How to set up an on-farm carrot cultivar trial for leaf blight resistance

Organic carrot farmers can evaluate variety resistance to leaf blight caused by Alternaria dauci, Cercospora carotae, and Xanthomonas campestris pv. carotae through on-farm trials. Trials use 2–3 strips per variety in low-variability soil, with a known tolerant variety as reference. Regular symptom scoring—spots on leaf margins, lesions on petioles and stems, leaf curling, defoliation—throughout the season enables real-world assessment. Complementary practices include disease-free seeds, wider row spacing, raised beds, 2–3 year crop rotation, organic fertilisation, stress-reducing irrigation, timely harvest, and ploughing under debris to limit pathogen survival. These methods support effective disease management in organic systems.