Occurrence and Severity of Cercospora Leaf Spot on Cowpea (Vigna unguiculata) in Plateau State, North Central Nigeria

Cowpea (Vigna unguiculata) is a critical legume crop in Plateau State, providing affordable protein and income to farming households across the Jos Plateau and surrounding lowlands. Cercospora leaf spot, caused by Cercospora canescens, has been observed with increasing frequency during recent cropping seasons and is suspected to contribute to measurable yield reductions. This study documented the occurrence and assessed the severity of Cercospora leaf spot in cowpea fields across six local government areas in Plateau State during the 2023 growing season. A total of 72 farms were surveyed and disease severity assessed using a standard 1-9 rating scale. Laboratory analyses confirmed C. canescens as the causative agent in all tested samples. Disease severity scores ranged from 3 to 7, with the highest ratings recorded in mid-season plantings coinciding with peak rainfall. Farms with no crop rotation history and narrow row spacings recorded higher disease levels, consistent with published reports of the pathogen's epidemiology. Farmer interviews revealed that many cowpea growers were unfamiliar with the specific identity of the pathogen responsible for foliar symptoms and frequently misattributed damage to insect pests. Awareness of resistant cowpea varieties released by research institutes was also low. The study recommends a coordinated extension programme to disseminate information on improved cowpea varieties and integrated disease management strategies to farmers in Plateau State. Keywords: cowpea, Cercospora leaf spot, Vigna unguiculata, Plateau State, disease severity.