Biological activities and synergistic effects of Elsholtzia stauntoni essential oil from flowers and leaves and their major constituents against Tribolium castaneum

Stored-product pests are a major problem in food production and storage. Essential oils (EOs) have been reported to have a wide range of insecticidal activities. In this study, the EOs of flowers and leaves from Elsholtzia stauntoni were analyzed for their chemical composition by GC–MS. The two EOs and their two common main components (cuminol and caryophyllene) were evaluated for their bioactivities against T. castaneum adults. Results of GC–MS analysis indicated that the chemical composition of EOs of flowers and leaves from E. stauntoni had certain similarity and diversity. The two same major components of EOs of flowers and leaves were cuminol (27.81% and 27.62%, respectively) and caryophyllene (5.78% and 10.95%, respectively). The results of bioassays indicated that the EOs of flowers and leaves possessed obvious contact toxicities (LD 50  = 19.05 and 18.75 µg/Adult, respectively) and repellent activities against T. castaneum . In addition, the EOs of flowers (LC 50  = 16.26 mg/L Air) showed the higher fumigant toxicity than that of leaves (LC 50  = 44.42 mg/L Air). Cuminol and caryophyllene exhibited contact toxicity and repellency against T. castaneum , but showed no fumigant toxicity. In particular, cuminol was still significantly repellent to T. castaneum within the testing concentration range of 78.63–0.13 nL/cm 2 after 48 h. Furthermore, cuminol and caryophyllene exhibited synergistic contact activity against T. castaneum in all experimental ratios. Altogether, it suggests that EOs of E. stauntoni and their two major monomers have promising potential to serve as bio-insecticides for controlling T. castaneum .