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Plant diseases
Honey fungus
Armillaria species · Fungus
Also called Armillaria root rot (USA and Australia), bootlace fungus (UK).
Illustration
A root-rotting fungus that kills trees and shrubs, spreading underground through black 'bootlace' cords. There are no chemical controls for gardeners, so dig out infected stumps and roots and replant with less susceptible plants.
How to spot it
- Dieback with smaller, paler leaves, and sometimes sudden death in hot, dry spells.
- A creamy-white fan of fungus between the bark and wood at ground level, smelling of mushrooms.
- Black or brown bootlace-like cords in the soil or under the bark.
- Clumps of honey-coloured toadstools with a whitish ring on the stem, at the base of the tree or stump, in autumn.
Easily confused with
Root rot
Reddish-brown inner bark but no white fungal sheet.
Drought or waterlogging
The crown can look the same: check under the bark at ground level.
Ordinary roots
Bootlaces are darker and smoother, with no woody core.
Where it's a problem
- United Kingdom: Common in gardens; privet, birch, rhododendron, lilac and Leyland cypress are among the most susceptible.
- Australia: A native species attacks more than 200 plants, especially where forest was cleared and stumps were left.
- North America and New Zealand: Native species occur in both.
What to do
- Confirm it by peeling back the bark at the base of the trunk.
- Dig out infected stumps and large roots.
- If you like, sink a vertical rubber barrier about 45 cm deep to stop it spreading.
- Keep nearby plants healthy and unstressed, avoiding waterlogging.
- Replant with less susceptible plants, such as bamboo, box or pittosporum.
There are no chemical controls available to gardeners.
Follow your local council's guidance for disposing of diseased plant material. Official guides usually advise against putting it in a home compost heap.
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Sources
- RHS: Honey fungus
- University of California IPM: Armillaria root rot
- Penn State Extension: Armillaria root rot of trees
- Business Queensland: Armillaria root rot
- WA DBCA: Armillaria root disease
Facts checked Sunday 27 September 2026. General guidance only: follow your local council, agency and product label.