Pesticide Contamination in Native North American Crops, Part II—Comparison of Flower, Honey Bee Workers, and Native Bee Residues in Lowbush Blueberry.

Simple Summary: Working in lowbush blueberry fields, we studied how to provide a holistic measure of pesticide exposure to bees. Several different taxa of bees can be involved in blueberry pollination, including honey bees, bumble bees (which are native), and other native bees, such as mason, mining, and leafcutter bees. Using chemical analysis, we compared and contrasted samples from different sources to (1) measure pesticide exposure and (2) predict exposure risk in light of established levels of concern established by the U.S. Environmental Protection Agency. We trapped honey bee pollen as foragers entered the hive and, within the three years of the study, found considerable similarity of these samples to treated flowers; the measures were the number and concentration of pesticide residues, as well as the predicted level of risk. We found differences among two or three of these measures when comparing trapped honey bee pollen and trapped mason bee pollen, as well as between trapped honey bee pollen and whole bodies of captured honey bees. In these comparisons, the number of residues detected in honey bee pollen was typically greater, as was the estimated risk. The residues found when comparing whole body analysis of honey bee workers, bumble bee queens, and other native bees showed similarity in total residue concentrations and risk, but there was a higher number of different residues detected on honey bees. This research complements another study (Part I) focused on honey bee pollen trapping in lowbush blueberry and cranberry. Both studies provide a toxicological baseline for pesticide residue exposure to pollinators in the lowbush blueberry agroecosystem. In lowbush blueberry fields, we conducted residue analysis comparing flowers, trapped pollen (honey bee and Osmia spp.), and collected bees (honey bee workers, bumble bee queens, and non-Bombus spp. wild native bees). The study was conducted from 2012 to 2014. The number of pesticide residues, total concentrations, and risk to honey bees (Risk Quotient) on flowers were not significantly different from those determined for trapped honey bee pollen (except in one study year when residues detected in flower samples were significantly lower than residue numbers detected in trapped pollen). The compositions of residues were similar on flowers and trapped pollen. The number of residues detected in honey bee pollen was significantly greater than the number detected in Osmia spp. pollen, while the total concentration of residue was not different between the two types of pollen. The risk to honey bees was higher in trapped honey bee pollen than in trapped Osmia spp. pollen. The analysis of honey bee workers, native bumble bee queens, and native solitary bees showed that although more pesticide residues were detected on honey bee workers, there were no differences among the bee taxa in total residue concentrations or risk (as estimated in terms of risk to honey bees). [ABSTRACT FROM AUTHOR]