Contact Toxicity and Repellent Efficacy of Essential Oil from Aerial Parts ofMelaleuca bracteataand its Major Compositions against Three Kinds of Insects

Synthetic insecticides, a traditional tool to avoid the reduction of stored-product due to insects, have emerged a serious of hazards to the environment for years, therefore, botanicals have entered people’s vision. This work aimed to present the essential oil composition of Melaleuca bracteata, and the contact as well as repellent activities against three stored-product insects, i.e. Lasioderma serricorne (Coleoptera: Ptinidae), Tribolium castaneum (Coleoptera: Tenebrionidae), and Sitophilus oryzae (Coleoptera: Curculionidae). For determining the composition, the analysis was performed by GC/FID and GC/MS. Among 11 identified compounds, the principal compounds were methyl eugenol (88.52 %) and methyl cinnamate (7.90 %). The essential oil demonstrated contact toxicity against L. serricorne, T. castaneum, and S. oryzae which LD50 values were 3.2, 22.6, and 20.4 μg/adult, respectively. Methyl cinnamate was more effective than methyl eugenol. The repellent activity indicated that essential oil and major compositions of M. bracteata were effective against L. serricorne and T. castaneum, but no use for S. oryzae. In the contact assay, L. serricorne showed more sensitivity, however, in repellency assay, T. castaneum was susceptible. We seek to provide a new application of the popular ornamental plant, M. bracteata, and offer an alternative material to botanical insecticides development.