Estimating resistance to methomyl in the tomato pinworm (Lepidoptera: Gelechiidae) using a pheromone trap bioassay

Abstract

The tomato pinworm, Keiferia lycopersicella (Walsingham), is an important pest of tomatoes in the southern and southwestern United States and Mexico. A field-based method for assessing resistance of adults to the carbamate insecticide, methomyl, was developed by incorporating varying doses of technical insecticide into the adhesive of pheromone traps. The mortalities of male and female adults were similar whether exposed to methomyl, either by topical or pheromone trap bioassays. Larvae were less susceptible than adults to methomyl by topical application. Therefore, adult male susceptibility provides a good estimate of adult female susceptibility but may overestimate larval susceptibility. Nevertheless, using the pheromone trap bioassay and making comparisons of field populations with a laboratory strain suggested that all field populations evaluated were less susceptible to methomyl than the laboratory strain. Populations in Mexico were more susceptible than populations in California, where methomyl is used more often. Populations in Florida were either intermediate in susceptibility or were similar to those in California.