Efficacy of the entomopathogenic nematode, Steinernema carpocapsae on Pupal stage of the common Lepidopteran pests, Ostrinia furnacalis, Mythimna separata, and Spodoptera litura.

Steinernema carpocapsae is an entomopathogenic nematode with established efficacy against various agricultural pests. However, its impact on key lepidopteran pests, including Ostrinia furnacalis, Mythimna separata, and Spodoptera litura, remains underexplored, particularly at the pupal stage. This study evaluates the efficacy of the nematode through a combination of choice-based attraction assays, non-choice infection performance bioassays involving direct application to specific pupal body parts, and assessments of sublethal effects on adult survival and oviposition following pupal-stage exposure. S. carpocapsae exhibited a clear preference for pupae of all three pests over blank controls and for previously infected pupae over healthy pupae. When presented with different pupal genders, S. carpocapsae preferred female M. separata over males but showed no gender preference for O. furnacalis and S. litura. Infection performance varied by body part, with a higher infection performance on the abdomen and thorax compared to the head for O. furnacalis and S. litura, and on the abdomen over the thorax and head for M. separata. Adult survival probability was significantly lower when pupae were infected, and female oviposition was reduced when either member of a mating pair had been infected. These findings highlight the efficacy of S. carpocapsae as a promising biological control agent against these lepidopteran pests, particularly when targeting the pupal stage.