Laboratory evaluation of Alsystin, a chitin synthesis inhibitor, against <i>Culex pipiens pipiens</i> L. (Dip., Culicidae): effects on development and cuticle secretion

Abstract

Alsystin, a benzoylphenylurea derivative, was evaluated on Culex pipiens pipiens L. Treatment was made on newly third‐ and fourth‐instar larvae for 24 h. Mortality occurred at various developmental stages following treatment. However, death as larvae was relatively important compared with the mortality recorded for the other later developmental stages. Treatment resulted in a dose‐dependent reduction in adult emergence. Moreover, treatment caused morphological aberrations depending upon the importance of larval–adult transformation and significantly increased the duration of both third and fourth larval instars. A histological study conducted on fourth instar larval integument, revealed that Alsystin delayed the ecdysis and significantly reduced the thickness of both larval and pupal cuticles secreted compared with controls. Moreover, the apolysis that occurred at day 4 in controls was not affected by treatment.