Effects of diflubenzuron on growth and glutathione in mosquito fish (Gambusia affinis)

Although some biological control agents and related biorational approaches are available for mosquito control, insecticides remain the principal control method. In addition, the secondary affects of conventional insecticides in environment has led to the discovery of more target-specific chemical such as insect growth regulators. Dimilin (25% WP), the common name of diflubenzuron, prevent molting by interfering with chitin synthesis in several insect orders. This study evaluate toxicity of this insecticide on a larvivorous non-target species, Gambusia affinis (Cyprinodontiformes: Poeciliidae). Dimilin, applied for 24 h at a concentration of 78 ng/l, corresponding to the LD90 against the fourth instar larvae of Culex pipiens (Diptera: Culicidae) was first tested on growth and development of 7-day old juvenile mosquitofish during 45 days following treatment. Results showed that dimilin caused significant (p < 0.01) reduction in both length and weight of juveniles from days 30 following treatment, compared to controls. In a second series of experiments, designated for measurements of glutathione (GSH), adults of G. affinis were exposed continuously to a concentration of 78 ng/l for 30 days. Treatment resulted in a significant reduction in the amount of glutathione in mosquitofish bodies starting day 15 during treatment, compared to controls.