Researchers have unearthed another reason that bees might be getting sick, and they suspect it's connected to common fungicides used on crops, such as blueberries and almonds, for which commercial honeybees are brought in as pollinators.
A study the University of Maryland released Wednesday found that bees are more susceptible to a lethal parasite when they're exposed to fungus-killing chemicals. The reasons remain unknown, but they'll be studied further.
"Bees are bringing a lot of agriculture products home with them in the colony," said Dennis vanEngelsdorp, the study's senior author, "which is not new. We knew there were a lot of different exposures."
What caught the researchers' attention was the amount of fungicide coming into the hive, he said, "and how that fungicide, which you don't expect to have a negative effect on bees, had this measurable effect on the bees' ability to fight infection."
They're calling for federal regulations to restrict the use of fungicides, which had been seen as safe for bees, at times when pollinating insects are foraging, similar to those that affect the use of insecticides.
The research builds on a government-sponsored report last spring that took a comprehensive look at what was contributing to honeybee colony declines, which first emerged in 2006. The report, by the Environmental Protection Agency and the U.S. Department of Agriculture, suggested a complex mix of problems.
It blamed parasites and disease, genetics, poor nutrition and pesticide exposure, as well as farming practices that don't give bees a pesticide-free buffer zone to forage in heavily developed agricultural regions.
The fungicide development presents a crucial dilemma, because bee colony collapse touches all aspects of American agriculture. The USDA estimates that a third of all food and beverages are made possible by pollination, mainly by honeybees. Pollination contributes to an estimated $20 billion to $30 billion in U.S. agricultural production each year.
Commercial beekeepers are worried. Tim Tucker of Niotaze, Kan., the vice president of the American Beekeeping Federation, said many beekeepers had experienced problems in areas where fungicides were being used in combination with herbicides and other chemicals.
The combination seems "to be really be kicking bees back hard. We've definitely noticed it, since the amount of fungicide increased," said Tucker, who's shifted from making honey to raising bees for other keepers who've lost their hives in recent years.
Environmentalists are concerned about a class of pesticides known as neonicotinoids, which the European Union intends to ban from use on corn and sunflowers at the end of the year.
Laurie Davies Adams, the executive director of the San Francisco-based Pollinator Partnership, said she hadn't yet read the fungicides study but was "heartened by this discovery."
"What it underscores is the complexity of this circumstance," she said. "There are a variety of influences and they're in the full range of pesticides, from insecticides to fungicides to herbicides. . . . But they're not the only thing. Anybody who tries to paint this as 'We found one problem' is probably not standing back far enough to look at the full picture."
The partnership is funding research this summer into bee declines that it suspects are connected to the dust that's raised when corn seeds are planted. Corn seeds are coated with pesticides, and farmers use air pressure to move the seeds from spreaders to the soil. The dust that's added to help move the seeds gets blown out of the machines, and lands on nearby plants that might be fodder for honeybees.
"Report on the National Stakeholders Conference on Honey Bee Health"
By Erika Bolstad
McClatchy Washington Bureau