Armillaria Root Rot
Armillaria mellea, Armillaria spp.
Overview
A destructive root disease caused by honey fungus, affecting a wide range of woody plants and some herbaceous species. The fungus spreads through soil via dark, root-like rhizomorphs and can persist for decades.
Symptoms
Decline in vigor, yellowing and wilting of foliage, dieback of branches. White mycelial fans under bark at the base of the trunk and on major roots. Dark brown to black rhizomorphs (shoestring-like structures) on roots. Honey-colored mushrooms at base in fall.
Environmental Conditions
Humid
Prevention
Remove old stumps and roots before replanting. Avoid planting susceptible species in known infested areas. Improve soil drainage. Maintain plant vigor. Plant resistant species.
Management
No effective chemical control. Remove infected plants including as much root system as possible. Expose root crown to air by removing soil. Plant resistant species. Soil fumigation in severe cases.