Challenges for developing pathogen-based biopesticides against Varroa destructor (Mesostigmata: Varroidae)

Control of the major pest of apiculture, the ectoparasitic mite Varroa destructor using pathogen-based biopesticides would resolve many of the problems experienced with other forms of control, such as chemical control, hive manipulation, or selection of resistant honeybee strains. Several research groups have developed and tested fungus-based biopesticides in laboratory and field experiments, with varying results. While biopesticides have many desirable qualities, including much lower risk of honey contamination and of pest resistance, future research needs to focus on: (1) identification of the sub-population(s) of V. destructor affected by biopesticides and the duration and impact of the application on mite population dynamics; (2) development of an effective, easily applied formulation, and (3) evaluation of possible side or sublethal effects on bees themselves. Biopesticides need to be evaluated on the field (colony) level in addition to the laboratory level. Researchers should consider providing data that can be easily used to evaluate effect, such as mite drop counts onto sticky boards coupled with assessments of phoretic mite density or brood cell mite density. Exploration for naturally occurring pathogens should be conducted in the native range of V. destructor in Asia.