High pesticide risk to honey bees despite low focal crop pollen collection during pollination of a mass blooming crop

This study, conducted in New York, sought to understand how the landscape affects honey bee foraging and pesticide exposure. Researchers placed hives in blooming orchards then compared pesticide contamination levels detected in bee bread to established regulatory levels of concern (based on each chemical’s LD50, the amount found to cause lethality to 50 percent of a test population). Assuming that pesticides found interacted additively, the researchers determined that pesticide risk in recently accumulated bee bread sometimes exceeded regulatory levels of concern. More specifically, acute levels of concern were exceeded for bees in 5 of the 30 apple orchards (16.6 percent of the time) and chronic levels of concern were exceeded for bees in 22 or the 30 orchards (73.3 percent of the time). Furthermore, they found that the drivers of risk were not the chemicals sprayed in the orchard during bloom, but insecticides that might have been collected from contaminated wildflowers.

The researchers also found that fungicides made up 94% of total residues in bee bread. Fungicides were not found to be a driver of risk. This finding is likely due to the fact that for most fungicides a very large exposure level is required to cause lethality to 50% of test populations. This study did not measure sublethal concerns and fungicides have recently been linked with subtle harm to bees (see Sanchez-Bayo et al. 2016, Traynor et al. 2016, and DeGrandi-Hoffman et al. 2015).

McArt, S. H., A. A. Fersch, N. J. Milano, L. L. Truitt, and K. Boroczky
Scientific Reports
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