Biological Effects of Essential Oils Against Rice Weevil Sitophilus oryzae L. (Coleoptera: Curculionidae)

Abstract Essential oils were isolated by hydrodistillating dried fruits of Trachyspermum ammi (Apiaceae) and Nigella sativa (Ranunculaceae) and repellant, fumigant toxicity, effect on acetylcholinesterase enzyme activity and persistent nature of essential oils was determined against rice weevil, Sitophilus oryzae. T. ammi and N. sativa essential oils showed significant repellant activity and caused fumigant toxicity against S. oryzae. Median lethal concentration (LC50) of T. ammi and N. sativa essential oils were 0.37 and 0.46 μL/cm3 respectively. Inhibition in acetylcholinesterase enzyme activity was observed in S. oryzae adults when fumigated with sublethal concentrations of T. ammi and N. sativa essential oils. Persistence of insecticidal activity of both essential oils was recorded upto 48 h at LC100. These essential oils probably induce toxicity by inhibiting acetylcholinesterase enzyme activity.