The effect of surface treatment of grain bags with the botanical insecticide Neemazal-T (a liquid formulation containing 5% Azadirach‌tin), the petroleum ether extracts of dill seeds and african chilli fruits in comparison to the organophosphorus insecticide actellic 5% EC (Pirimiphos-methyl) on insect population and weight loss of stored wheat and maize grains due to infestation with rice weevil Sitophilus ory‌zae (L.) was studied. Results showed that weight loss of both wheat and maize grains was positively correlated to insect population and storage period. Insect population and weight loss of both wheat and maize grains were signifi‌cantly reduced in the treated grain bags during storage period extended to 12 months in comparison to untreated one. Weight loss and population of S.oryzae were generally less on maize than wheat grains. Actellic treatment resulted in comperatively lower weight losses in both wheat and maize grains than the plant ex‌tracts, while Neemazal was the least effective product.