EVALUATION OF A BOTANICAL INSECTICIDE, LAVENDER (LAVANDULA ANGUSTIFOLIA (M.)) ESSENTIAL OIL AS TOXICANT, REPELLENT AND ANTIFEEDANT AGAINST LESSER GRAIN BORER (RHYZOPERTHA DOMINICA (F.))

Abstract

In this study, the chemical composition of Lavandula angustifolia (Miller.1768) have been determined by gas chromatography-mass spectrometry. Then, we have evaluated the fumigant toxicity, the repellent and antifeedant properties, and also the effects on some biomarkers of essential oil extracted from L. angustifolia on adult of Rhyzopertha dominica (F. 1792) (Coleoptera: Bostrichidae). GC-MS analysis showed that this oil contains 56 compounds with linalool (20.42%) and linalyl acetate (13.24%) as the major components. This essential oil was found to exhibit insecticidal activity depending on the concentration and exposure period. In addition, the obtained results revealed an increase in the percent repellency. The enzymatic measurements showed a neurotoxic activity as evidenced by an inhibition of acetylcholinesterase (AChE). In addition, we observe a stimulation of the detoxification system as showed by an increase in glutathione-S-transferase (GST) activity and a decrease in gluthatione (GSH) rate. Lastly, essential oil was investigated on nutritional indices. Results showed a decrease in the relative growth rate, relative consumption rate, efficiency of conversion of ingested food, and an increase in feeding deterrent index, accompanied by a decrease in digestive enzymes tested, α-amylase and protease in treated series when compared with control.