What Is Eating My Tree Trunk

If you’ve noticed holes, scrapes, or missing bark on your tree, you’re likely wondering what is eating my tree trunk. This kind of damage can be alarming, but identifying the culprit is the first step to protecting your tree. Let’s look at the common causes, from insects to animals, and figure out what you can do about it.

Trunk damage falls into a few main categories. The pattern of the injury—like the size of holes, the height on the tree, and the presence of sawdust—acts like a clue. By learning to read these signs, you can narrow down the list of suspects quickly.

Common Insect Borers

Many insects tunnel into tree trunks to lay eggs or feed. These are called borers, and they leave telltale signs.

Round or Oval Holes: Perfectly round, small holes (like drilled by a tiny bit) often indicate beetles. Ragged or oval-shaped holes might be from moths or clearwing borers.
Frass: This is a fancy word for insect poop and sawdust. It’s a major clue. Fine, powdery frass suggests powderpost beetles. Coarse, gritty frass points to carpenterworms. Bark beetles pack their frass into winding galleries under the bark.
Sap or Gumming: Trees sometimes try to push out borers by oozing sap, creating sticky patches on the trunk.

Identifying Specific Borers

Bark Beetles: These are tiny but deadly. They create intricate, branching patterns (galleries) just under the bark. Look for very small holes, sawdust in bark crevices, and fading foliage in the crown. Pine and spruce trees are common targets.

Clearwing Moths (like Peach Tree Borers): They mimic wasps. Their larvae create tunnels packed with coarse frass, often near the base of the tree or in branch crotches. You might see a gummy substance mixed with the frass.

Flatheaded Borers (Metallic Wood Borers): Their holes are D-shaped. The larvae make wide, flat tunnels that can girdle branches or trunks, causing dieback.

Animal Culprits

Insects aren’t the only ones. Mammals and birds can also cause significant trunk harm.

Rodents: Voles and Mice

These small rodents gnaw on bark, especially in winter when other food is scarce. Damage is typically near the ground, often completely encircling the trunk (girdling), which can kill the tree. Look for tooth marks and missing bark in a band up to a few inches high.

Rabbits

Rabbit damage is similar but higher—usually from the ground up to about two feet. The gnaw marks are larger than vole marks. In snowy winters, the damage height can show you how deep the snow was!

Deer

Male deer (bucks) rub their antlers on tree trunks to remove velvet and mark territory. This creates large, vertical scrapes where the bark is shredded. This usually happens in the fall and can severely damage or kill young trees.

Woodpeckers and Sapsuckers

These birds are often a sign of another problem. Woodpeckers drill for insects already inside the tree. Their holes are deep and irregular. Sapsuckers, a type of woodpecker, drill neat rows of small holes to drink sap, which can weaken the tree over time if the rows are extensive.

Environmental and Mechanical Damage

Not all trunk wounds come from living creatures. Sometimes, the environment or our own actions are to blame.

Sunscald: On cold, sunny winter days, the south-facing side of a thin-barked tree (like maple or cherry) can warm up and then freeze rapidly at night, killing the bark tissue. This creates long, vertical cracks or sunken areas.
Lawn Equipment: String trimmers and lawn mowers hitting the trunk cause “lawnmower blight.” It removes bark in patches at the base, opening the tree to disease and borers.
Storms: Lightning strikes can strip bark in a spiral pattern. Strong winds can cause branches to tear away, creating large wounds.

How to Diagnose the Damage

Follow these steps to play tree detective.

Examine the Pattern: Is the damage high or low? Are holes round or ragged? Is bark stripped or scraped?
Look for Frass or Debris: Check the ground and bark crevices for sawdust, insect casings, or bits of chewed bark.
Check the Season: Animal damage is most common in fall and winter. Insect activity is usually visible in late spring and summer.
Assess Tree Health: Are the leaves wilting or turning color prematurely? Is there dieback in the upper branches? This can indicate a serious pest problem beneath the bark.
Consider the Tree Type: Some pests target specific trees. Knowing your tree species helps alot.

Treatment and Prevention Strategies

Once you know the cause, you can take action. The goal is to help the tree heal and prevent future attacks.

For Insect Borers

Promote Tree Health: A stressed tree is a target. Water during droughts, mulch properly (not against the trunk!), and avoid root damage. Healthy trees can often fend off borers on their own.
Remove Heavily Infested Wood: If a branch is dead and full of holes, prune it off in the dormant season. Burn or chip the wood to kill any remaining larvae.
Insecticides: These are usually a last resort and timing is critical. Contact insecticides applied to the trunk may kill adults. Systemic treatments applied to the soil can help for some borers, but consult an arborist for the correct product and application.

For Animal Damage

Physical Barriers: This is the most effective method. Use hardware cloth or plastic tree guards to protect the lower trunk from rodents and rabbits. Install them in fall and remove in spring to avoid moisture buildup.
Fencing: For deer, a sturdy fence around the tree or your property is often necessary. Repellents can work but need frequent reapplication, especially after rain.
Wound Care: For fresh scrapes, carefully trim any loose bark back to where it’s firmly attached. Do not apply paint or tar. Let the tree form its own callus to seal the wound.

For Environmental Damage

Use a white tree wrap in fall to reflect winter sun and prevent sunscald on young trees. Remember to remove it in spring.
Create a mulch ring around the tree base to eliminate the need for trimming grass right next to the trunk.
Prune properly to prevent storm damage, making clean cuts just outside the branch collar.

When to Call a Professional Arborist

Some situations are to serious to handle alone. Call a certified arborist if:

The damage has girdled more than 50% of the trunk’s circumference.
The tree is large, and the damage is high up or poses a safety risk.
You cannot identify the pest and the tree continues to decline.
There are signs of a major infestation, like numerous holes and extensive dieback.

An arborist has the tools and knowledge to provide an accurate diagnosis and recommend safe, effective treatments. They can also help with cabling or bracing if the tree’s structure is compromised.

FAQ: Common Questions About Trunk Damage

Can a tree recover from bark being eaten?

Yes, if the damage isn’t too severe. If the thin layer beneath the bark (the cambium) is intact all the way around, the tree can heal. If the bark is removed in a complete ring (girdling), recovery is unlikely, especially for young trees.

What makes holes in a tree trunk?

Holes are typically made by wood-boring insects like beetles or moths, or by birds like woodpeckers and sapsuckers. The size and shape of the hole helps identify which one.

How do I stop animals from eating my tree bark?

Physical barriers are best. Install tree guards made of hardware cloth around the base to stop rodents. For deer, you may need taller fencing or commercial repellents applied regularly.

Are woodpeckers harming my tree?

Often, woodpeckers are feeding on insects that are already harming the tree. While their holes can create entry points for disease, they are usually a symptom, not the primary cause. Sapsucker damage, however, can be harmful if it’s extensive.

Should I fill tree trunk holes?

No. Old advice suggested filling holes with cement or foam, but this traps moisture and promotes decay. It’s better to let the tree compartmentalize the wound. If water collects in a large cavity, you can gently drill a small downward-sloping hole at the bottom to allow drainage.

Finding damage on your tree trunk can be worrying, but careful observation will usually reveal the cause. By providing consistent care and using protective measures when needed, you can give your tree the best chance to stay healthy and continue thriving in your landscape for years to come.