This is part of a series highlighting Wisconsin DNR’s impressive Forest Health Team. photos courtesy of Alex Feltmeyer.

If you have conifers growing on your land, you should be aware of Heterobasidion Root Disease (HRD), formerly known as Annosum Root Rot. This fungus can kill your trees, and once it is established in the soil, there is no known way to get rid of it, according to DNR Forest Health Specialist Alex Feltmeyer.

HDR can kill red, white and jack pine as well as white spruce, Norway spruce, balsam fir, and has been found in red cedar. The most common and the biggest infections are commonly found in red and white pine plantations. This disease was only confirmed in Wisconsin in 1993. HRD is still not found everywhere in Wisconsin but has since been found in 30 counties. Research is ongoing, but its origin is presently unknown.

TRANSMISSION

The fungal spores are airborne. “We have found that the fungus comes in when there is a timber sale or thinning in plantations,” says Feltmeyer. “If the spores land on freshly cut stumps, they work their way to the roots. We often see one tree will become infected, then the trees around it will become infected, and it will progress outward in a circular pocket.”

Red pine growing near each other are root grafted together, so especially in a plantation planted closely —with roots touching underground — there is a pathway for the fungus to move into healthy neighboring trees.

SYMPTOMS

Once it gets into the system, HRD usually takes two to five years to kill a tree. “You start seeing thin crowns, reduced height, reduced branch growth. The most visible symptom is really thin foliage. Then the needles turn brownish, and the tree will die.” Feltmeyer says.

This fungus also produces a fruiting body, like a white bracket fungus on the base of affected trees that have been dead for a while. It stays in the same spot and adds new layers of growth every year. When it is really small, it can resemble popcorn. Owners can look for it by pulling back the needles around the base of a tree. Each of these fruiting bodies can produce millions of spores that can infect other trees.

To read more of this article, check out this link to My Wisconsin Woods.