Larvicidal Effect of Hyptis spicigera Aqueous Plant Extract on Anopheles and Culex Mosquito Larvae

Background: Mosquitoes are insects of public health importance because they transmit pathogens that cause a wide range of diseases. In recent times, attention has been shifted from the synthetic insecticides used in their control to plant extracts as potential insecticides for the control of mosquitoes. Objective: The current study aimed to evaluate the effect of Hyptis spicigera aqueous leaf extract on Anopheles and Culex mosquito larvae. Methods: Field-collected Anopheles and Culex larvae were used as test organisms and exposed to aqueous extract of H. spicigera in graded concentrations of 0.125g/250ml, 0.25g/250ml, 0.375g/250ml, 0.5g/250ml and a control containing only distilled water. Mortality was observed and recorded over 24hrs, 48hrs and 72hrs respectively. Result: Phytochemical screening of the leaf extract indicated the presence of alkaloids, saponins, phenol, anthraquinones, flavonoids, carbohydrates, steroids, tannins, and cardiac glycosides as bioactive components. The LC50 values obtained for H. spicigera tested on the mosquito larvae were 0.01g/ml for Anopheles species and 0.04g/ml for Culex species. This indicates that the extract had the highest toxicity on Anopheles larvae compared to the Culex larvae at 72 hours of exposure. However, it was observed that larval mortality for both mosquito species decreased with treatment concentration but increased with prolonged exposure time, with 0.125 g/ml recording the highest mortality on both larvae. Conclusion: While H. spicigera shows promise as a larvicide against mosquito larvae, additional research is needed to investigate the mechanism of resistance that occurs at higher dosages and to explore the potential use of synergists to enhance the efficacy of the plant extract as a mosquito control tool.