The study, published July 24 in the online journal PLOS ONE, is the first analysis of real-world conditions encountered by honey bees as their hives pollinate a wide range of crops, from apples to watermelons.
The researchers collected pollen from honey bee hives in fields from Delaware to Maine. They analyzed the samples to find out which flowering plants were the bees’ main pollen sources and what agricultural chemicals were commingled with the pollen. The researchers fed the pesticide-laden pollen samples to healthy bees, which were then tested for their ability to resist infection with Nosema ceranae – a parasite of adult honey bees that has been linked to a lethal phenomenon known as colony collapse disorder.
On average, the pollen samples contained 9 different agricultural chemicals, including fungicides, insecticides, herbicides and miticides. Sublethal levels of multiple agricultural chemicals were present in every sample, with one sample containing 21 different pesticides. Pesticides found most frequently in the bees’ pollen were the fungicide chlorothalonil, used on apples and other crops, and the insecticide fluvalinate, used by beekeepers to control Varroa mites, common honey bee pests.
In the study’s most surprising result, bees that were fed the collected pollen samples containing chlorothonatil were nearly three times more likely to be infected by Nosema than bees that were not exposed to these chemicals, said Jeff Pettis, research leader of the USDA’s Bee Research Laboratory and the study’s lead author. The miticides used to control Varroa mites also harmed the bees’ ability to withstand parasitic infection...
Honey bee photo by Lip Kee, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license
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