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Title: Colonies of bumble bees (Bombus impatiens) produce fewer workers, less bee biomass, and have smaller mother queens following fungicide exposure

Author
item BERNAUER, OLIVIA - University Of Wisconsin
item GAINES-DAY, HANNAN - University Of Wisconsin
item Steffan, Shawn

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2015
Publication Date: 6/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61029
Citation: Bernauer, O.M., Gaines-Day, H.R., Steffan, S.A. 2015. Colonies of bumble bees (Bombus impatiens) produce fewer workers, less bee biomass, and have smaller mother queens following fungicide exposure. Insects. 6(2):478-488.

Interpretive Summary: Bumble bees are particularly important pollinators in the cranberry systems of the Upper Midwest. Past work has shown that bumble bees and other natives can provide all the pollination services required for adequate cranberry fruit set. During bloom, however, fungicides are commonly applied, exposing native pollinators (and rented honey bees) to fungicide residues. Recent evidence in honey bee systems has shown that colonies often decline following exposure to fungicide, even though fungicide residue is not toxic to adult bees. The major losses following exposure to fungicides may result from residues on pollen being fed to immature bees. We investigated whether bumble bee colonies would experience the same types of detrimental effects following exposure to fungicides. We show that a common bumble bee species (Bombus impatiens) suffered significant losses following exposure to field-relevant fungicide residues on flowers. Impact Statement: This represents the first evidence that native bee species are being impacted by widespread fungicide use during bloom.

Technical Abstract: Bees provide vital pollination services to the majority of flowering plants in both natural and agricultural systems. Unfortunately, both native and managed bee populations are experiencing serious declines, threatening the persistence of these plants and crops. Agricultural chemicals are one possible culprit contributing to bee decline. Even fungicides, generally considered safe for bees, have been shown to disrupt honey bee development and impair bumble bee behavior. Little is known, however, how fungicides may affect bumble bee colony growth. We conducted a controlled cage study to determine the effects of fungicide exposure on colonies of a wild, native bumble bee species (Bombus impatiens). Colonies of B. impatiens were exposed to flowers treated with field-relevant levels of chlorothalonil over the course of one month. Colony success was assessed by the number and biomass of larvae, pupae, and adult bumble bees. Bumble bee colonies exposed to fungicide produced fewer adult females, lower total bee biomass, and lighter queens than control colonies. Our results suggest that fungicides negatively affect the colony success of a native bumble bee species and that the use of fungicides during bloom has the potential to severely impact the success of native bumble bee populations foraging in agroecosystems.