Larvicidal activity of medicinal plant extracts against Anopheles subpictus & Culex tritaeniorhynchus

BACKGROUND & OBJECTIVES: Mosquitoes transmit serious human diseases, causing millions of deaths every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. Plants may be alternative sources of mosquito control agents. The present study assessed the role of larvicidal activities of hexane, chloroform, ethyl acetate, acetone, and methanol dried leaf and bark extracts of Annona squamosa L., Chrysanthemum indicum L., and Tridax procumbens L. against the fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae). METHODS: Larvicidal activities of three medicinal plant extracts were studied in the range of 4.69 to 1000 mg/l in the laboratory bioassays against early 4(th) instar larvae of An. subpictus and Cx. tritaeniorhynchus. The mortality data were subjected to probit analysis to determine the lethal concentrations (LC(50) and LC(90)) to kill 50 and 90 per cent of the treated larvae of the respective species. RESULTS: All plant extracts showed moderate effects after 24 h of exposure; however, the highest toxic effect of bark methanol extract of A. squamosa, leaf ethyl acetate extract of C. indicum and leaf acetone extract of T. procumbens against the larvae of An. subpictus (LC(50) = 93.80, 39.98 and 51.57 mg/l) and bark methanol extract of A. squamosa, leaf methanol extract of C. indicum and leaf ethyl acetate extract of T. procumbens against the larvae of Cx. tritaeniorhynchus (LC(50) =104.94, 42.29 and 69.16 mg/l) respectively. INTERPRETATION & CONCLUSIONS: Our data suggest that the bark ethyl acetate and methanol extract of A. squamosa, leaf ethyl acetate and methanol extract of C. indicum, acetone and ethyl acetate extract of T. procumbens have the potential to be used as an ecofriendly approach for the control of the An. subpictus, and Cx. tritaeniorhynchus.