Exposure to field-realistic levels of fungicide causes sublethal effects in the common eastern bumble bee (Bombus impatiens)

Bees are frequently exposed to fungicides in agricultural landscapes, and while these chemicals are generally not considered to be harmful to insect pollinators, the sublethal effects of fungicides are not well understood. We investigated the non-target effects of exposure to field-realistic concentrations of the fungicide, Pristine®, for the common eastern bumble bee (Bombus impatiens). We fed queenless microcolonies of bumble bees pollen patties contaminated with Pristine® ranging from 0 ppb-150,000 ppb for a total of 64 days, and evaluated the effects of chronic fungicide exposure on brood production, colony weight change, pollen consumption, and drone body quality. We found that while microcolonies fed pollen containing 1,500 ppb consumed the most pollen and produced the most brood, microcolonies exposed to 15,000 ppb gained weight at significantly lower rates. Fungicide exposure also negatively impacted brood development time and drone body quality. Our findings indicate that Pristine® has sublethal effects on bumble bee microcolony growth and brood development, highlighting the potential negative impacts of chronic fungicide exposure to bee health. In the face of the global decline of pollinator species, it is important for us to broaden our understanding of how bees react towards exposure of often overlooked stressors, such as fungicides, to account for potential consequences for pollinator health and pollination services.