EFFICACY OF THREE PLANT EXTRACTS AGAINST RICE WEEVIL, SITOPHILUS ORYZAE L. (COLEOPTERA: CURCULIONIDAE)

Abstract

The experiment was carried out in the laboratory of the Department of Entomology, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur during June to October 2017 to find out the effectiveness of nishinda, karabi and eucalyptus leaf extracts for their toxicity, repellency and residual effects against rice weevil, Sitophilus oryzae. The doses were 1.7680, 1.4144, 1.0608 mg/cm2 for their toxicity effect and 30, 40, 50 mg/ml for repellency and residual effects against rice weevil. The results of the present study revealed that all the plant extracts had moderately toxic, repellent and residual effect as well as effective for controlling rice weevil in storage. Average mortality percentage of rice weevil at 24, 48 and 72 HAT indicated that nishinda plant extracts possessed the highest mortality (39.72 %) and eucalyptus leaf extract showed the lowest mortality (17.77 %). Mortality percentage was also found directly proportional to the level of concentrations of plant extracts and to the exposure period. Concidering all the concentration and efficacy, the order of toxicity level of leaf extracts were found as nishinda >karabi >eucalyptus. The repellent effect of nisinda, karabi, and eucalyptus extracts showed that the three plant extracts had moderate repellent action on rice weevil. Nishinda leaf extract also showed the highest repellency (36.89 %) while eucalyptus extract provided the lowest repellency (29.78 %). Among the tested leaf extracts, nishinda extract showed the lowest number (15.95%) of F1 progeny production and lowest (21.11 %) weight loss but eucalyptus extract showed the highest number (22.23 %) of F1 progeny production and highest weight loss (30.09%).