t a l l e d on p r e v i o u s l y i n f e s t e d t r e e s . Naphalene f l a k e s s h o u l d not be used under guards o r on young t r e e s because of p h y t o t o x i c e f f e c t s (Snapp & S w i n g l e 1929; Snapp 1932, S t e r n 1933, Smit h 1962). Nor can p a i n t i n g w i t h l a t e x be recommended. The ve r y h i g h r a t e of e s t a b l i s h m e n t of l a r v a e i n 1984 was r e l a t e d t o t r e e growth d u r i n g the season which caused the l a t e x t o c r a c k , e x p o s i n g the b a r k . Females seek c r a c k s i n which to l a y t h e i r eggs ( B e c k e r 1917; E s s i g 1938; B a r r y and N i e l s e n 1984) and 56 appear t o a c c e p t a r t i f i c a l ones as r e a d i l y as n a t u r a l ones. I o b s e r v e d t h a t l a r v a e a l s o r e a d i l y e s t a b l i s h e d i n the a r t i f i c a l c r a c k s which p o s s i b l y p r o v i d e d h i g h l e v e l s of p r o t e c t i o n a g a i n s t p r e d a t i o n and d e s i c c a t i o n ( B u t l e r 1931, 1932; Armstrong 1940; Smith 1965, Davidson and Lyon 1979). 57 CONCLUSIONS Improving our u n d e r s t a n d i n g of the e c o l o g y of any i n s e c t p e s t i n e v i t a b l y w i l l improve our a b i l i t y t o use any c o n t r o l measures, c h e m i c a l and o t h e r w i s e , a g a i n s t them. N a t i v e i n s e c t s , such as the p e a c h t r e e b o r e r , p r o v i d e s p e c i a l o p p o r t u n i t i e s i n t h a t r e g a r d , s i n c e t h e i r b e h a v i o u r under n a t u r a l c o n d i t i o n s can be c o n t r a s t e d w i t h those found i n man-made s e t t i n g s . P e a c h t r e e b o r e r i n f e s t a t i o n s are v e r y s m a l l i n n a t i v e h o s t s and r a r e i n n e g l e c t e d p l a n t i n g s o r abandoned t r e e s , but they f l o u r i s h i n o r c h a r d s i f they are not checked. F e r t i l i z a t i o n and i r r i g a t i o n appear to markedly improve the r a t e of l a r v a l e s t a b l i s h m e n t and s u r v i v a l . Both t r e a t m e n t s c o u l d p r o b a b l y be m a n i p u l a t e d t o decrease b o r e r s u c c e s s , s i n c e the normal tendency i s t o overdo b o t h i n commercial o r c h a r d s . E x p e r i m e n t s have demonstrated t h a t d e c r e a s i n g d a i l y water i n t a k e of peaches by 1/8 and 1/4 f o r p e r i o d s of time had no e f f e c t on f r u i t s i z e , y i e l d or numbers (Chalmers e t a l . 1984). O v e r l y v i g o r o u s growth i n many o r c h a r d s i n d i c a t e s t h a t most growers c o u l d a l s o reduce n i t r o g e n a p p l i c a t i o n s w i t h o u t r e d u c i n g y i e l d . O r chard monocultures have a l s o i n c r e a s e d the o p p o r t u n i t i e s f o r t h i s b o r e r t o s u r v i v e and i n much h i g h e r numbers. The p e a c h t r e e b o r e r must once have been c o m p a r a t i v e l y r a r e i n the Okanagan V a l l e y b e f o r e the i n t r o d u c t i o n of e x t e n s i v e stone 58 f r u i t p l a n t i n g s . C h o k e c h e r r i e s , the s o l e n a t i v e h o s t i n the Okanagan would have been o n l y s c a t t e r e d clumps of d r o u g h t - and n u t r i e n t - s t r e s s e d t r e e s . E s t a b l i s h m e n t of w e l l - w a t e r e d and w e l l - f e r t i l i z e d Prunus monoclutures has t u r n e d an e r s t w h i l e c o l l e c t o r s ' item i n t o a common p e s t . Age and s