Vol. 7, Issue 2, Part A (2020)

Author(s): Bouba Théophile, Saotoing Pierre and Ndjonka Dieudonné

Abstract: The results of biological tests carried out according to a methodology inspired by the standard protocol of the World Health Organization revealed that methanolic extracts of Cyperus rotundus and Leucas martinicensis have larvicidal and pupecidal effects. Treatment with methanolic extract of Cyperus rotundus induced 60% mortality in one instar larvae at 50 ppm, 100% mortality at 350 ppm in 24 hours of exposure. A similar trend was observed for all other life instar of Anopheles gambiae sl at different concentrations (50-450 ppm). The LC₅₀ values recorded were 61.27ppm, 70.84ppm, 85.86ppm, 104.44ppm for I to IV instars and 339.18ppm for the pupal instar, respectively. Leucas martinicensis induces 80% one instar mortality at 50 ppm and 100% at 250 ppm. The toxic effect of the extracts was also demonstrated with LC₅₀ values of 28.24ppm, 39.1ppm, 54.79ppm, 80.78ppm for I to IV instars and 244.3ppm for the pupal instar, respectively. The lethal hours 50 (LH₅₀) of Cyperus rotundus are 10h19mn13s, 11h31mn55s, 13h31mn49s, 16h04mn13s, 36h58mn27s for first, second, third, fourth instar larvae and pupae, respectively. Those of Leucas martinicensis are 06h29mn37s, 08h02mn45s, 06h24mn47s, 13h29mn45s, 27h05mn50s respectively for the same larval instars.