Abstract
Ethanolic, acetone and petroleum ether extracts of leaves from the Egyptian plant Cupressus sempervirens (Cupressaceae) were tested against 3 rd instar larvae of the mosquito Culex pipiens L. The obtained results indicated that petroleum ether extracts were more efficient than ethanolic and acetone extracts. The toxicity, based on Lc50 values, are arranged in a descending order as follows: ethanolic (Lc50 263.6ppm) > acetone extract (Lc50 104.3ppm) > petroleum ether extracts (Lc50 37.8 ppm). As shown by the present results, a remarkable reduction in both the pupation percent and adult emergence was obtained. Moreover, all plant extracts exerted a delayed toxic effect on the pupae and adults after treatment of larvae. Also, various degrees of morphogenic abnormalities were observed in the immature and adult stages. Thus, these results may provide an opportunity to develop alternatives to costly organic pesticides and environmentally hazardous chemicals with some available cheap plants which are uaually environmentally safe to different living organisms.
Highlights
Mosquitoes are vectors of many vertebrate blood parasites
The present study aimed to evaluate the biological activity of leaf extracts of C. sempervirens (Cupressaceae) against the third instar larvae of the mosquito vector, C. pipiens
The present results can be arranged as follows: Ethanolic extract: Data given in table (1) indicated the biological activity of ethanolic extract of C. sempervirens against the 3rd instar larvae of C. pipiens
Summary
Mosquitoes are vectors of many vertebrate blood parasites. In Egypt, Culex pipiens has a wide distribution and is the main vector of Rift valley fever virus (Darwish and Hoogastrall, 1981), Wuchereria bancrofti (Gad et al, 1996) and Western Nile virus (Pelah et al, 2002). Hassan et al (2003) studied the possibility of C. pipiens for the transmission of Hepatitis C virus (HCV). Insecticide applications highly efficacious against the target species, vector control is facing a threat due to the development of resistance to chemical insecticides resulting in rebounding vectorial capacity (Liu et al, 2006). They are responsible for substantial hazards to a variety of non-target organisms and environment in the form of biomagnification (Gold et al, 2001)
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