Evaluation of insecticidal activity of the essential oil of Allium chinense G. Don and its major constituents against Liposcelis bostrychophila Badonnel

Water-distilled essential oil from the dried bulbs of Allium chinense (Liliaceae) was analyzed by gas chromatography–mass spectrometry (GC–MS). Eighteen compounds, accounting for 98.4% of the total oil, were identified and the main components of the essential oil of A. chinense were methyl allyl trisulfide (30.7%), dimethyl trisulfide (24.1%), methyl propyl disulfide (12.8%) and dimethyl disulfide (9.6%) followed by methyl allyl disulfide (3.4%) and methyl propyl trisulfide (3.6%). The essential oil exhibited contact toxicity against the booklice ( Liposcelis bostrychophila ) with an LC 50 value of 441.8   μg/cm 2 while the two major constituents, dimethyl trisulfide and methyl propyl disulfide had LC 50 values of 153.0   μg/cm 2 and 738.0   μg/cm 2 against the booklice, respectively. The essential oil of A. chinense possessed strong fumigant toxicity against the booklice with an LC 50 value of 186.5   μg/l while methyl allyl trisulfide (LC 50   =   90.4   μg/l) and dimethyl trisulfide (LC 50   =   114.2   μg/l) exhibited stronger fumigant toxicity than methyl propyl disulfide (LC 50   =   243.4   μg/l) and dimethyl disulfide (LC 50   =   340.8   μg/l) against the booklice. The results indicated that the essential oil and its major constituents have potential for development into natural insecticides or fumigants for control of insects in stored grains.