Contact Bioassay of an Endemic Plant to Ethiopia on Three Aphid Species

Abstract

Millettia ferruginea (Hochst.) Baker (Abaca: Papilionoideae) is endemic to Ethiopia and is a multipurpose tree which is known locally as birbira. Although it was confirmed effective particularly on the bean bruchids, Chalosobruchus chinensis L., its potential as a botanical for the control of insect pests has received little attention. Different workers had done extraction and characterization of the allelochemicals present in birbira. However, none looked into the possible usages of what they extracted such as insecticidal potency. In order to achieve applied meaning and significance, natural product chemistry must incorporate bioassays. Based on this, extracts from birbira with water or chloroform were assayed on three aphid species. Substance extracted both by water and chloroform caused significantly higher mortality on the three aphid species than the residue in chloroform and the untreated control. The LC50 amounts of water and chloroform extracts, for the respective aphid species, were verified under field conditions and similar toxicity was observed for the pea aphid and the brassica aphid whereas reduced mortality was noted for the barley aphid, which was apparently due to the leaf rolling habit of the aphid, which prevented contact between the aphids in the enrolled leaves and the extracts. Therefore, it can be concluded that birbira is an effective aphicide with contact activity and hence could be developed for practical use by small scale farmers.

Keywords: Allelochemical; Birbira; Bioassay; Chloroform; Extracts; Residue; Water.

Ethiopian Journal of Biological Sciences Vol. 6 (1) 2007: pp. 51-62