Effect of Certain Plant Extracts on Mortality, Development and Haemogram of Culex pipiens L. Mosquitoes Larvae

The effect of methanolic plant extracts from Solanum nigrum, Acokanthera spectabilis and Heliotropium aegyptiacum were investigated on the larval mortality and development of Culex pipiens L. Also, the effects of the LC50 of the three plant extracts on the larval haemogram were studied. Plant extracts exhibited variable bioactivities. The greatest activity was observed for  S. nigrum which showed LC50 values of 130.8 ppm after 48 hr of exposure, respectively. Percentage of larval mortality was 67.5% in the treatment with extracts of S. nigrum and 66.5% in case of A. spectabilis at 500ppm. Egg hatchability was not significantly reduced in all S. nigrum concentrations. All concentrations of the plant extracts from S. nigrum, A. spectabilis and H. aegyptiacum caused significant hindrance to the subsequent larval development and reduced both pupation and adult emergence. Drastic retardation of development was shown by S. nigrum extracts, where only 18.1% and 8.5% of the larval managed to reach pupal and adult stages, respectively, when reared in 100 ppm of the extract. However, A. spectabilis and H. aegyptiacum were more effective at higher concentrations. Moreover, the effects of the LC50 of tested plant extracts caused a reduction in the number of haemocytes and also markedly decreased the haemocytes surface areas. Application of such plant extracts to mosquito breeding site may have great practical importance in relation to non-synthetic chemical control of this serious disease vectors.