Plant Health Initiative

Cercospora Leaf Blight - Symptoms

Cercospora leaf blight is fairly easy to recognize. Photo credit: S.S. Navi, Iowa State University

The first sign of Cercospora leaf blight is usually a purplish discoloration of the young uppermost leaves of the canopy during pod-filling stages and as the plant approaches maturity. Severely-affected upper leaves are often shed while lower leaves remain attached.

If the fungus infects the seed, symptoms can range from no symptoms at all to pink or purple discoloration that cover part or all of the seed. This phase of the disease is called purple seed stain.

This seed shows symptoms of purple seed stain caused by the fungus Cercospora kikuchii. Photo credit: X. B. Yang. Iowa State University

If infected seed is planted, seedlings will show symptoms of the disease. The cotyledons shrivel, turn purple and drop. Dark stem lesions form which can girdle and kill the seedling. Mildly- infected seedlings survive but produce stunted plants.