Insecticides Linked to Honeybee Deaths

What is killing off honey bees? Since 2006, there have been significant losses of honey bees from a mysterious condition called Colony Collapse Disorder, or CCD. Now a new study has added to evidence suggesting that a widely used class of insecticides appear to be harming the insects over winter — especially during colder winters.

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“We demonstrated again in this study that neonicotinoids are highly likely to be responsible for triggering CCD in honey bee hives that were healthy prior to the arrival of winter,” said lead author Chensheng (Alex) Lu, associate professor of environmental exposure biology at HSPH in a press release.

It appears that something about at least two kinds of neonicotinoids – a class of insecticide — prompts bees to abandon their hives during winter. Left out in the elements, the bees die.

The finding focused on the two insecticides, imidacloprid and clothianidin, and replicates a 2012 study that had focused only on imidacloprid. The 2012 study determined the chemical had the same effect on the pollinators — causing them to abandon house in winter.

Lu and his co-authors from the Worcester County Beekeepers Association monitored 18 bee colonies in three locations in central Massachusetts from October 2012 through April 2013. At each location, the researchers separated six colonies into three groups — one treated with imidacloprid, one with clothianidin, and one untreated.

All three of the bee colonies dwindled as winter set in, as was expected during the cold New England winter months. But by January 2013, bees in the control colony began to increase, while the bees in the insecticide-treated colonies continued to decline. By spring, half of the insecticide treated colonies were lost — with hives left empty after bees abandoned them.