Acute Toxicity Of Some Parts Of Balanitis Aegyptiaca (L.) Against The Larvae Of Culex Quienquefasciatus

Abstract

The present work dealt with the laboratory evaluation of ethanol and acetone crude extracts of leaves and kernel meso- and exocarp of the indigenous plant Balanites aegyptiaca (L.) Delile, as mosquito larvicides. Both 24 hour acute toxicity and behaviour of the third instar larvae of Culex quinquefasciatus Say to Balanites test extracts were recorded. One major effect of fruit mesocarp contributing to the death of mosquito larvae is that the contained saponin(s), beside being toxic, lower the surface tension and prevent the larvae to get a hold on the air/water interface and they dope down and suffocate to death. Leaf acetone extract was significantly more potent than all other extracts(LD50 =602.56 ppm), while leaf ethanol (LD50 =1380.38 ppm)extract and mesocarp acetone extract (LD50 =1412.57 ppm) showed moderate potencies. However the difference in their LD50s was not statistically significant. Exocarp acetone extract(LD50=1621.81 ppm), although toxic, was significantly the least potent. Exocarp ethanol crude extract and mesocarp ethanol crude extract did not show any potency against the larvae within the range of doses tested (up to 4000 ppm). In all potent extract there was a strong correlation between the log dose of the extract and probit mortality of larvae. Since: (a) the tree, B. aegyptiaca, and its fruit are abundant in urban and peri-urban areas and in the wild throughout the year, (b) the fruit is cheap, (c) the mesocarp is potent against mosquito larvae, snails and fish and safe for mammals; The fruit extracts can be used effectively in confined aquatic habitats viz. shallow water, air cooler tanks, septic V tanks and pit latrines against mosquito larvae and snails. However, more work pertinent to chemical fractionation and identification of the active ingredients in various parts of the tree and use them in field trials to assess their potential as alternatives of chemical larvicides