Imidacloprid toxicity to insecticide resistant and susceptible strains of the greenbug, Schizaphis graminum (Rondani) (Homoptera : Aphididae)

Because the greenbug, Schizaphis graminum (Rondani), has developed resistan ce to a number of carbamate and organophosphorous compounds that inhibit ch olinesterase, we were interested in its response to insecticides with diffe rent biochemical targets. A susceptible (S) greenbug strain showing no elev ated esterase activity and three (R) resistant strains with different patte rns of elevated esterase activity were compared for their response to imida cloprid using a surface residue vial bioassay. Two S clones, two clones des ignated pattern 1 (R1), two clones designated pattern 2 (R2), and one clone designated pattern 3 (R3) showed no significant differences in responses t o imidacloprid. Imidacloprid's mode of action provides another means to con trol greenbugs that are tolerant to conventional organophosphorous insectic ides and have the ability to adapt to previously resistant plant cultivars.