The oak wilt fungus only attacks oaks. Other tree species are not susceptible. All species of oaks native to Minnesota are susceptible. However, there are significant differences in the resistance shown among the various oak species. Minnesota oaks are organized into two groups, the red oaks and the white oaks. Trees in the red oak group have leaves with sharply pointed tips; those in the white oak group have leaves with rounded or blunt tips.
Species in the red oak group are highly susceptible to infection by the oak wilt fungus. Under some circumstances red oaks can die within three weeks of infection. In most cases, however, trees linger over several weeks or months. Recovery is rare among red oaks affected by oak wilt. Within the white oak group, all species are moderately resistant to oak wilt, but infected trees can be killed over a period of one to several years. Bur oaks typically die within two to three years, while infected white oaks may linger for years.