Insecticidal and larvicidal activities of medicinal plant extracts against mosquitoes.

In recent years, use of environment friendly and biodegradable natural insecticides of plant origin have received renewed attention as agents for vector control because they are rich in bioactive chemicals, active against a limited number of species including specific target insects, and biodegradable. The present study was carried out to evaluate the adulticidal, repellent, and larvicidal activity of crude hexane, ethyl acetate, and methanol extracts of eight plants, viz. Aristolochia indica L., Cassia angustifolia Vahl, Diospyros melanoxylon Roxb., Dolichos biflorus L., Gymnema sylvestre (Retz) Schult, Justicia procumbens L., Mimosa pudica L., and Zingiber zerumbet L., were tested against adult and early fourth instar larvae of Culex gelidus Theobald and Culex quinquefasciatus Say (Diptera: Culicidae). The effective adult mortality was observed in methanol extract of A. indica, ethyl acetate extract of D. biflorus, and ethyl acetate and hexane extract of Z. zerumbet against C. gelidus and C. quinquefasciatus (LD(50) =37.75, 78.56, 129.44, 86.13, 80.06, 112.42, 53.83, and 46.61; LD(90) =166.83, 379.14, 521.50, 289.83, 328.18, 455.72, 181.15, and 354.50 ppm, respectively). Complete protections for 150 min were found in hexane and methanol extract of A. indica and Z. zerumbet at 1,000 ppm against mosquito bites. The highest larval mortality was found in the hexane extract of Z. zerumbet, ethyl acetate extract of D. biflorus, and methanol extracts of A. indica against C. gelidus (LC(50) =26.48, 33.02, and 12.47 ppm; LC(90) =127.73, 128.79, and 62.33 ppm) and against C. quinquefasciatus (LC(50) =69.18, 34.76, and 25.60 ppm; LC(90) =324.40, 172.78, and 105.52 ppm), respectively, after 24 h. The plant extracts are potential to be used as an ideal eco-friendly approach for the control of the Japanese encephalitis vector, C. gelidus, and lymphatic filariasis vector, C. quinquefasciatus.