May 11, 2014
Though parasitic mites continue to infect and kill honeybees, a new study suggests they are not to blame for colony collapse disorder (CCD), the phenomenon blamed for rapidly depleting the world’s honeybee population — pesticides are.
Harvard researchers, working with beekeepers in Massachusetts, kept tabs on 18 bee colonies, six hives in three different locations — from October 2012 to April 2013. Half the colonies were treated with a non-lethal dose of two neonicotinoid pesticides.
The researchers found that at least a portion of bees abandoned all 18 nests throughout the cold winter. But whereas warmer temperatures encouraged the return of colonies to the pesticide-free nests, those sprayed with imidacloprid or clothianidin — two of the world’s most popular neonicotinoids pesticides, mainstays of industrial farming — continued to suffer declining numbers into April.
The results suggest cold winters may exacerbate the ill effects of pesticides on bees and the colonizing behaviors.