PROTECTIVE EFFECTS OF SELECTED ESSENTIAL OILS AGAINST PADDY RICE INFESTATIONBY THE RICE WEEVIL, Sitophilus oryzae (COLEOPTERA: CURCULIONIDAE)

Rice (Oryza sativa L.) is a staple food in Nigeria, but storage losses caused by the rice weevil, Sitophilus oryzae (L.), remain a major challenge. This study evaluated the susceptibility of different paddy rice varieties to S. oryzae and the repellency of selected plant essential oils under laboratory conditions. Eighteen paddy rice varieties—15 improved FARO and three local varieties—were obtained from the National Cereals Research Institute, Badeggi, and local farmers in Lafia. Essential oils from clove (Syzygium aromaticum), West African black pepper (Piper guineense), and ginger (Zingiber officinale) were extracted by hydro-distillation. Sitophilus oryzae adults were cultured for three generations before use. Rice varieties differed significantly in infestation susceptibility. FARO 37 was extremely susceptible, whereas FARO 30, 61, and 22 ranged from highly to slightly susceptible. Seven varieties were moderately to slightly susceptible, while seven others, including all local varieties, were non-susceptible with no adult emergence. Infestation caused significant differences in seed damage and weight loss; FARO 37 recorded the greatest losses, whereas local varieties and FAROs 32, 44, 50, and 57 recorded none. All essential oils significantly repelled S. oryzae, with repellency increasing with dosage. Ginger oil at 1.00 mg/20 g of paddy rice produced the highest repellency (92.22 %, Class V), followed by West African black pepper (85.56 %, Class V) and clove (77.78 %, Class IV), all significantly superior to the control (P<0.05). These findings indicate that resistant rice varieties and plant derived essential oils offer sustainable, eco-friendly options for protecting stored rice against S. oryzae.