Laboratory Evaluation of a Biorational Insecticide, Kinoprene, against Culex pipiens Larvae: Effects on Growth and Development

Abstract

Aims: In the present study, the objective was to estimate the toxicity of an insect growth regulator with juvenile hormone-like activity, kinoprene, on Culex pipiens, the most abundant and investigated mosquito species. Effects of this compound on growth and development were also evaluated. Methodology: A commercial formulation (Enstar 65% EC) was tested at different concentrations ranging between 162.5 and 650µg/L on newly molted fourth-instar larvae that were exposed for 24 h under standard laboratory conditions according to World Health Organization recommendations. Results: Kinoprene exhibited insecticidal activity by direct action on the treated fourth-instar larvae but also by differed action on the other following stages of development. Mortality occurred after earlier inhibition of their development or by their inability to complete their ecdysis. The LC50 values were 1287.4µg/L for the direct action on fourth instar larvae, and 246.8µg/L for the differed action until adult emergence. Moreover, the compound disturbed growth and development since several morphological types and an increase in the duration of larval and pupal stages were recorded. In a second series of experiments, the effects of kinoprene were examined on morphometric measurements of larvae, pupae and adults, respectively. The compound affected body volume. Conclusion: The overall results are discussed in relation to previous reports and suggested that kinoprene have potential as a biorational insecticide for controlling of mosquitoes in an environmentally-friendly manner to the aquatic ecosystem.