p e c i e s of the t r e e s a l s o appear t o be imp o r t a n t i n f l u e n c e s on a t t a c k r a t e s . On the n a t i v e h o s t , i t i s to the b o r e r ' s advantage to s e l e c t o l d e r specimens. C h o k e c h e r r i e s , l i k e d o m e s t i c Prunus, have a smooth bark when young. As the t r e e ages, the bark becomes s c a l y and f i s s u r e d (Lyon 1952; Brockman 1968), t h e r e b y e nhancing l a r v a l s u r v i v a l . F u r t h e r m o r e , when the p r i m i t i v e h o s t i s as s c a t t e r e d as c h o k e c h e r r y i s , growing o n l y i n the damper a r e a s of d r y r e g i o n s (Lyon 1952; Can. Dept. F o r e s t r y 1963; E l i a s 1980), females l a y i n g eggs on the t r e e from which they emerged would p r o v i d e b e t t e r chances f o r t h e i r progeny than moths which d i s p e r s e d f a r t h e r b e f o r e o v i p o s i t i n g . A l t h o u g h c h o k e c h e r r i e s produce seeds, they a l s o s p r e a d by s u c k e r i n g (Can. Dept. F o r e s t r y 1963) thus p r o v i d i n g e x t r a l o c a l o p p o r t u n i t i e s f o r females emerging from the o r i g i n a l h o s t . V a r i e t a l d i f f e r e n c e s i n Prunus h o s t s were not pronounced i n t h i s s t u d y . However, the v a r i e t y of the t r e e c o u l d not always be a s c e r t a i n e d so sample s i z e s were s m a l l and the r e s u l t s i n c o n c l u s i v e . R e s u l t s from work done elsewhere i n d i c a t e t h a t v a r i e t a l d i f f e r e n c e s may be a 59 w o r t h w h i l e a r e a f o r f u r t h e r r e s e a r c h . In c o n t r a s t t o the v a r i e t a l r e s u l t s , t h e r e were marked d i f f e r e n c e s i n r a t e s of a t t a c k on d i f f e r e n t s p e c i e s of Prunus. The low r a t e s of i n f e s t a t i o n and damage to c h e r r i e s and prunes suggest t h a t the e f f e c t of i n t e r s p e c i f i c d i f f e r e n c e s might be a w o r t h w h i l e avenue to p ursue. B r e e d i n g Prunus s p e c i e s f o r r e s i s t a n c e t o i n s e c t p e s t s i s s t i l l a n e g l e c t e d f i e l d (Moore & J a n i c k 1983). Any h e r i t a b l e d i f f e r e n c e i n bark t e x t u r e between t y p e s of t r e e s would c l e a r l y be an i m p o r t a n t f a c t o r i n f i r s t i n s t a r l a r v a l s u r v i v a l . Mature o r c h a r d s can p r o b a b l y t o l e r a t e a 10% i n f e s t a t i o n r a t e w i t h o u t s i g n i f i c a n t economic l o s s . The h i s t o r i e s of the o r c h a r d s s u r v e y e d show, however, t h a t w i t h o u t i n t e r v e n t i o n , i n f e s t a t i o n s grow s t e a d i l y u n t i l most of the t r e e s are i n f e s t e d . Young t r e e s , a l t h o u g h i n i t i a l l y l e s s l i k e l y to be a t t a c k e d , r e q u i r e more p r o t e c t i o n because of the g r e a t e r harm they s u f f e r i f t hey are a t t a c k e d . S o i l type and v e g e t a t i o n management do not appear t o i n f l u e n c e l a r v a l s u r v i v a l d i r e c t l y . They do, however, i n f l u e n c e emergence p a t t e r n s t h rough t h e i r m i c r o c l i m a t e e f f e c t s , and i n the case of t a n g l e d g round v e g e t a t i o n , may a l s o e f f e c t i v e l y c o n c e a l e v i d e n c e of a t t a c k . P r e d a t o r s and p a r a s i t e s are p r e s e n t l y not i m p o r t a n t f a c t