“It’s a hard-knock life, scouring the landscape for pollen to sustain a beehive. Alight upon the wrong field, and you might encounter fungicides, increasingly used on corn and soybean crops, and shown to harm honeybees at tiny levels. Get hauled in to pollinate California’s vast almond groves, as 60 percent of US honeybees do, and you’ll likely make contact with a group of chemicals called adjuvants—allegedly “inert” pesticide additives that have emerged as a prime suspect for a large bee die-off during this year’s almond bloom.
The hardest-to-avoid menace of all might be the neonicotinoid class of pesticides, widely used not only on big Midwestern crops like corn and soybeans but also on cotton, sorghum, sugar beets, apples, cherries, peaches, oranges, berries, leafy greens, tomatoes, and potatoes. They’re even common in yard and landscaping products. I’ve written before about the growing weight of science linking these lucrative pesticides, marketed by European agrichemical giants Bayer and Syngenta, to declining bee health, including the annual die-offs known as colony collapse disorder, which began in the winter of 2005-06.
And now, a new Harvard study fingers neonics as the key driver of colony collapse disorder. The experiment couldn’t have been simpler. Working with nearby beekeepers, Harvard researcher Chensheng Lu and his team treated 12 colonies with tiny levels of neonics and kept six control hives free of the popular chemicals. All 18 hives made it through summer without any apparent trouble. Come winter, though, the bees in six of the treated hives vanished, leaving behind empty colonies—the classic behavior of colony collapse disorder. None of the six control hives experienced a CCD-style disappearing act, although one did succumb to a common-to-bees gut pathogen called nosema.
Other studies have shown negative “sublethal” impacts of neonics on bees—that is, that the chemicals harm bees in subtle ways at doses too low to kill them outright. For example, this 2012 Science paper found that tiny amounts of the chemicals significantly affects bees’ ability to find their way back to their hives—”at levels that could put a colony at risk of collapse.” Another 2012 study, also published inScience, found that bumblebees exposed to “field-realistic levels” of a neonicotinoid called imidacloprid exhibited a severely diminished capacity to produce new queens. What makes the new Harvard study remarkable is that it actually simulated colony collapse disorder—neonic-treated bees suddenly abandoned hives that had been healthy all summer, while untreated bees hung around and repopulated their hives….”