Ozone Might Help Make Bee Hives Cleaner And Safer

James tested ozone's effects on two pesticides, coumophos and tau-fluvalinate, both widely used by beekeepers to control varroa mites, a major enemy of bees. Studies elsewhere indicate that residues of these chemicals can accumulate in hives, including in the honeycomb. Beekeepers typically reuse the honeycomb after the honey has been extracted.

For the experiment, she placed glass vials of the pesticides in a small, tightly sealed chamber, then exposed the chemicals to a flow of ozone gas. Keeping the chamber at 50 percent relative humidity, she tested different temperatures and different ozone and pesticide concentrations.

Applying 500 parts per million of ozone in an approximately 93 degree Fahrenheit chamber for 10 to 15 hours degraded low concentrations of both pesticides, but 20 hours were needed to break down higher concentrations of tau-fluvalinate.

James also looked at ozone's ability to zap the greater wax moth, a honeycomb pest, in all of its life stages, from egg to adult. Wax moths attack bee young and damage the honeycomb.

Young wax moth larvae and adults were killed by just a few hours of ozone exposure. However, eggs, the most resistant life stage, had to be exposed to the gas for a few days.

Further tests are needed to find out whether the breakdown products of the degraded pesticides pose a hazard to bees, James noted.

In related work, James is finding that ozone can destroy microbes that cause major bee diseases such as chalkbrood and American foulbrood, but much higher ozone concentrations and longer fumigation times are needed.

ARS, along with the National Honey Board, headquartered in Firestone, Colo., and O3Co., Inc., of Idaho Falls, Idaho, provided research support.