Heterobasidion root disease (HRD) is a serious fungal infection that kills pines, spruces, and other conifers in Wisconsin. / Photo credit: Wisconsin DNR
MADISON, Wis. – The Wisconsin Department of Natural Resources (DNR) is asking the public to check needle trees for signs of harmful disease and report their findings to the department.
Heterobasidion root disease (HRD) is a serious fungal infection that kills pines, spruces, and other conifers in Wisconsin. This fall, watch for bright white new growth on conifer bases, stumps, seedlings and saplings. To find the mushrooms, you may need to scrape off the needles and other debris. The DNR maintains a online map with all known HRD locations. Please report suspected cases to your forest health specialist.
HRD can spread through the roots of evergreens connected under the ground and often shows up as clumps of trees that seem to be dying off one by one. Fungi are most visible on seedlings, young trees and tree stumps. HRD is a rot fungus that breaks down root and lower stem wood, so infected trees can have a stringy yellow rot that causes stems to break.
Prevention of HRD is essential as it is difficult to control once established in coniferous forests. New infections are more common when spores from nearby fungi land on freshly cut stumps. Using preventative fungicides on freshly cut conifer stumps is therefore the best way to protect Wisconsin forests from HRD. Fungicides are mixed with water, so application is not possible when temperatures are below freezing.
HRD is not the only health problem affecting pines. Several other insect and disease problems cause similar symptoms, so it’s important to properly diagnose the cause of pine mortality before deciding on the best management approach.
More information on HRD and other diseases of conifers is at MNR’s webpage on root disease of heterobasidion.