Preimaginal treatment of Trichogramma evanescens and T. pintoi with two novel insecticides, afidopyropen and broflanilide: the lethal, sublethal and transgenerational effects

Abstract

The egg parasitoids, Trichogramma evanescens Westwood and T. pinto Voegelé (Hymenoptera: Trichogrammatidae), play central roles in the management of lepidopteran crop pests. However, their effectiveness highly depends on the employment of compatible pesticides, with a particular focus on novel insecticides that are promising in pest control. This study investigated the lethal, sublethal and transgenerational effects of two novel insecticides, afidopyropen and broflanilide, on T. evanescens and T. pintoi in terms of biological and behavioral traits. The eggs of the factitious host, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), with parasitoids at the preimaginal developmental stages (egg-larval, prepupal and pupal) were immersed in insecticide solutions. The emergence rates of both parasitoids were negatively affected by preimaginal treatments with different concentrations of afidopyropen and broflanilide. In transgenerational experiments, broflanilide treatments significantly reduced the parasitism performance of the treated generation (F0), emergence rate of F1 and F2, sex ratio of F1 T. evanescens and the emergence rate and sex ratio of F1 T. pintoi. Afidopyropen treatments reduced the emergence rate of F3 T. evanescens adults. The longevity of the F0 females and males of both parasitoids and that of the F1 females of T. evanescens were significantly reduced by broflanilide treatments. Broflanilide also decreased the walking speed of both species while afidopyropen enhanced the resting frequency of T. evanescens. This comprehensive study provides insights into the toxicological assessment of afidopyropen and broflanilide on Trichogramma species, employing parameters corresponding to their population and behavioral dynamics. Finally, this study concludes that the integration of afidopyropen and broflanilide into integrated pest management (IPM) strategies necessitates careful consideration, particularly regarding potential non-target effects on Trichogramma species.