What Is Eating My Tree Trunk

Finding marks or holes on your tree trunk is the first clue in identifying the animal or insect responsible. If you’re wondering what is eating my tree trunk, you’re in the right place. This guide will help you become a tree detective, matching the damage you see to the likely culprit.

Tree trunk damage can range from superficial scratches to deep, girdling wounds that threaten the tree’s life. The type of mark, its height on the trunk, the time of year, and even your location all provide vital clues. Correct identification is the essential first step before taking any action.

Let’s examine the common suspects, from tiny insects to large mammals, and outline the specific signs they leave behind.

This section breaks down the primary categories of pests that target tree trunks. We’ll start with insects, which are often the most destructive, before moving on to larger animals.

Insect Pests Boring Into Wood

Many insects spend part or all of their life cycle inside tree trunks, feeding on the inner bark (cambium) or the wood itself. Their damage is often hidden until it becomes severe.

Bark Beetles

Bark beetles are among the most significant tree killers. These tiny insects bore through the outer bark to create galleries in the cambium layer, where they lay eggs. The larvae then feed, disrupting the tree’s nutrient flow.

Signs: Small, round entry/exit holes (about the size of a pencil lead). Sawdust-like frass (bore dust) in bark crevices or at the tree base. Patches of fading or yellowing foliage (often starting at the top). Sometimes, pitch tubes (globules of sap) around holes as the tree tries to defend itself.
Common Types: Mountain pine beetle, Ips engraver beetle, Southern pine beetle, Emerald ash borer (a type of borer, but similar damage).

Clearwing Moths and Wood-Boring Beetle Larvae

The larvae of moths and beetles, like the peachtree borer or flatheaded borers, tunnel into the trunk and larger branches.

Signs: Larger, oval or D-shaped exit holes. Coarse frass pushed out of holes. Weeping sap or gumming on the trunk. Dieback of branches above the infestation.
Important Note: The adult insects do not eat the wood; it’s the growing larvae inside that cause the damage.

Carpenter Ants and Termites

These insects excavate wood, but for different reasons. Carpenter ants do not eat wood; they remove it to create nesting galleries. Termites actually consume wood for nutrition.

Carpenter Ant Signs: Sawdust-like shavings (frass) containing insect parts near the base. Rustling sounds from the trunk. They prefer moist, decaying wood but will tunnel into sound wood.
Termite Signs: Mud tubes on the trunk surface connecting the ground to the wood. Hollow-sounding wood when tapped. They often consume wood from the inside out, leaving a thin veneer.

Animal Pests That Gnaw And Strip

Mammals cause more visible, external damage. The size of the tooth marks and the height of the damage are key identifiers.

Rodents: Voles, Mice, and Porcupines

Rodents gnaw on bark, especially in winter when other food is scarce.

Voles/Mice: Gnaw marks near the base of the trunk, usually no more than a few inches up. They remove thin strips of bark, often completely girdling the tree underground or under snow cover. The damage is typically at or below the snow line.
Porcupines: Leave large, chisel-like tooth marks and can strip large sections of bark high up in a tree. They often return to the same tree repeatedly.

Rabbits and Hares

Similar to voles but typically a bit higher off the ground. Rabbits can remove bark in patches up to about two feet high, depending on snow depth. The tooth marks are smaller than a porcupine’s but larger than a vole’s.

Deer, Elk, and Moose

These animals “rub” their antlers on tree trunks to remove velvet or mark territory, not to eat the wood. However, this behavior can severely damage or kill young trees.

Signs: Vertical scrapes and shredded bark on the trunk, usually 1-4 feet off the ground. The underlying wood will be exposed and may show parallel scrape marks.

Squirrels

Squirrels typically don’t eat trunk bark but may strip it for nesting material. They also chew on branches. Look for irregular patches of missing bark higher in the tree, not usually at the base.

Other Causes Of Trunk Damage

Not all trunk wounds are from pests. It’s important to rule out these other factors.

Mechanical Damage: Lawn mowers, string trimmers, and vehicles can gouge bark.
Weather and Sunscald: Frost cracks or sunscald can split bark, which may later attract insects.
Birds: Woodpeckers and sapsuckers create rows of small holes. Woodpeckers are often hunting for insects inside, indicating a secondary problem.

How To Diagnose The Damage On Your Tree

Follow these steps to systematically identify the culprit damaging your tree.

Examine the Height and Location: Is the damage at the base (voles), mid-trunk (deer rub), or high up (porcupine, squirrels)? Is it on one side or all around?
Inspect the Type of Marking: Are they small holes (insects), gnaw marks (rodents), or scrapes (deer)? Measure the size of holes or tooth marks.
Look for Secondary Evidence: Search for frass, sap, mud tubes, or tracks in soft soil around the base. Use a flashlight to look closely at bark crevices.
Consider the Tree Species and Health: Some pests target specific trees (e.g., emerald ash borer only attacks ash). Stressed trees are more vulnerable to insect attacks.
Note the Time of Year: Deer rub in fall. Rodent damage is most apparent in spring after snow melt. Many insects are active in warm months.

