Biological control of pollen beetles with the entomopathogenic fungus Beauveria bassiana – the tricky path to an efficient formulation

Abstract: Pollen beetles are a main pest in oilseed rape throughout Europe. A laboratory screening of Swiss isolates of entomopathogenic fungi revealed high potential of Beauveria bassiana for biological pollen beetle control. To improve efficacy of fungus spore suspensions in the field, we explored formulations with vegetable oils or stone dusts that have previously been shown to reduce pollen beetle abundancy in the field. The combined application of fungus spores and vegetable oil showed increased pollen beetle mortality in laboratory experiments and indicated increased yield in a field trial. To reduce fungus spore inactivation by ultraviolet irradiance upon field application, natural compounds were tested as UV-protectant additives to spore formulations. Formulation of B. bassiana spores with natural UV protectants tested in laboratory bioassays increased the number of surviving spores up to a factor of two, relative to untreated spores.