By Brandon Keim
Neonicotinoid pesticides are ubiquitous in everday consumer plant treatments, and may expose bees to far higher doses than those found on farms, where neonicotinoids used in seed coatings are already considered a major problem by many scientists.
“It’s amazing how much research is out there on seed treatments, and in a way that’s distracted everyone from what may be a bigger problem,” said Mace Vaughan, pollinator program director at the Xerces society, an invertebrate conservation group.
The vast majority of attention paid to neonicotinoids, the world’s most popular class of pesticides, has focused on their agricultural uses and possible effects. A growing body of research suggests that, even at non-lethal doses, the pesticides can disrupt bee navigation and make them vulnerable to disease and stress.
Neonicotinoids are now a leading suspect in colony collapse disorder, a mysterious condition that’s decimating domestic and wild bee colonies across much of North America and Europe. The emergence of colony collapse disorder coincided with a dramatic increase in agricultural neonicotinoid use.
Several European countries, including France, Germany and Italy, have banned agricultural neonicotinoids, though some researchers and pesticide-manufacturing companies say evidence of low-dose harm is still incomplete and methodologically unsound.
Few researchers, however, doubt that high doses of neonicotinoids are harmful to bees — and though research on neonicotinoid use by gardeners, nurseries and urban landscapers has proceeded slowly, a troubling picture has emerged of products found on the shelves of most any garden center.
“For homeowner use products, for backyard plants, the amount of neonicotinoids used is like 40 times greater than anything allowable in agricultural systems,” said entomologist James Frazier of Penn State University.
The Environmental Protection Agency sets its LD50 — the dose at which 50 percent of exposed honeybees will die — for imidacloprid, a common neonicotinoid, at a range of 40 to 400 parts per billion. In a recent study on the effects of imidacloprid, a food dose of just 20 ppb destroyed honeybee colonies. Critics said that bees in the wild wouldn’t be exposed to such a high dose.
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