Oak wilt is caused by the exotic fungus, Ceratocystis fagacearum. The disease kills tens to hundreds of thousands of oak trees in the Midwest every year.
The fungus causes clogging of water-conducting xylem vessels, leading to wilting and death of infected trees. The fungus can spread from infected to healthy trees through grafted roots.
The fungus is carried by certain species of sap beetles. If these beetles land on fresh wounds (e.g. such as those resulting from storms or tree pruning), the tree will likely become infected.
Researchers at the Northern Research Station work to provide natural resource managers of state, county and urban forests with new or improved tools for integrated management of oak wilt.
Oak wilt studies have identified principal insect vectors, evaluated the efficacy of tree trunk injections with fungicides, and the use of root graft disruption (shown in the photo) to prevent the spread of the disease via root grafts.