Comparing the efficacy of synthetic Varroacides and Varroa destructor phenotypic resistance using Apiarium and Mason jar bioassay techniques.

Background: Varroa mite, Varroa destructor, is a major threat for honey bee, Apis mellifera, colonies. Beekeepers have used synthetic Varroacides against Varroa mite for decades, but resistance to organophosphates, pyrethroids and formamidine has been reported in many locations worldwide. The goals of this study were to develop a reliable bioassay to assess efficacy and phenotypic resistance to commercial Varroacides. In this study, efficacy and Varroa resistance was evaluated using the Apiarium technique in comparison to the Mason jar method.

Results: Among tested Varroacides, a high efficacy (89%) for Apivar was identified when compared to Bayvarol (58%), Apistan (44%) and CheckMite (6%), in a 24 h assessment. We also found that CheckMite was toxic to bees in the Mason jar method. In addition, the Apiarium technique revealed a case of phenotypic resistance to Bayvarol, Apistan and CheckMite in the mite population evaluated.

Conclusion: A laboratory protocol was developed using the Apiarium method to evaluate Apivar efficacy. Collectively, the findings indicated that the Apiarium methodology provided a reliable technique to measure Varroacide efficacy and determine the presence of phenotypic resistance in V. destructor. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.