Assessing Varroa destructor acaricide resistance in Apis mellifera colonies of Virginia

Survival of European honey bee (Apis mellifera) colonies has been threatened over the past few decades as Varroa destructor has become a growing concern on a near-global scale. Prominent treatment methods have included the synthetic acaricides amitraz, coumaphos, and tau-fluvalinate. Since widespread resistance to these compounds has been noted, this study sought to investigate V. destructor resistance in Virginia. V. destructor infestation levels in apiaries located in three geographic regions of Virginia were monitored throughout the 2018 field season. By autumn, all apiaries had mite populations above the recommended treatment threshold. The results of resistance screening with glass surface contact bioassays indicated no resistance to amitraz, coumaphos, or tau-fluvalinate. These results have implications in future control strategies and responsible use of these acaricides may offer an additional option to those battling these aggressive ectoparasites.