Are all insects on trees a problem?
No. Most insects are part of normal woodland life, and many are food for birds or help other plants. Trees tolerate a fair amount of leaf loss, especially in early summer. Problems arise when damage is heavy, repeated year after year, or when the insect attacks the trunk or the wood. A beginner is often most alarmed by caterpillar outbreaks, which can strip a tree for a few weeks. Healthy broadleaf trees usually recover and leaf out again, though repeated years of loss wear them down.
Before reacting, note what the insect is doing and where. Chewing on leaves, boring into wood, sucking sap and forming galls are different kinds of damage with different consequences.
Weather and the season change what you see, too. A leaf feeder that looks alarming in early summer may be finished by midsummer, and trees often grow a second set of leaves. Watching over time tells you more than a single glance.
What kinds of damage should I look for?
Leaf chewers leave holes or skeletonized leaves. Sap feeders may leave sticky residue or cause curling. Borers leave small holes in bark, sawdust-like material called frass, or winding tunnels under the bark. Gall makers cause odd growths on leaves or twigs. Photograph the damage from a few feet away and again from a distance so an expert can see the scale and where it sits on the tree.
Borers and bark beetles deserve the most attention because they can kill trees. Dying branches, woodpecker activity and exit holes in the bark are common clues.
Keep a note of which species of tree is affected. Many pests have favorite hosts, and that detail narrows the possibilities a lot for an expert looking at your photos.
- Round or oval exit holes in bark
- Sawdust or frass at the base or in crevices
- Thinning crowns and dead branches
- Large numbers of insects or webbing
How do I identify an insect?
Take clear, close-up photos of the insect and of the damage, and note the date and the tree species. If you can collect a specimen safely, place it in a sealed container following your extension office's instructions. Several state and university sites let you submit images for identification, and your county office can show you how.
Look up your region's extension or state agency resources, which often include photo guides. Do not rely on a single image from an internet search, since many insects look alike.
What are invasive pests and why do they matter?
Invasive pests are species that arrived from other regions and have few natural enemies. Some have killed large numbers of trees in the regions they reached. Because they spread quickly, early reporting helps. Learn the names of the invasive pests your state is watching for. Many state agencies publish a short list with pictures, and a quick look now could help you recognize one later.
State departments of agriculture and forestry agencies track these pests. If you see unusual damage or an insect you do not recognize, contact them promptly. Reporting is free and helps your neighbors.
Should I spray or treat?
Often not. Many pests are controlled naturally, and sprays can harm helpful insects. Some serious pests do have recommended treatments, usually timed carefully, and sometimes professionals apply them.
Always follow the label and state rules, and ask your extension office whether treatment is warranted. Never mix or apply products on a guess.
Healthy trees are the best defense. Water in drought, avoid wounding trunks and avoid piling soil on roots, because stressed trees draw many borers that healthy ones can resist.
How does moving firewood spread pests?
Pests can hide in logs and firewood for a long time. Moving wood from one area to another is a known way for them to travel far beyond where they would naturally spread. Fire pits, campgrounds and neighbors are places where firewood often changes hands, so it pays to ask where wood came from before you accept it.
Buy or cut firewood near where you will burn it, and ask your state agency about local rules. Rules vary and some areas have quarantines.
Where do I report or learn more?
County extension offices, state forestry agencies and state departments of agriculture can help identify pests and take reports. The U.S. Forest Service also provides information on forest health. Do not move an insect specimen across state lines, since that could spread the very pest you are worried about; ask the agency for guidance on how to send images or samples instead.
Keep your photos and notes. They are useful to experts and help you track changes over time.
A short log of when you saw damage, what weather came before it and what you did about it helps both you and any expert who visits. Include dates, photos, the species of tree and the position on the tree where you saw the problem. If you cut down an affected tree, take a photograph of the cut stump and any tunnels under the bark. That evidence can show whether borers were the cause, which helps neighbors and agencies understand what is moving through your area.
- Date of each observation
- Photos of insect, damage and whole tree
- Tree species and location on the farm
- Any treatments tried and results
Key takeaways
- Most leaf chewing does little lasting harm
- Borer damage and bark beetles deserve prompt expert attention
- Report unusual insects to your state agency
- Do not move firewood long distances
- Keep dated photos and notes to share with an expert
Sources and further reading
Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.