title: Ovicidal activity of three insect growth regulators against Aedes and Culex mosquitoes.
abstract: Interspecific variations in the susceptibility of freshly and embryonated eggs of Aedes albopictus, Ae. aegypti, Ae. atropalpus and Culex pipiens were tested against three classes of insect growth regulators (IGRs) including ecdysone agonist (azadirachtin), chitin synthesis inhibitor (diflubenzuron) and juvenile hormone analog (pyriproxyfen) at 0.001, 0.01, 0.1 and 1.0ppm concentrations. Egg hatching inhibition was dose dependent, the highest being at 1.0ppm concentration for freshly laid eggs of Ae. albopictus (pyriproxyfen: 80.6%, azadirachtin: 42.9% and diflubenzuron: 35.8%). Aedes aegypti showed lower egg hatching inhibition when exposed to pyriproxyfen (47.3%), azadirachtin (15.7%) and diflubenzuron (25.5%). Freshly laid eggs of Cx. pipiens were most susceptible to diflubenzuron. Aedes atropalpus eggs were tolerant to all three classes of IGRs. Embryonated eggs of Ae. albopictus, Ae. aegypti, Ae. atropalpus and Cx. pipiens were resistant to pyriproxyfen, azadirachtin and diflubenzuron than freshly laid eggs. The median desiccation time (DT50) of Ae. atropalpus eggs was maximum (5.1h) as compared to Ae. aegypti (4.9h), Ae. albopictus (3.9h) or Cx. pipiens (1.7h) eggs. Insignificant relationship between the rates of desiccation and egg hatching inhibition suggests other factors than physical providing eggs the ability to tolerate exposures to various IGRs. Egg hatching inhibition was due to the alteration in embryonic development caused by IGRs. Changes in the egg shell morphology and abnormal egg hatching from the side of the egg wall instead of operculum, was observed at higher concentrations of diflubenzuron. Morphological and physiological variations in eggs may be the key factor to influence the ovicidal efficacy of IGRs. The present data provide a base line for the improvement of the ovicidal efficacy of the insecticide and its formulation.
authors.affiliation: Center for Vector Biology, Rutgers University, 180 Jones Avenue, New Brunswick, NJ 08901-8536, USA. Electronic address: dssuman@rci.rutgers.edu.
authors.forename: Devi S
authors.initials: DS
authors.lastname: Suman
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Anwar L
authors.initials: AL
authors.lastname: Bilgrami
authors.forename: Randy
authors.initials: R
authors.lastname: Gaugler
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D003465:Culex / Q000187:drug effects* / Q000502:physiology; D004132:Diflubenzuron / Q000494:pharmacology; D007605:Juvenile Hormones / Q000494:pharmacology*; D036701:Limonins / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D015053:Zygote / Q000187:drug effects* / Q000502:physiology
chemical_list: D007605:Juvenile Hormones; D036701:Limonins; D011725:Pyridines; C055613:pyriproxyfen; D004132:Diflubenzuron; C010329:azadirachtin
keywords: Egg desiccation; Egg hatching; Insect growth regulators; Interspecific variations; Mosquitoes; Ovicidal activity