Abstract
To monitor the insecticide resistance of male adults captured in a sex-pheromone trap, the susceptibility to methomyl and permethrin was determined by topical application and residual film methods using susceptible (S) and resistant (R) strains of the common cutworm, Spodoptera litura FABRICIUS. Comparison was made between male adults and 3rd instar larvae. The resistance ratio of the R strain to methomyl with topical application was more than 1, 000 times for 3rd instar larvae, but only 8-9 times for male adults. The resistance ratio of the R strain to permethrin was 41 times for larvae, and 14 times for male adults. The resistance ratio of the R strain to methomyl and permethrin with the residual film method was very similar to that with topical application. Susceptibility to methomyl in male adults determined by topical application increased with age, whereas that determined by the residual film method did not change within 3-day ages. On the basis of these results, the residual film method is more suitable for monitoring insecticide resistance of male adults captured in a sex-pheromone trap.
