Tree problems · Disease
Ganoderma root and butt rot: signs and what to do
Ganoderma root and butt rot is a tree disease, often seen on oaks, maples, honeylocust. Look for: large, shelf-like or bracket-shaped fruiting bodies (conks) on the lower trunk or at the root flare.
General information, not a diagnosis. A certified arborist or your county extension office can confirm.
- Disease
- Oaks
- Maples
- Honeylocust
- Beech
- Elms
- Many other hardwoods
Signs to look for
Tick what you see. More ticks make it more likely, but only an on-site look can confirm.
0 of 6 signs ticked. Ticks stay in this browser only.
Season
Conks usually appear in summer and fall, often after wet weather. The decay itself works inside the roots and lower trunk all year, so a tree can look fairly normal while it is weakening.
How it spreads
Spores land on wounds on the lower trunk or roots and start the decay. Mower damage, root cuts from digging and old pruning wounds are common entry points.
Where it is found
Ganoderma root and butt rot fungi occur on hardwoods across the United States. They are common wood-decay fungi, not regulated pests.
Official sources
What to do
- 1
Keep people, cars and play areas away from the base of a tree that has conks until it is checked.
- 2
Take photos of the conks, the base of the tree and the crown.
- 3
Have a certified arborist inspect the tree. Decay at the base can weaken a tree without clear warning.
- 4
Do not dig, pile soil or mulch against the root flare.
- 5
Ask the arborist about the tree's chance of failing and what options fit the site: monitor, reduce the load, or remove.
- 6
Plan removal of a high-risk tree near a house, road or power line instead of waiting for a storm.
Safety first: do not climb, do not cut near power lines and do not use a chainsaw on storm-loaded wood. Call the utility for downed lines and 911 if anyone is in danger.
Prevention
There is no control once a tree is infected. Prevent wounds to the lower trunk and roots: protect against mowers and trimmers, keep root flares clear of mulch piles, and guard roots during building work. Use good planting, watering and pruning practices to keep trees vigorous.
When to call a pro
Call a certified arborist when you see conks at the base, a leaning tree or hollow wood near the roots, especially next to a house, road or play area. Removing a decayed tree is risky because the base may fail while the crew is working, so use a trained and insured crew.
Not sure who to call? Read how to hire a tree service or check is my tree dangerous?
Trees it affects
Usually seen on: Oaks, Maples, Honeylocust, Beech, Elms, Many other hardwoods.
- Northern Red Oak
- White Oak
- Pin Oak
- Red Maple
- Sugar Maple
- Silver Maple
- Honeylocust
- American Beech
- American Elm
See all species in our tree library, or pick a tougher tree with the tree picker.
For tree companies
How to explain ganoderma root and butt rot to a customer
Be careful and honest. Conks do mean decay, but the size of the risk depends on how much wood is gone and where the tree stands. Explain what you can see from the ground, recommend a proper inspection for big trees near targets, and give a written plan with options. Do not use fear to sell a removal.
Send this page to the customer after your visit so they can read the signs in plain words. See also selling plant health care and the job photo checklist.
Questions
What is Ganoderma root rot?
It is a wood-rotting fungus that decays the roots and lower trunk of many hardwoods. Large bracket-shaped conks at the base are a common sign.
Does a conk mean my tree must come down?
Not always, but it means there is decay. How dangerous it is depends on how much wood is affected. A certified arborist should inspect the tree.
Can it be treated?
No. Sources say there is no control once a tree is infected. The tree's health slowly declines, and the risk of failure can rise.
How did my tree get it?
Spores usually enter through wounds on the roots or lower trunk. Mower damage, root cutting and old pruning wounds are common causes.
Is it dangerous in a storm?
It can be. Decayed roots and butt wood can make a tree more likely to fall in strong winds. Have it checked before storm season.
How can I prevent it?
Avoid wounds to the base and roots, keep mulch off the trunk, and use good planting and care practices.
Can Lirevon diagnose ganoderma root and butt rot on my tree?
No. Lirevon is a remote marketing team for tree service companies and does not do tree work. This page is general information, not a diagnosis. A certified arborist or your county extension office can confirm what is wrong with your tree.
How do I find a good local pro for this?
Search Google Maps for certified arborists or tree services near you, read their reviews and ask for proof of insurance. Get two or three written quotes. Our guide on how to hire a tree service lists the questions to ask.
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