INTEGRATED MANAGEMENT OF VARROA DESTRUCTOR ANDERSON & TRUEMAN (ACARI: VARROIDAE) IN HONEY BEES, APIS MELLIFERA L. (HYMENOPTERA: APIDAE), IN WESTERN WASHINGTON STATE, USA By Samuel David Hapke A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN ENTOMOLOGY WASHINGTON STATE UNIVERSITY Department of Entomology DECEMBER 2008 To the faculty of Washington State University: The members of the Committee appointed to examine the thesis of SAMUEL DAVID HAPKE find it satisfactory and recommend that it be accepted. Chair ii ACKNOWLEDGEMENTS A great many individuals deserve thanks for their contributions to the completion of this degree. I would like to thank my advisor, Steve Sheppard, for his patient grooming of a novice beekeeper, a fledgling biologist, and a wide-eyed graduate student. His breadth of understanding and unique enthusiasm will forever influence my life and career. I would also like to thank the other members of my committee, Drs. John Stark and Steve Clement, for their guidance throughout the graduate process. Each member of the Sheppard Lab deserves ample thanks for sharing their thoughts and energy with me during my time at WSU. Debbie Delaney, Ben Horwath, Marina Meixner, Devrim Oskay, Matthew Smart, and Judy Wu, I wish each of you boundless success and satisfaction in your endeavors. Thank you to Dory, Sally, and Barb for you work, which helped this process run so smoothly. A special thank you and congratulations go to my father, Ken Hapke, for being an eternal pillar in my life and for showing me that I had it easy tackling this process at only twenty-five years old. Bob Delisle has been a constant source of wisdom and integrity since he became a part of my family. I would like to express my immense gratitude to him. I would also like to thank my mother, Beth Hapke, for her unconditional love and her undying support of my goals and choices. To my siblings, Becca and Nathan, thank you with all my heart for continuing to grow as yourselves. And, thank you Gen Ernst, for your open arms and ears. iii INTEGRATED MANAGEMENT OF VARROA DESTRUCTOR ANDERSON & TRUEMAN (ACARI: VARROIDAE) IN HONEY BEES, APIS MELLIFERA L. (HYMENOPTERA: APIDAE), IN WESTERN WASHINGTON STATE, USA Abstract by Samuel David Hapke Washington State University December 2008 Chair: Walter S. Sheppard The ectoparasitic mite Varroa destructor (Anderson & Trueman) continues to threaten honey bee colonies worldwide. Emerging resistance in mite populations to available chemical acaricides coupled with fears of chemical contamination of hive products has illuminated the need to explore alternative options to control the mite. Formic acid is one of several “soft” alternatives being explored to replace synthetic acaricides. Five treatments for the management of V. destructor were tested to determine the efficacy and optimal timing of formic acid as an acaricide in western Washington State, USA. Treatment with formic acid led to no significant effects on bee population size, adult bee weight, or brood area. Mite levels were significantly diminished after August treatment, but rebounded by the following April. No significant differences in bee and mite population data were found between treatment groups during the following spring, but colonies treated with formic acid had higher survivorship than those untreated. The efficacy of the sticky board, which measures natural mite death in the colony, as an accurate predictor of total mite infestation was also examined. This study compared iv counts from 48hr sticky boards with total mite populations estimated from infestations of adult bee and capped brood samples. A strong linear relationship between the two methods was found using regression analysis and a mathematical model for estimating total infestation from 48hr sticky board counts is reported. This model may have utility in integrated management programs. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS............................................................................ iii ABSTRACT................................................................................................. iv LIST OF FIGURES...................................................................................... vii CHAPTER 1. INTRODUCTION………………………………………………………. 1 2. EFFICACY OF NATURAL MITE FALL AS AN ESTIMATOR OF COLONY-WIDE VARROA DESTRUCTOR (ACARI: VARROIDAE) INFESTATION LEVEL…………………….…………. 17 3. CONTROL OF VARROA DESTRUCTOR (ACARI: VARROIDAE) IN APIS MELLIFERA (HYMENOPTERA: APIDAE) WITH FORMIC ACID IN WESTERN WASHINGTON STATE, USA…….. 