ABSTRACT.- This study evaluated the in vitro effects of common insecticides used for stink bug (Hemiptera: Pentatomidae) control in soybeans on Beauveria bassiana and Lecanicillium attenuatum. The effects of thiamethoxam + lambda-cyalothrin, imidacloprid + beta-cyfluthrin, thiamethoxam and trichlorfon were tested at field-recommended (FD), half and double FD doses for their impact on vegetative growth and conidial production. At FD only thiamethoxam did not significantly affect the mycelial growth of both strains 14 d after inoculation. The mixture of neonicotinoids and pyrethroids at FD reduced the conidiogenesis of both strains while trichlorfon affected L. attenuatum strain negatively. Understanding these side effects highlights the need for rational pest management strategies. © 2024 Informa UK Limited, trading as Taylor & Francis Group.