author(s)
Debjyoti Chakraborty, T Madhumathi and SVS Gopalaswamy

abstract
A laboratory experiment was implemented in the Department of Entomology Agricultural College, Bapatla to know the resistance levels of malathion and deltamethrin against Rusty grain beetle, Cryptolestes ferrugenius (Stephens) and management with novel insecticide molecule Spinosad. The degree of resistance developed by resistant population of C. ferrugenius shows 34.66 and 21.35 folds resistant at LC₅₀ level; 4.14 and 9.89 folds resistant at LC_99.9 level to malathion and deltamethrin, respectively in comparison with laboratory susceptible strain at 72 HAT. Insecticide tested for the management of malathion and deltamethrin resistant population of C. ferrugenius, Spinosad was found to be the finest at LC_99.9 level with the relative toxicity (3.43 and 1.48 times) than malathion and deltamethrin respectively.