Insecticidal effect of selected weed extracts for controlling rice Weevil, Sitophilus oryzae

Stored product insects became a major problem for the rice grain industry, leading to losses in quality and quantity. The main pest of stored product insects, particularly in rice grains, is the rice weevil, Sitophilus oryzae. Numerous studies have shown that using chemicals can have unfavorable impacts and lead to major health issues. Currently, chemicals identified in weed extracts have been suggested as an alternative to conventional synthetic insecticides for the control of insects. The chosen weed samples had spread widely in the open land area and were categorized as broad-leaved weeds. These weeds were identified as prospective weeds due to their high nutritional value and chemical components for several bioactivities, including insecticidal activity. In this study, the insecticidal activity of acetone weed extracts of Melastoma malabatrichum, Clidemia hirta, Chromolaena odorata, and Ageratum conyzoides were investigated against S. oryzae. The insecticidal activity was evaluated using repellent, contact, and fumigation tests. The weed extracts exhibited insecticidal activity against S. oryzae adults. The effective extract with 100 ± 0.00 % mortality of contact and fumigation test was C. odorata extract. This rice weevil was exposed to C. odorata extracts for two to seventy-two hours, at a concentration of 100 to 30,000 ppm, and in three different ways: as a repellent, a contact, and a fumigation test. Acetone was used as a solvent to show that the extracts repelled and killed the rice weevils. The present study is indicative of the potential of using C. odorata extracts for S. oryzae management.