By Bill McNee, DNR Forest Health Specialist, Oshkosh, firstname.lastname@example.org or 920-360-0942
Heterobasidion root disease (HRD), formerly known as annosum root rot, was recently found in Fond du Lac and Racine counties for the first time. Thinned pine stands were surveyed by DNR forestry staff in four eastern counties where the disease had not been previously found (Fond du Lac, Manitowoc, Racine and Winnebago counties).
Suspect fruiting bodies were observed on a red pine stump in the town of Auburn in southeast Fond du Lac County, and on several red pine stumps in the towns of Burlington and Waterford in western Racine County. The Auburn and Burlington pine stands were thinned about 10 years ago and did not receive any preventative stump treatments at that time. The Waterford stand was thinned in 2017 and a preventative stump treatment was applied with a backpack sprayer after the harvest. The infected Waterford stumps may have been missed during the preventative treatment. Interestingly, none of the adjacent trees at these sites appeared to be in decline from HRD.
The identity of the pathogen (Heterobasidion irregulare) was confirmed through DNA testing at the DNR Forest Health Lab in Fitchburg. With these detections, HRD is now known to occur in 30 of Wisconsin’s 72 counties.
These new detections have resulted in an expansion of the 25-mile buffer zone surrounding known infections, used to determine appropriate management activities in the HRD Management Guidelines. The guidelines incorporate a grace period following new detections of the pathogen, where users can choose between an existing map in the guidelines (updated each January) or the revised online map. The new grace period will expire in June 2022. Use of the most recent map is encouraged when practical, in order to reduce the spread and impacts of this disease.
Additional information about HRD, detection sites and management advice is available on the DNR Forest Health website. The Forest Health Program has records of all confirmed HRD detections. Regional forest health specialists should be contacted if HRD is suspected to be present in a stand.