Increased persistence of Beauveria bassiana spore viability under high ultraviolet-blocking greenhouse plastic

Abstract

A field study was conducted to assess the effect of various commercially available polyethylene plastic greenhouse coverings on the persistence of viable spores of the microbial insecticide Beauveria bassiana. Selected coverings blocked the transmission of UV light with wavelengths of 360 nm and below or 380 nm and below. Two coverings also contained an infrared blocking component. A commercial formulation of B. bassiana was applied for 3 consecutive weeks to plants growing in the plastic covered hoop houses. The percentage of viable spores was calculated up to 13 days after the final application. The persistence of viable B. bassiana spores was significantly longer under the plastic that blocked a greater portion of the UV spectrum (<380 nm) than the plastics that only blocked UV wavelengths below 360 nm. One week after application, percentage of spore germination was at least twice as high under the <380 nm blocking plastic compared to <360 nm blocking plastics.