Decay fungi South East Queensland

Tree Fungus: Wood Decay Fungi, Rot and What to Do

Fungus on a tree is the visible sign of wood decay fungi rotting the wood inside, and in South East Queensland's warm, wet climate it is common on large, old and wounded trees. This guide shows you what tree fungus does, how to identify dangerous fungus on a tree and what to do about tree rot.

By Sam Schriever, Diploma of Arboriculture (AQF Level 5) · 22 October 2026

What it is: Fungi that rot the wood inside a tree
Scientific name: Various, including Ganoderma and Laetiporus
Trees affected: Any tree, especially large, old or wounded trees, including eucalypts and figs
Peak season: Fruiting bodies appear after rain, mostly in summer and autumn
How it spreads: Airborne spores entering wounds, and root contact for some root rots
Key sign: Brackets, crusts or mushrooms growing from the trunk, base or roots
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What are wood decay fungi?

Wood decay fungi, also called wood-rotting fungi, are the fungi that grow inside a tree and rot its wood, breaking down the material that gives the trunk, roots and branches their strength. The tree fungus you see on the outside, a bracket, crust or mushroom, is only their fruiting body: by the time it appears, the fungus has usually been decaying the wood inside for years.

How decay fungi damage a tree

Most decay fungi feed on the dead heartwood at the centre of the trunk and roots, so the tree can stay green and healthy while it is weakened from within. The damage is structural, and it starts early: in laboratory studies, wood lost almost all its toughness, its ability to withstand a sudden load such as a gust of wind, before it had lost even 10% of its weight to decay. Decay that can be seen is therefore well advanced.

Brown rot, white rot and soft rot in wood

Wood decay comes in three types, brown rot, white rot and soft rot, which differ in what they eat and in how the decayed wood breaks. The type matters, because brown rot makes wood brittle far sooner than white rot. Brown rot is a type of decay, not the same thing as brown root rot, which is a specific root disease.

Rot type	What it eats	What the wood looks like	What it does to strength
Brown rot	Cellulose, leaving the lignin	Brown, cracking across the grain into cubes, crumbling dry	Drops fast and early; failure is brittle
White rot	Cellulose and lignin	Pale and bleached, often with dark lines, spongy or stringy	Drops more gradually, though toughness goes sooner
Soft rot	Cellulose, in constantly wet wood	Soft and cheesy when wet, usually shallow	Mainly a surface problem, at wet bases and in cavities

Sources: Australian National Botanic Gardens, Fungi: wood rots; Wilcox (1978), Wood and Fiber 9.

Close-up of dark brown decayed wood cracked across the grain into small cubes — Brown rot: the cellulose has gone, leaving brown wood that cracks across the grain into cubes and crumbles in the hand. Photo: Beentree, Wikimedia Commons, CC BY-SA 3.0.

How to identify decay fungi on a tree

The main sign of decay fungi is a bracket, crust or mushroom growing out of the trunk, the base or the roots of a living tree. Fungus growing from the soil, mulch or dead wood nearby is usually harmless, so the first question is always what the fungus is growing from.

Signs and symptoms of decay fungi

Worth getting checked

Brackets on the trunk or base
Shelf-like fruiting bodies growing from living wood, most seriously at the base or on buttress roots.
Crusts at the base
Flat, hard or charcoal-like crusts on the trunk base or roots, easily mistaken for fire damage.
Rusty-brown dust
Spores settling on the bark, ground or cars beneath, often visible before the bracket itself.
Cavities and soft wood
Hollows, open wounds or wood that crumbles, alongside any fungus.

Usually harmless

Mushrooms in mulch or lawn
Living on the mulch or buried wood, or partnering with the tree’s roots.
Fungus on rotting wood
Brackets on stumps, fallen branches or dead stubs are recycling dead material, not attacking the tree.
Stinkhorns and slime moulds
Alarming to look at, but living in the mulch, not the tree.
Lichens on bark
Grey, green or orange patches on the bark surface, which do not harm the tree.

How to diagnose decay in a tree

To diagnose decay in a tree, an arborist identifies the fungus where possible, then measures the decay rather than judging it by eye, using drilling resistance or sonic tomography to map how much sound wood remains. The location matters as much as the fungus: decay in the base and roots is the most serious, because that is what holds the tree up.

Which decay fungi are found in South East Queensland trees?

The decay fungi that matter most in South East Queensland trees are Ganoderma and brown root rot at the base and roots, and white punk and other brown-rot brackets on eucalypt trunks. Many other fungi found on trees are recycling dead wood and pose little risk.

Fungus	Rot type	Where on the tree	Risk
Ganoderma (Ganoderma australe and relatives)	White rot	Base, buttress and roots of living trees	High: decays the wood that holds the tree up
Brown root rot (Pyrrhoderma noxium)	White rot	Roots and base, with a brown crust or stocking	High: kills the tree and spreads to neighbouring trees
White punk (Laetiporus portentosus)	Brown rot	Trunks of living eucalypts	High: brown rot makes wood brittle early
Fomitopsis brackets	Brown rot	Living and dead wood	Moderate to high on living trunks and limbs
Orange bracket (Trametes coccinea)	White rot	Dead wood and stubs	Low: recycling dead wood
Split gill (Schizophyllum commune)	White rot	Dead and damaged wood	Low: usually a sign the wood is already dead

Sources: Business Queensland, Brown root rot; Australian National Botanic Gardens, Fungi: wood rots.

Ganoderma brackets at the base of a tree, a young white bracket above older brown ones — Ganoderma australe at the base of a tree at Mount Glorious: a young white bracket above older brown ones. Fungus at the base is the most serious place to find it. Photo: Auradyme, iNaturalist, CC BY.

