Larvicidal activity of Ipomoea cairica (L.) Sweet and Ageratina adenophora (Spreng.) King & H. Rob. plant extracts against arboviral and filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae)

Abstract

Culex quinquefasciatus Say, an arboviral and filarial vector, is one of the most widespread mosquitoes in the world, and insecticide-resistant populations have been reported worldwide. Due to the emergence of resistance in C. quinquefasciatus plant based products or plant extracts may be alternative sources in integrated vector management program. The present study was carried out to establish the larvicidal activities of crude solvent extracts prepared from flowers and leaves of Ipomoea cairica and Ageratina adenophora against third instar larvae of C. quinquefasciatus as target species. The plant extracts were prepared with petroleum ether, chloroform and methanol solvents using sequential extraction method to determine the best extractant for subsequent isolation and characterization of active ingredient. The total yield of plant extract in the Soxhlet extraction ranged between 0.79% and 19.35%. The qualitative phytochemical study of the plant extracts from different solvents showed the presence of alkaloids, flavonoids, phenols, terpenes, saponins and tannins in different combinations. I. cairica and A. adenophora plant extracts were found to be effective against third instar larvae of C. quinquefasciatus causing 77–100% mortality at 48h. Highest mortality was observed at 500ppm and the order of larvicidal action was observed to be of methanol extract of I. cairica flower>petroleum ether extract of A. adenophora leaf>chloroform extract of I. cairica leaf. High mortality (100%) with low LC50 and LT50 were observed in methanolic flower extract (LC50 – 8.43ppm; LT50 – 2.51h at 48h) of I. cairica, and petroleum ether (LC50 – 133.56ppm; LT50 – 9.45h at 48h) leaf extract of A. adenophora. Lethal concentration (LC50 and LC90) values gradually decreased with the exposure periods, lethal time (LT50 and LT90) decreased with the concentration in bioassay experiment with the crude plant extracts. There was a significant correlation (three-way factorial ANOVA) was noticed among concentration of the plant extracts, exposure time and solvent extraction in relation to larval mortality (P<0.0001), which indicates that larval mortality is concentration dependent as well as time-dependent. Further in-depth study is needed to identify and characterize the active components present in the plant solvent extracts and implement the effective arboviral and filarial mosquito vector management program.