Distribution and Relative Importance of Common Bean Angular Leaf Spot in Subsistence Farming Systems in Southern Ethiopia

Abstract

Angular leaf spot (ALS), incited by Phaeoisariopsis griseola, is one of the most destructive diseases of common bean in Ethiopia. Field surveys were conducted in southern Ethiopia during 2016 and 2016 cropping season to determine distribution, relative importance and association of bean ALS severity with cultural practices and environmental factors. A total of 190 common bean fields were inspected in five major bean-growing districts in both years. The association of ALS severity with independent variables was analyzed using logistic regression model. Angular leaf spot was widely distributed with variable importance among the surveyed districts. Common bean ALS severities of 61.38, 40.98, 28.63 and 13.94% were recorded in Burjdi, Konso, Demba Gofa and Mihirab Arbaya districts, respectively, compared to Arbamich areas. The year 2016 attained 11.35% disease severity that was higher than the severity in 2017 cropping season. District, cropping season, altitude, seed source, cropping system, planting date, fertilizer application, growth stage and weed infestation were very highly and significantly (P<0.0001) associated with ALS severity in a multiple variable model. High (>50%) disease severity was highly associated with Arbaminch, Mihirab Arbaya and Demba Gofa districts, <2000 altitude ranges, poorly prepared farms, farm saved and local market seed sources, intercropping systems, pre-flowering to pod forming growth stages in 2016 cropping season. Also, early planting, none to less level of fertilizer application and high weed infestation contributed to high disease severity in the model. Conversely, low disease severity had strong association with the remaining variables in 2017. Survey results demonstrated that ALS was a major bean production constraint in the study areas and, thus, comprehensive and effective management options should be targeted to sustain bean productivity in the study areas and other locations having similar agro-ecologies.