The Efficacy of Neem Extracts on The Control of Brown Blotch of Cowpea in Mubi, Nigeria

The effect of aqueous and ethanolic extracts of neem plant parts (leaves, stembark and roots) on Colletotrichum capsici the causal agent of brown blotch of cowpea was carried out in Mubi. The isolate C. capsici was identified and proven through a pathogenicity test to be pathogenic. Cowpea plant parts (leaves, and pods) with similar symptoms of brown blotch such as dark brown to black patches were collected from farmers’ fields in four districts of Mubi North during November 2018. The locations included Mubi, Mayo Bani, Ba’a and Fali districts. A total of 240 samples of two plant parts (leaves and pods) were collected using a simple random sampling technique. The causal agent of brown blotch was isolated from an infected pod of cowpea collected from the periphery of Mubi North in November 2017. The in vitro control trial was carried out on the Potato Dextrose Agar (PDA) polluted with aqueous and ethanolic extracts of Neem (Leaves, stembark and roots) in a completely randomized design with duplicates of 3; a restrain mycelial growth was observed in all the treatments 0.60 cm for leaves and stembark, 1.22cm for roots extract as against 0% inhibition by control. There was a corresponding growth of the action of ethanolic extract as to aqueous in vitro in all the treatments (leaves, stembark and roots) 0.63cm, 0.57cm, 0.57cm as for the ethanolic extract and 0.63cm, 0.67cm and 1.88cm for aqueous treatments respectively. It may be concluded from this study that C. capsici is a common pathogenic fungus that causes brown blotch of cowpea in the Study Area; result from the pathogenicity test indicated that the isolated fungus is pathogenic and attributed to the cause of brown blotch of cowpea in Mubi North. The inhibitory effect of the extract from neem tree against fungal isolate could be due to the anti-fungal substances present in the extract. Higher inhibition of fungus growth was observed at a higher concentration of the ethanolic extract as recorded. The result also indicates that ethanolic extract has more inhibitory compounds than aqueous extracts. This shows a clear indication of the potentials of plant extracts in control of the fungal pathogens.