Efficacy of plant extracts against rice weevil Sitophilus oryzae (L.) in stored maize

The acetone extracts of Adathoda vasica, Lantana camera, Vitex negundo and Catharanthus roseus at 1% and 2% w/v were evaluated for their contact toxicity and repellent activity against rice weevil. Adults were exposed to 1 and 2% plant extracts treated maize and mortality assessed after 14 days. The plant extracts of A. vasica, L.camera, V. negundo and C. roseus at two doses showed significantly higher mortality and less seed damage. Mortality increased in dose dependent manner and from 63.30 to 83.33% with A. vasica, 76.60 to 80% with L. camera and 60 to 73.30% with V. negundo while it was 53.33 to 56.60% with C. roseus for 1% and 2%. The plant extracts of A. vasica, L. camera and V.negundo at 2% (w/v) showed strong repellency from 71.66 to 77.11% while the acetone extract of C. roseus showed the moderate mean repellency of 58.88%. Moreover the germination of grains treated with plant extracts was not significantly affected. These results revealed that the plant extracts have toxicidal and repellent properties, and seed protective effect to a promising level and can reduce the dependency on chemical pesticides against rice weevil in stored maize.