Occasionally, large branches of trees infected late in the summer survive the winter but die the following spring after producing a few scattered leaves. Oak wilt is the primary suspect when localized areas of dead and dying red and black oaks showing the described symptoms continue to increase. Click on image for larger version Figure 3. The leaves on affected branches usually become light brown or straw-colored from the leaf tip toward the base. The leaves curl and remain attached to the branches.
Infection generally occurs in scattered branches of the crown.
The trees may die in one year, but usually die slowly over a period of several years or more. After two or more years of progressive die-back, infected white oaks have sparse crowns and eventually die from oak wilt or secondary causes. Bur oaks are intermediate in susceptibility and may be killed as quickly as red and black oaks or as slowly as white oaks. Sapwood discoloration, similar to that in red and black oaks, has occasionally been observed in wilting bur oak trees. White oaks have been known to recover after one season of infection when new wood is laid down over an infected annual ring effectively walling off the fungus and allowing tree recovery.