Phytotoxic effect of selected crude plant extracts on soil-borne fungi of common bean

Abstract

Common bean (Phaseolus vulgaris L.) is an important food and cash crop particularly in Eastern, Southern and Great lake region. The efficacy of water based crude plant extracts of Neem (Azadirachta indica), Mexican marigold (Tagetes minuta), Tobacco (Nicotiana tobacum) and Peri-winkle (Vinca rosea) in controlling soil-borne fungi (Fusarium oxysporum Schl. f. sp. phaseoli) of common bean (Phaseolus vulgaris L.) was studied in the western province of Kenya. Thirty farms were used in the study carried out in August-September 2005 and March-June 2006. Broth microdilution method was used to determine minimum inhibitory concentration (MIC). All crude plant extracts controlled Fusarium yellows with varying efficacy. Neem extract was the most effective, while peri-winkle was the least. Wilt incidence was not affected by dosage regime. Neem is inhibitory to Fusarium growth at lower dosage than tobacco, Mexican marigold and peri-winkle with MIC ranging between 2.5 and 10.0 mg ml-1