New research suggests that a particular class of pesticides called "neonicotinoids" do not kill bees but impair their brain function to disturb learning, blunt food gathering skills and harm reproduction.
These pesticides kill bee brain cells, rendering them unable to learn, gather food and reproduce.
"Our study shows that the neonicotinoid pesticides are a risk to our bees and we should stop using them on plants that bees visit," said Christopher N. Connolly from the Medical Research Institute at University of Dundee, UK.
The effects of these pesticides on bee colonies may be reversible by decreasing or eliminating the use of these pesticides on plants pollenated by bees.
For the study, Connolly and colleagues fed bees a sugar solution with very low neonicotinoid pesticide levels typically found in flowers (2.5 parts per billion) and tracked the toxins to the bee brain.
They found that pesticide levels in the bees' brains were sufficient to cause the learning cells to run out of energy.
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When the ability of the bee's brain to learn is limited, the bee is unable to master key skills such as recognizing the presence of nectar and pollen from the smell emitted from flowers.
They also fed bumblebee colonies this same very low level of pesticide in a remote site, where they were unlikely to be exposed to any other pesticides.
"It is ironic that neonicotinoids, pesticides developed to preserve the health of plants, ultimately inflict tremendous damage on plant life," said Gerald Weissmann, editor-in-chief of The FASEB Journal, where the study appeared.