Repellency and toxicity of azadirachtin against granary weevil Sitophilus granarius L. (Coleoptera: Curculionidae)

Abstract

International audienceThe granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), is known as a primary pest; and is able to feed on whole and undamaged cereal grains. This pest is probably one of the most destructive stored-product insect pests throughout the world affecting the quantity as well as quality of the grains. We have evaluated the fumigant and contact toxicity and the repellent property of azadirachtin a neem-based insecticide against S. granarius adults. Azadirachtin was found to exhibit fumigant and contact toxicity and the mortality increased as function the concentration and exposure time. In addition, the obtained results revealed an increase in the percent repellency as a function of concentration. Biomarker measurements in treated adult (LC25 and LC50) revealed, activation of detoxification system as showed by an increase in CAT and GST activity and also a decrease in GSH rate. Moreover, nutrition depletion index was found to be concentration dependent depicting maximum reduction at LC50 concentration. The biochemical compositions show that azadirachtin affected the energy reserves of adult of S. granarius. The results of persistence testing of azadirachtin applied by fumigation showed that their toxicity decrease as function the time. This study has highlighted the bioinsecticide activity of azadirachtin against granary weevil