Stage-Specific Toxicity of Novaluron to Second-Instar Spodoptera frugiperda and Plutella xylostella and Associated Enzyme Responses

Simple SummaryInvestigations into the insecticidal activity of novaluron against the fall armyworm (Spodoptera frugiperda) and diamondback moth (Plutella xylostella) provide valuable data on its efficacy against these pests. Utilizing the leaf-dip method to assess toxicity to second-instar larvae and enzyme-linked immunosorbent assays (ELISA) to monitor changes in detoxifying enzymes and ecdysteroid levels, the study highlights distinct detoxification pathways in each pest species. The results indicate that physiological and ecological differences between the fall armyworm and diamondback moth influence their response to novaluron, offering valuable data for its application in integrated pest management.To provide a scientific basis for pest control, this study evaluated the insecticidal activity of novaluron against the fall armyworm (Spodoptera frugiperda) and diamondback moth (Plutella xylostella). The leaf-dip method determined the toxicity of novaluron to second-instar larvae, while corn leaves and cabbage treated with sublethal (LC10) and median lethal concentrations (LC50) of novaluron were used to feed the larvae. Enzyme-linked immunosorbent assays (ELISA) measured the activities of detoxifying enzymes [carboxylesterase (CarE), cytochrome P450 (P450), glutathione S-transferase (GST), and acetylcholinesterase (AChE)] and ecdysteroid (Ecd) levels in the pests after 24 and 48 h of treatment. Results indicated that after 24 h, AChE was involved in diamondback moth metabolism and CarE activity was inhibited. After 48 h, P450 and GST participated in fall armyworm detoxification, whereas P450 and GST were active in diamondback moth detoxification, with other enzyme activities normalizing. Novaluron also altered Ecd levels in both pests. These results demonstrate differing detoxification mechanisms in fall armyworm and diamondback moth, likely due to their unique physiological and ecological traits, and support the potential use of novaluron in pest management strategies.