Oak wilt in the red oak group can be identified by the rapid wilting of the entire canopy. As previously mentioned, an infected tree of the red oak family could be entirely defoliated within just a few weeks. The wilting begins at the top of the tree and progresses downward. As the wilt progresses, the tree begins to shed its leaves. Individual leaves tend to wilt from the edges inward toward the midrib or stem of the leaf and from the tip down toward the base.
Infected trees in the white oak group show similar symptoms; however, the process is much slower, often times over a period of several years. Another possible sign of oak wilt is discoloration or streaking of the wood just below the bark surface. However, this symptom is not always evident and should not be solely relied upon when trying to determine whether a tree is infected with oak wilt.
Cross Section of Red Oak Showing Dark Colored Streaking