Functional response of an egg parasitoid,Trichogramma chilonisIshii to sublethal imidacloprid exposure

Abstract

AbstractBACKGROUNDThe effectiveness of a biological control agent depends on how well it can control pests and how compatible it is with pesticides. Therefore, we reported the multigenerational effect of a commonly used insecticide, imidacloprid, on the functional response of a widely acclaimed egg parasitoid,Trichogramma chilonisIshii, to different densities of the hostCorcyra cephalonicaStainton eggs. The study investigated the outcomes of the median lethal concentration (LC50) and sublethal concentrations (LC5, LC30), along with control treatments for five continuous generations (F1to F5).RESULTSThe results showed that the F5generation of LC30, both of the F1and F5generations of LC50, and the control all had a Type II functional response. A Type I functional response was exhibited for the F1generation of LC30and both generations of LC5. The attack rate on host eggs treated with LC5and LC30did not change (decrease) with the shift in the type of functional response as compared to the control. A significant increase in the searching efficiency (a) was observed in the later generation (F5) under the exposure of LC5and LC30imidacloprid concentrations. A lower handling time (Th) in both generations of the LC5followed by LC30treated individuals was observed when compared with the control and LC50treatments. Theper capitaparasitization efficiency (1/Th) and the rate of parasitization per handling time (a/Th) were also considerably higher in both the generations of LC5and LC30than in the control and LC50, thereby implying positive effects of imidacloprid on the parasitization potential ofT.chilonis.CONCLUSIONAltogether, these multigenerational outcomes on the functional response ofT.chiloniscould be leveraged to control the intractable lepidopteran pests under the mild exposure of imidacloprid in integrated pest management (IPM) programs as well as in the mass rearing of the parasitoid,T.chilonis. © 2023 Society of Chemical Industry.