Susceptibility of the diamondback moth, Plutella xylostella L., to insecticides in Kagoshima Prefecture

Abstract

Susceptibility to a mixture of fenvalerate and malathion was tested by using the leaf dipping method for the diamondback moth, Plutella xylostella, collected from 17 different localities in Kagoshima Prefecture. The field-population in Mizobe has been noted to exhibit a high resistance level since 1984. This tendency was reconfirmed in 1986 and 1987. The resistance level had also increased in some of the populations examined. In the Mizobe population, the resistance level fluctuated seasonally, being relatively lower in spring and higher in summer and autumn. In addition the susceptibility to several other insecticides, except cartap, also decreased in the Mizobe population. Field experiments showed that mixtures of Bacillus thuringiensis and fenthoate or prothiofos were effective in controlling the Mizobe population. Soil treatment by benfuracarb at the time of transplant was highly effective against the Ibusuki population.