Effects of Pesticides, Pathogens and Mites on Honey Bee Colony Health in a Commercial Beekeeping Setting: What Can Hobby and Sideliner Beekeepers Learn from this Study? 

Susan Kegley,^a Rose Radford^a, Geoffrey Marcy^a, Timothy Brown^a, Jeff Anderson,^b Steve Ellis,^c Darren Cox,^d Michelle Flenniken^e

^a Pesticide Research Institute, ^b California-Minnesota Honey Farm, ^c Old Mill Honey Farm, ^d Cox Honey, ^e Montana State University

Beekeepers have been experiencing unsustainably high levels of colony loss in the last decade. Factors thought to be associated with the decline of honey bee colony health include pesticides, pathogens, parasites like the Varroa mite and inadequate nutrition. Determining the relative contribution of the different factors is paramount to solving the problem, yet few studies are focused on this outcome. In this study, conducted by scientists at the Pesticide Research Institute (PRI) and Montana State University (MSU) and beekeepers with the Pollinator Stewardship Council (PSC) and National Honey Bee Advisory Board (NHBAB), the health of 60 colonies in three commercial beekeeping operations was tracked over the course of one year and evaluated as a function of Varroa mite loads, pesticide residue concentrations in pollen, and pathogen levels. Measurements of pesticides and pathogens were made four times during the year, mites were measured 5–6 times during the year, and colony strength was assessed every 4–6 weeks during the time the bees were active. The results of the study show statistically significant correlations between exposure to specific fungicides and insect growth regulators and impaired colony strength. Observational data suggest that colony failures were driven by poor queen and larval health. The presentation will describe the study methods and results in detail and provide insights into the significance of the results for hobby and sideliner beekeepers.