Repellent effect of plant extracts for management of rice weevil, Sitophilous oryzae L

The leaf and seed/fruit extracts of karanja, Pongamia pinnata (L.); mahogany, Swietenia mahogani Jacq.; neem, Azadirachta indica and urmoi, Sapium indicum Willd. @ 2.0, 4.0, 6.0, 8.0 and 10.0% (w/v) concentrations were evaluated for their repellent effect against rice weevil, Sitophilus oryzae. Among the four extracts tested, urmoi showed the highest mean repellent effect (53.04%). The rate of repellency differed with the extract type. The repellency effects of fruit extracts were higher than that of leaf extracts i.e. mean repellency of urmoi fruit extract was 56.17% and leaf extract was 49.86%. Among three solvents neem n-hexane extract showed the highest repellency effect (59.86%). The repellency rates of insects were influenced by concentrations of the extracts. Repellency rate increased proportionally with the increase of doses. The results indicated the possibility of further use of 10% urmoi extracts as an alternative control measure for rice weevil instead of using the costly and hazardous synthetic insecticides.

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