Effect of Solenostemma argel on oviposition, egg hatchability and viability of Culex pipiens L. larvae.

Methanolic extracts of aerial parts of the medicinal plant Argel (Solenostemma argel (Del.) Hayne), incorporated into rearing media of Culex pipiens L. showed effect on oviposition, egg hatchability and larval viability. Acute toxicity of S. argel extract was found to possess LC(50) of 0.037, 0.031, 0.009 and 0.007 ppm and the LC(95) was found 0.394, 0.293, 0.065 and 0.030 ppm, after 1, 2, 4 and 7 days against the larva of C. pipiens under laboratory conditions. The ovicidal effect of S. argel was relatively less pronounced, however, the 0.1% concentration reduced egg hatch by 33.7%. The mortality of the newly hatched larvae, reared from eggs in this media, reached 100% at concentrations as low as 0.025%, 2 days post hatching. Complete suppression of oviposition within the first 2 days was observed, however its action was gradually lost thereafter. Bioactive effects were mainly attributed to the presence of a variety of bioactive organic substances mainly terpenes, pergenine glucosides, alkaloids and sterols. Copyright 2004 John Wiley & Sons, Ltd.