Monitoring for miticide resistance in Varroa destructor, the ectoparasitic mite of honey bee, Apis mellifera colonies

A glass vial bioassay procedure was developed to monitor for miticide resistance in Varroa mite populations. Diagnostic concentrations needed to separate susceptible from resistant individuals were determined for cypermethrin (0.1 µg per vial), fluvalinate (5.0 µg per vial), malathion (0.01 µg per vial), coumaphos (10.0 µg per vial), diazinon (5.0 µg per vial), methomyl (0.5 µg per vial), propoxur (0.1 µg per vial) and endosulfan (2.5 µg per vial). Resistance to organophosphorus insecticides (malathion, coumaphos) and pyrethroids (cypermetrhrin, fluvalinate) was widespread in both La Media Ranch, TX and Wewahitchka, FL from 2007 to 2010. There was no resistance to endosulfan, diazinon, methomyl, propoxur, imadacloprid, chlofenapyr, indoxacarb, and fenpyroximate in field populations of Varroa mite in the two locations where resistance was monitored. The seasonal patterns of resistance in Florida were different from those of Texas. In the former, the frequency of resistance to all insecticides tested decreased significantly from 2007 to 2010 while it increased in the latter. Overall, this user-friendly procedure provides the basis for the development of a resistance management strategy designed to extend the efficacy of all classes of insecticides used for control of Varroa mite..