Archives for July 18, 2020

Prevent the Spread of Oak Wilt

Recent brushing operations on the River Road right-of-way damaged oak trees, creating the possibility of an oak wilt outbreak. Paul Cigan, WDNR Forest Health Specialist in the Hayward office, shared a flyer about oak wilt in our area and how to prevent its spread (click here).  He also wrote the following:

Oak wilt disease was confirmed for the first time in Bayfield and Douglas counties and in 16 new northern townships in 2018. Oak wilt is caused by a deadly fungal disease that causes tree death within just a few weeks after infection. Oak wilt negatively impacts property values, forest producer and industry earnings, property aesthetics, wildlife habitat, and recreational opportunities across the county and northern region.

Bayfield County is home to some of the densest, most valuable oak woods in the entire state. In Bayfield County, the disease was found in the towns of Barnes, Cable, and Drummond. In Barnes and Drummond, all of the roughly half dozen diseased oaks were found along the right-of-way of County Highways N and A. The primary cause of infection was ROW brushing during the riskiest time of the year: April 15 to July 15, when fungal spores readily infect open wounds. These infected oaks were cut down and destroyed to prevent fungal spore production in this area. After tree death, healthy oaks growing up to 100 feet away may also become infected if the disease continues to spread belowground through root grafts, which is often the case. This makes the disease very costly and often impossible to control—so disease prevention is key.

A number of state, county, and municipal organizations have policies and practices in place to prevent the spread and damaging impact of oak wilt. The main theme of all of them is to avoid harvesting, pruning, brushing, and any injury to oak trees between the months of April through July. Another strategy by one county is to conduct brushing activities only on non-oak areas such as: non-forests, aspen stands, lowland forests, or pine stands. Here are some examples of oak wilt prevention measures in place by various entities.
1. Bayfield County Forestry Department lands & other Wisconsin County Forest Association lands
• “Do not harvest or conduct activities that may wound oaks April 15 – July 15.” Certain exceptions and modifications may apply subject to proper documentation and forester approval.
2. WI DOT – Section 201 Clearing and Grubbing 2017 201.3 (4)
• “From April 15 through July 1 of each year, pruning paint must be applied to all final cuts on oak trees immediately after cutting.”
3. Public Service Commission – PSC 113.0511 Oak tree cutting and pruning
• “In urban/residential areas: From April 15 through July 1 of each year, no pruning or cutting of live oak trees is permitted except in emergencies.”
• “In rural areas: From April 15 through July 1 of each year, pruning paint must be applied to all final cuts on live oak trees immediately after cutting.”
4. WI DNR lands
• “Do not harvest or conduct activities that may wound oaks April 15 – July 15.” Certain exceptions and modifications may apply subject to proper documentation and forester approval.
5. USDS National Forest Service Lands
• “No harvesting (or other activities that may damage oak trees) will be allowed in stands with greater than 20 square feet of oak basal area per acre between April 1 and July 15 except under the following conditions”
6. Town of Woodboro roadside brushing ordinance:
• “The Town of Woodboro will not mow or brush the town roads before July 15.”

For more information, contact Paul Cigan at Paul.Cigan@wisconsin.gov; 715-416-4920.  Also visit “Northern Oak Wilt Detections” on the WDNR website.