Studies on sensitivity of serpentine leaf miner to insecticides revealed that serpentine leaf miner maggots collected from different crop ecosystems at Regional Research station, Raichur where least pesticides are applied were highly sensitive to all insecticides when compared to maggots collected from farmers cotton field in Kasbe camp. Among the different insecticides tested viz., oxydemeton methyl, acephate, dimethoate, monocrotophos, endosulfan, cypermethrin and imidachloprid, the maggots (from all four locations) were most sensitive to imidacloprid. This was followed by oxydemeton methyl and acephate which resulted in considerable higher mortality. Endosulfan was totally ineffective and caused low mortality. Bioassay study indicated that highest resistance ratio of 25.72 was recorded in Kasbe camp culture to cypermethrin. The level of resistance was lowest (8.11 folds) to imidacloprid followed by endosulfan (9.25 folds) and acephate (12.32 folds).