TOXICITY, REPELLENCY AND RESIDUAL EFFECTS OF FIVE SPICES AGAINST RICE WEEVIL, Sitophilus oryzae L. (COLEOPTERA: CURCULIONIDAE)

Abstract

Rice weevil, Sitophilus oryzae L. is one of the most destructive and notorious insect pests of raw cereal in store. The experiment was conducted in the laboratory of the Department of Entomology, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur to evaluate the efficacy of five spices against rice weevil during March to August 2019. Ethanol was used as solvent to prepare extracts and four different doses (2.5,2.0,1.5 and 1.0 mg/ml)along with control were applied for their toxicity, repellency, and residual effects. All treatments were replicated thrice. Results showed that all the extracts had toxic, repellent and residual effects on rice weevil. Mortality at 24,48 and 72 hours after treatments indicated chili extract possessed the highest mortality (29.33%) whereas the lowest (10%) was in turmeric extracts. Mortality percentage was directly proportional to the level of concentrations of extracts and to the exposure time as well. Considering all the concentration and extracts, the order of toxicity was found as chili> black pepper> ginger> turmeric> cinnamon. The chili, black pepper, cinnamon, turmeric and ginger spices extracts had moderate repellent action against rice weevil. The chili extract showed the highest repellency (85.83%) while the turmeric provided the lowest (61.64%). The highest inhibition rate of egg (60.30%) and adult (72.72%), and seed infestation (64.41%) and the lowest rate of egg (58.87%), adult (67.15%), and seed infestation (61.26%) were found in chili and cinnamon, respectively. However, the toxic, repellent and residual effect of chili extract was more effective against rice weevil among the all spices extracts applied.