Tree problems · Insect
Two-lined chestnut borer: signs and what to do
Two-lined chestnut borer is an insect pest, often seen on red oaks, white oaks. Look for: leaves that wilt and turn brown in late summer while still on the tree.
General information, not a diagnosis. A certified arborist or your county extension office can confirm.
- Insect
- Red oaks (such as northern red, scarlet, black, pin)
- White oaks (such as white, chestnut, bur)
- Other oaks that are stressed
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
Adults come out in spring or early summer. The larvae feed under the bark during the growing season and spend the winter inside the tree. Damage usually shows in late summer.
How it spreads
This is a native beetle that is already in the woods. It mostly attacks oaks that are weak from drought, root damage or heavy loss of leaves, rather than moving in from far away.
Where it is found
The twolined chestnut borer is a native insect of oaks in the eastern United States. Check your state official map and your extension office for what is happening near you.
Official sources
What to do
- 1
Look at the oak's crown, bark and base. Take clear photos of any exit holes and of the thin or browning branches.
- 2
Think about what stressed the tree: a dry summer, heavy leaf loss from insects, root damage or soil changes.
- 3
Water the tree deeply during dry spells and keep a ring of mulch around it, not touching the trunk.
- 4
Do not fertilize a stressed oak unless a soil test shows a need.
- 5
Ask a certified arborist or your county extension office to confirm the cause. Dieback on oaks can also come from other problems, including oak wilt.
- 6
Plan removal early if the tree is mostly dead and stands near a house, driveway or play area.
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
Healthy oaks resist this beetle well. Water in long dry periods, mulch, and protect roots and trunks from mowers, trenching and building work. Choose oak species that suit your site when you plant. If leaf-eating insects strip your oaks, ask your extension office how to manage them, because repeated leaf loss makes oaks easier to attack.
When to call a pro
Call a certified arborist if an oak has dying branches, a thinning crown or exit holes in the bark, especially if it stands near a building or line. Dead oak limbs can drop without warning, so removal near targets is work for 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: Red oaks (such as northern red, scarlet, black, pin), White oaks (such as white, chestnut, bur), Other oaks that are stressed.
- White Oak
- Northern Red Oak
- Scarlet Oak
- Chestnut Oak
- Black Oak
- Pin Oak
- Bur Oak
- Post Oak
- Southern Red Oak
- Shumard Oak
See all species in our tree library, or pick a tougher tree with the tree picker.
For tree companies
How to explain two-lined chestnut borer to a customer
Be clear that this beetle usually follows stress, so the beetle is often a symptom and not the first cause. Explain what you see, say that other problems such as oak wilt can look similar, and suggest confirmation when the cause is not clear. Give the owner simple options: improve care, watch, or remove. Avoid fear and always give a written quote.
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 the two-lined chestnut borer?
It is a small native beetle whose larvae tunnel under the bark of oaks. The tunnels cut off the flow of water and food, and branches die back.
Does it attack healthy oaks?
Mostly no. It tends to go after oaks that are already stressed by drought, root damage or repeated loss of leaves. Good care is the best protection.
How can I tell it from oak wilt?
They can look alike, because both cause browning leaves and dieback. Exit holes and tunnels under the bark point to the borer, but only a pro or a lab can be sure. Ask your extension office or a certified arborist.
Can an infested oak be saved?
Sometimes, if it is caught early and the cause of the stress is fixed. Trees that have lost most of their crown usually do not recover. A certified arborist can judge your tree.
Should I spray or inject my oak?
Ask a certified arborist or your extension office first. Treatment is not right for every tree, and it works best on trees that are still mostly healthy.
Is a dead oak dangerous?
It can be. Dead oak wood can become brittle and limbs may fall without warning. Keep people and vehicles away and have a qualified pro look at any dead oak near a building or road.
Can I use the firewood from a borer-killed oak?
Burning wood close to where it was cut is safest. Check your state rules before moving firewood, and ask your extension office if you are not sure.
Can Lirevon diagnose two-lined chestnut borer 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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