Larvicidal efficacy of methanol leaf extracts of Hippocratea africana WILD and Lasianthera africana P. BEAUV against Anopheles gambiae (Diptera:Culicidae)

Abstract

Developing potent adulticidal and larvicidal products for mosquito control remains a major control strategy for several mosquito-borne parasitic disease. The bio-efficacy of Hippocratea africana and Lasianthera africana methanol leaf extracts were assessed against the larvae of Anopheles gambiae. Plant extracts were shade dried at room temperature and powdered coarsely. Extracts concentrations used for larvicidal bioassays were 0.15, 0.30, 0.45, 0.60 and 0.75 w/v. Observations were made after 24, 48 and 72 h of exposure. The LC₅₀ and LC₉₀ of L. africana and H. africana against the larval of Anopheles species were determined. The larvicidal activities of both plant extracts increased as their concentrations and duration of exposure increased. The highest concentrations (0.75 w/v) of the extract of H. africana resulted in the highest mortality (85%) at 72 h. The highest concentrations (0.75 w/v) of the extract of L. africana resulted in 70% mortality. No death of larvae A. gambiae occurred in the control experiment. Mortality of A. gambiae larvae increased significantly as the concentration of the extracts were increased (r = 0.648, p < 0.0001). Increase in the mosquito larval mortality was significant for H. africana (r = 0.634, p = 0.005), and L. africana (r = 0.854, p < 0.0001), but H. africana was a more potent larvicide. This study has shown that leaf extract of H. africana and L. africana could be incorporated in the formulation of potent larvicides against Anopheles gambiae.