Fungitoxic properties of four crude plant extacts on fusarium oxysporum schl. F. sp phaseoli.
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Fusarium yellows is a disease of common beans (Phaseolus vulgaris, L.) caused by Fusarium oxysporum Schl. F. sp. phaseoli, it has been found to be important in Busia district of Western province, Kenya. The study on fungitoxic properties of four locally available crude plant extracts was aimed at evaluating their efficacy in controlling Fusarium yellows infestation under the field conditions. Crude plant extracts from Azadirachta indica, Tagetes minuta, Nicotiana tobacum and Vinca rosea were tested against Fusarium oxysporum Schl. F. sp. phaseoli. Participatory On-Farm Trials (POFT) in six (6) divisions were carried out in August-September 2005 and March- June 2006; a total of thirty (30) farms were randomly surveyed. Minimum Inhibitory Concentration (MIC) of crude plant extracts against Fusarium was determined by broth microdilution method. Analysis of variance (ANOVA) was performed on the data, using Genstat 8th edition statistical program (Release 8.11, Lawes Agricultural Trust, Rothamsted Experimental Station, Harpenden, UK). Means were separated using LSD. Crude plant extracts exhibited fungitoxic activity against Fusarium oxysporum Schl. F. sp. phaseoli, with varying degree of efficacy. Nicotiana tobacum and Vinca rosea were not effective, Azadirachta indica and Tagetes minuta exhibited significant control over Fusarium. Azadirachta indica performed better amongst all the plant extracts. Common bean treatment with Benomyl 1 significantly reduced (P≤0.05) wilt incidence and increased growth in comparison to negative (–ve) control. Azadirachta indica formulation gave a significant reduction in wilt incidence compared to the other three crude plant extracts formulations. It reduced the wilt incidence by 17.24% in comparison to Tagetes minuta, Nicotiana tobacum and Vinca rosea whose wilt incidence reduction ranged from 5.84-9.8%. Azadirachta indica inhibited Fusarium growth at lower dosage than Tagetes minuta, Nicotiana tobacum and Vinca rosea. Extracts from Azadirachta indica and Tagetes minuta are effective, cheap and ecofriendly promising methods for protecting common bean against Fusarium oxysporum Schl. F. sp. phaseoli.