When honey bees bring pollen and nectar to the hive, they also bring along a wide variety of pesticides, say Penn State researchers.

Add the outside assault to the pesticides already in the waxy structure of the hive, and bee researchers see a problem difficult to evaluate and correct.

But an innovative approach may mitigate at least some beeswax contamination.

The researchers presented their findings at the recent 236th national American Chemical Society meeting in Philadelphia.

Those results show unprecedented levels of fluvalinate and coumaphos—pesticides used in the hives to combat varroa mites—in all comb and foundation wax samples. They also found lower levels of 70 other pesticides and metabolites of those pesticides in pollen and bees.

"Everyone figured that the acaricides (anti-mite chemicals) would be present in the wax because the wax is reprocessed to form the structure of the hives," says Maryann Frazier, senior Extension associate. "It was a bit of a shock to see the levels and the widespread presence of these pesticides."

All of the bees tested showed at least one pesticide, and pollen averaged six pesticides with as many as 31 in a sample.

"We already had in place ways to test for viruses, bacteria and fungi, but it was difficult to find an analytical laboratory that could analyze for unknown pesticides," says Christopher Mullin, an entomology professor. "We needed them to take a comprehensive look at all pesticides, not just those associated with beekeeping."

While beekeepers will have a difficult time controlling pesticide exposure outside the hive, the researchers tested a method for reducing the acaricide load in beeswax.

Using gamma radiation from a cobalt 60 source housed at Penn State's Breazeale Reactor, they irradiated the sheets of beeswax that beekeepers use as the structural foundation for the bees to build their combs.

They used radiation levels at the high end of that used to irradiate foods. Irradiation broke down about 50 percent of the acaricides in the wax.

The researchers tried irradiation at a commercial plant, and though some modifications were necessary to irradiate the wax sheets, it is possible. Some beekeepers already irradiate their equipment to get rid of disease-causing agents. But it might be more efficient if the wax sheet suppliers irradiated their product before sale to the beekeepers.

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