Toxicity and Synergistic Effect of Essential Oil and Its Main Components Against the Adult and Larval Stages of .

Investigations have indicated that storage pests pose a great threat to global food security by damaging food crops and other food products derived from plants. Essential oils are proven to have significant effects on a large number of stored grain insects. This study evaluated the contact toxicity and fumigant activity of the essential oil extract from the aerial parts of and its two major biochemical components against adults and larvae of the food storage pest beetle . Gas chromatography-mass spectrometry analysis revealed 16 different components derived from the essential oil of , which included carvone (31.63%), limonene (22.05%), and -caryophyllene (15.47%). Contact toxicity assay showed that the essential oil extract exhibited a microgram-level of killing activity against adults (lethal dose 50 (LD) = 7.79 μg/adult) and larvae (LD = 24.87 μg/larva). Fumigant toxicity assay showed LD of 11.61 mg/L air for adults and 8.73 mg/L air for larvae. Carvone and limonene also exhibited various levels of bioactivity. A binary mixture (2:6) of carvone and limonene displayed obvious contact toxicity against adults (LD = 10.84 μg/adult) and larvae (LD = 30.62 μg/larva). Furthermore, carvone and limonene exhibited synergistic fumigant activity against larvae at a 1:7 ratio. Altogether, our results suggest that essential oil and its two monomers have a potential application value to eliminate .