Identification of Leaf Blight Pathogens on Cowpea (Vigna unguiculata) in Anambra State, South East Nigeria

Cowpea (Vigna unguiculata) is a fundamental legume crop in Anambra State, where it is consumed as a protein-rich food and cultivated both for subsistence and sale in local markets. Leaf blight symptoms have been reported with increasing frequency in cowpea farms across the state during recent growing seasons, yet formal identification of the causative organisms has been limited. This study aimed to identify and characterise the fungal and bacterial agents responsible for leaf blight in cowpea farms across four local government areas in Anambra State. Systematic field surveys covering 55 farms were conducted during the 2023 growing season, and symptomatic plant materials were collected for laboratory analysis. Morphological and molecular characterisation identified Phoma exigua var. diversispora and Colletotrichum truncatum as major fungal contributors to blight symptoms, while Xanthomonas axonopodis pv. vignicola was confirmed as a bacterial blight agent. Mixed infections were observed in approximately 30 percent of surveyed farms, complicating symptom interpretation by farmers. Disease incidence ranged from 22 to 58 percent across locations. Farms adopting minimum tillage practices without residue removal showed the highest blight pressure. The study contributes original pathogen identification data for the South East zone and recommends improved cultural management, including residue incorporation, as a primary prevention strategy. Keywords: cowpea, leaf blight, Colletotrichum truncatum, Anambra, disease identification.