o r s i n the c o n t r o l of p e a c h t r e e b o r e r . Egg and pupal p a r a s i t e s have been r e c o r d e d but never a t r a t e s above 3 % 60 (Armstrong 1940; Davidson & Lyon 1979). Pupal p r e d a t o r s such as mice ( B u t l e r 1931,1932) and a n t s , l a c e w i n g l a r v a e , s p i d e r s , moles, and b i r d s ( D a v i d s o n & Lyon 1979) have been n o t e d . I have obser v e d l a c e w i n g l a r v a e and a n t s p r e y i n g on newly-hatched b o r e r s on two o c c a s i o n s . A r e v i e w of the l i t e r a t u r e and d i s c u s s i o n s w i t h a g r i c u l t u r a l e x t e n s i o n p e r s o n n e l suggest t h a t c o n t r o l of t h i s i n s e c t i n Prunus p l a n t i n g s i s an easy, s t r a i g h t f o r w a r d m a t t e r ; a c h e m i c a l t r u n k s p r a y c a r r i e d out a t l e a s t t w i c e per season. My e x p e r i m e n t s s u p p o r t e d t h i s c o n t e n t i o n . S i n c e o n l y 5 of 40 growers were c a r r y i n g out such a program, however, and b o t h the number of o r c h a r d s a t t a c k e d and the number of i n f e s t e d t r e e s w i t h i n o r c h a r d s were much h i g h e r than a n t i c i p a t e d , m a t t e r s i n r e a l o r c h a r d s may not be so s t r a i g h t f o r w a r d as p e s t managers and r e s e a r c h e r s have supposed. My s u r v e y showed s e r i o u s i n f e s t a t i o n s o f t e n o c c u r r e d i n o r c h a r d s where ongoing c h e m i c a l c o n t r o l programs f o r o t h e r t y p e s of p e s t s were s u c c e s s f u l l y b e i n g c a r r i e d o u t . B u t , as noted e a r l i e r , the m a j o r i t y of growers were s i m p l y not t a k i n g any a c t i o n a g a i n s t b o r e r s and t h i s l a c k of c o n t r o l u l t i m a t e l y can be equated w i t h i n c r e a s i n g b o r e r p o p u l a t i o n s ; e.g. t h e r e was no u n t r e a t e d p l a n t i n g o l d e r than 5 y e a r s t h a t d i d not have a b o r e r p o p u l a t i o n . From the growers' p o i n t of view, the o v e r l a p i n two l a b o r - i n t e n s i v e t a s k s , a handgun s p r a y i n g and h a r v e s t i n g , c r e a t e s a d i f f i c u l t s i t u a t i o n t h a t i s 61 i n v a r i a b l y r e s o l v e d i n f a v o u r of h a r v e s t i n g . T h i s s i t u a t i o n w i l l not improve u n t i l g rowers' a t t i t u d e s , t i m i n g , problems and p r i o r i t i e s have been f u l l y c o n s i d e r e d i n the d e s i g n of a more adequate c o n t r o l program. The o t h e r most f r e q u e n t l y used c o n t r o l method, removal of l a r v a e by hand i s , i n the f i n a l a n a l y s i s , i n e f f e c t i v e . The i n s e c t s ' b e h a v i o u r and o v i p o s i t i o n r a t e more than compensate f o r any i n d i v i d u a l s t h a t are d e s t r o y e d i n t h i s way. The two new c o n t r o l methods t e s t e d d u r i n g t h i s s t u d y were based on my o b s e r v a t i o n s of o v i p o s i t i o n b e h a v i o u r and l a r v a l e s t a b l i s h m e n t . The l a t e x c o a t i n g , w h i l e i n i t i a l l y p r o t e c t i n g the v u l n e r a b l e a r e a , o f t e n i n c r e a s e d l a t e r chances of s u c c e s s f u l l a r v a l e s t a b l i s h m e n t when i t c r a c k e d , t h e r e b y l e n d i n g credence to the h y p o t h e s i s t h a t bark t e x t u r e i s a c r i t i c a l f