Effect of the entomopathogenic fungus Beauveria bassiana on the predatory mite Amblyseius swirskii (Acari: Phytoseiidae) as a non-target organism

An ongoing debate in biological control consists of whether interference between biological agents can disrupt pest control. This study investigated the direct spray of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (three isolates: DEBI008, F and J.B.) against the predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) in laboratory conditions. A. swirskii adults were highly susceptible to isolate F (total mortality +/- SE: 49.62 +/- 1.75% on the seventh day) but least susceptible to isolate DEBI008 (total mortality +/- SE: 16.25 +/- 0.81% on the seventh day). Viability of A. swirskii after spraying fungal isolate of DEBI008 on cucumber leaf discs at 4 time intervals (0, 24, 48 and 72 hours) was surveyed, but no significant difference was found. Our study showed that A. swirskii was susceptible to B. bassiana when conidia were applied directly to the mites. Further knowledge is needed to adjust the timing of various releases of both biological control agents to obtain maximum effectiveness in the greenhouse with minimum impact of the fungus on the predator.