The risk of using synthetic insecticides to the environment, human health, and the emergence of new genera of pests resistant to that kind of drugs, have led to attention in natural compounds. The present study aimed at evaluating the insecticidal activity of 0.25-6 mg/cm2 of basil (Ocimum basilicum), black seeds (Nigella sativa), and lavender (Lavandula angustifolia) essential oils (EOs) against one of the major stored product pests, Sitophilus oryzae (L.). This was done by assessing mortality and repellent percentage assay in the adult stage, as well as analysing up and down-regulated genes associated with toxicity effect of selected EOs. The three studied EOs showed a toxic effect on S. oryzae; where O. basilicum and L. angustifolia EOs explicated 100% mortality at 6 mg/cm2 after 48 and 24 h, respectively. The highest repellence activity was recorded for O. basilicum EO at 0.75 mg/cm2 with value 82.3% after exposure time 5 h. In the highest dose (6 mg/cm2), the maximum up-regulated expression level of detoxification DEGs genes (CL1294 and CL 8) and cytochrome p45o gene (CYP4Q4) in Lavandula angustifolia EOs exhibited 8.32, 6.08, and 3.75 fold changes, respectively, as compared with 4.76 fold at 10 ppm malathion and 1.02 fold change in acetone control.
Keywords: Sitophilus oryzae; antioxidant activity; cytochrome gene; detoxification; essential oils; phytochemical constituents.