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September 17, 2014
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Studies say pesticides are killing bees; Manufacturers call studies flawed

A cone flower attracts a honey bee.
TRR photos by Fritz Mayer

By Fritz Mayer
July 16, 2014

The volume of the debate surrounding the death of up to a third of all honey bees in the United States during the winter, in a phenomena known as colony collapse disorder (CCD), was increased a notch this year as the results of a new Harvard study were released in May.

A press release from the study said, “Two widely used neonicotinoids—a class of insecticide—appear to significantly harm honey bee colonies over the winter, particularly during colder winters…. The study replicated a 2012 finding from the same research group that found a link between low doses of imidacloprid and CCD, in which bees abandon their hives over the winter and eventually die. The new study also found that low doses of a second neonicotinoid, clothianidin, had the same negative effect.”

The companies that make the two pesticides were quick to say the Harvard study is flawed. Dr. Julian Little, spokesman for Bayer CropScience UK, told the Farmer’s Weekly website that the study exposed test bees to amounts of the two pesticides that were 10 to 100 times higher than the bees would ever experience in a real-world situation and that there was no chance of a bee colony suffering that much exposure.

The Harvard researchers studied 18 hives divided into three groups. One group was treated with clothianidin, another was treated with imidacloprid and the third was not treated.

From the press release: “There was a steady decline in the size of all the bee colonies through the beginning of winter—typical among hives during the colder months in New England. Beginning in January 2013, bee populations in the control colonies began to increase as expected, but populations in the neonicotinoid-treated hives continued to decline. By April 2013, six out of 12 of the neonicotinoid-treated colonies were lost, with abandoned hives that are typical of CCD. Only one of the control colonies was lost—thousands of dead bees were found inside the hive—with what appeared to be symptoms of a common intestinal parasite called Nosema ceranae.

“While the 12 pesticide-treated hives in the current study experienced a 50% CCD mortality rate, the authors noted that, in their 2012 study, bees in pesticide-treated hives had a much higher CCD mortality rate—94%. That earlier bee die-off occurred during the particularly cold and prolonged winter of 2010-2011 in central Massachusetts, leading the authors to speculate that colder temperatures, in combination with neonicotinoids, may play a role in the severity of CCD.