Oak Wilt

Oak Wilt on Cranberry Lake

Oak Wilt, a deadly fungal disease affecting red oaks, was diagnosed in two trees on Cranberry Lake. These trees have been removed to prevent spread.

Oak Wilt Leaves

Here is some helpful information on Oak Wilt:

  • Oak wilt is a fatal disease of red oaks (those with pointy leaves). Red oaks die the summer they get the disease, which helps distinguish between death caused by oak wilt and death caused from defoliation, drought, root rot, or chestnut borers.
  • The Cranberry Lake infestation most certainly occurred because, at some point, some local resident brought infected firewood to the area from an infested part of the Midwest.
  • There may be other infected oaks in the Cranberry Lake area.
  • The first symptoms of oak wilt are branches with wilted leaves and finding green to bronze-green leaves on the ground in summer. Once symptoms are noticed, the tree loses most of its leaves and dies very quickly, often within a matter of weeks.
  • To prevent oak wilt, it is critical NOT to prune or wound oak trees from April 1 until August 1, and to take an extremely cautious approach through October.
  • Wounding red oaks in any way (including pruning) between April 1 and August 1 greatly increases an oak's risk of getting oak wilt. It is highly recommended not to wound/prune ornamental oaks between April 1 and August 1.
  • Infected red oaks cannot be saved with fungicides. Only uninfected red oaks can be protected temporarily with fungicides.
  • Residents who see their oaks lose all leaves in a couple months should contact the DNR forest health specialist Linda Williams at 920-662-5172 or email at Linda.Williams@wisconsin.gov.
  • Alternatively, they should contact an ISA certified arborist. Find ISA certified arborists at http://www.waa-isa.org/arborists/search.asp

Oak Wilt Tree

More information on this deadly infestation can be found by clicking on the links here:

Oak Wilt tree disease found in Oneida County http://dnr.wi.gov/news/releases/article/?id=1808

Oak Wilt in Wisconsin http://dnr.wi.gov/topic/foresthealth/oakwilt.html

Oak Wilt Management http://learningstore.uwex.edu/Assets/pdfs/G3590.pdf

Oak Wilt in Vilas and Oneida Counties PDF document

Oak Wilt and Emerald Ash Borer in the Northwoods PDF document