Exposure of native bees foraging in an agricultural landscape to current-use pesticides

The U.S. Geological Survey released the first ever study evaluating pesticide exposures to native bees. The study was conducted in mixed use agricultural areas of Colorado. In total, 18 pesticides, and one pesticide breakdown product, were detected in the 54 samples of wild bees collected. Seventy percent of the bee samples contained pesticides. The most commonly found pesticide was the neonicotinoid thiamethoxam, which is highly toxic to bees. Two other neonicotinoids as well as a variety of other insecticides, fungicides, and herbicides were also commonly found in the bees. Sampling methods precluded collection of dead bees; as such, no exposure levels considered lethal to bees were found. Still, some of the contamination levels found in the bees were high enough to cause sublethal effects. Pesticides were often found jointly in the samples, adding to the potential risk. Forty-eight percent of the samples had two or more pesticides with up to nine pesticides being found in a single sample.