Armillaria Root Rot
HIGHArmillaria mellea complex
Overview
One of the most widespread and destructive forest diseases in the world, caused by a complex of honey mushroom species. It attacks stressed trees through root contact and can persist in dead stumps for decades, infecting nearby healthy trees.
- Type
- Fungus
- Severity
- HIGH
- Source
- USFS
Symptoms
Clusters of honey-colored mushrooms at the base of the tree in autumn, white mycelial fans under the bark of roots and lower trunk, black shoestring-like rhizomorphs in soil, crown dieback and resinous bleeding at root collar
Affected Species
Geographic Spread
Treatments
Remove Infected Stumps and Roots
Excavation and removal of infected stumps and large root pieces to reduce inoculum. Allow removed areas to dry and decompose before replanting with less susceptible species.
Improve Drainage and Reduce Stress
Correct poor drainage, avoid soil compaction, and maintain tree vigor through proper cultural practices. Armillaria primarily kills trees already weakened by other stresses.
Recommended Products & Tools
Helpful supplies for managing Armillaria Root Rot. Always read and follow label directions, and confirm a diagnosis before treating.
Broad-spectrum protectant for many fungal leaf and bark diseases.
Preventive spray for needle cast, leaf spots, and blights.
Sharp, clean cuts to remove affected wood — a tree-care essential.
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Frequently Asked Questions
What is Armillaria Root Rot?
One of the most widespread and destructive forest diseases in the world, caused by a complex of honey mushroom species. It attacks stressed trees through root contact and can persist in dead stumps for decades, infecting nearby healthy trees.
What are the symptoms of Armillaria Root Rot?
Clusters of honey-colored mushrooms at the base of the tree in autumn, white mycelial fans under the bark of roots and lower trunk, black shoestring-like rhizomorphs in soil, crown dieback and resinous bleeding at root collar
Where is Armillaria Root Rot currently found?
Armillaria Root Rot is currently active in Alabama, Arkansas, California, Connecticut, Florida, Georgia, Iowa, Idaho, Illinois, Indiana, Kentucky, Louisiana, Massachusetts, Maryland, Maine, Michigan, Minnesota, Missouri, Mississippi, Montana, North Carolina, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, Vermont, Washington, Wisconsin, West Virginia. It has been reported in 36 total states across the United States.
What plants are affected by Armillaria Root Rot?
Armillaria Root Rot affects Douglas Fir, White Oak, Red Oak, Sugar Maple, Eastern White Pine, Peach. Susceptibility varies by species.
How do I treat Armillaria Root Rot?
Treatment options for Armillaria Root Rot include: Remove Infected Stumps and Roots, Improve Drainage and Reduce Stress. Treatment approaches may include chemical, biological, cultural, and mechanical methods depending on the severity and context.
Compare with Similar Ailments
Not sure if it's Armillaria Root Rot? Compare it side-by-side with similar ailments.