Oak wilt is a deadly disease that affects all species of oaks (Quercus) found in Minnesota. It is caused by a non-native, invasive fungus (Bretziella fagacearum, formerly Ceratocystis fagacearum). The fungus invades the water-conducting vessels of oaks, eventually killing infected trees. While the oak wilt pathogen can infect all oak species, those in the red oak group (leaves with pointed lobes) die about two months after infections. Bur oaks die between one and seven years after infection, while white oaks die from one to over 20 years after infection.
Oak wilt infection spreads in two ways: above ground by sap beetles and below ground through roots that have grown together, called root grafts. See a great video created by Wisconsin DNR on identifying and managing Oak Wilt for more on oak wilt's disease biology and life cycle.
Other oak problems can easily be confused with oak wilt. Read more about diagnosing oak wilt in the Identification section.
Find detailed methods for managing oak wilt in the Minnesota DNR Oak Wilt Guide.
Location
Oak wilt was first discovered in Minnesota around 1945. Today oak wilt is widespread in east-central and southeast Minnesota and continues to expand its range northward. To date, oak wilt covers about one-third of the area where most Minnesota oaks grow. The DNR's Forest Health Program aims to help slow the northward progression of oak wilt, focusing on early detection and coordinating control efforts along and beyond the northern known edge of oak wilt.
Please report known or highly suspected oak wilt in the following areas:
- Kanabec County
- northern Mille Lacs County
- northern Morrison County
- northern Pine County
- central Stearns County
- all areas to the west or north of those listed above
Report either through the EDDMaps app, the GLEDN app, the EDDMapS website, to your local DNR forestry office, or by submitting samples to the University of Minnesota Plant Disease Clinic. If submitting or showing photos for diagnosis, you must include a photograph of the entire canopy in summer and a close-up showing freshly fallen leaves or wilting leaves on a branch.
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The shaded area shows the known range of oak wilt in Minnesota as of February 2024. List of affected counties.