REDUCED SUSCEPTIBILITY OF ORGANOPHOSPHATE-RESISTANT TOBACCO APHIDS (HOMOPTERA, APHIDIDAE) TO ALDICARB

Field and greenhouse experiments were conducted to determine if organo phosphate (OP)-resistant (R) and OP-susceptible (S) tobacco aphids exh ibited tolerance or resistance to aldicarb, a carbamate insecticide. I n the greenhouse, OP-R and OP-S aphids were placed in leaf cages on gr eenhouse-grown, flue-cured tobacco plants treated with various doses ( 0.0 to 1.0 g per plant) of aldicarb in the potting soil. Mortality was recorded after 24 h, and a dose-mortality relationship was examined. OP-S aphids were more susceptible as compared with OP-R aphids, to all doses of aldicarb. Leaf disks were collected on several dates from he ld-grown, flue-cured tobacco plants treated with 0, 11.2 or 22.4 kg pe r ha of aldicarb before transplanting. The leaf disks were taken to th e laboratory, transferred to Petri dishes, and infested with ten OP-R or ten OP-S aphids. After 36 h, significantly higher mortality was obs erved in the OP-S aphids as compared with the OP-R aphids. These are t he first test results to demonstrate a reduced susceptibility of OP-R tobacco aphids to aldicarb, a carbamate insecticide. The hypothesis th at tobacco aphids with a chromosomal translocation are less susceptibl e to other types of insecticides is supported.