Insecticidal Effect of Extracts Against .

Of the various plant extracts from 10 plant species tested against larvae of in the laboratory, only extracts from exhibited larvicidal activity. A chloroform leaf extract of exhibited relatively high activity with a lethal concentration causing 50% mortality (LC) of 15.89 ppm, while chloroform and ethyl acetate extracts of fruits were 19.70 and 19.52 ppm, respectively. The chloroform fruit extract at 10 ppm reduced the hatchability of eggs by 20% whereas the chloroform leaf extract was found to be less effective (5% reduction). At 10 ppm, adult emergence was reduced by 84% and 75% for chloroform and ethyl acetate extracts of fruits, respectively. Metamorphosis of larvae exposed to chloroform fruit extract (10 ppm) was extended to 15 days, as compared to 10 days for control larvae. It took 12 days at 1 ppm, and 15 days at 6 and 10 ppm for chloroform fruit extract-treated embryos to develop into adult mosquito while it took 10 days in the control treatment. However, 100% toxicity was observed in the embryos of zebrafish, , treated with the ethyl acetate fruit extracts (LC of 20 ppm and LC of 40 ppm) and chloroform leaf extract (LC of 30 ppm and LC of 60 ppm). These findings emphasize the need to further isolate the bioactive molecules in crude extracts that may still be mosquitocidal but produce no, or minimal, adverse effects on nontarget organisms such as zebrafish.