39 4. DISCUSSION…………………………………………………….…….. 58 5. BIBLIOGRAPHY……………………………………………………….. 64 vi LIST OF FIGURES 1. Comparison of 48hr natural mite fall in colonies measured by sticky board and total mite population estimated by sampling adult bee and capped brood infestation…..….28 2. Comparison of 48hr natural mite fall in colonies measured by sticky board and the ratio of mites per 100 bees in those colonies……………………………………………………29 3. Comparison of 48hr natural mite fall in colonies measured by sticky board and the number of mites killed by formic acid treatment in those colonies....………..………….30 4. Comparison of mites killed by formic acid treatment measured by sticky board and the total mite population estimated by sampling adult bee and brood infestation………….31 vii Dedication This thesis is dedicated to my mother’s parents, Benjamin and Hannah Weinstein, who showed me how large the world is and how full life can be. viii INTRODUCTION Varroa destructor (Anderson & Trueman) is an ectoparasitic mite that feeds on the hemolymph of honey bees, Apis mellifera L. (Anderson & Trueman 2000). Parasitism by V. destructor is multi-faceted stressor on colony health and may be a key contributing factor in Colony Collapse Disorder (CCD) (Cox-Foster et al 2007, Oldroyd 2007). The mite exhibits both a phoretic phase, during which it clings to the abdomen of adult bees, and a reproductive phase, when it feeds on bee larvae and pupae inside capped brood cells (Martin 1994). The phoretic phase facilitates the spread of the mite both within and between colonies via adult bees (Rademacher 1991, Sammataro et al 2000). Feeding by reproductive mites and their offspring physically damages the developing host, leading to a weakened, unproductive adult bee that is characterized by deformed wings and legs (De Jong 1982). Mite populations increase exponentially within colonies (Martin & Kemp 1997) and thus feeding damage can rapidly affect colony performance. If left untreated, V. destructor infestations may lead to colony mortality in two years after introduction (De Jong 1997). Furthermore, the mites facilitate the spread of pathogens in colonies by weakening the immune systems of their hosts (Shen et al 2005) and, in some cases, directly vector viruses between individual bees (Bowen-Walker et al 1999). On its natural host, Apis cerana Fabricius (Asian honey bee), V. destructor evolved a non-virulent host-parasite relationship, in which it infests and damages only drone brood. However, the mite is able to infest both drone and worker brood in A. mellifera colonies (Boot et al 1997), which impacts colony productivity. The host-shift from A. 1 cerana to A. mellifera appears to have occurred at least twice, once in Japan in the early 1950’s and in eastern Russia in the late 1950’s (Crane 1978, de Guzman et al 1997). The Russian haplotype of V. destructor exhibits higher virulence on A. mellifera than the Japanese haplotype (Anderson & Trueman 2000). Differential virulence between mite haplotypes may explain reports of bee colonies in the Americas surviving with long-term Varroa infestations in the absence of chemical treatment (Oldroyd 1999). After its introduction in the United States in 1987 (Anonymous 1987a), the Russian haplotype spread rapidly through managed honey bee populations (Wenner and Bushing 1996) and remains a ubiquitous threat today. Commercial beekeepers rely heavily on chemical acaricides to control V. destructor populations in hives, but these compounds may negatively impact host health and the quality of hive products. Although chemical treatments typically keep mite populations under economically damaging levels, such practices have been shown to damage colonies. Treatment doses of Apistan (tau-fluvalinate; Wellmark International, Bensenville, IL) decreased average body mass and lifespan of drones (Rinderer et al 1999). Residues of fluvalinate (a synthetic pyrethroid), amitraz (a formamidine) and coumaphos (an organophospate), the three most widely employed acaricides for V. destructor control, have been detected in wax, honey and other hive products (Bogdanov 2006, Chauzat and Faucon 2007). Sublethal effects, including anatomical and behavioral abnormalities, were observed in queens reared in wax containing high doses of fluvalinate (Haarman et al 2002). Coumaphos residues in queen cells led to significantly decreased acceptance rates and long-term performance of reared queens 2