Tiwari, S.N.Trivedi, Priyanka2019-11-012019-11-012019-07http://krishikosh.egranth.ac.in/handle/1/5810133709An investigation was undertaken to evaluate the level of resistance in different populations of Sitophilus oryzae, Tribolium castaneum, Rhyzopertha dominica and Callosobruchus chinensis against Malathion, Dichlorvos and Deltamethrin. All the experiments were conducted in Post-Harvest Laboratory of Department of Entomology, G.B Pant University of Agriculture and Technology, Pantnagar in the year 2018-19. The population (strain) of insects were collected from different godowns situated located at Pantnagar and Dehradun (Crop Research Centre, Pantnagar; Regional Food Corporation, Dehradun; Breeder Seed Production Center, Pantnagar; Uttarakhand Seeds Tarai Development Corporation, Nagla; Uttarakhand Seeds &Tarai Development Corporation, Haldi). The collected strains of insects were exposed to different insecticides at different concentrations to determine the median lethal concentration (LC50). Based on the LC50 values, the resistance ratios of the insect strains against all the insecticides mentioned above were determined with respect to susceptible Laboratory population. The results revealed that the resistance ratios (RR) for different insect varied greatly for different insecticides when applied by dry film method viz., malathion (2.673 to 3.442), deltamethrin (1.819 to 3.305) & dichlorvos (1.885 to 2.199) for S. oryzae; malathion (4.225 to 7.771), deltamethrin (5.74 to 12.973) & dichlorvos (1.012 to1.35) for T. castaneum; malathion (1.236 to1.409), deltamethrin (1.430 to 3.456) & dichlorvos (1.225 to 2.173) for R. dominica and malathion (1.189 to 1.561), deltamethrin (1.183 to 2.211) and dicholrvos (1.078 to 1.435) in case of C. chinensis. When the insect population were exposed to seed treated with insecticides, the RR values were comparatively less viz., malathion (1.464 to 2.069), deltamethrin (1.272 to 1.895) and dichlorvos (1.973 to 2.929) for S. oryzae; malathion (1.486 to 2.141), deltamethrin (1.175 to 1.701) and dichlorvos (1.331 to 2.154) for T. castaneum; malathion (1.134 to 1.783), deltamethrin (1.291 to 1.817) and dichlorvos (1.365 to 2.341) in case of R. domininca and malathion (1.593 to 2.031), deltamethrin (1.305 to 1.673) and dichlorvos (1.494 to 2.661) for C. chinensis. It is recommended that insecticides should be applied in the godowns after studying the level of resistance in insects.ennullThesis