Monitoring Permethrin Resistance in Soybean Looper (Lepidoptera: Noctuidae) Adults

A glass vial monitoring technique was developed to test for permethrin resistance in soybean looper, Pseudoplusia includens (Walker), adults. Male and female moths from laboratory permethrin-resistant and-susceptible soybean looper strains were exposed to permethrin residues in glass vials to estimate concentration-mortality lines. Probit analysis of results indicated that male and female LC₅₀ values were not significantly different within each strain. The resistant male and female moths were 13.4 and 12.2-fold more tolerant of permethrin, respectively, when compared to the same sex from the susceptible strain. A discriminating concentration of 2.5 μg permethrin per vial was identified for detection of permethrin resistance in soybean looper adults. Male soybean looper moths were captured during the 1991 growing season at three locations in Louisiana using wire cone traps baited with pheromone. Results of discriminating concentration tests on these moths indicated that all strains were resistant to permethrin, but frequencies of resistance varied within locations over time.