Co-formulation of Beauveria bassiana with natural substances to control pollen beetles - Synergy between fungal spores and colza oil

摘要

Pollen beetles (Brassicogethes spp.) are a major pest in colza (Brassica napus L., also known as oilseed rape) and show increasing resistance to commonly used insecticides. Entomopathogenic fungi (EPF) such as Beauveria bassiana have potential as a sustainable alternative means of control. However, field applications of fungal spores targeting the immigrated beetles on the crop have not been efficient to date. To enhance the effectiveness of fungal spores in insect pest control, this study focused on co-formulations of B. bassiana blastospores with vegetable oil and stone dust, which have already shown effects against pollen beetles as single treatments in previous studies. To estimate synergistic effects of these combinations, we developed a novel statistical approach based on a generalized linear mixed effect model and a parametric bootstrapping method. The combination of B. bassiana and colza oil increased pollen beetle mortality much more than expected from the additive effect of single applications, indicating a strong synergistic effect. In contrast, the combination of B. bassiana and stone dust showed an antagonistic effect, i.e. mortality was lower than expected from the additive effect of single substances.