Larvicidal efficacy of six medicinal plants on Anopheles gambiae s.l mosquito

The larvicidal efficacy of some medicinal plants (Ocimum gratissimum, Chromoleana odorata, Terminalia catappa, Carica papaya, Vernonia amygdalina and Cymbopogon  itrates) against the larvae of Anopheles gambiae mosquitoes was investigated in acute bioassay. Ten healthy laboratory bred larvae were tested using five different concentrations 200, 400, 600, 800 and 1000ppm ) and a simultaneous control at 24, 48 and 72 hours of exposure. The results showed that all the plant extracts were seen to be effective at less than 1% (1000ppm), thus possessing good to moderate effect against the larvae; C. citrates has been the most effective with 451.8ppm followed very closely by O. gratissimum with 458ppm, C. papaya with 510.2ppm, V. amygdalina with 582.3ppm, T. catappa with 620.9ppm, the least was C. odorata with 744ppm at the end of the exposure time. The efficacy of the extracts as seen from this study can be used as potential substitutes of synthetic larvicides and local environment due to their availability. The effects of the extracts were seen to be largely independent on external factors, hence the need for further study on the characterization and profiling of the active ingredients, their effect against non-target species and the best time of application is highly recommended as they fit in  as alternative larvicides in reducing Anopheles menace infestation.