Laboratory studies on mosquito larvicidal efficacy of aqueous & hexane extracts of dried fruit of Solanum nigrum Linn.

BACKGROUND & OBJECTIVE Aqueous and organic solvent extracts of plants/plant parts were effective in killing the mosquito larvae. Comparative efficacy of the aqueous and hexane extracts of dried fruit of Solanum nigrum was tested against five laboratory colonized strains of mosquito species, namely Anopheles culicifacies species A, An. culicifacies species C, An. stephensi, Culex quinquefasciatus and Aedes aegypti to assess the possibility for use of these extracts for their control. METHODS Concentrations of aqueous extract of dried fruit in the range of 62.5 to 2000 ppm and hexane extract of dried fruit in the range of 0.781 to 150 ppm were used in bioassays. The mortality data were subjected to log probit regression analysis to determine the median lethal concentrations (LC(50) and LC(90)) to kill 50 and 90 per cent of the treated larvae of the respective species. RESULTS All the five species registered 100 per cent mortality in larval bioassays at 1000 ppm with aqueous extract and at 100 ppm with hexane extract of dried fruit. In bioassays with aqueous extract An. culicifacies species A registered the lowest LC(50) of 208.5 ppm (range-208.5-359 ppm for different mosquito species) while with hexane extract, An. stephensi registered the lowest LC(50) of 6.25 ppm (6.25- 17.63 ppm for different mosquito species). The LC(50) of aqueous extract was 13-39 fold higher than the values of hexane extract of dried fruit for different species. The calculated LC(90) for hexane extract of dried fruit for different species was in the range of 43.38-95.28 ppm. INTERPRETATION & CONCLUSION Hexane extract showed good mosquito larvicidal efficacy than that of the aqueous extract. The calculated LC(90) for the extract for different species was below 100 ppm and could be effective for comprehensive control of disease vectors.