Compatibility of Beauveria bassiana (Balsamo) Vuillemin with Amblyseius cucumeris Oudemans (Acarina: Phytoseiidae) to Control Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) on Cucumber Plants

The effects of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin on populations of the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) feeding on cucumbers, and its compatibility with the predatory mite, Amblyseius cucumeris [Neoseiulus cucumeris] Oudemans (Acarina: Phytoseiidae), were studied in laboratory and glasshouse experiments. Two proprietary B. bassiana based mycopesticides were used: Naturalis-L (Troy Biosciences Inc., USA) and BotaniGard WP (Mycotech Corp., USA). Two high volume sprays of Naturalis-L, applied with a six day interval to glasshouse-grown cucumber crops, reduced numbers of immature F. occidentalis by 75% compared to an untreated control during the three weeks following the first application. Glasshouse populations of F. occidentalis were also reduced by 65-87% with three consecutive high volume sprays or low volume mist applications of Naturalis-L or BotaniGard WP, applied at six day intervals. Prophylactic release of A. cucumeris in glasshouse-grown cucumbers prevented population increases of F. occidentalis . Naturalis-L had no detrimental effect on A. cucumeris when sprayed onto excised cucumber leaves in a laboratory bioassay, or when sprayed onto glasshouse-grown cucumbers. There was no evidence that control of F. occidentalis was impaired by application of Naturalis-L onto plants already treated with A. cucumeris . The study suggests that a mycopesticide could be used as a second line of defence to support preventative pest management with A. cucumeris . This strategy provides a way forward for biological control in protected crops.