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A common type of pesticide is dramatically harming wild bees, according to a new in-the-field study that outside experts say may help shift the way the U.S. government looks at a controversial class of chemicals.
But in the study published by the journal Nature on Wednesday, managed honeybees — which get trucked from place to place to pollinate major crops like almonds — didn't show the significant ill effects that wild cousins like bumblebees did.
A second study published in the same journal showed that in lab tests bees are not repelled by the pesticides, and may even prefer pesticide-coated crops, making the problem worse.
Bees of all kinds — crucial to pollinating plants, including major agricultural crops — have been in decline for several reasons. Pesticide problems are just one of many problems facing pollinators; this is separate from colony collapse disorder, which devastated honeybee populations in recent years but is now abating, experts said.
Exposure to neonicotinoid insecticides reduced the density of wild bees, resulted in less reproduction, and colonies that didn't grow when compared to bees not exposed to the pesticide, the study found. Scientists in Sweden were able to conduct a study that was in the wild, but still had the in-the-lab qualities of having control groups that researchers covet. They used 16 patches of landscape, eight where canola seeds were coated with the pesticide and eight where they weren't, and compared the two areas.
When the first results came in, "I was quite, 'Oh my God,'" said study lead author Maj Rundlof of Lund University. She said the reduction in bee health was "much more dramatic than I ever expected."
In areas treated with the pesticide, there were half as many wild bees per square meter than there were in areas not treated, Rundlof said. In the pesticide patches, bumblebee colonies had "almost no weight gain" compared to the normal colonies that gained about a pound, she said.
University of Illinois entomologist May Berenbaum, who wasn't part of either study, said in an email that the studies "indicate that, at least with current technology, systemic use of pesticides is fraught with environmental problems." The European Union has a moratorium on the use of neonicotinoids and some environmentalists are pushing for the same in the United States. Rundlof conducted her study just before the European ban went into effect in 2013.
"This paper has the potential of really shifting the conversation," said University of Maryland entomologist Dennis vanEnglesdorp, who wasn't part of the study. "Neonics may have a very dramatic effect on these non-managed pollinators in the environment. This is the most definitive work I've seen in the area."
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