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

Abstract

The study was conducted to evaluate the efficacy of three indigenous leaf extracts viz. Ata (Annona reticulata), marigold (Tagetes erecta) and karobi (Nerium oleander) extracts for their toxic, repellent and residual effect against adult rice weevil (Sitophilus oryzae) under laboratory condition in the Department of Entomology, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur during June to October 2017. These botanicals were applied at four doses (10 mg/ml, 7.5mg/ml,5mg/ml/ and 2.5mg/ml) along with control and replicated three times. The results of the present study revealed that all the leaf extracts had toxic effect on rice weevil. The mortality was maximum in ata (45.56%) followed by marigold (40.89%) and karobi (21.11%). Mortality percentage was also found directly proportional to the level of concentrations of leaf extracts and to the exposure period. The order of toxicity level of leaf extracts were found as ata >marigold >karobi. All the leaf extracts had moderate repellent action on rice weevil where ata leaf extract showed the highest mean repellency (55.00 %) followed by marigold (49.33 %) and karobi ( 44.67%). On the basis of repellency class, it was found that all the plants were in the same repellency class i.e. class III. Among the tested leaf extracts, ata showed the lowest number (14.92%) of F1 progeny production with lowest weight loss (16.18 %) whereas the highest number (45.56 %) of F1 progeny production with highest weight loss (45.33%) in the control treatment. The findings of the current study indicated that ata leaf extracts was more effective against rice weevil compared to the other two extracts.