Effect of 1-(4-phenoxyphenoxypropyl)imidazole (KS-175) on larval growth inthe silkworm Bombyx mori

1-(4-Phenoxyphenoxypropyl)imidazole (KS-175), which has two types of charac teristic moieties of insect growth regulators (IGRs), the phenoxyphenoxyalk yl group of juvenile hormone analogs (JHAs) and imidazole of 1,5-disubstitu ted imidazole such as KK-42, was tested for its biological activity on the silkworm, Bombyx mori. Penultimate (4th) instar larvae topically treated wi th KS-175 did not molt for more than 20 days. This activity was different f rom that reported for any IGRs. After the treatment, ecdysteroid levels in the hemolymph did not increase and the cells of the prothoracic gland had s hrunk. When the treated penultimate larvae were fed an artificial diet supp lemented with 20 ppm of 20-hydroxyecdysone, the larvae molted to the ultima te (5th) instar with a timing similar to that of control larvae fed a diet with or without 20-hydroxyecdysone. These results suggest that topical appl ication of KS-175 irreversibly damages ecdysone biosynthesis in the prothor acic glands. (C) 1999 Elsevier Science Ltd. All rights reserved.