Heterobasidion Root Disease Interactive Guide

Before a timber sale is established, it is extremely important to examine the stand in an effort to detect HRD. Look for a pocket of dead trees and fading trees (those with thinning crowns). If H. irregulare infected the stumps at the time of the previous thinning, these symptoms will begin to appear 3–8 years after that thinning. HRD also attacks understory conifer regeneration, so look for dead or fading regeneration. The number of HRD pockets in a stand can vary widely. Look for characteristic fruit bodies of H. irregulare at the base of dead/fading trees and old stumps from previous thinnings as well as symptomatic understory conifers.

Fruit bodies may be buried among soil and duff layers so move the duff layer from immediately around the base of the tree or old stump to adequately look for them. Fruit bodies are most commonly observed in the fall, but can be found any time of the year. Young fruit bodies look like popcorn and are firmly attached to the stump, tree, or root. Under favorable environmental conditions, fruit bodies grow into bracket-shaped or shelf-like fungi, which feel leathery (not hard) and remain attached to the stump, dead tree, or root. These shelf forms are sometimes perennial, but can disintegrate quickly. Fruit bodies vary in color but are usually light to dark brown above and white to tan below. Fruit bodies found below the duff layer or soil may be completely white.

HRD is not the only disease that creates a pocket of mortality in a pine or spruce stand. For example, similarly appearing groups of dying conifers can be caused by insects and associated root disease fungus, Leptographium species, or lightning strikes. If you need assistance diagnosing the causal agent, contact a forester and/or forest health staff.

If HRD is suspected but no fruit bodies are found, consider collecting wood samples from the base of dead trees for laboratory assessment. Wood samples can be sent to:

WI DNR Forest Health Lab
3911 Fish Hatchery Rd.
Fitchburg, WI 53711
608-235-7532

End interactive guidelines Proceed as HRD is not in the stand