Chemical composition, insecticidal and biochemical effects of essential oils of different plant species from Northern Egypt on the rice weevil, Sitophilus oryzae L.

The extensive use of synthetic insecticides and fumigants for control stored-product insects has led to the development of resistance. Essential oils from aromatic plants may provide proper alternatives to currently used insect control agents. Essential oils from 20 Egyptian plants were obtained by hydrodistillation. The chemical composition of the oils was identified by gas chromatograph/mass spectrometer. Fumigant and contact toxicities of the essential oils were evaluated against Sitophilus oryzae. The inhibitory effects of the essential oils on acetylcholinesterase and adenosine triphosphatases activities were examined. The oils were composed of monoterpene hydrocarbons (i.e., limonene, sabinene, beta-pinene and gamma-terpinene) and oxygenated monoterpenes (i.e., terpinen-4-ol, beta-thujone, 4-terpineol, alpha-citral and 1,8-cineole) with the exception of the oil of Schinus terebinthifolius which was contained sesquiterpenes, and the oil of Vitex agnus-castus which contained similar amounts of monoterpenes and sesquiterpenes. In the fumigation assay, the oils of Origanum vulgare (LC50 = 1.64 mg/L air), Citrus lemon (LC50 = 9.89 mg/L air), Callistemon viminals (LC50 = 16.17 mg/L air), Cupressus sempervirens (LC50 = 17.16 mg/L air), and Citrus sinensis (LC50 = 19.65 mg/L air) showed high toxicity to S. oryzae. In the contact assay, the oils of Artemisia judaica, C. viminals, and O. vulgare caused the highest toxicity to S. oryzae with LC50 values of 0.08, 0.09, and 0.11 mg/cm(2), respectively. The oil of A. judaica (I-50 = 16.1 mg/L) invoked the highest inhibitory effect on AChE activity, while the oils of C. viminals and O. vulgare were the most potent inhibitors to ATPases activity with I-50 values of 4.69 and 6.07 mg/L, respectively. The results indicate that the essential oils of A. Judaica, O. vulgare, C. limon, C. viminals, and C. sempervirens could be applicable to the management of populations of S. oryzae.