The oak harvesting guidelines specify a harvesting-restricted period due to oak wilt starting April 1 south of the tension zone, and April 15 north of the tension zone. However, the guidelines also allow flexibility at the stand level when the landowner/property manager and other affected parties all agree based on local information (temperature data, etc.) to a change. When experiencing an unusually warm spring, an earlier implementation of the harvesting-restricted period will be at the discretion of the landowner/property manager based on the weather, risks involved and relative importance of completing the harvest as scheduled. We strongly recommend that you start communications among all parties involved in the harvest (landowner/property manager, foresters, loggers, etc.) as soon as possible if a change is being considered.
The recent warm-up in temperatures has made forestry professionals wonder whether the insects that are responsible for the movement of oak wilt have already emerged and if we are now at high risk of overland oak wilt transmission. As you know, insects don't follow calendar dates and their emergence and behavior are highly weather-dependent. Based on extensive insect flight studies in Minnesota, Dr. Jennifer Juzwik recommends this rule of thumb - "Temperatures above 60 degrees for 7 consecutive days" puts a stand at high risk in March. If local weather conditions reach this threshold, it is likely that the insects have emerged and overland oak wilt transmission is occurring in the area.
An early implementation of the harvesting-restricted period is considered a "modification" in the oak harvesting guidelines. Justification for modifications needs to be documented and included in the normal approval process for harvesting. For example, for Form 2460-001 (Timber Sale and Cutting Report) for public lands, the forester or property manager should use the comment box to document a change from the original approval. For Form 2450-032 (Cutting Notice and Report for Wood Product) for MFL lands, the DNR Forester should work with the landowner and their agent (e.g. logger, consulting forester) to agree upon the change and then document it on the cutting notice in the file.
Please note that the oak harvesting guidelines were recently updated and may contain additional opportunities for flexibility based on site and stand characteristics. These opportunities should be investigated to see if they are applicable to the stand in question. The opportunities for flexibility identified in the newly revised guidelines may help alleviate some of the concerns with our early spring weather. The guideline document is available on-line at http://dnr.wi.gov/ keyword "oak wilt" (see links for 'Oak wilt guides' on right sidebar).
If you have regional or site-specific questions on this issue, please contact your Regional DNR Forest Health Specialist.