a c t o r f o r s u c c e s s f u l a t t a c k and e s t a b l i s h m e n t . In c o n t r a s t , the guard cone f u n c t i o n e d v e r y s u c c e s s f u l l y , f u l l y p r o t e c t i n g the most v u l n e r a b l e p o r t i o n of the t r e e . T h i s cone i s c u r r e n t l y b e s t - s u i t e d f o r b a c k y a r d use. I t c o u l d , however, be c o m m e r c i a l l y s u c c e s s f u l , e s p e c i a l l y f o r young t r e e s , i f a cheap method of m a s s - p r o d u c t i o n c o u l d be d e v e l o p e d . Meanwhile, the cones have c o n c l u s i v e l y demonstrated not o n l y the p a r t of the t r e e t o be p r o t e c t e d , but the need t o take i n t o account the b i o l o g y and b e h a v i o u r of the i n s e c t i n d e s i g n i n g a c o n t r o l program. In a r e a s w i t h m i l d e r w i n t e r s , the cone 62 may not be so s u c c e s s f u l because of the p o s s i b i l i t y of s u c c e s s f u l l a r v a l e s t a b l i s h m e n t h i g h e r i n the t r e e . P e a c h t r e e b o r e r s ' l o n g and asynchronous p e r i o d of a d u l t emergence and o v i p o s i t i o n , and the a b i l i t y of the l a r v a e to remain i n the t r u n k f o r as l o n g as 2 y e a r s are a p p r o p r i a t e c h a r a c t e r i s t i c s f o r s u r v i v a l i n a h a r s h and v a r i a b l e p r i m i t i v e environment. I n o r c h a r d m o n o c u l t u r e s , these same t r a i t s have become mechanisms t h a t o f t e n c i r c u m v e n t the c o n t r o l programs d e v e l o p e d a g a i n s t the i n s e c t . Any attempt to improve the c u r r e n t c o n t r o l programs o r to d e v e l o p new more e f f e c t i v e ones w i l l f a i l i f i t does not c o u n t e r the h i g h l y s u c c e s s f u l p h e n o l o g i c a l and b e h a v i o u r a l t a c t i c s which t h i s p e s t uses t o s u r v i v e . That i s the c h a l l e n g e p e a c h t r e e b o r e r p r e s e n t s to p e s t managers. 63 REFERENCES A g r i c u l t u r e R esearch S e r v i c e - 1974. A g r i c u l t u r e Handbook # 463:Peach p r o d u c t i o n . U.S.D.A., Wash. D.C. A r m s t r o n g , T. 1940. The l i f e h i s t o r y of the peach b o r e r , Svnanthedon e x i t i o s a . i n O n t a r i o . S c i . A g r i c . 20: 557-565. A t k i n s o n , D. and G.C. White 1980. The e f f e c t of weeds and weed c o n t r o l on temperate f r u i t o r c h a r d s and t h e i r e n vironment. In P e s t s . Pathogens and V e g e t a t i o n , V.M. Thresh ed. Pitman P u b l . I n c . New York, pp 415-428. Banham, F.L. 1982. A new m o n i t o r i n g method f o r peach t r e e b o r e r c o n t o l . Canadex B u l l e t i n #212.624 B a r r y , M.W., D.G. N i e l s o n , F.F. P u r r i n g t o n , & J.H. Tumlinson 1978. A t t r a c t i v i t y of pheromone b l e n d s to male p e a c h t r e e b o r e r s (Svnanthedon e x i t i o s a Say.) E n v i r o n . Entomol. 7.: 1-3 B a r r y , M.W. and D.G. N i e l s e n 1984. B e h a v i o u r of a d u l t p e a c h - t r e e b o r e r ( L e p i d o p t e r a : S e s i i d a e ) . Ann. Entomol. Soc. Amer 77.: 246-250. B e c k e r , G.G. 1917. Notes on the p e a c h - t r e e b o r e r ( S a n n i n o i d i a e x i t i o s a ) . J . Econ. Entomol. 10:49-59. Bobb, M.L. 1949. S p r a y s f o r c o n t r o l of the peach t r e e b o r e r . J . Econ. Entomol. 