Effect of commercial bioinsecticides formulated from entomopathogenic fungi on Apis mellifera (Hymenoptera: Apidae)

Abstract

Bees are essential for agricultural productivity, however, during foraging, they can be exposed to contamination with the residue of synthetic insecticides. Entomopathogenic fungi, an efficient and economically viable alternative to the use of these insecticides, are increasingly used in pest control. However, the viability of agricultural use of these fungi depends on formulations that can increase nontarget organism mortality. Thus, the objective of this study was to evaluate the effects of commercial bioinsecticides formulated from isolates of Beauveria bassiana (Boveril®) and Metarhizium anisopliae (Metarril®) on Apis mellifera workers under laboratory conditions and record the infectious process by scanning electron microscopy. To accomplish this, bees were exposed by direct contact to concentrations of 1.0 × 104,105,106 and 107 conidia.mL−1 applied by means of a continuous-flow manual sprayer. Evaluations were performed at 24-h intervals for five days. Among the different concentrations of bioinsecticides, pathogenicity did not significantly differ, but the effects reduced the mobility of A. mellifera and caused mortality between 55 and 58% at the highest concentration tested after 120h. Scanning electron microscopy analyses showed an accumulation of non-germinated conidia in pollen combs, indicating that grooming performed by workers can attenuate infection by entomopathogenic fungi. Results indicate a moderate lethal effect on bees in the laboratory, requiring further studies to determine the impact of bioinsecticides formulated from entomopathogenic fungi on colonies of A. mellifera under field conditions.