Sublethal effects of spinetoram on the functional response of Drosophila parasitoid Trichopria drosophilae (Hymenoptera: Diapriidae) and its potential for biological control.

Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae) is a pupal parasitoid wasp of the globally invasive pest Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and exhibits significant biocontrol potential against D. suzukii. However, chemical management strategies within integrated pest management (IPM) often adversely affect natural enemies. This study investigated the parasitism efficiency of T. drosophilae under sublethal concentrations of spinetoram (LC10, LC25, and LC50). The results showed that the functional response of T. drosophilae was type II after treatment with LC10, LC25, and LC50 of spinetoram and the control. Spinetoram treatment reduced the attack rate (a) and prolonged the handling time (Th) on the host. The parasitism and searching efficiency of T. drosophilae decreased with increasing spinetoram concentrations. Meanwhile, the area of discovery of T. drosophilae decreased with increasing parasitoid wasp density, indicating that there was mutual interference between individuals within the species, and spinetoram treatment would reduce the interference effect. Spinetoram negatively impacted functional response parameters, searching efficiency and area of discovery with effects intensifying at higher concentrations. These findings provide valuable insights for optimizing IPM strategies of D. suzukii and conserving T. drosophilae.