Symptoms

Trees of highly susceptible red and white oak species wilt rapidly from the top down and are killed completely within four to six weeks. Moderately susceptible species wilt more slowly. Trees of species with low susceptibility may "wall off" the disease and survive with only partial death of branches.

Healthy trees are infected by fungal spores that enter wounds on branches and trunks. Insects such as sap beetles (Nitidulidae) and bark beetles (Scolytidae) are attracted to oozing sap from fresh tree wounds. The beetles become contaminated with fungal spores and are believed to be the primary agents of long-distance spread from diseased to healthy trees. Thus, the importation of all wood with bark is prohibited since it may contain contaminated beetles. The disease also spreads slowly from tree to tree via natural root graphs.