Prepare a fine but firm seedbed if seeding using conventional tillage. Use high-quality seed of adapted varieties. Plant varieties with resistance to Aphanomyces where this disease occurs. Broadcast soil treatments with fungicides at planting are not recommended. Small black spots appear on infected leaves, which turn yellow and fall off soon after infection.
Spots are usually more severe on older leaves.
Stem lesions are dark brown to black and may girdle stem. Can also attack crowns and roots, turning them black. Very common fungus in Kentucky alfalfa fields. Survives in stubble of old cuttings, and spreads easily by rainsplash, running water, and equipment. Leaf infections are most common during spring and early summer.