Prolonged Effect on Pupae and Adults of the Diamondback Moth, Plutella xylostella(L.)(Lepidoptera:Yponomeutidae)after Larval Treatment with Chlorfluazuron

The prolonged effect of larval treatment with chlorfluazuron on pupation and adult emergence in the diamondback moth (DBM), Plutella xylostella (L.) was investigated. Two chlorfluazuron resistant and two susceptible strains of DBM were tested. The leaf-dipping technique was adopted and the insecticide was applied to third instar larvae. Larval mortalities were counted one week after application then pupated larvae were observed until adult emergence. Results indicated that chlorfluazuron applied to larvae exhibited a prolonged effect on pupae observed as pupal death or failure of emergence and on adults observed as deformed or dead adults. The failure of emergence was more obvious in the chlorfluazuron resistant strains, which were exposed to higher doses, than in the susceptible strains.