Insect-resistant activities of Elsholtzia ciliata essential oil and its main components carvone against Tribolium castaneum in different development stages

The main objectives of the present study are to introduce a ecologically safe, and natural compound for controlling the red flour beetle, Tribolium castaneum. This study aims to thoroughly examine the effects of Elsholtzia ciliata essential oil (E. ciliata EO) and its primary components, carvone, on Tribolium castaneum eggs, larvae, pupae, and adults. The study also includes a simulated warehouse test to assess the efficacy of these substances as contact agents, fumigants, repellents, and antifeedants. All of these anti-insect activities were positively correlated with the concentrations of E. ciliata EO and carvone. Firstly, in the contact activity assay, E. ciliata EO and carvone completely inhibited the hatching of eggs and pupae of the T. castaneum at a concentration of 2.5 μL/cm². The LC₅₀ of E. ciliata EO and carvone were 7.62 and 4.33 μg/adult, respectively, against senior adults (5 weeks old). Secondly, in the fumigant activity assay, 60 mg/L of E. ciliata EO and carvone essentially completely inhibited pupae eclosion. On the other hand, the LD₅₀ of E. ciliata EO and carvone against senior adults (5 weeks old) were 8.72 and 5.02 mg/L, respectively. Thirdly, for T. castaneum adults, at the highest test concentration, the repellent rate of the E. ciliata EO was above 90%. Fourthly, the larvae and adults of the T. castaneum could reach complete antifeedant activity by E. ciliata EO and carvone at the highest test concentrations. Finally, 3000 ppm of carvone was sufficient to kill all the pests in the warehouse in the simulated warehouse test. In conclusion, the results of this study will contribute to the better control of the storage pest, T. castaneum, and the development of environmentally friendly insecticides based on E. ciliata EO and carvone.