Effects of systemic pesticide pollution on honey bee (Apis mellifera L.) colony health and productivity

Exposure to pesticides negatively impacts honey bee colony health and functioning, and chronic sub-lethal exposure to pesticide-contaminated resources compromises colony productivity and survival. Previous studies show that colony-level impacts from pesticides include the disruption of critical behaviors (i.e. foraging, brood care, social immunity) that then impairs the health of individual worker bees, as well as reproductive queens and drones. From 2017 to 2021, the University of Nebraska-Lincoln Bee Lab experienced consistent and repeated colony losses in apiaries located near an ethanol facility that processed surplus pesticide-treated seeds for ethanol production and became responsible for widespread systemic pesticide pollution and contamination of the surrounding air, water, and plant vegetation. High levels of the neonicotinoid insecticides, like thiamethoxam and clothianidin (as high as 35,000 and 554,000 ppb, respectively), and several fungicides (as high as 200,000 ppb) were detected in waste byproducts that were stockpiled without run-off mitigation measures and land-applied to nearby farms. This study examined the effects of landscape-level pesticide exposure originating from a real-life pollution event on honey bee colonies. From 2019-2023, 3-8 sentinel bee colonies were situated approximately 1.5-5km (1-3 miles) surrounding the ethanol plant and the data collected was analyzed to determine trends in colony health and productivity, including brood and adult production, queen status, food stores, and pest loads. Results from this long-term monitoring effort facilitates a better understanding of field realistic consequences and potential recovery of honey bee colonies from widespread environmental pesticide contamination.