Efficacy of Indigenous Botanicals for Controlling Rice Weevil, Sitophilus oryzae L.

Significant losses and damage have been incurred in rice storage due to rice weevils (S. oryzae). Chemical pesticides have been used to control them, but this has had detrimental impacts on the environment and limited storage facilities. The n-hexane, dichloromethane (DCM) and methanol extracts of leaf and seed/fruit of karanja, Pongamia pinnata (L.); mahogany, Swietenia mahogani Jacq.; neem, Azadirachta indica A. Juss and urmoi, Sapium indicum Willd. at 2.0, 4.0, 6.0, 8.0 and 10.0% (w/v) concentrations were evaluated for their insecticidal effect against rice weevil, Sitophilus oryzae. Among the test plants, the highest mortality percentage was observed in Urmoi (47.00%) and Neem (44.22 %), respectively at 72 HAT. Among the solvents, dichloromethane extract showed more toxicity (mortality 52.67%) than other extracts. The effectiveness of most of the plant extracts were found to increase proportionately with the increase of doses. Mortality percentage increased with the progress of time. Among four plant extracts, the LC50 values (0.72%) at 72 HAT indicated that the urmoi extract also maintained its highest toxicity, followed by neem extract (LC50 values 0.91%). Thus, urmoi plant extracts can be utilized as botanical pesticides to control infestations of rice weevil.