This fungus is common throughout the Lake States in red pine plantations.
Damage is especially severe on trees under stress and trees growing in cutover hard-wood stands.
Armillaria causes a decay, seldom extending more than a few feet above ground. It kills trees by girdling at the root collar. But it may also live in roots as a parasite on living tissue. Resin exudate may be present on roots or near the root collar. These strands may radiate into the soil where they may cause infection if they come in contact with the roots of other red pine.