In recent years, secondary metabolites of plants have attracted researchers' interest as a substitute for synthetic insecticides with many advantages. Elsholtzia kachinensis is an annual herb with medicinal and edible value. In this study, the essential oil (EO) of the aerial part of E. kachinensis was extracted by hydrodistillation, and GC-MS analysed essential oil components. The results show that carvone and dehydroelsholtzia ketone are the main components of the essential oil, accounting for 32.298% and 31.540%, respectively. EO, carvone and dehydroelsholtzia ketone are used to determine the effects against stored-product insects Lasioderma serricorne, Tribolium castaneum, Sitophilus oryzae and Liposcelis bostrychophila. The essential oil showed the most vital contact and fumigation toxicity to L. serricorne, of which LD50 and LC50 values were 3.85 μg/adult and 7.74 mg/L air, respectively. S. oryzae did not show repellent activity, but the repellent rate of the other three species reached 90% under EO treatment at a concentration of 78.63 nL/cm2. Therefore, the essential oil of E. kachinensis has an insecticidal effect and has the potential to be developed as a new eco-friendly insecticide.
Keywords: Elsholtzia kachinensis; contact toxicity; fumigant toxicity; repellency; stored-product insects.