Journal of Scientific Research and Reports

The rice weevil, Sitophilus oryzae, is a primary insect pest that infests stored grains, causing damage as internal feeders and resulting in both quantitative and qualitative 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 study aimed to evaluate the insecticidal activity of essential oil derived from patchouli Pogostemon cablin on rice weevil S. oryzae by contact, fumigant, and repellent bioassays. Bioassays were performed on same-aged adult rice weevils under laboratory conditions. The essential oil of P. cablin leaves exhibited acute toxicity against S. oryzae adults with an LC₅₀ value of 94.55 ppm (0.75 µg/cm²) in contact toxicity bioassay after 24 hours, whereas the LC₅₀ value in the fumigant toxicity assay was 15.81 µLL^-1 air. The essential oil of P. cablin exhibited strong repellent activity against test insect at a concentration of 400 ppm (4.4 µg/cm²). The obtained results indicate that Patchouli essential oil could be developed as a safe and effective alternative for controlling rice weevils.