42.: 343-345. Boyce, H.R. 1961. P e a c h t r e e b o r e r s ( L e p i d o p t e r a : A e g e r i e d a e ) i n O n t a r i o . P r o c . Entomol. Soc. Ont. Report 92:45-57. B.C. P r o d u c t i o n Guide 1984. B.C. M i n i s t r y of A g r i c u l t u r e and Food. V i c t o r i a , B.C. B r i t t a i n , W. H. 1914. Report from the Okanagan d i s t r i c t : i n s e c t p e s t s of the year i n the Okanagan. P r o c . Entmol. Soc. B.C. 4.: 16 Brockman, C F . 1968. Trees of N o r t h America. Golden P r e s s , New York. p. 166. B u t l e r , H.G. 1932 O b s e r v a t i o n s on the b i o l o g y of the peach b o r e r i n Roane County, Tenn.,Harriman, Tenn.,1931. J . Econ. Entomol. 25:781-786. Canadian Dept. of F o r e s t r y , 1963. N a t i v e t r e e s of Canada pp 214-227. 64 Chalmers, D. J . , P.D. M i t c h e l l & P.H. J e r i e , 1984. The p h y s i o l o g y of growth c o n t r o l of peach and pear t r e e s u s i n g reduced i r r i g a t i o n . A c t a H o r t . C o n t r o l l i n g V i g o r  i n T r e e s , pp 146-149. C h a p l i n , C.E. and G.W. S c h n e i d e r 1975. R e s i s t a n c e t o the common peach t r e e b o r e r ( S a n n i n i o d e a e x i t i o s a ) i n s e e d l i n g s of R u t g e r s Red Leaf peach. H o r t S c . 10:400. D a v i d s o n , R.H. and W.T. Lyon 1979. I n s e c t p e s t s of farm,  garden and o r c h a r d . 7 t h ed. J . W i l e y & Sons, New York, p. 420-422. E l i a s , T.S. 1980. The complete t r e e s of N o r t h America:  f i e l d g u ide and n a t u r a l h i s t o r y . Outdoor L i f e Nature Books, Von N o s t r a n d R e i n h o l d Co. New York. p 562-587. E s s i g , E.0. 1938. I n s e c t s of Western N o r t h America. The M a c m i l l i a n Co., New York. G e n t r y , C.R., R.L. Hol l o w a y , and D.K. P o l l e t 1978. Pheromone m o n i t o r i n g of p e a c h t r e e b o r e r s and l e s s e r p e a c h t r e e b o r e r s i n South C a r o l i n a . J . Econ. Entomol. 71:247-248. G e n t r y , C R . and J.M. W e l l s 1982. Evidence of an o v i p o s i t i o n s t i m u l a n t f o r p e a c h t r e e b o r e r . J . Chem. E c o l . 8:1125-1132. G e n t r y , C R . & C.E. Yonce, 1982. D i s r u p t i o n of mating of pe a c h t r e e b o r e r . In " I n s e c t s u p p r e s s i o n w i t h c o n t r o l l e d  r e l e a s e pheromone systems". A. F. Kydonieus & M. Be r o z a eds. CRC P r e s s I n c . Boca Raton, F l o r i d a pp.99-106. Go u l d , H.P. 1923. Peach-grow i n g . The M a c m i l l i a n Co. New York. Pp. 222-225. He f l e b o w e r , R. 1984. B e t t e r not prune your peaches u n t i l you've checked f o r bud damage. F r . Grower, A p r i l . 16-19. K i n g , R.D. & H.F. M o r r i s , 1956. B i o l o g i e s of the p e a c h t r e e b o r e r and l e s s e r p e a c h t r e e b o r e r i n E a s t Texas. J . Econ. Entomol. 49:397-398. Lyne, W.H. 1913. Two i n j u r o u s i n s e c t s of economic importance a t t a c k i n g peach, a p r i c o t and plum t r e e s . P r o c . E n t . Soc. B.C. 13:34-36. Lyon, C P . 1952. Tree, shrubs and f l o w e r s t o know i n B.C J.M. Dent & Sons L t d . Vancouver, p 47. 65 MacCreary, D. 1954. E v a l u a t i o n of t r u n k s p r a y s a g a i n s t p e a c h t r e e b o r e r s i n Delaware. J . Econ. Entomol. 47:359-360 Madsen, H.F. and J.B. B a i l e y 1959. C o n t r o l of Sannino i d e a  ex i t i o s a g r a e f i (Hy. Edw.) on a p r i c o t s . J . Econ. Entomol. 52.: 804-806. M a r t i n , D.F. 1953. P e a c h t r e e b o r e r c o n t r o l . J . Econ. Entmol. 