Virulence of entomopathogenic fungi to Euschistus heros and selectivity to the egg parasitoid Telenomus podisi

Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana and the egg parasitoid Telenomus podisi are complementary strategies for managing the brown stink bug, Euschistus heros. This study evaluated fungal virulence against E. heros and selectivity to T. podisi in two experiments: (1) virulence assessment of M. anisopliae (CG 168; IBCB 425) and B. bassiana (LPP 129; LPP S1) applied at 1×10⁸ viable conidia mL⁻¹; and (2) selectivity tests in which eggs were immersed in fungal suspensions before (pre-parasitism) and after (post-parasitism) oviposition by T. podisi. Isolates CG 168 and IBCB 425 prolonged egg incubation and significantly reduced egg viability, with CG 168 showing hatching below 5%. At the nymphal stage, all isolates were pathogenic, and CG 168 and LPP 129 were the most virulent, causing higher mortality and shorter lethal times. In adults, CG 168 was the most effective, reducing survival to 8% by day seven, whereas IBCB 425, LPP 129, and LPP S1 caused intermediate effects, with 30–32% survival. Control treatments and Tween 80 maintained high survival. Fertility varied among isolates, increasing under LPP S1 and decreasing under LPP 129. Regarding selectivity, CG 168 reduced parasitism and emergence of T. podisi when applied after parasitism, whereas IBCB 425 showed performance similar to the control. Overall, CG 168 is highly effective against E. heros but shows low selectivity to T. podisi, while IBCB 425 combines efficacy and compatibility with the parasitoid, supporting its use in integrated management of the brown stink bug in soybean crops under agricultural production systems conditions.