Analysis of Spatio-Temporal Distribution and Agro-Ecological Factors Influencing Carrot Leaf Blight (Alternaria dauci) in East Hararghe, Ethiopia

Carrot (Daucus carota L.) is a popular vegetable crop of nutritional and economic importance worldwide, including in Ethiopia. However, the productivity of the crop is constrained by carrot leaf blight (CLB) caused by Alternaria dauci. Field surveys were conducted during the 2020 and 2021 cropping seasons to assess the distribution and intensity of CLB and to determine its association with agro-ecological factors in East Hararghe, Ethiopia. A total of 170 carrot fields were inspected from three major carrot-growing (Haramaya, Kersa, and Kombolcha) districts of East Hararghe Zone, Ethiopia. Association of the disease incidence and severity with agro-ecological factors were analyzed using a logistic regression model. Out of 170 fields assessed over the 2 years, 98% of the fields were affected by CLB. From the field survey districts, Kersa had the highest mean disease incidence (63.2%) and severity (51.9%), while Haramaya district had the lowest disease incidence (41.6%) and severity (36.2%). Planting carrot in April, circulating farm-saved seed, poor crop residue management, sole cropping, fields that were adjacent to nearby carrot fields, unfertilized fields, and high weed density had significant association with higher CLB incidence (≥50%) and severity (≥35%) in the 2 survey years. In contrast, planting carrot in August, crop residue burial, planting commercial seeds, intercropping, planting carrot away from other carrot fields, crop rotation, soil fertilization, and good weed management were significantly associated with lower CLB intensity, which could be recommended as vital components for designing integrated management strategies against the disease and sustaining carrot production and productivity.