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Oak wilt guide

This guide is designed to provide information for landowners, managers and loggers on the relationship between the risk of introduction of oak wilt (caused by the fungus Ceratocystis fagacearum) and the timing of any activities that may wound oaks or leave oak stumps. This guide also provides information on the relationship between various site and stand factors and the expected level of disease impact (based on root-graft spread).

The guidelines were developed by the multi-agency committees that consisted of consulting, industrial, county and DNR foresters, DNR conservation biologist and silviculturists, U.S. Forest Service and University of Wisconsin researchers, and representatives from Wisconsin Woodland Owners Association, Society of American Foresters, Great Lakes Timber Professionals Association, Wisconsin Paper Council and Lake States Lumber Association. Relevant research articles [PDF] were reviewed, and scientific, economic and operational aspects of oak wilt management were evaluated throughout the review process.

Guide usage

Red and White GroupsWhen your management plan includes keeping oak as part of the timber type and your oak includes any of the following red oak-group species:

  • Northern red, Quercus rubra;
  • Black, Q. velutina; and
  • Northern pin oak, Q. ellipsoidalis.

You should also include white oak-group species:

  • White oak, Q. alba;
  • Bur, Q. macrocarpa; and
  • Swamp white oak , Q. bicolor.

The risk of spread will decrease as the component of white oak-group trees increases because root grafting is rare between white and red oaks.


If your property is part of the Managed Forest Law (MFL) program, you should use the guide to help make decisions about when harvesting may occur. Also consider other factors that influence the timing of harvest (such as site factors, soil moisture) that are not related to oak wilt.

Use this guide if you want to follow generally accepted practices to minimize the impact and risk of introducing oak wilt.

It is not necessary to use this guide if you are converting to a non-oak type or if oak is not considered to be an important part of the stand’s future.

If you choose not to use the guide or if you make decisions that could introduce oak wilt, be aware of the potential impact of introducing oak wilt from your property onto nearby properties through connected roots (root-grafts).

Please note

It is impossible to eliminate all risk of introducing oak wilt into a forest stand. Use of this guide is not intended to eliminate risk. Instead, the guide provides information about the levels of risk of introduction and spread so you may make informed decisions to greatly reduce risk.

Scientific basis

Wisconsin tension zone map
Tension zone dividing the two climate regions in Wisconsin.

Climate data and research on vector activity and fungal mat formation have shown that the risk for overland spread through fresh wounds increases significantly around April 1 south of the tension zone and April 15 north of the tension zone. The risk of overland infection decreases significantly after July 15 statewide.

A research study further examining the risk of cutting in the summer was conducted from 2006-2009. Twelve stands in Adams, Clark, Jackson, Waupaca and Wood counties were monitored for two years after thinning. Seven stands were thinned in mid-summer to early fall (July 15-October 15) and five stands were unthinned control. Though mortality of red oak was observed on some stands after thinning, oak wilt was not confirmed by the lab test. The study showed no evidence that the pathogen Ceratocystis fagacearum initiated oak wilt in any of the stands that were cut from July 15-October 15 due to harvesting.

Additional research has shown that root grafts--which facilitate underground spread--are more common in light textured soils and less common in heavy soils. Observations in varying terrain has revealed that root grafts are more common in areas that are flat or rolling (0-12 percent slope) and less common in terrain that has steep hills and deep valleys (greater than 12 percent slope).

Varying from guidelines

It is appropriate to vary from the guidelines if:

  • Your stand is in an area where oak wilt is rare and locations are well documented (contact your DNR regional forest health specialist for location information).
  • If multiple forest health issues are affecting your stand and unusual circumstances prohibit harvesting during low-risk time periods, varying from the guidelines may be appropriate.

If there is no oak wilt within six miles of your stand--and you wish to harvest oak during the high risk time period--the risk of introduction will be reduced, thus cutting during high risk time periods (April 1 (south) or April 15 (north) to July 15) may be acceptable. In general, oak wilt is so common in the southern two-thirds of Wisconsin that it would be unusual to have an area that is oak-wilt free for six miles in all directions.

If you want to vary from the guidelines, and the land with the stand is enrolled in the Managed Forest Law (MFL) program, county forestry program or is state land:

  • Contact your regional forest health specialist to discuss whether or not varying from the guidelines is appropriate; and
  • If determined to be appropriate by the DNR regional forest health specialist, document justification for varying from the guidelines and include the documentation or a reference to it into your normal approval process for harvesting i.e. on form 2460-001 [Word] (timber sale and cutting report) for public lands and on form 2450-032 [PDF] (cutting notice) for MFL lands. Documentation is the responsibility of the landowner.

Stump treatment

Apply tree wound dressing to the last 3 growth rings.
Apply tree wound dressing to the last three growth rings.

Treatment of stumps is recommended as an option only for stands that have a basal area of oak less than 15 square feet/acre (if you are cutting in the spring and are in a county with oak wilt). To treat stumps, apply a tree wound dressing product (available at most hardware stores) to the last three growth rings. Only one treatment is necessary but this must be done each day to the stumps that were created that same day.

Other methods

Trees that wilt during the summer and early fall will produce small mats of the fungus under the bark the following spring and early summer. If you are moving oak firewood or logs that were killed by oak wilt, use the material before April to minimize the risk of the fungus spreading overland by sap-feeding beetles. Wood is no longer infectious once the bark has naturally fallen off.

Last revised: Tuesday July 30 2019