Abstract: 【Aim】 In this study, the fumigation and repellent activities of the optical isomers of carvone and menthol were tested against adult Culex pipiens pallens to evaluate their differences in insecticidal activity. It would provide guidance for the utilization of carvone and menthol. 【Methods】 The fumigation and knock-down activities of the five optical isomers of carvone and menthol against 3-day-old female adults of C. pipiens pallens were detected with the Erlenmeyer flask method, Y-tube olfactometer was used to determine the repellent activity, and the single compound with better activity was developed into vaporizing mat for further efficacy assessment. 【Results】 All five isomers had a certain degree of knock-down and fumigation activities against female adults of C. pipiens pallens. Compared with other isomers, L-carvone possessed the highest knock-down activity against female adults of C. pipiens pallens, with the KT₅₀ value of 9.75 min. D-carvone had the highest lethal effect on female adults of C. pipiens pallens, with the LC₅₀ value of 0.26 μL/L. Both L-carvone and D-carvone showed strong repellent activity against female adults of C. pipiens pallens, with the repellent rate of 100% lasting for 30 min at the dose of 0.5 μL. The vaporizing mat with L-carvone as the active ingredient had stronger activity against C. pipiens pallens than that with D-carvone as the active ingredient after heating for 1 h, and their KT₅₀ values were 13.70 and 17.90 min, respectively. 【Conclusion】 Carvone has stronger fumigation activity against female adults of C. pipiens pallens than menthol. The two optical isomers of carvone show a significant difference in fumigation and knock-down toxicities. L-carvone possesses a potential of being developed as a botanical pesticide for the control of C. pipiens pallens.    

Key words: Culex pipiens pallens, carvone, menthol, optical isomers, fumigation activity, repellent activity