What is Oak Wilt and Why Do We Care About it? Trees are a valuable resource, so we do not want to lose them to disease. Oak Wilt is caused by Bretziella fagacearum, (formerly called Ceratocystis fagacearum), a non-native invasive fungus. It can be found in MN, NY, Tx, IL, OH all together 21 states are infected. In 1944 it was discovered in oak trees in the Midwest. It is spread through the vascular (water-conducting system) roots at about 75 feet per year. All oak trees are susceptible… Read More →