Abstract— The study on “Effectiveness of some chemical and biological pesticides against S. zeamais” was carried out at National Entomology Research Center, NARC, Khumaltar, and Lalitpur. This study was carried out to find the residual effect of the pesticides on S. zeamais mortality. Each pesticide was applied in 3 concentrations.: Emmamectin Benzoate @ 0.3ml/ltr, @0.1ml/ltr and @0.6ml/ltr, Neem @ 5ml/ltr, @2.5ml/ltr and @10ml/ltr, Chloropyrifos (50%) + Cypermethrin (5%) @ 1.5ml/ltr, @0.75ml/ltr and @3ml/ltr; and Malathion @ 2ml/ltr, @1ml/ltr and 4ml/ltr. The residue of pesticide on weevil mortality was seen the highest on Chloropyrifos (50%) + Cypermethrin (5%) till the 87th Day and was least on Neem even on the 1st day of observation. The mortality % was highest (100%) on Chloropyrifos (50%) + Cypermethrin (5%) and Malathion and was lowest (0%) on Neem. The maximum weight loss was observed on Neem @2.5ml/ltr which was 9.4% whereas, minimum wt. loss was observed on Chloropyrifos (50%) + Cypermethrin (5%) @ 3ml/ltr which was 0.25% of the total grain weight. The maximum percent of damaged grain was observed on Neem which was 100% while the minimum percent of damaged grain was observed on Chloropyrifos (50%) + Cypermethrin (5%) @1.5ml/ltr which was 11.21% of the total grain. No weevil progeny emerged from Chloropyrifos (50%) + Cypermethrin (5%) @1.5ml/ltr treated seeds whereas the maximum number of progeny emerged from Neem @2.5ml/ltr treated seeds which were 149.67. Out of the 4 pesticides tested on the adult of Sitophilus Zeamais, Chloropyrifos (50%) + Cypermethrin (5%) was found to be most effective while Neem was the least effective. Since the residual of the chemical pesticides are long lasting, it is not recommend to use pesticides for consumption but can be used to store for seed purpose.