Larvicidal Efficacy of Aqueous Extracts of Leaf of Ocimum gratissimum and Bark of Terminalia catappa against Aedes sp

Abstract

The resistance of vectors to conventional insecticides has resulted in a renewed attention to natural products such as botanicals as a means of controlling mosquito vector population seeing that they are readily available and are eco-friendly. This study investigated the larvicidal efficacy of aqueous extracts of Ocimum gratissimum (leaf) and Terminalia catappa (bark) against Aedes sp. larvae and the evaluation of the phytochemical constituents present in them. The extracts were tested on laboratory bred Aedes sp. larvae at different concentrations (500, 750 and 1000ppm) at 24, 48 and 72 hrs. Data was analysed statistically using Analysis of Variance (ANOVA). The mortalities of the extracts were observed to increase with increase in concentration and time of exposure. Larval mortality recorded at 72 hrs of exposure to 1000ppm of O gratissimum and T. catappa were 46.7% and 13.3% respectively. LC₅₀ and LC₉₀ values at 72 hrs were 1017.70 and 1372.10ppm respectively for O. gratissimum and 4043.60 and 15678.10ppm for T. catappa. While only steroids were identified as the phytochemicals present in T. catappa, those identified in O. gratissimum include alkaloids, flavonoids, saponins, steroids and tannins. The efficacy of both study plant extracts showed promising larvicidal potency. This is useful considering the current drive on Integrated Vector Management in controlling mosquito vector species on many fronts.