Associations of biophysical factors with faba bean root rot (Fusarium solani) epidemics in the northeastern highlands of Ethiopia

Two field surveys were conducted during the 2010 and 2011 cropping seasons to determine the distribution and importance of faba bean root rot, Fusarium solani (Mart) Apple and Sacc. in the northeastern highlands of Ethiopia. The associations of the root rot incidence and severity with independent variables was analyzed using a logistic regression model. The associations of disease incidence and severity with biophysical factors were evaluated. The disease incidence and severity varied among soil types, crop management practices and cropping seasons. Disease incidence and percentage severity index were higher in 2010 (44.6%) than 2011 (44.4%) due to the high rainfall in 2010. Cropping season, soil type, land preparation and weed management practices were significantly associated with faba bean root rot incidence and percentage severity index in a multiple-variable model. A root rot incidence of ≤50% and severity of ≤40% showed high probability of association with season, furrow sowing and weed management practice, whereas vertisols, flat sowing, high soil moisture and high weed density had significant contributions to root rot epidemics. In contrast, elevation, cropping system and crop density were not associated with the root rot incidence and percentage severity index. Our results showed that root rot is a major biotic constraint in the study area and suggested that proper soil drainage and weed management practices could contribute to reduce the impact of the disease until resistant faba bean genotypes are developed and distributed to small-scale faba bean growers in northeastern Ethiopia and other similar areas of the country.