Tree problems · Insect
Leaf and stem galls: signs and what to do
Leaf and stem galls is an insect pest, often seen on oaks, maples, hackberry. Look for: small bumps, spots, felt-like patches or pouches on the top or underside of leaves.
General information, not a diagnosis. A certified arborist or your county extension office can confirm.
- Insect
- Oaks (the most gall-prone group)
- Maples
- Hackberry
- Cottonwood and willows
- Lindens
- Black cherry
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
Most galls start in spring, when insects or mites feed or lay eggs on fresh growth. They are easiest to see from late spring through fall, and woody twig galls stay on the tree through winter.
How it spreads
Galls are caused mostly by small insects such as wasps, midges and aphids, and by mites. Each kind of gall maker usually sticks to certain trees. Galls do not spread from tree to tree like a disease, but the insects can return to the same tree year after year.
Where it is found
Galls are found on trees in every part of the United States. Which gall makers are common depends on your region and tree species. Check with your local extension office for what is common near you.
Official sources
What to do
- 1
Take clear photos of the growths, the leaf or twig they are on, and the whole tree.
- 2
Note the tree species. Gall type often depends on the host tree.
- 3
For leaf galls, most extension sources say no treatment is needed. They look odd but rarely hurt a healthy tree.
- 4
For woody twig galls, ask an arborist whether pruning out heavily galled twigs makes sense.
- 5
Rake and dispose of fallen galled leaves if your extension office suggests it.
- 6
Do not spray insecticide without advice. The insect is protected inside the gall, so timing is hard and spraying often does not help.
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 simple way to stop galls. Keep the tree healthy with proper watering, mulch and no root damage. A healthy tree handles galls better. Spraying to prevent leaf galls is seldom worth it, so ask your extension office before you buy any product.
When to call a pro
Call a certified arborist if twig galls are heavy, if branches are dying back, or if you are not sure the growths are galls at all. Other problems, including fungal and bacterial diseases, can look similar.
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 (the most gall-prone group), Maples, Hackberry, Cottonwood and willows, Lindens, Black cherry.
- White Oak
- Northern Red Oak
- Pin Oak
- Post Oak
- Bur Oak
- Southern Live Oak
- Red Maple
- Silver Maple
- Sugar Maple
- Hackberry
- Eastern cottonwood
- Weeping Willow
- Black Willow
- American Linden
- Black Cherry
See all species in our tree library, or pick a tougher tree with the tree picker.
For tree companies
How to explain leaf and stem galls to a customer
Most leaf galls are a cosmetic worry, and homeowners often panic when they see them. Say so plainly. Explain what you see, show the photo, and do not sell a spray for a problem that does not need one. Honest advice here earns trust for the jobs that do need a crew.
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 are galls on a tree?
Galls are abnormal growths on leaves, twigs or other parts. They are triggered mostly by small insects and mites that feed or lay eggs on the plant. The tree grows extra tissue around them.
Will galls kill my tree?
Usually not. Extension sources say galls are mostly cosmetic, especially on leaves. A few woody twig galls can weaken or kill small branches when they are heavy.
Do I need to spray for galls?
In most cases, no. The insect or mite lives inside the gall, so sprays rarely reach it. Ask your extension office before you spend money.
Can galls spread to my other trees?
They do not spread like a disease. The gall makers often stay with one kind of tree, so nearby trees of the same type may get them too.
Should I rake up the leaves?
Your extension office may suggest it for some gall types. It is a simple step that costs nothing, but it will not fix every case.
How do I know it is a gall and not a disease?
Photos help. If you are unsure, send them to your county extension office or ask a certified arborist to take a look.
Can Lirevon diagnose leaf and stem galls 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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- Drought Stress (Other damage)
- Frost cracks (Other damage)