The Potential for Using Ozone to Decrease Pesticide Residues in Honey Bee Comb

Ozone is a strong oxidizer, and we evaluated its potential to eliminate pesticides from honeycomb and empty honey bee hives. Honey bees are exposed to pesticides when foraging for nectar and pollen and when beekeepers use in-hive chemical pest control measures. Persistent pesticides can accumulate in the hive over years, potentially harming the bees. Honeycomb is removed from bee colonies for honey extraction and then placed back on the colonies at a later date, providing a time when combs could be fumigated to eliminate or reduce pesticide residues. We found that ozone gas at a rate >920 mg O3/m for 10-20 h lowers coumaphos residues on a glass surface by 93-100% and tau-fluvalinate by 75-98%. Ozone was less effective at eliminating pesticides on beeswax, and residues were more effectively eliminated with new combs (comb built by bees within 3 y) than with old combs (combs used by beekeepers for >10 y). Ozone significantly reduced dimethylphenyl formamide, chlorpyrifos, and fenpyroximate contaminations in comb. When comb is treated with ozone, an off-odor is created, but the volatiles were found to be primarily straight chain aldehydes and carboxylic acids that are probably harmless to bees and humans. Ozone may have some utility for lowering pesticide residues in bee hives, but it would be more effective if a mechanism could be found that provides better penetration into wax, a goal not fully accomplished in our method.