Colony Collapse: Are Potent Pesticides Killing Honeybees?
With a third of honeybee colonies disappearing due to “colony collapse disorder,” it’s time to move into high gear to find a solution.
October/November 2009
By Amanda Kimble-Evans
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Two common pesticides are being linked to colony collapse disorder symptoms in honeybees.
ISTOCKPHOTO
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Colony collapse disorder has wreaked havoc on U.S. beekeeping businesses (and the agriculture industry) since its devastating arrival in 2006. The veiled killer entered hives across Japan for the first time earlier this year, affecting 25 percent of the national beekeeping association members. Now the U.S. Environmental Protection Agency (EPA) is being sued by the nonprofit Natural Resources Defense Council (NRDC) for withholding details about the impact of neonicotinoids — a class of widely used pesticides — on honeybees and other pollinators.
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Nasty Neonicotinoid Pesticides
The EPA identifies two specific neonicotinoids, imidacloprid and clothianidin, as highly toxic to bees. Both chemicals cause symptoms in bees such as memory loss, navigation disruption, paralysis and death.
Both chemicals have been linked in dramatic honeybee deaths and subsequent suspensions of their use in France and Germany. Several European countries have already suspended them. Last year Slovenia and Italy also suspended their use for what they consider a significant risk to honeybee populations.
While Bayer CropScience, the primary producer of both pesticides, maintains honeybee deaths reported in Europe were caused by unusual application errors, they don’t dispute the proven toxicity of their products. Instead, they maintain bees do not encounter enough of an exposure to cause harm. Now even that assertion is under the microscope.
A report by Maryann Frazier, senior extension associate at Pennsylvania State University, points to a new study from Italy suggests honeybees may be ingesting neonicotinoids at levels 1,000 times higher than that in pollen or nectar via water droplets expressed from the leaves of corn grown from the pesticide-coated seed. This “guttation water” is a common source of liquid for forager bees. The concentrations in the droplets were high enough to kill bees within five minutes of consumption.
Frazier also highlights a study from North Carolina University that found the neonicotinoid Terraguard and the fungicide Procure had synergistic affects when combined, increasing the danger of the neonicotinoid to honeybees to over 1,000 times its original toxicity. The researchers at Penn State are concerned that even sub-lethal doses of these pesticides, while not killing the bees, are impairing their behavior and suppressing their immune systems.
“Their use has increased dramatically over the past few years and they are now the most widely used group of insecticides in the United States,” writes Frazier.
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