Managed honey bees, Apis mellifera (Hymenoptera: Apidae), face greater risk from parasites and pathogens than mosquito control insecticide applications.

Abstract

As the primary pollinator for many crops, honey bees (Apis mellifera) are critically important to food production and the agricultural economy. Adult mosquito control is often suspected by the public and commercial beekeepers to harm honey bees, creating conflicts between industries. To investigate this matter, a two-year field study was conducted on vegetated wetlands in Salt Lake City, Utah, U.S.A. where honey bee colonies were placed in areas subjected to aerial adult mosquito control applications using the organophosphate naled. Comparison colonies were placed in areas not exposed to insecticides. Colony conditions were documented over the two-year period to capture both immediate and cumulative season-long effects of naled to honey bee health. A Before-After-Control-Impact (BACI) analysis of mortality data from treated and non-treated colonies using mixed effects models revealed no statistically significant differences, indicating that aerial applications of naled for mosquito control did not adversely affect these honey bee colonies. A Random Forest machine-learning model identified that Nosema infection, maximum temperatures, and seasonal progression were more significant contributors to bee mortality during the study period, whereas cumulative naled applications were among the least significant predictors. Non-parametric statistical tests (NMDS and PERMANOVA) indicated no differences in colony resources (pollen/honey/nectar; open/capped brood) and parasite (Varroa mites; Vairimorpha microsporidians) loads between exposed colonies and non-treatment colonies. These findings were consistent across different seasons and varying environmental conditions. Our results suggest that naled, when used as intended for mosquito control, does not pose a significant risk to managed honey bee populations in rural settings.