Lethal and sublethal effects of different biopesticides on Bombus terrestris (Hymenoptera: Apidae)

The use of biopesticides against agricultural pests is of great importance for the sustainability of pest management. The goal of the present study was to determine the lethal (acute) and sublethal (first male and young queen emerge time, competition point, total number of workers, males and young queens) effects of four commercial biopesticides [Nibortem (1.5% Lecanicillium ( Verticillium ) lecanii strain V1-1, Nostalgist (1.5% Beauveria bassiana strain Bb-1), Priority (1.5% Isaria fumosorosea (= Paecilomyces fumosoroseus ) strain PFs-1) and Nimbecidine (0.3 g/L Azadirachtin)] on Bombus terrestris . The impacts of biopesticides were investigated at the individual and colony level on worker bees by two application methods, namely topical and residual contact. While, the worker deaths were significantly higher in each biopesticide used than in the control in the residual contact application, those except Nibortem were found higher than the control in the topical application. The sublethal effect bioassays showed that there were no differences in terms of first male emergence time in the colonies for both topical and residual contact applications. However, the total number of workers was not affected by biopesticides in the residual contact method. The highest number of males was produced in the colonies exposed to Nimbecidine in both application methods. The number of young queens produced in the colonies was not affected by the application methods. In conclusion, Nimbecidine, among the tested biopesticides, caused vitally negative effects on the bumblebee in the residual contact application, in particular.