Armillaria Root Rot in California
HIGHFungus
Armillaria Root Rot is currently active in California. Watch your susceptible trees closely and act early.
About 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.
Symptoms to watch for
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
Trees at risk in California
Tracking one of these? Add it to My Yard to get alerts when threats go active near you.
Treatment options
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.
As an Amazon Associate, TreeIssues may earn a commission from qualifying purchases made through these links — at no extra cost to you.
Need help with Armillaria Root Rot in California?
Connect with ISA Certified Arborists serving California:
Browse all California arborists →Frequently asked questions
Is Armillaria Root Rot in California?
Armillaria Root Rot is currently active in California. Watch your susceptible trees closely and act early.
What does Armillaria Root Rot look like?
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
What trees does Armillaria Root Rot affect in California?
It affects Douglas Fir, White Oak, Red Oak, Sugar Maple, Eastern White Pine, Peach. Susceptibility varies by species.
How do I treat Armillaria Root Rot?
Options include: Remove Infected Stumps and Roots, Improve Drainage and Reduce Stress. Confirm the diagnosis before treating, and consider a certified arborist for high-value trees.