Evaluation of pyriproxyfen, a juvenile hormone analog, on Drosophila melanogaster (Diptera: Drosophilidae): Insecticidal activity, ecdysteroid contents and cuticle formation

The efficacy of pyriproxyfen, a juvenile hormone analog (JHA), was evaluated using third instar larvae of Drosophila melanogaster Meigen, 1830 (Diptera: Drosophilidae). Various doses of the compound, ranging from 0.01 to 2 ng/larva, were applied topically to larvae (12 h before pupariation). Treatment did not prevent pupariation but inhibited adult emergence at all the doses tested. In a second series of experiments the ecdysteroid content of pupae was determined following application of pyriproxyfen at two doses, 0.108 and 0.29 ng/larva, corresponding to ID25 and ID50, the doses required for 25 and 50% inhibition of adult emergence, respectively. Pyriproxyfen treatment increased the duration of pupal development. In addition, enzyme immunoassay measurements of ecdysteroids in whole body extracts of pupae indicated that pyriproxyfen decreased the ecdysteroid content in a dose-dependent manner. Finally, the effects on the cuticle of pyriproxyfen (ID50) were studied histologically, which revealed that this compound increased the thickness of the new adult cuticle and suppressed the formation of bristles. Biochemical analyzes revealed that an increase in chitin content of the cuticle is only recorded at the highest dose. Thus, a topical application of pyriproxyfen to third instar larvae interfered with the molting hormone and disrupted the normal development of this insect.