Eco-Friendly Toxicity and Repellent Effects of Selected Medicinal Plant Extracts against the Rice Weevil, Sitophilus oryzae (L.).

Background and Objective: Rice weevils, Sitophilus oryzae (L.), are major pests of stored grains, causing substantial post-harvest losses. This study evaluated the efficacy of selected medicinal plant extracts for the control and repellency of rice weevils as eco-friendly alternatives to synthetic pesticides. Materials and Methods: Twenty-one medicinal plants were initially screened and four plants were selected for extraction using 70% ethanol and distilled water. Contact toxicity was assessed at concentrations of 5, 10 and 15% (w/v) using plastic cup bioassays. Repellency tests were conducted to determine the effectiveness of extracts over time. Data were analyzed using one-way ANOVA followed by Tukey's HSD test (p<0.05) in SPSS. Results: Among ethanolic extracts, tobacco leaves at 15% showed the highest insect mortality (93.3±3.3%), significantly higher than clover flowers (29.9±15.3%). All concentrations of aqueous tobacco extract resulted in 100% mortality, while lemon and long pepper extracts demonstrated moderate toxicity (>50%). In repellency assays, ethanolic clover flowers (10%) and aqueous clover flowers (15%) exhibited the highest average repellent efficiencies of 95.6±2.9 and 92.2±4.8%, respectively, with maximum repellency observed within 30 min. Conclusion: The findings indicate that selected medicinal plant extracts, particularly tobacco and clover, are effective and eco-friendly agents for the control and repellency of rice weevils. These plant-based extracts show promise as sustainable alternatives to synthetic pesticides for stored grain protection.