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Are trees with fungus dangerous?

A tree with fungus can be dangerous, because the decay weakens it from the inside while it still looks healthy. How dangerous depends on where the decay is and how much sound wood remains, and neither can be judged from the outside.

Decay at the base or in the roots, brown rot anywhere in the trunk, and a large tree over a house, road or play area are the findings that raise the risk most. A widely used guideline treats a trunk as high risk once the sound shell of wood around the decay is thinner than about 30% of the trunk’s radius. Measuring that needs an AQF Level 5 arborist with decay detection equipment, as part of a tree risk assessment.

A thick pale cushion-shaped bracket fungus on the smooth trunk of a eucalypt — White punk (Laetiporus portentosus) on a eucalypt at Mount Coot-tha. It causes brown rot, which makes wood brittle early. Photo: Mark Clarke, iNaturalist, CC BY.

When decay fungi appear in South East Queensland

In South East Queensland, the fruiting bodies of decay fungi mostly appear after rain, particularly through the warm, wet summer and autumn. The decay itself works year-round inside the tree, so a bracket that appears after rain usually marks decay that has been developing for years.

Some brackets are perennial and stay on the tree for years, adding a new layer each season; others are soft and short-lived, lasting only days or weeks. A short-lived fungus that has disappeared has not taken the decay with it.

How decay fungi spread

Effectiveness

Does nothing to the decay. Removing brackets also removes the evidence an arborist uses to identify the fungus, so leave them in place until the tree has been assessed.

How to prevent decay fungi in trees

Preventing decay relies mainly on avoiding the wounds that let decay fungi in, and keeping trees healthy enough to wall off any infection. Most serious decay starts at a wound that could have been avoided.

Prune correctly, to AS 4373, cutting at the branch collar rather than flush with the trunk or leaving stubs.
Protect the roots from trenching, soil level changes, compaction and construction damage.
Keep mowers and trimmers away from the trunk base, using a mulched ring.
Have storm damage cleaned up promptly, so torn limbs are cut back to sound wood.

Is fungus at the base of your tree a problem?

Fungus at the base of a tree is the most serious place to find it, because decay there weakens the roots and lower trunk that hold the whole tree up. It is also where decay is hardest to judge, since much of it can be below ground.

Growing from the trunk or roots – a bracket, crust or cluster of mushrooms growing out of the wood needs assessing.
Growing from the soil nearby – mushrooms a metre or more from the trunk may be on buried roots, or harmless in the soil.
In mulch or lawn – fungi in mulch or lawn are usually living on the mulch, and are not a sign of decay in the tree.

Where fungus is growing from the base or roots of a large tree near a house, road or play area, have it assessed rather than waiting for it to grow.

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Tree fungus: common questions

Is fungus on a tree bad?

It depends on what it is growing from. A bracket or crust growing out of living wood, especially at the base or on the roots, means the wood inside is decaying and the tree needs assessing. Mushrooms in the mulch or lawn beneath a tree are usually living on the mulch or partnering with the roots, and are harmless.

Mushrooms growing on my tree: what should I do?

First, work out what the mushrooms are growing from. If they are coming out of the trunk, the base or the roots, photograph them, note where they are and leave them in place, because an arborist uses them to identify the fungus. Then have the tree assessed, sooner if it is large, near a house, road or play area, or if it is leaning, cracking or lifting at the base. If they are growing from mulch, lawn or a dead stump nearby, they are usually harmless.

What causes tree rot?

Tree rot is caused by wood decay fungi, which enter through wounds such as pruning cuts, storm damage, root damage and mower wounds, then slowly rot the wood inside. Some rots start in the roots instead, such as brown root rot and phytophthora root rot. Avoiding wounds and protecting the roots are the best defences.

Should I remove fungus growing on my tree?

No. The bracket is only the fruiting body; the fungus lives inside the wood, so knocking it off does nothing to the decay. Leave it in place, because an arborist uses it to identify the fungus and judge how serious the decay is.

Will a tree with fungus die?

Not necessarily. Most decay fungi rot the dead heartwood rather than the living tissue, so the tree can keep growing for many years. The real risk is structural: decay weakens the trunk, roots or limbs, so the tree can break or fall while it still looks healthy. Root rots such as brown root rot are the exception, and can kill the tree.

Can fungus on a tree be treated?

The decay itself cannot be cured, because no treatment reaches the fungus inside the wood. What can be managed is the risk: an assessment measures how much sound wood remains, and crown reduction, monitoring or removal follow from what it finds.

Are mushrooms at the base of a tree dangerous?

Mushrooms or brackets growing from the base of the trunk or the roots are the most serious place to find fungus, because decay there weakens the part of the tree that holds it up. Mushrooms growing from the soil or mulch nearby may be harmless. An arborist can tell which, often by tracing what the fungus is growing from.

Does fungus mean a tree has to be removed?

No. Many trees with decay are retained safely for years, with crown reduction and regular monitoring. Removal depends on how much sound wood remains, where the decay is, and what the tree could hit, which is what a tree risk assessment establishes.

References

Australian National Botanic Gardens. Fungi: wood rots. Source
Business Queensland. Brown root rot. Queensland Government. Source
Mattheck, C., & Breloer, H. (1994). The Body Language of Trees: A Handbook for Failure Analysis. HMSO, London.
Wilcox, W. W. (1978). Review of literature on the effects of early stages of decay on wood strength. Wood and Fiber, 9(4). Source

General information, not a diagnosis. Many tree problems look alike, and only an inspection, and sometimes a laboratory test, can confirm what is wrong. Any treatment product must be registered for the use and applied strictly to its label.

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