Reduced Susceptibility of Organophosphate-resistant Tobacco Aphids (Homoptera: Aphididae) to Aldicarb

Abstract

Field and greenhouse experiments were conducted to determine if organophosphate (OP)-resistant (R) and OP-susceptible (S) tobacco aphids exhibited tolerance or resistance to aldicarb, a carbamate insecticide. In the greenhouse, OP-R and OP-S aphids were placed in leaf cages on greenhouse-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 field-grown, flue-cured tobacco plants treated with 0, 11.2 or 22.4 kg per ha of aldicarb before transplanting. The leaf disks were taken to the laboratory, transferred to Petri dishes, and infested with ten OP-R or ten OP-S aphids. After 36 h, significantly higher mortality was observed in the OP-S aphids as compared with the OP-R aphids. These are the first test results to demonstrate a reduced susceptibility of OP-R tobacco aphids to aldicarb, a carbamate insecticide. The hypothesis that tobacco aphids with a chromosomal translocation are less susceptible to other types of insecticides is supported.