Botanical products are widely investigated as alternatives to conventional mosquito larvicides, yet many candidate extracts are reported without quantitative dose-response metrics. Here we evaluated ethanolic extracts of five African medicinal plants against third-instar Aedes aegypti larvae using laboratory bioassays and probit analysis. Larvae were exposed for 24 h to 0.2% - 1.0% w/v extract concentrations, equivalent to 2,000 - 10,000 mg/L. Carissa spinarum, Croton macrostachyus and Tylosema fassoglense produced negligible mortality under the tested conditions. Plectranthus barbatus and Albizia coriaria produced concentration-dependent mortality, with LC50 estimates of 0.79% and 0.91%, respectively. However, LC90 estimates for both extracts exceeded the highest tested concentration, indicating that high mortality would require concentrations beyond the experimental range. These results suggest that the crude ethanolic extracts tested here are unlikely to be suitable for direct operational larval control. The observed activity in P. barbatus and A. coriaria is better interpreted as a basis for bioassay-guided fractionation, compound identification, formulation work, selectivity testing and environmental fate studies.
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