46:704 M e t c a l f , C.L., and W.P. F l i n t 1962. D e s t r u c t i v e and u s e f u l  i n s e c t s : t h e i r h a b i t s and c o n t r o l s . 4th E. McGraw H i l l , pp.757-760. Moore, J.N. and J . J a n i c k 1983. Methods i n f r u i t b r e e d i n g . Purdue U n i v . P r e s s , p 400. O n t a r i o Tree F r u i t P r o d u c t i o n Guide 1984. O n t a r i o Dept. of Food and A g r i c u l t u r e , Ottawa, Ont. P a c i f i c Northwest I n s e c t C o n t r o l Handbook. 1984. B u l l e t i n Dept. U n i v e r s i t y of Washington, P u l l m a n Wash. Ruhman, M.H. 1923. Report of a s s i s t a n t e n t o m o l o g i s t , Vernon, B.C. 18th Ann. Rept. Dept. of A g r i . B.C. p 45. Saunders, W. 1871. On the l a r v a of the p e a c h t r e e b o r e r E g e r i a e x i t i o s a . Can. E n t . 3_:22-23. S l i n g e r l a n d , M.V. and C R . Crosby 1915. Manual of f r u i t  i n s e c t s . The M a c m i l l i a n Co. New York. 503p. S m i t h , E. H. and R.W. H a r r i s 1952. I n f l u e n c e of t r e e v i g o r and w i n t e r i n j u r y on the l e s s e r p e a c h t r e e b o r e r . J . Econ. Entomol. 45_: 607-610. S m i t h , E.H. 1952. C o n t r o l of p e a c h t r e e b o r e r and l e s s e r p e a c h t r e e b o r e r i n New York. J . Econ. Entomol. 45.:61 1-615. S m i t h , E.H. and A.W. Avens 1954. The o v i c i d a l a c t i o n of p a r a t h i o n i n c o n t r o l of the p e a c h t r e e b o r e r . J . Econ. Entomol. 47:912-917 S m i t h , E.H. 1962. C o n t r o l of the p e a c h t r e e b o r e r on young t r e e s by a t r e a t m e n t b e f o r e p l a n t i n g . J . Econ. Entomol. 55:294-297. Smith,E.H. 1965. L a b o r a t o r y r e a r i n g of the p e a c h t r e e b o r e r and n o t e s on i t s b i o l o g y . J . Econ. Entomol. 58:228-236. 66 Snapp, O.I. & J.R. S w i n g l e , 1929. R e s u l t s of f u r t h e r i n v e s t i g a t i o n s w i t h p a r a d i c h l o r o b e n z e n e around peach t r e e s w i t h s p e c i a l r e f e r e n c e t o i n j u r y . J . Econ. Entomol. 22:782-785. Snapp, O.I. and J.R. Thomson, 1943. L i f e h i s t o r y and h a b i t s of the p e a c h t r e e b o r e r i n the s o u t h e a s t e r n s t a t e s . USDA Tech. B u l l e t i n #854. 24pp. Snapp, 0.1. 1958. Trunk s p r a y s f o r c o n t r o l of the p e a c h t r e e b o r e r . J . Econ. Entomol. 51;557-558• Snapp, 0. I . 1962. P e a c h t r e e b o r e r e x p e r i m e n t s i n peach o r c h a r d s . J . Econ. Entomol. 55;418-419. S t e r n , J.R. 1933. I n v e s t i g a t i o n of n a p t h a l e n e as a fumigant a g a i n s t the p e a c h t r e e b o r e r and s o i l i n s e c t s . J . Econ. Entomol. 26;903-906. Weaver, G.M. and H.R. Boyce 1965. P r e l i m i n a r y e v i d e n c e of h o s t r e s i s t a n c e to the peach t r e e b o r e r , Sann i no i d e a  e x i t i o s a . Can J . P l a n t Sc. 45_: 293-294. W i l s o n , C.L., A.L. S h i g o and P.L. Pusey 1983. Long l i v e the peach t r e e . F r . Grower Feb. 22-23. W y l i e , W.P. 1956. Trunk s p r a y s f o r p e a c h t r e e b o r e r c o n t r o l . J . Econ. Entomol. 49:574. Yonce, C.E. and R.R. Pate 1979. S e a s o n a l d i s t r i b u t i o n of Svnanthedon e x i t i o s a i n the G e o r g i a peach b e l t ; m o n i t o r e d by pheromone t r a p p i n g . Env. Entomol. 8_:32-33. 

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