AN INVESTIGATION INTO THE RELATIONSHIP BETWEEN WESTERN FLOWER THRIPS DAMAGE AND ORCHARD FLOOR MANAGEMENT IN BRITISH COLUMBIA APPLE ORCHARDS Tamila L. Hubscher B.Sc., Simon Fraser University, 1983 PROFESSIONAL PAPER SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PEST MANAGEMENT in the Department of Biological Sciences @ Tamila L. Hubscher 1988 SIMON FRASER UNIVERSITY December 1988 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. APPROVAL Name : Tamila Louise Hubscher Degree : Master of Pest Management Title of Professional Paper: AN INVESTIGATION INTO THE RELATIONSHIP BETWEEN WESTERN FLOWER THRIPS DAMAGE AND ORCHARD FLOOR MANAGEMENT IN BRITISH COLUMBIA APPLE ORCHARDS Examining Committee : Chairman : Dr. M. Winston, Professor iPCI.CY L .- N - J.E. Rahe, ~rofesw~eniorSupervisor Dr. J?H. Borden, Professor Dr. N. Angerilli, Eastern Indonesia University Development Project (EIUDP), S.F.U. I&-. /n x- v /v - 6 w. Gillespie, Agassiz Research Station, Agriculture Canada, Agassiz, B.C., Public Examiner PARTIAL COPYRIGHT LICENSE I horoby grant to S lmon. Frasor Un ivors 1 ty tho r I ght to i ond my thesis, ,proJoct or oxtondod ossay' (tho ?It lo of whlch Is shown bolow) to users of tho S lmh Frasor ~nlvors1 ty ~ibr&, and to moho part lo l or sing lo coplcs only for such usors or In rosponso to a roquost f rm tho I ibrary of any othor unlvorslty, or othor oducatlona 1 Institution, on its own bohalf or for ono of Its usors. I furthor agroo that pormission for multiplo copylng of thls work for scholarly purposos may bo gran-tod by mo or tho Doan of'Graduato Stud 10s. It I s understood that,copy I ng or publlcatlon of thls work for flnanclal jaln,shall not bo allowod without my wrltton pormlsslon. % . *: . Tlt J a of Thas 1 s/ProJoct/Extondod Essay An Investigation Into The Relationship '~etweenWestern Fl'ower Thrips Damage And Orchard Floor ~ana~ementIn British Columbia Apple Orcha~ds Author:- --cc,-- I (. t y.i x-7~. v -tr~ L (stgnaturo) Tamila Louise ~ubscher . ABSTRACT The western flower thrips Frankliniella occidentalis is a general flower feeder with a wide host range that includes apples and dandelions. Flowers provide the thrips with food, a protective habitat and oviposition sites. The western flower thrips has the potential to cause three types of damage to its hosts: damage to the fruit, reduced photosynthetic capacity due to feeding on the leaves and transmission of plant pathogens. Oviposition by thrips into apple fruits can cause the fruit to abort or to develop an irregular shaped blemish called a pansy spot, caused by a physiological reaction of the fruit. Apples with large or numerous pansy spots are downgraded which results in a direct financial loss to the orchardist. The current recommended control for western flower thrips is to apply an insecticide spray at petal-fall. Since adult thrips enter the apple blossoms at the pink stage of development and migrate to new hosts as soon as the flowers start to wither, this petal-fall spray is often too late to control the thrips. The application of insecticides during the bloom period is not recommended because of the risk of honey bee poisoning. The majority of orchardists mow the erchard ground cover just prior to b1001ii to eliminate dandelion biossoms. The dandeiions are thought to compete with apple blossoms for honey bee pollination. It is possible, however, that mowing forces the thrips from dandelions to apple blossoms in greater numbers or sooner than would otherwise be the case. Mowing did not increase the numbers of thrips caught in the flower clusters, on sticky traps or increase the damage in the mowed plot compared to the control plot. When there was a significant difference between the number of thrips caught per trap per day between the upper and lower sticky traps, the upper traps always caught significantly more thrips than - the lower traps. There were no positional effects caused by the location of the trap trees on the number of thrips caught in the sticky traps. The majority of the pansy spots observed were small. iii ACKNOWLEDGEMENTS I would like to thank my senior supervisor, Dr. James Rahe, for his advice and guidance. I would also like to thank my supervisory committee, Dr. John Borden and Dr. Nello Angerilli, for their helpful comments and suggestions. I will always be in debt to Mr. W. Ritchie, Mr. M. Herz and Mr. B. Harker for allowing me to conduct my research in their orchards. I would also like to thank Dr. J. Procter, Mr. J. Parsons, Mr. T. Swales, Mr. D. Sharp, and Mr. J. Price for their advice in selecting field sites. Ms. H. Sampson supplied me with all the weather records for Cawston, B.C.. I would also like to thank Mr. D. Bergvinson for reviewing all the chemical names listed in this paper. Finally, I would like to thank Ms. G. Anderson and Ms. K. Tricker for assisting me in the set up of my plots and for supplying advice and moral support. TABLE OF CONTENTS Approval ........................................................................................................................................................................ ii Abstract .........................................................................................................................................................................iii Acknowledgements .....................................................................................................................................................iv List of Tables ..........................................................................................................................................................vii List of Figures .......................................................................................................................................................viii I . Introduction ......................................................................................................................................................1 Objectives ..........................................................................................................................................................1 Introduction ......................................................................................................................................................1 Biology of Frankliniella occidentalis ......................................................................................................3 I1 . Damage ..............................................................................................................................................................9 Thrips Damage in Apple Orchards .......................................................................................................9 I11 . Control .............................................................................................................................................................12 Biological Control ........................................................................................................................................12 Chemical Control .........................................................................................................................................19 Cultural Control ...........................................................................................................................................21 IV . Orchard Floor Cover. Pollinators and Thrips ................................................................................. 24 V. Methods ...........................................................................................................................................................26 Materials and Methods .............................................................................................................................26 VI . Results .............................................................................................................................................................30 Blossom Samples ..........................................................................................................................................30 Dandelion Samples ......................................................................................................................................35 Sticky Trap Samples ..................................................................................................................................36 June-drop Samples ......................................................................................................................................42 Harvest Samples ...........................................................................................................................................42 VII . Discussion .......................................................................................................................................................48 VIII . References .......................................................................................................................................................56 Appendix A ............................................................................................................................................................... 64 Appendix B .............................................................................................................................................................