Larvicidal potential and ultra-structural changes induced after treatment of Culex pipiens L. (Diptera: Culicidae) larvae with some botanical extracted oils

Abstract

Searching for new alternatives for the limitation of the vector of diseases, Culex pipiens, the larvicidal actions of three plant oil extracts were assessed. On the base of 24hr. LC50 values, the supreme toxic extract against Culex pipiens larvae was Piper nigrum (black pepper), followed by Eucalyptus regnans and Azadirachta indica (neem) oil (6.99 x 10-3, 2.24 x 10-2, and 0.44 ppm, respectively). The histopathological results assured the toxicological data. The most characteristic disorder signs visualized in the mid gut region of treated larvae were epithelial cells elongation and vacuolization, rupturing of the peritrophic membrane, detachment of basement membrane, disorganization of microvilli, and furthermore, muscle layer degeneration. The most dramatic changes were observed in the midgut of mosquito larvae treated with Piper nigrum; that could serve as a potential larvicidal agent. Further studies should be considered to discover the stability and residual activity of the tested oils under field conditions.