All oaks are affected, but white oak suffers the most damage from the disease. The disease is serious in set seasons, and the young leaves have the appearance of frost injury, becoming entirely black and shriveled.
Older leaves have dark brown blotches or triangular areas that are mostly along the veins.
Pinkish spores ooze out from the lower leaf surfaces during wet weather and are splashed to other leaves. White oak is the most susceptible of the oak species attacked by this disease. Symptoms first appear as brown spots on the leaves or in many cases these spots coalesce and form large brown areas that tend to follow the veins to the margins of the leaf. The fungus may spread to the twigs and cause cankers, but the damage is not as serious as on the sycamore. Severe defoliation may occur in wet weather.