Immediate Actions To Protect Your Tree

Once you’ve identified the likely pest, you can take targeted steps to mitigate the damage and prevent further attack.

For Insect Borers

Confirm Active Infestation: If holes are old and you see no fresh frass, the insects may be gone. Scrape bark lightly near a hole; if it’s sticky or you see live larvae, it’s active.
Cultural Controls: Keep your tree healthy with proper watering (deep, infrequent watering) and mulching. Avoid injury to the trunk. Remove and destroy severely infested trees to protect nearby ones.
Insecticide Options: For some borers like emerald ash borer, professional trunk-injected systemic insecticides can be effective. Contact sprays are rarely useful once insects are inside the wood. Always consult an arborist for diagnosis and treatment options.

For Gnawing Animals

Physical Barriers: This is the most effective method. Install hardware cloth or plastic tree guards around the base of young trees. Ensure guards are buried an inch or two in the soil and extend high enough above the expected snow line.
Repellents: Taste or odor repellents can deter rabbits and deer, but they require frequent reapplication, especially after rain.
Habitat Modification: Remove brush piles and tall grass near trees to reduce vole and mouse habitat. Fencing is the only reliable long-term solution for deer in areas with high populations.

Wound Care and Tree Repair

Trees do not “heal” like humans; they compartmentalize wounds. Your goal is to support this natural process.

Clean the Wound: Gently remove any loose, shredded bark around the edges with a sharp, sterilized knife. Cut in an oval shape, but do not cut into healthy bark or enlarge the wound unnecessarily.
Do Not Apply Sealants: Modern arboriculture advises against using tar, paint, or wound dressings. They can trap moisture and promote decay. Let the tree form its own callus.
Monitor and Support: Ensure the tree recieves adequate water during dry periods. Watch for signs of stress like wilting or early fall color. A tree with significant girdling damage (bark removed all around the trunk) may need to be removed, as it cannot transport nutrients.

When To Call A Professional Arborist

Some situations require expert assessment and intervention. Consider calling a certified arborist if:

The tree is large and the damage is extensive or in the upper canopy.
You suspect a major insect infestation like bark beetles or emerald ash borer.
The main trunk is girdled (more than 50% around).
The tree is showing significant dieback, yellowing leaves, or other signs of severe stress.
You are unsure of the cause or the best treatment method.

A professional can provide accurate diagnosis, safe treatment options, and advise on whether the tree can be saved or should be removed for safety.

Preventative Measures For Long-Term Tree Health

Prevention is always easier than cure when it comes to tree trunk pests.

Promote Overall Tree Vigor

Proper Planting: Plant trees at the correct depth and in a suitable location for their species.
Mulching: Apply a 2-4 inch layer of organic mulch (like wood chips) in a wide ring around the tree, keeping it a few inches away from the trunk itself. This retains moisture, regulates soil temperature, and prevents lawnmower damage.
Watering: Water deeply during prolonged droughts, especially for young trees.
Pruning: Prune correctly during the dormant season to remove dead or diseased wood and improve air circulation.

Proactive Pest Deterrence

Install tree guards in the fall before winter rodent feeding begins.
Apply repellents before animals establish a feeding pattern.
Remove attractants like fallen fruit or dense ground cover near valuable trees.
Inspect your trees regularly, at least once a season, for early signs of trouble.

Frequently Asked Questions (FAQ)

What Animal Is Eating The Bark Off My Tree Trunk?

This depends on the height and pattern. Near the base, it’s likely voles, mice, or rabbits. Higher up, consider squirrels or porcupines. Large, shredded patches 1-4 feet high are typical of deer or elk rubbing their antlers.

How Do I Stop Animals From Eating My Tree Bark?

Physical barriers like hardware cloth tree guards are the most reliable method for small rodents. For larger animals like deer, fencing or commercial repellents may be necessary. Removing shelter and food sources around the tree also helps.

Can A Tree Recover From Bark Being Eaten?

Yes, if the damage is not too severe. If the cambium layer (the green, moist layer under the bark) is intact and the tree is not girdled, it can recover. The tree will slowly grow new bark over the wound. If the cambium is destroyed all the way around the trunk (girdling), recovery is unlikely.

What Insects Bore Holes In Tree Trunks?

Many insects do, including bark beetles, clearwing moth larvae (like peach tree borers), longhorned beetle larvae, and emerald ash borer larvae. The size and shape of the hole, along with the type of frass, help identify the specific insect.

Should I Plug Holes In My Tree Trunk?

No, you should not plug holes with cement, epoxy, or any other material. This can trap moisture and decay organisms inside, making the problem worse. Focus on treating the underlying pest issue and supporting the tree’s health so it can compartmentalize the damage itself.