Olfactory responses, oviposition deterrence and fumigant toxicity of plant volatiles for controlling Callosobruchus chinensis in stored mung beans

The adzuki bean weevil, Callosobruchus chinensis , is a major stored-legume pest. To develop low-toxicity, safe and efficient botanical insecticides, this study investigated the electroantennogram (EAG) responses and olfactory behavioural responses of C. chinensis to eight plant volatiles, evaluated the oviposition repellent effect of these volatiles against the weevil, and further explored the fumigant activity of the screened volatiles with the optimal repellent performance. Of the eight screened plant volatiles, four exhibited significant repellency, and three of them were further subjected to fumigation bioassay. The results showed that acetophenone, α-terpineol, 4-isopropylbenzyl alcohol, and limonene, elicited strong EAG responses and exerted significant repellent effects on adult C. chinensis . Among them, acetophenone, 4-isopropylbenzyl alcohol, and limonene markedly reduced the fecundity of C. chinensis . Acetophenone and limonene possessed strong fumigant toxicity against C. chinensis , and their fumigation efficacy against different developmental stages of the pest ranked in the order: egg > adult > larva > pupa. Further research found that acetophenone has an inhibitory effect on the activities of acetylcholinesterase (AChE) and carboxylesterase (CarE) in C. chinensis . The activity of superoxide dismutase (SOD) was transiently induced and then returned to levels not significantly different from controls, while acetophenone exerted an activating effect on the activities of glutathione-S-transferase (GST), peroxidase (POD), and catalase (CAT). Notably, acetophenone exhibited the pronounced fumigant effect on C. chinensis eggs, showing promise for the development of green control strategies against C. chinensis .