Spatial distribution and biophysical relationships of common bean angular leaf spot ( <i>Pseudocercospora griseola</i> ) with agronomic factors in west and southwest Ethiopia

Abstract

Abstract The prevalence of angular leaf spot (ALS) in common beans ( Phaseolus vulgaris L.) poses significant challenges to productivity in the western and southwestern regions of Ethiopia. This agricultural study was conducted to assess the distribution of ALS and examine the relationship between ALS and biophysical and agronomic factors. Field assessments of ALS severity and associated agronomic factors were conducted in the 2022 and 2023 main cropping seasons. A total of 165 common bean fields were assessed in six districts across three zones. The magnitude and the associations of disease parameters with biophysical factors were determined using a multiple regression model. The survey results showed that out of 165 assessed fields, 151 (91.5%) were 100% infected with ALS, with many exhibiting severe disease. The incidence and severity of ALS were significantly associated with biophysical factors with varied magnitudes of 88%, 64.8%, 78.2%, 79.9%, 69.7%, and 57.2% severity and 82.8%, 57.9%, 71.2%, 74.8%, 68.3%, and 61.1% incidence in Bako Tibe, Ilu Galan, Gobu Sayo, Bilo Boshe, Didessa, and Gechi districts, respectively. Variations in disease intensity were significantly associated with agronomic practices. Source of seed, weed infestation level, crop rotation and tillage frequency, plant density, weeding frequency, and cropping system had a significant effect to common bean ALS intensity. Pearson correlation analysis showed that tillage frequency (r = −0.71) and weeding frequency (r = −0.60) were identified as the most influential variables affecting disease intensity in the study area. These findings indicate that future ALS management strategies should incorporate integrated agronomic and biophysical considerations to effectively manage ALS.