Impact of hive placement on blueberry pollination and honey bee exposure to pesticide drift – Kayla Brouwer, MS Student, Horticulture, WSU

Northern highbush blueberry (Vaccinium corymbosum; hereafter “blueberry”) is an economically important crop with Michigan, Oregon, and Washington collectively producing 64% of all blueberries grown in the United States. Blueberry production relies on insect-mediated pollination in order to obtain profitable yields and growers primarily use rented honey bee (Apis mellifera) hives for pollination services. Blueberry flower morphology is not conducive to efficient pollination by honey bees and poor weather can further reduce honey bee activity and pollination success. Additionally, commercial blueberry production depends on pesticide inputs during the pollination period to protect flowers and limit the spread of diseases and viruses. This can put rented honey bees at risk of pesticide exposure while hives are stationed in blueberry. Honey bees are in high demand as the cultivation of entomophilous crops increases and beekeepers are sometimes hesitant to place their hives in blueberry as colony health tends to decrease during and after hives are stationed in blueberry. Strategic hive placement may be utilized by growers and beekeepers to improve pollination in blueberry and limit honey bee hive exposure to pesticides, but research informing these practices is limited. In this study, commercial fields in Michigan, Oregon, and Washington received either clumped or dispersed hive placement treatments to determine how these placement strategies impact honey bee activity, crop pollination, and the amount of pesticide drift landing on hive boxes. Clumping was characterized by several pallets of hives concentrated in a single or few drop locations around a blueberry field, while the dispersed treatment was characterized by single pallets of hives spread along the field edge. Furthermore, hives in the dispersed treatment were closer to the field edge, while hives in the clumped treatment were further from the field edge. Clumping hives increased honey bee activity but did not impact overall crop pollination. The overall amount of pesticides detected on hives was not different by hive placement treatment, but the lack of differences may be due to high variability across sites, differences in grower management, and broader landscape effects. Further analysis of case study data in Washington, where management was held more consistent, shows clumping can reduce pesticide exposure and increasing the distance between hives and the field edge can reduce pesticide drift. Overall, growers and beekeepers can consider clumping as a strategy to reduce potential exposure to pesticides from drift, but they should also factor in broader landscape effects such as pesticide exposure from neighboring sites. This placement strategy should also be more efficient for beekeepers and not reduce pollination outcomes.

This talk will be provided in the Horticulture Department’s weekly seminar series. Please contact the organizers if you would like a video conference link to attend remotely.