Biological studies on the effect of some plant extracts on the different stages of Culex pipiens.

Abstract

The larvicidal efficacy of four commercially variable plant oils, with different concentrations, was tested against the third instar larvae and pupae of Culex pipiens. The larval and pupal mortality was determined every 12 hrs. Bioassays showed that the larval and pupal mortality were varied according to the plant oils concentration and period of exposure. The LC50 and LC90 values of the larval mortality were 0.29 & 1.02 μl/ ml, 4.70 & 43.90 μl/ ml, 79.80 & 154.90 μl/ ml and 119.00 & 237.9 μl/ ml, while the values of the pupal mortality were 0.31 & 0.94 μl/ ml, 18.52 & 114.56μl/ ml, 70.10 &150.80 μl/ ml and 138.70 & 199.75μl/ ml for Lupinus sp., Citrullus colocynthis, Eruca sativa, and Lactuca sativa, respectively. It could be concluded that Lupinus oil was the most effective plant as it killed the larvae and pupae with lowest values of LC50 and LC90. On the other hand, Lactuca sativa had very low lethal effect on the mortality of Culex pipiens larvae and pupae.