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Chances are, you haven't seen honeybees in your flower garden for quite some time. Bumblebees and carpenter bees, perhaps, but not honeybees. Parasitic mites have dramatically reduced the honeybee population in this country, wreaking havoc on commercial bee farms and threatening farmers who rely on bees to pollinate their crops.
Researchers with the U. S. Department of Agriculture in Beltsville, Md., report they may be able to stem the decline in the honeybee population with a gel containing formic acid. Writing in the Sept. 20 issue of the Journal of Agricultural and Food Chemistry, the researchers report that the gel kills 70 - 85 percent of varroa mites, which literally suck the life from bees by feeding on their body fluids, and 100 percent of tracheal mites, which live in bees' tracheae and interfere with breathing. The peer-reviewed journal is published by the American Chemical Society, the world's largest scientific society. The article was initially published on the journal's web site on Aug. 21.
Produced naturally by some ants as a defense against predators, formic acid can be dangerous in large quantities if handled improperly. And it must be reapplied frequently to be effective against bee mites, according to the article's lead author, Jan Kochansky, Ph.D., of the USDA's Bee Research Laboratory in Beltsville.
"Formic acid has been used in other countries for years to control parasitic mites of honeybees," says Kochansky. But until now, he says, large-scale use has been impractical.
"Formic acid's mobility and corrosive properties make it dangerous to the user and have made bee supply companies unwilling to risk the liability associated with its use," according to Kochansky. "We have developed a gel formulation that is easier and safer to handle [than the liquid form] and emits formic acid vapors over two to three weeks, reducing the labor associated with its use."
The varroa and tracheal mites entered the U.S. in the mid-1980s. Since then, they have decimated both wild and commercial bee populations.
"Both mites now inhabit honeybee colonies in most of the country," states the research article. "Infestation of a honeybee colony with either mite can lead to loss of the colony, but colony mortality caused by the varroa mite can reach essentially 100 percent in temperate regions."
Two compounds are widely used in the United States to control bee mites: the pesticide fluvalinate used for varroa mites and menthol used for tracheal mites. While menthol remains effective against tracheal mites, varroa mites in some regions of the United States have developed resistance to fluvalinate, as has already occurred in parts of Europe. "The migratory nature of commercial beekeeping means that this resistance will spread rapidly to most areas of the country," claims Kochansky. Another compound, coumaphos, is used in some states to help control fluvalinate-resistant varroa mites, he notes.
A patent for the formic acid gel is pending; a manufacturing license has been issued to BetterBee, Inc. of Greenwich, N.Y. EPA registered the gel in August.
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