Heterobasidion Root Disease (HRD), once called annosum root rot, is a disease that affects conifers in 30 Wisconsin counties. It most commonly affects red and white pine plantations, but a lot of tree species can be hosts of HRD. This disease can be very detrimental to conifer populations, as it can cause reduced height and diameter and thin foliage, which leads to mortality. There is no cure for this disease, only methods to treat and control, making the prevention of HDR very important.
The most common way HRD spreads is when the fungus spores land on a freshly cut stump. As the HRD spores germinate, the fungus overtakes the stump and moves to the roots and soil. It can spread through the soil and by root contact between 3-6.5 feet per year. Spores can spread many miles by wind as well, which is how they can land on freshly cut tree stumps.
To identify if your stand has been infected with HRD, there are some signs to look for. At the base of dead or dying trees and stumps, white or tan fungus fruit bodies will appear on or just below the soil. These fruit bodies look like popped popcorn at a young age but turn into shelf-like structures as they mature. Standing trees will have a thinner diameter, reduced height, and a thinning of needles, or will be dead. The roots of dead trees can appear yellow and stringy. These symptoms occur between 3-8 years after a thinning has taken place and HRD has infected the area.
To prevent HRD from entering a stand, treat stumps within 24 hours of being cut. This can decrease the chance HRD will be introduced into a stand. It is important to spray equipment down before and after usages because HRD can also spread by soil contamination.
To learn more about HRD in Wisconsin, visit https://bit.ly/3Y7lcHw.
If you think your stand is infected, want to prevent, or are close to an infected site, visit https://bit.ly/3Yrt6wT to read an in-depth guideline about treating for HRD.
To find your forest health zone specialist, visit https://bit.ly/40ar05B.
If you think your stand is infected, want to prevent, or are close to an infected site, visit https://bit.ly/3Yrt6wT to read an in-depth guideline about treating for HRD.
To find your forest health zone specialist, visit https://bit.ly/40ar05B.
A pine stand in Wisconsin infected with HRD.
Photo source: https://forestrynews.blogs.govdelivery.com/tag/disease/page/10/
HRD in the “popcorn stage.”
Photo source: https://programs.ifas.ufl.edu/florida-4-h-forest-ecology/forest-ecology-contest/contest-stations/forest-health/diseases/annosum-root-rot/images/
Mature HRD on the base of a pine tree.
Photo source: https://minnesotamycologicalsociety.org/biosurveillance-for-invasive-forest-pathogens-in-minnesota/