Evaluation of toxic effect of methylamine avermactin on malondialdhyde activity in the rice red weevil Sitophilus oryzae L. (coleoptera: Curculionidae) in stored rice grains

Abstract

The rice weevil, Sitophilus oryzae is one of the major pests of stored rice in the world. Methylamine avermactine (Radical) is a novel semi-synthetic derivative of natural product abamactin in avermactin family. This study investigates the effectiveness of the methylamine avermactine in controlling infestations of the rice weevil. Five concentrations were tested to control the weevil adults. Concentrations 0.3, 0.1, 0.07, 0.04 and 0.02 ppm produced weevil mortality as high as 100, 100, 88.75, 68.22 and 53.7 % respectively after 8 days. LC25, LC50 LC80, and LC90 values were calculated from the plotted toxicity regression lines from the mortality percentages as a result of treatment. Methylamine avermactine afforded significant increase in MDA level in S.oryzae after exposure to different concentrations especially conc.0.3 ppm which showed highly significant increase in MDA level which revealed the occurrence of lipid peroxidation in insect tissues and affect on insect antioxidant capacities and thus revealed its efficiency in controlling the infestations of the rice weevil.