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) Vui llemin on populations of the western flower thrips, Frankliniella occidenta lis Pergande (Thysanoptera: Thripidae) feeding on cucumbers, and its compat ibility with the predatory mite, Amblyseius cucumeris [Neoseiulus cucumeris ] Oudemans (Acarina. Phytoseiidae), were studied in laboratory and glasshou se 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 inter val to glasshouse-grown cucumber crops, reduced numbers of immature F. occi dentalis by 75% compared to an untreated control during the three weeks fol lowing the first application. Glasshouse populations of F occidentalis were also reduced by 65-87% with three consecutive high volume sprays or low vo lume mist applications of Naturalis-L or BotaniGard WP, applied at six day intervals. Prophylactic release of A. cucumeris in glasshouse-grown cucumbe rs prevented population increases of F. occidentalis. Naturalis-L had no de trimental 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 appli cation of Naturalis-L onto plants already treated with A. cucumeris. The st udy suggests that a mycopesticide could be used as a second line of defence to support preventative pest management with A. cucumeris. This strategy p rovides a way forward for biological control in protected crops.