Mosquito larvicidal activity of Vitex negundo

Vector borne diseases are of major concern in today's busy world. The increasing problem with chloroquine resistance to plasmodium and resistance of mosquito to insecticides still worsen the case. The scenario therefore demands the development of newer methods and the usages of natural products derived from plants, as they are biodegradable, ecologically safe and have significant toxicity on target species and safe for human being. In the present study an attempt was made to screen Vitex negundo Linn for its larvicidal activity against three different mosquito species namely Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. Standard procedure of larval bioassay recommended, by the WHO was followed. Early IVth instar larvae of each species were selected and exposed to different concentration of Vitex nugundo. When the control mortality lies between 5-20% the corrected mortality percentage was obtained by probit regression analysis. LC₅₀ values were estimated by fitting a probit regression model to the observed relationship between percentage mortality of larvae and logarithmic concentration of the substance. The aqueous extract of Vitex nugundo was found to be effective against Culex quinquefasciatus with the IC₅₀ values of 167.88 PPM, and Anopheles stephensi with the IC₅₀ values of 167.88 PPM and followed by Aedes aegypti with the IC₅₀ values of 231.17 PPM which when compared to that of the methanolic extract the IC₅₀ values were 167.88 PPM for Culex quinquefasciatus, 199.52 PPM for Anopheles stephensi and 211.34 PPM for Aedes aegypti respectively. Thus the plant Vitex negundo Linn has significant larvicidal activity. Overall it was observed that the plant is very effective against Culex quinquefasciatus, Anopheles stephensi and moderately effective against Aedes aegypti.