This disease is caused by an Armillaria fungus, a native parasite often found in tree roots on newly cleared land. It can live many years in old tree roots and stumps. The fungus breaks down root tissue and eventually girdles plants. Infected plants may die rapidly or may linger for years. Infection is most severe in heavy, poorly drained soil. Armillaria Root Rot fungus, invades the roots of many woody and non-woody plants. Oaks are often lightly infected with this fungus for years with no damage. When the trees are under stress from drought, over watering, physical injury, insects, or disease, they often succumb to Armillaria.
On infected plants, the initial symptoms are a decline and die-back in which the leaves turn yellow, wilt, and die. The fungus is spread short distances through the soil by the root-like fungal strands, and contact plant roots, and penetrate the host. Once the fungus enters the bark tissue, it produces a white fan-shaped mat of fungal strands that invade and decay the tissue of the roots and lower trunk. During the fall and wet winter weather, honey-colored mushrooms (the reproductive bodies of the fungus), each 2-5 inches across, may appear on the crown of infected plants or on nearby soil if roots are near the surface. White fans of felt-like fungus grow on an infected plant's crown and roots between the bark and wood at ground level and just below it.
Infected trees, should be removed and destroyed, including the STUMP and the root system. No chemical control is available.