Insecticide-induced hormesis in a factitious host, Corcyra cephalonica, stimulates the development of its gregarious ecto-parasitoid, Habrobracon hebetor

Abstract

Hormesis phenomena in insect pests can have a negative impact, but for beneficial insects, it might be used to optimize mass rearing and increase the quality of biocontrol agents. Here, we report the multigenerational stimulatory effects of deltamethrin in a factitious laboratory host, Corcyra cephalonica, and the subsequent performance of its parasitoid, Habrobracon hebetor. The effects of sublethal (LC10), low lethal (LC15, LC20, LC25 and LC30) and median lethal (LC50) concentrations of deltamethrin along with the control were evaluated on biological traits and nutrient reserves of the host for three consecutive generations (G0, G1, and G2). The biological traits of C. cephalonica (fecundity, developmental duration and larval weight gain) did not differ significantly in the parental generation (G0), whereas in the later generation (G2), significant differences were observed with the control. Nutrient reserves (protein and lipid content) in C. cephalonica were significantly influenced by sublethal concentrations in all three generations (G0, G1, and G2). The performance of H. hebetor on the factitious host C. cephalonica (G2) revealed a significant increase in parasitoid fecundity of 65% when host larvae were exposed to LC15. However, no difference in hatch and pupation rates of parasitoids were observed across treatments. The emergence of both males and females and the longevity of only female wasps were significantly different. No effects were observed on male longevity. Taken together, insecticide-induced hormesis in host C. cephalonica, especially at LC15 exposure, stimulates the development of parasitoid H. hebetor without obvious major trade-off. The results might be helpful in mass rearing of H. hebetor as a biocontrol agent.