(Beyond Pesticides, June 19, 2007) Scientists investigating a mysterious die-off of many of the nation’s honeybees are concentrating on pesticides and microorganisms as possible causes of the disorder, and some beekeepers are refusing to place their hives near chemically treated fields out of fear that pesticides may be contributing to the die-off.
Scientists from Penn State University and the U.S. Department of Agriculture are leading the research into the disease, which has killed tens of thousands of bee colonies in at least 35 states.
The die-off has threatened the livelihood of commercial beekeepers and strained fruit growers and other farmers who rely on bees to pollinate more than 90 flowering crops, including apples, nuts and citrus trees.
After months of study, researchers cannot tie the ailment to any single factor. But scientists have zeroed in on a new, unnamed pathogen found in the dead bees, and on the role of pesticides, said Maryann Frazier, a senior extension associate in the university’s entomology department.
David Hackenberg was the first beekeeper to report the disorder to Penn State last fall after losing nearly 75 percent of his 3,200 colonies. He has since rebuilt his business to 2,400 colonies, but now asks growers whether they use chemicals because he believes that pesticides, especially a class of pesticides called neonicotinoids, are harming the bees. ”I’m quizzing every farmer around,” Mr. Hackenberg said. â€œIf you’re going to use that stuff, then you’re going to have to go to somebody else.”
Neonicotinoids are a class of chemicals that target nerve cells in a similar way as nicotine, acting as neurotoxins to insects. One of the most commonly used neonicotinoid is the insecticide imidacloprid, manufactured by Bayer Crop Science and used in agriculture to control aphids, beetles, and other sucking insects. The use of imidacloprid was banned in France after it was suspected to be responsible for the decline of honeybee populations in the late 1990s.
Imidacloprid has been linked to neural effects in honeybees, including disruptions in mobility, navigation, and feeding behavior – similar behaviors that are being displayed by bees suffering from Colony Collapse Disorder (CCD). In CCD, bees are flying off in search of pollen and nectar and simply never returning to their colonies. Researchers say the bees are presumably dying in the fields, perhaps becoming exhausted or simply disoriented and eventually falling victim to the cold (See Daily News).
A 2004 study by researchers in France found that exposure to imidacloprid causes decreased foraging activity, along with a reduction in olfactory learning performance and decreased hive activity in honeybees. Moreover, a 2003 study in Italy that dosed honeybees with sublethal amounts of imidacloprid found that the honeybees became disoriented and failed to return to the hive. The authors concluded, â€œ[I]n certain conditions, the administration of imidacloprid can lead to the disappearance of honey bees from the hive, probably due to the disorientation caused by the substance.”
Beekeeper Jim Aucker of Millville was left with just 240 of his 1,200 hives earlier this spring after the illness struck. He’s back up to nearly 600 hives now and is convinced pesticides are playing a role after finding chemicals that had been sprayed on crops in the dead hives.
”Whether it’s 100 percent the cause, I’m not sure, but I’m positive it’s not helping,” Mr. Aucker said.
Daniel Weaver, president of the American Beekeeping Federation, said he is not surprised some beekeepers are avoiding fields with pesticides, but he also cautioned that the bees’ immune systems may have been weakened for reasons unrelated to pathogens or pesticides, such as mites. ”I try to limit my association to growers that I know will be responsible” he said, referring to farmers who avoid applying pesticide while the bees are flying. â€œOf course, I can’t escape it completely.”
TAKE ACTION: The fact that numerous registered pesticides are harmful and/or lethal to the very pollinators we depend upon for a prolific food system indicates there are fundamental problems with the pesticide regulatory system. Contact the House Committee on Agriculture (Chairman Collin Peterson (D-MN)) and ask for hearings on the failures of the pesticide registration system to protect the environment, ecological services, such as pollinators, and public health.