LAUSR

BACKGROUND The parasitic mite, Varroa destructor (Anderson and Trueman), is a leading cause of honey bee colony losses around the world. Application of miticides such as amitraz are often the primary method of Varroa control in commercial beekeeping operations in the US. It is likely that excessive and exclusive amitraz application has led to the development of amitraz resistance in Varroa. A mutation of tyrosine at amino acid position 215 to histidine (Y215H) in the β2 -octopamine receptor was identified in putatively amitraz resistant Varroa in the US. This research investigated the presence of the Y215H mutation in quantitatively confirmed amitraz resistant Varroa from the US. RESULTS There was a strong association of susceptible and resistant phenotypes with the corresponding susceptible and resistant genotypes, respectively, and vice versa. The resistance bioassay may understate resistance levels due to the influence of environmental conditions on the outcome of the test whereby Varroa with an amitraz resistant genotype may appear with a susceptible phenotype. CONCLUSION Confirmation of the Y215H mutation in the β2 -octopamine receptor of amitraz resistant Varroa encourages the development and validation of low-cost, high throughput genotyping protocols to assess amitraz resistance. Resistance monitoring via genotyping will allow for large-scale passive monitoring to accurately determine the prevalence of amitraz resistance rather than directed sampling of apiaries with known resistance issues. Genotyping of Varroa for amitraz resistance early in the beekeeping season may predict late season resistance at the colony level and provide beekeepers with enough time to develop an effective Varroa management strategy. This article is protected by copyright. All rights reserved.