The fungal disease Armillaria is responsible for the "white rot" root disease.The Armillaria fungus damages the root system.The fungus survives in the soil until the infected root breaks down. Characteristic white fan-shaped mycelial mats can be seen growing on the wood when the rotting bark is peeled back. Freshly infected roots have a strong mushroom smell. The wood of infected roots is rotted by the fungus, becoming either white and powdery ..