A bit of information that we are passing along to you.  I know we usually
don't have to worry much about Oak Wilt in the Northwoods, but just as a
reminder, several years ago Oak Wilt was confirmed in the Three Lakes area.
It was near Cranberry Lake close to the border of Vilas County. Another good
reason that firewood should not be transported!!  So please take a minute
and read the info is appreciated that you do. 

Important points:

· New oak wilt was confirmed on the northwest shore of Cranberry Lake during summer 2012 (1st find in Vilas Co.). DNR will do a press release in the future and is waiting for lab work to be completed.

· This newly discovered oak wilt center has been there since at least 2009.

· Landowner’s can educate themselves at They should memorize the literature under the Prevention tab, “In Urban/residential areas.”

· Landowner’s who hire tree care companies to do work on their property cannot assume the tree care workers know anything about oak wilt! They should interview the tree care worker, get references, and get multiple bids! Talk with your neighbor about which arborist actually knows anything about oak wilt! Do your homework first so you are not given misinformation!

· If property owners injure their oaks in any way (including drilling holes, pruning branches, scuffing tree base with lawnmower, etc.) from April through October, they are possibly helping to introduce oak wilt into their oaks. I recommend not touching oaks unless the ground is frozen.

· Residents who see their oaks lose all leaves in a couple months should contact the DNR forest health specialist out of Merrill - 715-499-1880 or Alternatively, they should contact an ISA certified arborist. Find ISA certified arborists at . Not all certified arborists know substantial information about tree insects and diseases. There are good arborists who are not certified! Landowners can also contact their local DNR forester.

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Oak Wilt Fact Sheet for Northern Wisconsin

Oak wilt is a fungal disease that affects the water conducting system within oaks. Red, black and pin oaks are highly susceptible to oak wilt. Once infected, they can die within a few weeks. There are only a few northern Wisconsin counties that are not yet known to have oak wilt (see the WDNR oak wilt page for further information:

What DOES oak wilt LOOK LIKE?
Oak wilt is identified by rapid leaf discoloration and wilting. Often a subtle off-green color is visible in the upper portion of the tree crown (June to early July in northern Wisconsin). Shortly after this initial color shift, leaves take on a "bronzed" appearance or wilt and then fall off the tree, usually from the top of the crown downward.

Infected trees are almost entirely defoliated within a few weeks of symptom onset. 


  1. Do not cut, prune or otherwise wound oaks from April through July. If an oak is wounded during this period, immediately apply pruning sealer over the wound. Torn branches or roots should be cut clean and the cut surface painted. For additional protection, cover treated roots with soil.
  2. If oaks are cut down from April through July, immediately apply pruning sealer in a 1”-wide band around the edge of the cut surface.
  3. Do not bring oak firewood onto your property that is less than 2 years old.


  1. Make sure the tree has oak wilt. Red oaks with oak wilt literally go from 100% healthy to dead in one growing season, and the wilted leaves are not chewed up by insects. Other problems on oak (e.g. drought, wood boring and defoliating insects) usually kill them over the course of several years.
  2. For trees in a forested setting, let your local DNR forester know. Consult a forester for control options since they are complicated and require in-depth knowledge of the disease.
  3. For trees located in yards, contact a certified arborist or send a sample to the University of Wisconsin Plant Disease and Diagnosis Lab for testing.

DNR Oak Wilt Website:
Oak Wilt Forest Management Guide:
Oak Wilt Diagnosis:
Find a Forester:
Find a Certified Arborist:



FACT SHEET SOURCE: Wisconsin DNR Forest Health Protection,






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