Evaluation of larvicidal activity of the essential oil of Allium macrostemon Bunge and its selected major constituent compounds against Aedes albopictus (Diptera: Culicidae)

Background: During the screening programme for new agrochemicals from Chinese medicinal herbs and local wild plants, the essential oil of dried bulbs of Allium macrostemon Bunge (Liliaceae) was found to possess larvicidal activity against mosquitoes. The aim of this research was to determine the larvicidal activity of the essential oil and its major constituent compounds against the larvae of the Culicidae mosquito, Aedes albopictus. Methods: Essential oil of A. macrostemon was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mass spectrometry (GC-MS). The activity of the essential oil and its two major constituents were evaluated, using World Health Organization (WHO) procedures, against the fourth instar larvae of Ae. albopictus for 24 h and larval mortalities were recorded at various essential oil/compound concentrations ranging from 9.0 -150 mu g/ml. Results: The essential oil of A. macrostemon exhibited larvicidal activity against the early fourth instar larvae of Ae. albopictus with an LC50 value of 72.86 mu g/ml. The two constituent compounds, dimethyl trisulfide and methyl propyl disulfide possessed strong larvicidal activity against the early fourth instar larvae of Ae. albopictus with LC50 values of 36.36 mu g/ml and 86.16 mu g/ml, respectively. Conclusion: The results indicated that the essential oil of A. macrostemon and its major constituents have good potential as a source for natural larvicides.