More evidence shows neonicotinoids harm bees

Researchers in Europe and Canada have new evidence that neonicotinoid pesticides reduce the survival and reproductive success of bees. The effects, however, vary with location and bee species, two teams report June 30 in Science.

The studies suggest that regulators need to weigh the benefits of neonicotinoids to production with the risks of harm to pollinators.

In one of the studies, a group led by researchers from the Centre for Ecology & Hydrology, in England, exposed three bee species to winter oilseed rape crops that had been treated with either clothianidin or thiamethoxam (2017, DOI: 10.1126/science.aaa1190). The experiment was conducted in the U.K., Germany, and Hungary.

The researchers found that honeybees exposed to the treated crops had lower overwintering success in Hungary and the U.K. They did not observe such effects in overwintering honeybees in Germany. In all three areas, bumblebees and red mason bees exposed to the treated crops had lower reproductive success.

The scientists suggest that the differences are associated with the overall health of the bee colonies and availability of alternative flowers for the bees to feed on.

In the second study, scientists at York University and Université Laval examined honeybees living near corn grown in Canada from neonicotinoid-treated seeds (2017, DOI: 10.1126/science.aam7470). The researchers found that neonicotinoid-contaminated pollen collected by the honeybees did not originate from the corn. “This indicates that neonicotinoids, which are water soluble, spill over from agricultural fields into the surrounding environment, where they are taken up by plants that are very attractive to bees,” says York’s Nadia Tsvetkov, a Ph.D. student who worked on the study.