Fumigant toxicity of Korean medicinal plant essential oils and components from Asiasarum sieboldi root against Sitophilus oryzae L.

Medicinal plant essential oils and components from Asiasarum sieboldi were tested for their insecticidal activities against the rice weevil Sitophilus oryzae, using a fumigation bioassay. Responses varied with plant material and concentration. The LC50 value of A. sieboldi essential oil against rice weevil was 2.37 mu g/ml air. Analysis by gas chromatography-mass spectrometry led to the identification of 20 compounds from A. sieboldi essential oil. Among identified compounds, five main compounds were tested for their insecticidal activity against rice weevil and compared to the toxicity of dichlorvos. Responses varied with compound and dose. Eucarvone was the most toxic, followed by safrole, with LC50 values of 3.32 and 11.27 mu g/ml, respectively. LC50 values of other compounds were >25 mu g/ml. The LC50 value of dichlorvos was 0.0081 mu g/ml. Copyright (C) 2008 John Wiley & Sons, Ltd.