Oak wilt is a native disease of oaks. It is caused by the fungus Ceratocystis fagacearum and spreads from tree to tree by insects feeding on wounds or through roots connecting diseased trees with healthy ones. The fungus causes pores and vessels to become plugged. Therefore, the foliage wilts and falls.
Oak wilt has been present in Garrett and Allegany counties for many years. While oak wilt is an aggressive disease in other parts of the country, it does not cause severe damage in Maryland. At this time, the disease does not appear to be advancing eastward.