Oak Wilt
Oak Wilt kills all species of our native oak trees: white oak, swamp white oak, northern pin oak, bur oak, northern red oak.
The Township works to control the spread of this epidemic disease through inspection, and education. The Township has two tree inspectors to identify and mark oaks with oak wilt. When an oak with oak wilt is found, the property owner is sent a letter regarding the tree’s condition and what needs to be done. Removal is usually required and other measures may be recommended. The Township tree inspectors work with property owners on how to best manage a stand of oaks that includes an infected oak.
Signs of Oak Wilt
The 1st sign of oak wilt disease is the yellowing of leaves in an isolated branch in the upper canopy. The leaves dry out quickly and turn a dark green or bronze, beginning at the leaf edge and moving toward the midrib and base of the leaf. Leaves may fall or may remain on the dying branch. The branch progressively dies back. Red oaks and pin oaks usually die within a growing season, while bur oaks and white oaks may take several years to die.
Other diseases, pests, or drought can make an oak tree appear to have oak wilt. If you suspect oak wilt, call the MDA "Arrest the Pest Hotline" at 651-201-6684 Metro Area, or 888-545-6684 Greater Minnesota or Email Arrest the Pest.
How Does Oak Wilt Spread?
There are two ways oaks can get infected with Oak Wilt:
Overland: The fungus is carried by the picnic beetle to a fresh wound on a healthy oak between mid-April and early-July. The tree is now infected.
Underground: After that first oak dies, other oaks of the same group - -connected via root grafts - - will be infected. This is what an "Infection Center" is. Rarely will a red oak join with a white oak and form root grafts. The Infection Center grows outward, compounding oak mortality every year. Unless stopped, the problem gets worse.
Every year, the majority of oaks die from root graft spread, not overland spread, of oakwilt disease.