Dose‐dependent efficacy of a novel dsRNA ‐based solution containing vadescana for Varroa destructor control

BACKGROUND: A novel dsRNA-based product, containing a molecule called vadescana, interferes with Varroa destructor (Anderson and Trueman) fecundity and shows promise as a new biopesticide strategy for Varroa management. This study defines optimal dosing rates for vadescana in the field by evaluating efficacy in full-sized honey bee (Apis mellifera Linneas) hives to contribute essential preliminary information for vadescana development and implementation. Additionally, this study examined the impacts of various doses of vadescana on colony health by counting frames of bees and brood. RESULTS: Various concentrations, application volumes, and regimens (single or split application 3 weeks apart) of vadescana (2, 4, or 8 g/L) were applied to colonies and impacts were compared to colonies left untreated or treated with amitraz (positive control). Vadescana (4 g/L) applied at 4 g per brood box in a single dose was most effective at reducing Varroa populations for up to 18 weeks. Colony populations (average number of frames of bees and brood) remained unaffected among treatments over time. CONCLUSION: The results presented provide critical information for the development of vadescana by defining an optimal dose to use in full-size honey bee colonies and supporting claims of insignificant honey bee colony-level impacts. This study also introduces further research needs for broader applications and future deployment of this dsRNA-based Varroa management option.