Effects of metarhizium anisopliae on host choice of the bee-parasitic mite varroa destructor

Abstract

The ectoparasitic mite Varroa destructor poses one of the biggest threats to the western honeybee Apis mellifera. Possibilities to control the mites are limited; therefore, it is important to assess the performance of novel alternatives like the use of biological control agents. The goal of our work was to evaluate the effects of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae BIPESCO 5, which is a potential biological control agent against the bee parasitic mite V. destructor, on the behavior of the parasite. In detail, we investigated whether the presence of fungal spores on the surface of host nurse bees, A. mellifera, affects the host choice behavior of adult female mites. We conducted two behavioral assays to monitor the behavior of the mites towards adult bees inoculated with a solution of fungal spores. Both choice and no-choice experiment revealed that M. anisopliae has a significant repellent influence on V. destructor‘s host selection behavior. The mites preferred, and stayed longer on, nurse bees free from fungal spores over bees carrying fungal spores. Our study provides the first evidence of sub-lethal behavioral effects of a fungal biocontrol agent against Varroa mites.