Larvicidal activity of Ageratum conyzoides L. extracts on Anopheles gambiae complex

Abstract

Larviciding is a useful approach in the control of Anopheles species the vector for Plasmodium and the extensive uses of synthetic organic insecticides during the past decades have resulted into environmental pollution and development of physiological resistance in major vector species, the search for compounds that are ecofriendly with improved mode of action is an area of study. The larvicidal potentials of leave, flower, stem and root of Ageratum conyzoides (goat weed plant) extracts against 3^rd - 4^th instar larvae of Anopheles gambiae complex was investigated. The n-hexane, ethyl-acetate and methanol Fractions of the different plant parts were obtained using Soxlet technique. These extracts were tested against 3^rd- 4^th instar larvae of A. gambiae complex with different concentrations in increasing order 100 ppm-500 ppm Using WHO procedure with slight modification. To observe the larvicidal efficacy, extracts of different plant parts were mixed at different concentration; four replications each with a control were set. The 24 hr. and 48 hr. LC₅₀ values of individual Plant part extracts were determine using Probit analysis. All the plant parts after 24 hr. showed moderate toxic effect on the larvae with relatively moderate LC₅₀ of leaf, 423.520 ppm (Methanol), and the lowest LC₅₀ in leaf (n-hexane)  627.904 ppm respectively. Highest LC₅₀ at 48 hr. were found in leaf extracts with LC₅₀ of 53.742 ppm (Methanol), 73.524 ppm (ethyl-acetate), and stem (n-hexane) were found to be least effective with LC₅₀ of 149.875 ppm respectively. The results demonstrate that plant extracts may serve as larvicidal agent in insect vector control and further research need to be done on the mode of the action of this plant extract.