Efficacy of Various Plant Extracts and Synergism Against Domestic Species of Rice Weevil Sitophilous Oryzae (Curculionidae: Coleoptera)

Despite being successful in preventing pests from entering stored goods, residual synthetic pesticides have had a negative impact on the environment. However, the prohibitive cost of synthetic pesticides and the risk of target pests developing insecticide resistance have prompted researchers to develop alternative management strategies. Since plant-based pesticides are biodegradable and less dangerous for organisms other than the target species, they are a useful alternative to chemical pesticides. The aim of the present study was to investigate the effectiveness of plant extract in preventing the rice weevil <i>Sitophilus oryzae</i> (<i>Linnaeous</i>) (<i>Coloptera: Curcolinidae</i>) from infesting stored-products. For toxicity and synergism against <i>S. oryzae</i>, aqueous extracts of <i>Cannabis sative</i> L., <i>Dodonaea visicosa</i> L., and <i>Parthenium hysterophorus</i> L., were evaluated at different concentrations. <i>D. viscosa</i> and <i>P. hysterophorus</i> extract concentrations were 0.25, 0.5, 1.0, 2.0, and 3.0%, and <i>C. sativa</i> extract concentrations were 0.62, 1.25, 2.5, 5.0, and 7.5%. A completely random design with three replications was used, with distilled water serving as the control. The experimental setting was kept at 27± 2oC and 65±5% R.H. The findings showed that <i>D. visicosa</i>, <i>P. hysterophorus</i>, and <i>C. sativa</i> caused 97%, 90%, and 83% of mortalities at the highest doses, respectively. At highest concentrations, the mortalities found for binary combinations of <i>D. viscosa</i> and <i>P. hysterophorus</i>, <i>D. viscosa</i> and <i>C. sativa</i>, and <i>P. hysterophorus</i> and <i>C. sativa</i>, respectively, were 80%, 77%, and 70%. When used in combination, the effects of <i>D. visicosa</i>, <i>P. hysterophorus</i>, and <i>C. sative</i> produce 100% mortalities, indicating synergism. In single applications for all treatments, plant extracts were the most toxic. However, when used in combination, <i>S. oryzae</i> is completely killed. Phytochemical screening test all the compounds were detected but saponins and coumarins were higher in <i>D. visicosa</i> and <i>P. hysterophorus</i>. As a result, mixing plant extract greatly increases the effectiveness of reducing <i>S. oryzae</i> in storage facilities. Smallscale farmers may benefit from the study's findings since they may offer them a grain storage approach that is both practical and affordable.