Abstract

• Two plant materials, aerial part of Spilanthes acmella L. (Pè-Laynyin) and bark of Melia azedarach L. (Pan-Tamar) were selected for the screening of mosquito larvicidal activity against third and fourth instar larvae (Aedes aegypti mosquito). Petroleum ether extract from aerial part of Pè-laynyin (LC50 = 0.0065 %, LC90 = 0.0146 %) and ethanol extract from Pan-tamar bark (LC50 = 1.008 %, LC90 = 3.693 %) showed potent larvicidal activities. The larvicidal activity of commercially available synthetic larvicide, Temephos, (Abate) was LC50 = 0.0034 ppm and LC90 = 0.0075 ppm. Ethanolic extract of S. acmella was not observed sign to be toxic in mice at 10 g/kg that is maximum permissible dose. Therefore, S. acmella extract did not show harmful effect to mammalian. The maximum giving dose for ethanolic extract of M. azedarach in mice was 8 g/kg within survival period for 7 days to be looked forward. At a dose of 10 g/kg, one out of three mice was found to be dead. Therefore, care must be taken if bark of M. azedarach is used as larvicide. Petroleum ether extract of S. acmella was not observed lethality on fish Clarias batrachus (Nga-khu) at 0.025 % concentration level. Therefore, petroleum ether extract was not found harmful effect on aquatic vertebrates and can safely be used as natural larvicide in fresh water.