Two new studies published yesterday in the journal Science, indicate low doses of insecticides interfere with bees’ sense of direction and the insect’s ability to reproduce.
In two separate experiments, researchers in Britain and France studied the interaction between bees and neonicotinoid pesticides, one of the most popular insecticides in the world, used on cereals, fruits, vegetables, legumes and many other crops.
In one study, scientists with the National Institute for Agricultural Research in France attached miniscule microchips to honeybees to monitor the bees’ movement.
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The scientists dosed one group of bees with thiamethoxam, a neonicotinoid insecticide, before releasing the bees and tracking their flight. Bees exposed to the pesticide were two to three times more likely to die away from the hive, compared to a control group. The chemical may have interfered with the bees’ homing system, the researchers said, preventing the insects from locating their hive.
In the British study, led by entomologists at the University of Stirling in Scotland, researchers treated colonies of bumblebees with imidacloprid, a neonicotinoid registered for use on more than 140 crops in 120 countries.
After the bees were exposed to the neonicotinoid in the lab, the bumblebees were released to fly around and collect pollen for six weeks.
“Treated colonies had a significantly reduced growth rate and suffered an 85 percent reduction in production of new queens compared to control colonies,” the researchers noted in the Science paper. “Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumblebee populations across the developed world.”
Jeff Pettis, lead bee researcher for the U.S. Department of Agriculture, said the French experiment isn’t unique, as other experiments have demonstrated that pesticides negatively affect bees’ homing abilities.
But the British study is noteworthy, he said.
“The bumblebee study was quite significant in that I think they used fairly realistic field doses,” Pettis said. “Those bumblebee colonies, at the end of the season, couldn’t produce new reproductives for the next phase of queens, in particular, for the next season. That was pretty striking. If you had that happen one or two seasons in a row … you’d have a massive decline in the bumblebee population.”
Bayer Crop Science, which manufactures imidacloprid and other neonictinoids, said the British experiment was flawed because the doses in the lab were higher than bees’ exposure to pesticides in the real world.
But that criticism is flawed, Pettis said.
“Bayer said those doses were high; I don’t think they were.”
