While leaves appear normal early in the season, leaf discoloration begins at the leaf margin and migrates with an undulating front toward the midrib and base of leaf beginning mid to late July. The light brown dead tissue along leaf margin is frequently bordered by narrow to wide zones of dark reddish brown tissue. The dead tissue is separated from green tissue by a narrrow but distinct yellow border or halo. Premature defoliation can occur in late August. This disease may make affected trees more sensitive to damage caused by site-related stresses such as deicing salts and limited growing space.
Leaf margins die and have a distinct yellow border separating the dead tissue from the green tissue.
Scorching begins on leaves at the base of the tree and moves upward through the canopy. Leaves on branches that were affected during the previous season appear normal in the Spring but later show symptoms. Some premature defoliation may occur. Affected trees are very attractive to elm bark beetles and are much more susceptible to Dutch elm disease than trees free of leaf scorch. This disease affects primarily pin and red oak but has also been found in white oak.