Larvicidal and Growth-Regulatory activities of Methanolic and n-hexane extracts of Leaf of Ficus vallis-choudae Delile (Rosales: Moraceae) against Culex quinquefasciatus (Diptera: Culicidae)

Abstract

The study aimed at determining the larvicidal and Insect-Growth-Regulating (IGR) potentials of n-hexane and methanolic extracts of Leaf of Ficus vallis-choudae against Culex quinquefasciatus mosquitoes in a bid to develop a cost effective and eco-friendly control lead. Collected leaves of the plants were air-dried, pulverized and sohxlet-extracted. Phytochemical screening of the crude extracts was done following standard protocols. Graded concentrations of 0.00625 to 0.05 mg/L (n-hexane extract) and 0.2 to 0.5 mg/L (methanolic extract) of the crude extract were assayed against fourth larval instar of the mosquito species. The mosquitoes were monitored from zero to 48 hours post-exposure to determine mortality. Sub lethal concentrations of 0.00625 (n-hexane) and 0.2 mg/L (methanol) were assayed for IGR activities. The phytochemical screening of crude extracts of the leaf revealed presence of seven secondary metabolites, whose presence was dependent on extraction solvent. They include flavonoids, tannins, saponins, cardiac glycosides, steroids, anthraquinones and terpenoids. After 48 hours post-exposure, analyses revealed a time and dose-dependent toxicity of the leaf extracts. The LC50 and LC90, respectively, of the n-hexane and methanolic extracts were, 0.022 and 0.042 mg/L, and 0.355 and 0.463 mg/L, respectively. IGR studies revealed significant increase in duration of development by the sub lethal concentrations. This study revealed larvicidal and IGR potential of n-hexane and methanolic extracts of the leaf of Ficus vallis-choudae, and therefore, a promising lead agent for development of larvicides for mosquito vector control.