Impact of a treatment ofBeauveria bassiana(Deuteromycota: Hyphomycetes) on honeybee (Apis mellifera) colony health and onVarroa destructormites (Acari: Varroidae)

Abstract

In 2 experiments bee colonies in southern France were treated with conidia of a Beauveria bassiana isolate collected from Varroa mites in the region. Objectives were to evaluate treatment effect on colony weight, adult bee mass, and capped brood and honey, and on Varroa fall onto sticky boards. Treatments included conidia formulated with either wax powder or wheat flour, flour alone, or control. Treatment did not affect colony health. Colonies treated with conidia and wax powder had higher mite fall compared to controls while those treated with conidia and wheat flour did not. The proportion fallen, infected mites in both conidia treatments was higher than controls for up to a week. Higher mite fall and infection rates were observed in treated hives in the 2nd, smaller experiment. The relationships between dosage and proportion fallen, infected mites, and between ambient temperature and infection duration, were examined. Future experiments will explore Varroa control using conidia.