{"Affiliation":[{"label":"Affiliation","value":"Land and Food Systems, Faculty of","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."}],"AggregatedSourceRepository":[{"label":"AggregatedSourceRepository","value":"DSpace","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","classmap":"ore:Aggregation","property":"edm:dataProvider"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","explain":"A Europeana Data Model Property; The name or identifier of the organization who contributes data indirectly to an aggregation service (e.g. Europeana)"}],"Campus":[{"label":"Campus","value":"UBCV","attrs":{"lang":"en","ns":"https:\/\/open.library.ubc.ca\/terms#degreeCampus","classmap":"oc:ThesisDescription","property":"oc:degreeCampus"},"iri":"https:\/\/open.library.ubc.ca\/terms#degreeCampus","explain":"UBC Open Collections Metadata Components; Local Field; Identifies the name of the campus from which the graduate completed their degree."}],"Creator":[{"label":"Creator","value":"Edwards, Linda Lynne","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."}],"DateAvailable":[{"label":"DateAvailable","value":"2010-06-20T15:39:19Z","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"edm:WebResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"DateIssued":[{"label":"DateIssued","value":"1986","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"oc:SourceResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"Degree":[{"label":"Degree","value":"Master of Science - MSc","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#relatedDegree","classmap":"vivo:ThesisDegree","property":"vivo:relatedDegree"},"iri":"http:\/\/vivoweb.org\/ontology\/core#relatedDegree","explain":"VIVO-ISF Ontology V1.6 Property; The thesis degree; Extended Property specified by UBC, as per https:\/\/wiki.duraspace.org\/display\/VIVO\/Ontology+Editor%27s+Guide"}],"DegreeGrantor":[{"label":"DegreeGrantor","value":"University of British Columbia","attrs":{"lang":"en","ns":"https:\/\/open.library.ubc.ca\/terms#degreeGrantor","classmap":"oc:ThesisDescription","property":"oc:degreeGrantor"},"iri":"https:\/\/open.library.ubc.ca\/terms#degreeGrantor","explain":"UBC Open Collections Metadata Components; Local Field; Indicates the institution where thesis was granted."}],"Description":[{"label":"Description","value":"The peachtree borer, Svnanthedon exitiosa (Say), (Sesiidae), was studied to determine factors influencing its distribution, and four possible methods for its control in Prunus orchards in the Okanagan Valley, B.C.\r\nA survey for peachtree borer infestation was made by inspecting more than 7000 Prunus trees in 49 orchards, and 34 chokecherry trees, Prunus virginiana L., the native host, at 9 sites. Seventy-five per cent of the Prunus plantings contained peachtree borer. Infestation levels ranged from 0.9-83.3 % of the trees per planting. Young trees were least often attacked. Peach was the most heavily attacked species, prunes and apricots were intermediate, and cherry was the least attacked. Differences in bark texture appeared to be an important factor influencing oviposition behaviour and larval survival and establishment. Trees in clay soil without vegetation around the trunk were more heavily infested than trees in loam or in clay with vegetation. No peachtree borers were found in any of the chokecherry trees examined nor in any abandoned Prunus plantings. Fertilization and irrigation were important in determining borer survival and establishment.\r\nMore than half of the forty growers surveyed did not know if their orchards were infested with peachtree borer, although all mature plantings where no controls were being carried out contained borers. Four possible control methods were tested in five infested orchards. Two methods, removal of borer larvae by hand and coating the trunk with rubber latex in an attempt to prevent larval entry, were ineffective. Chemical control was more successful but 20 % of the trees sprayed once with endosulfan (Thiodan) at the beginning of the period of adult emergence were successfully attacked during the summer. This was reduced to 7.8 % on trees that received a second spray 4 weeks later. An aluminum cone designed to protect the basal area of the tree trunk that is most susceptible to borer attack was completely successful in preventing infestation.\r\nThese results are compared with the results of growers' control programs. Conventional endosulfan trunk sprays are very effective when properly applied, but only 5 of 40 growers were using them. The advantages and disadvantages of all methods of control are discussed and the importance of growers' understanding the biology of the insect and compatibility of control methods within the context of the total orchard operation emphasized.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/description","classmap":"dpla:SourceResource","property":"dcterms:description"},"iri":"http:\/\/purl.org\/dc\/terms\/description","explain":"A Dublin Core Terms Property; An account of the resource.; Description may include but is not limited to: an abstract, a table of contents, a graphical representation, or a free-text account of the resource."}],"DigitalResourceOriginalRecord":[{"label":"DigitalResourceOriginalRecord","value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/25877?expand=metadata","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","classmap":"ore:Aggregation","property":"edm:aggregatedCHO"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","explain":"A Europeana Data Model Property; The identifier of the source object, e.g. the Mona Lisa itself. This could be a full linked open date URI or an internal identifier"}],"FullText":[{"label":"FullText","value":"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\u00a3) 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 \u2014 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
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\u00a3 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 . 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