Non-Target Effects of Trichoderma Spore Suspensions and Secondary Metabolites on Phytoseiid Predatory Mites

Fungi of the genus Trichoderma have attracted attention because of their potential activity against phytophagous mites; however, information regarding their non-target effects on predatory mites remains limited. This study evaluated the effects of spore suspensions and secondary metabolites of Trichoderma afroharzianum Tr132 and Trichoderma virens Tvr2 on three predatory mite species widely used in biological control programs: Phytoseiulus persimilis, Neoseiulus californicus, and Amblyseius swirskii. Predator egg hatchability and adult mortality were assessed under laboratory conditions. Spore suspension treatments did not significantly affect egg hatchability, which remained high (97–99%) across all predator species. In contrast, secondary metabolites slightly reduced egg hatchability to 94–96%, compared with 99.5% in the control. Exposure to spore suspensions caused moderate mortality in adult predatory mites, increasing from 10 to 13% at 3 days post-application (dpa) to 15–19% at 6 dpa. Secondary metabolites produced higher mortality that increased over time, reaching 9–11% at 1 dpa, 17–18% at 3 dpa, and up to 22–25% at 6 dpa. Mortality responses were similar among predator species. Overall, Trichoderma applications had minimal effects on predator egg hatchability but caused moderate mortality in adult predatory mites, particularly following exposure to secondary metabolites. These findings highlight the importance of evaluating the compatibility of Trichoderma-based products with beneficial predatory mites before their integration into IPM programs.