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Background: The 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 chilonis Ishii, to different densities of the host Corcyra cephalonica Stainton eggs. The study investigated the outcomes of the median lethal concentration (LC 50 ) and sublethal concentrations (LC 5 , LC 30 ), along with control treatments for five continuous generations (F 1 to F 5 )., Results: The results showed that the F 5 generation of LC 30 , both of the F 1 and F 5 generations of LC 50 , and the control all had a Type II functional response. A Type I functional response was exhibited for the F 1 generation of LC 30 and both generations of LC 5 . The attack rate on host eggs treated with LC 5 and LC 30 did 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 (F 5 ) under the exposure of LC 5 and LC 30 imidacloprid concentrations. A lower handling time (T h ) in both generations of the LC 5 followed by LC 30 treated individuals was observed when compared with the control and LC 50 treatments. The per capita parasitization efficiency (1/T h ) and the rate of parasitization per handling time (a/T h ) were also considerably higher in both the generations of LC 5 and LC 30 than in the control and LC 50 , thereby implying positive effects of imidacloprid on the parasitization potential of T. chilonis., Conclusion: Altogether, these multigenerational outcomes on the functional response of T. chilonis could 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., (© 2023 Society of Chemical Industry.)

Background: The rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) is a pest of stored grains and widely used as a factitious host during the mass rearing of several natural enemies of crop pests. Hormesis is well-documented in pest insects, to some extent in natural enemies of pests., Results: We report transgenerational stimulatory effects of the widely used fumigant, phosphine. The study reports the consequences of sublethal, low lethal and median lethal concentrations (LC 5 , LC 25 and LC 50 ) and untreated control for two sequential generations of the species (G 1 to G 2 ). In this study, we investigated the life-history traits, nutrient reserves (protein, lipid and carbohydrate) and larval gut microbiome (using 16 s rRNA V3-V4 metagenomics sequencing) of C. cephalonica. Stimulatory effects were observed for various biological traits of C. cephalonica, notably adult longevity, emergence and increased egg hatchability when exposed to LC 5 of phosphine. The total protein, lipid and carbohydrate contents of C. cephalonica also were found to be significantly increased by LC 5 in both generations. The microbial diversity of LC 5 treated larval gut was higher and found to be different from the rest of the treatments. This is the first report showing hormesis to a fumigant insecticide., Conclusion: Our findings increase knowledge on the interaction between hormesis, nutrient reserves and gut bacteria in C. cephalonica exposed to insecticides. Overall, the present study establishes phosphine-induced hormesis at LC 5 in the host C. cephalonica, which might help improve the quality of mass rearing of various natural enemies. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)