Larvicidal Activity of Sacoglottis gabonnensis Stem Bark Extracts against Culex quinquefasciatus and Aedes aegypti Mosquitoes in Uyo, Nigeria

Abstract

The quest for alternatives to synthetic chemical insecticides against mosquito vectors has necessitated studies on natural plant products. The larvicidal effect of ethanolic and aqueous extracts of a medicinal plant Sacoglottis gabonnensis stem bark were tested against 4th instar larvae of Culex quinquefasciatus and Aedes aegypti. Larval bioassays were carried out at different concentrations (0.45 – 0.75% w/v) of the extracts in accordance with the WHO standard protocol. Mortality was recorded after 24 and 48 exposure hours. The LC50 and LC90­ were also determined. The highest concentration (0.75% w/v) of the ethanolic extract of S. gabonnensis resulted in 80% mortality of Cu. quinquefasciatus with LC50 (2.59) and LC90­ (3.42) and 70% mortality of Ae. aegypti with LC50 (1.22) and LC90­­ (2.31). At a concentration of 0.75% w/v the aqueous extract of S. gabonennensis resulted in 65% mortality of Cu. quinquefasciatus with LC50 (2.84) and LC90­ (3.62) and 60% mortality of Ae. aegypti with LC50 (2.16) and LC90­ (2.70). Cu. quinquefasciatus was not significantly (X2=1.66, df 1, P>0.05) more susceptible to ethanolic extract of the plant than Ae. aegypti. The susceptibility of both mosquito species to the aqueous extract was also not significant (X2=2.20, df 1, P>0.05). This preliminary investigation has revealed that the stem bark of S. gabonnensis could be harnessed in the formulation of potent biocides against mosquito vector.