ABSTRACT

Larvicidal efficacy of Swietenia mahagoni (L.) Jacq., Aphanamixis polystachya and Mallotus nudiflorus seed and leaf extracts was evaluated on the mosquito larvae Culex quinquefasciatus Say under laboratory condition for 24 hours of exposures. Based on probit analysis, the larvicidal LC50 values of seed extracts of  S. mahagoni at the application doses for distilled water (5000-15000 ppm), methanol (1000-5000 ppm), 50% ethanol (2500-4500 ppm), and butanol (250-2000 ppm) were 10595.604, 2413.761, 3032.909 and       615.274 ppm respectively; for A. polystachya seed extracts, the LC50 for distilled water (12000-20000 ppm), methanol (500-2500 ppm), 50% ethanol (500-2500 ppm) and butanol (125-1500 ppm) were 15969.813, 1363.075, 1099.122 and 378.786 ppm respectively; and in M. nudiflorus seed extracts the LC50 were 24458.809, 2710.997, 1259.261, 467.143 ppm for distilled water (20000-30000 ppm), methanol (2000-   4000 ppm), 50% ethanol (500-2500 ppm) and butanol (200-1000 ppm) respectively. The LC50 values of leaf extracts of S. mahagoni at the application dosages for distilled Water (10000-30000 ppm), methanol (2000-4000 ppm), 50% ethanol (2000-4000 ppm) and butanol (1000-2000 ppm) were 16759.746, 2831.023, 2749.526 and 1401.129 ppm respectively; for A. polystachya leaf extracts, the LC50 for distilled Water (15000-35000), methanol (1000-3000 ppm), 50% ethanol (1000-3000 ppm) and butanol (1000-2000 ppm) were 25547.749, 1788.103, 1816.070 and 1315.032 ppm respectively; and for M. nudiflorus leaf extracts, the LC50 were 27644.562, 1371.408, 1443.832, 923.367 ppm for distilled Water (20000-40000 ppm), methanol (500-4000 ppm), 50% ethanol (500-2500 ppm) and butanol (500-1500 ppm), respectively.  Mortality was dose dependent. Of the three plants, seed extracts of A. polystachya was the most toxic, whereas leaf extracts of M.  nudiflorus was the most toxic to inhibit existence of the mosquito larvae as observed from LC50 and relative potency values.

Key words: Larvicidal effect, plant extracts, Culex quinquefasciatus larva.