Infection occurs primarily on the uppermost leaves and begins as reddish purple to reddish brown, angular to somewhat circular lesions. Leaves may show a yellowing from the leaf margin in towards the center of the leaf. The discoloration may expand to cover much of the leaf giving leaves a dark, reddish-brown appearance.

When this fungus infects the seed, the disease is called purple seed stain. Infected seed shows a conspicuous discoloration varying in color from pink to pale purple to dark purple. The discoloration may range from small specks to large blotches that cover the entire surface of the seed coat.

To manage Cercospora leaf blight and purple seed stain, rotate crops with at least one year between soybean crops and, if infected seed must be planted, use an appropriate seed treatment fungicide.