Mozes-Koch, R., Department of Entomology, Fac. Agric., Food and Environ. Sci., Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel
Slabezki, Y., Beekeeping Division, Extension Service, Ministry of Agriculture, POB 7054, Tel-Aviv, Israel
Efrat, H., Zerifin Breeding Apiary, ARS, Volcani Center, POB 6, Bet Dagan 50250, Israel
Kalev, H., Department of Entomology, Fac. Agric., Food and Environ. Sci., Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel
Kamer, Y., Zerifin Breeding Apiary, ARS, Volcani Center, POB 6, Bet Dagan 50250, Israel
Yakobson, B.A., Kimron Veterinary Institute, Bet Dagan 50250, Israel
Dag, A., Beekeeping Division, Extension Service, Ministry of Agriculture, POB 7054, Tel-Aviv, Israel
Gerson, U., Department of Entomology, Fac. Agric., Food and Environ. Sci., Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel

The aim of this study was to explore the extent of varroa mite resistance to fluvalinate in Israel and to determine the underlying biochemical mechanism. Assays at different apiaries indicated varroa mite resistance at three of the five sites tested. Dose response assays conducted with tau-fluvalinate on mites obtained from different sites indicated uneven resistance. A monooxygenase assay revealed an increased rate (approximately 20-fold) of activity in mites that were not controlled by the pesticide, as compared to activity in mites from untreated colonies. A minor, 1.5-2.5 fold, increase of esterase activity was also noted in the resistant mites. This first demonstration of a fluvalinate-resistance mechanism in varroa mites points to the need for more vigorous resistance management practices to control the pest.