Evaluation of larvicidal activity of the leaf extract of a weed plant, Ageratina adenophora, against two important species of mosquitoes, Aedes aegypti and Culex quinquefasciatus

An attempt is made in the present study to analyse the larvicidal effect of the leaf extract of a vastly grown (in the hilly regions of the Nilgiris district) weed plant, Ageratina adenophora on two important mosquito species, Aedes aegypti and Culex quinquefasciatus. The larval mortality of fourth instar larvae of A. aegypti and C.quinquefasciatus after 24 h of treatment were observed separately in control, 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 ppm concentrations of the leaf extract (acetone) of A.  adenophora. Based on the Probit analysis, the 24 h Lc50 value of the leaf extract of A.  adenophora was found to be 356.70 ppm for A. aegypti and 227.20 ppm for C. quinquefasciatus. When compared to neem, the leaf extract of A.  adenophora is more toxic to both  A. aegypti and C. quin-quefasciatus and could be effectively used for the control of mosquito larvae.