It appears as brown blotches along the midvein of leaves, which also may be spotted brown or purple. Affected leaves fall before autumn, but some may hang on the tree through the winter, presenting a serious source of reinfection. Badly infested trees turn brown, as if singed by a fire. It is necessary to remove all affected leaves and tree parts and destroy them. This includes removing the mulch around the base of the tree, which must be replaced with fresh material.
Smaller trees are easier to treat than larger specimens.
Spray a fungicide on what remains of the tree when leaves and buds emerge, and then again every two to three weeks until dry weather sets in. Construction damage can also gash trunks or rip off branches, leaving open wounds. Once oak wilt has been transmitted to a tree, it spreads rapidly and can kill the tree within a matter of weeks. As the name suggests, the symptom is a rapid wilting of the leaves. In areas where the roots of adjacent trees are intertwined, the fungus can spread from tree to tree.