Oak wilt

DNR forester and landowner walking in landowner's woodlands

Oak wilt is 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 species of oak, 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. For more on oak wilt's disease biology and life cycle, see Oak Wilt in Minnesota.

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 Oak Wilt guide for Minnesota.

Click to enlarge

map of known range of oak wilt

The pink area is the oak wilt high-risk zone and shows the known range of oak wilt in Minnesota as of October 2020.

Location

Oak wilt was first discovered in Minnesota around 1945. Today oak wilt is widespread in the southern half of 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 unit wants to slow the northward progression of oak wilt, so we focus on early detection, coordinating control efforts on private lands in Morrison and Pine counties, and helping control oak wilt on public lands at the northern edge of where oak wilt is found.

If you know of oak wilt anywhere in Pine, Kanabec, the northern half of Mille Lacs County, the northern half of Morrison County, Todd County, and all areas to the north, please report with the Great Lakes Early Detection Network app or the EDDMapS website. Take two photographs of a wilting tree to submit through the app or website: a photograph of the entire canopy and a close-up showing freshly fallen leaves or leaves on a branch. If you don't have a smart phone or the internet, report likely oak wilt to your local DNR forestry office.