Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 2000
Publication Date: N/A
Interpretive Summary: The Varroa mite is a serious pest of honey bees in most countries of the world, and has become widely resistant to certain insecticides, particularly fluvalinate. Coumaphos, another pesticide, has received emergency registration in the U. S. to combat Varroa mites, but no residues in hive products are allowed. Coumaphos would be expected to accumulate mostly in the wax in a hive, rather than the honey. We investigated the transfer of coumaphos from experimentally-contaminated wax into syrup and honey, and found that there was a small but detectable amount of coumaphos transferred from wax to honey or syrup over a period of a few months. This is an important factor in designing a treatment program using coumaphos, requiring precautions to prevent contact of coumaphos with combs used for extracted honey. This finding is important to beekeepers using coumaphos to control hive pests.
The organophosphate insecticide coumaphos has been used in Europe or the control of Varroa mites, and has received emergency registration in the United States for control of fluvalinate-resistant Varroa and the newly introduced small hive beetle. In order to investigate the transfer of coumaphos from wax into syrup and honey, we used an analytical method involving adsorption of coumaphos from diluted syrup/honey onto a solid-phase extraction cartridge, elution, and subsequent analysis. Coumaphos in syrup could be quantitated using HPLC using UV detection, and we found that coumaphos migrates from wax into syrup or honey, with concentrations increasing over a period of a few months. The resulting concentration is low, however, with only 200¿300 ppb in 100 g of syrup in contact with 10 g of wax containing 1000 ppm of coumaphos. Syrup in contact with wax containing 100 and 10 ppm of coumaphos also contained detectable amounts of coumaphos, but only 30 and 10 ppb, respectively. Determination of coumaphos extracted from wax into honey was complicated by the impurities in the honey, making HPLC determination difficult, but coumaphos could be extracted from honey with a similar solid-phase extraction, and then analyzed by gas chromatography/mass spectrometry. Concentrations in honey were similar to those in syrup for higher concentrations of coumaphos in wax, reaching 430 ppb after 26 weeks, but could not be determined in honey in contact with wax containing only 10 ppm.