Journal of Advances in Biology & Biotechnology

The rice weevil Sitophilus oryzae causes direct damage to stored grains of economic importance, resulting in large economic losses. Essential oils can be employed as a safe alternative to harmful chemical pesticides to manage rice weevils, since the chemical constituents of essential oils present a wide range of biological activities. The aim of this work was to evaluate the insecticidal activity of essential oil from citronella (Cymbopogon nardus) on S. oryzae by contact, fumigant and repellent bioassays. This study was conducted at Department of Agricultural Entomology, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, India during 2024-2025. The essential oil of C. nardus exhibited acute toxicity against S. oryzae adults with an LC₅₀ value of 116.05 ppm (0.9 µg/cm²), 16.40 ppm (0.1 µg/cm²), and 4.24 ppm (0.034 µg/cm²) after 12, 24, and 48 hours in the contact toxicity bioassay. Whereas the essential oil showed a good fumigant effect with an LC₅₀ value of 154.86, 71.97, and 19.18 µLL^-1 air after 12, 24, and 48 hours. The essential oil exhibited strong repellent activity against the test insect at a concentration of 300 ppm after 15 minutes. The obtained results indicate that the citronella essential oil has the potential to be developed as a safe and effective alternative for controlling rice weevils, which will decrease the harmful effects and risk of synthetic insecticides on human beings.