Healthy, thriving trees add beauty, shade, and value to your property. But when pests move in, they can silently cause damage that weakens or even kills your trees over time. The problem? Many infestations start subtly, with signs that are easy to miss until the damage is severe.

Whether it’s termites hollowing out the trunk, borers chewing beneath the bark, or caterpillars devouring the leaves, early detection is your best defense. In this guide, we’ll cover seven early warning signs of pest infestations in trees — and the steps you can take to protect your landscape.

1. Chewed or Distorted Leaves

One of the most obvious red flags of a pest problem is leaf damage. This could look like holes in the leaves, jagged edges, or leaves that are curled, distorted, or discolored. Different pests cause different patterns:

• Caterpillars and beetles: Often chew irregular holes through leaves.
• Aphids and mites: Suck sap, causing leaves to curl or yellow.
• Leaf miners: Leave squiggly trails inside the leaf tissue.

Why it matters: Leaves are essential for photosynthesis — the process that keeps your tree fed and healthy. If pests strip too many leaves, the tree’s energy reserves drop, making it more vulnerable to disease, drought, and cold weather.

What to do next:

• Check the undersides of leaves for pests or eggs.
• Prune heavily infested branches to reduce spread.
• Call a certified arborist if leaf damage is widespread — they can identify the exact pest and recommend treatment.

2. Bark Damage or Holes

The bark is your tree’s first line of defense against pests and disease. When it’s damaged, it’s often a sign of insect activity beneath the surface. Look for:

• Small, round exit holes (a sign of boring insects like emerald ash borer or Asian longhorned beetle).
• Peeling or cracking bark.
• Sawdust-like frass (insect waste) at the base of the tree.

Why it matters: Bark-boring insects attack the inner layers of a tree, disrupting its ability to transport water and nutrients. Without intervention, this can kill the tree from the inside out.

What to do next:

• Avoid peeling back bark yourself — this can cause further harm.
• Schedule a professional inspection to determine the extent of the damage.
• Consider preventative treatments if you have other at-risk trees nearby.

3. Unusual Sap Flow or Oozing

While some trees naturally release sap, excessive oozing or sticky patches on the trunk can signal a pest problem.

• Borers: May trigger sap flow as the tree attempts to push them out.
• Scale insects: Produce sticky honeydew that can coat leaves, branches, and surrounding plants.

Why it matters: Sticky residue can attract ants and mold growth, creating additional problems beyond the initial infestation.

What to do next:

• Identify the source of the sap — is it from an injury or pest entry point?
• Remove and destroy any heavily infested branches.
• Hire a tree care professional to apply targeted treatments if pests are confirmed.

4. Thinning Canopy or Bare Branches

If parts of your tree’s canopy look sparse or bare compared to the rest, pests may be the culprit.

• Defoliating insects: Remove leaves directly.
• Sap-sucking insects: Drain nutrients, causing premature leaf drop.
• Bark borers: Interrupt nutrient flow to specific branches, leading to dieback.

Why it matters: A thinning canopy not only weakens the tree but also reduces shade, which can stress surrounding plants and change the microclimate of your yard.

What to do next:

• Track when the thinning occurs — sudden thinning in spring or summer is often pest-related.
• Don’t fertilize immediately; stressed trees can be more attractive to pests.
• Get an arborist assessment to identify whether pests, disease, or environmental stress is causing the problem.

5. Presence of Pests or Eggs

Sometimes, the most direct evidence of an infestation is spotting the pests themselves. Look closely at:

• The undersides of leaves.
• The joints where branches meet the trunk.
• Any cracks or crevices in bark.

You might see adult insects, larvae, egg masses, or cocoons. Common culprits in the Northern Virginia area include aphids, Japanese beetles, bagworms, tent caterpillars, and various borers.

Why it matters: The earlier you spot pests or eggs, the easier and more affordable it is to control them before they multiply.

What to do next:

• Take clear photos to help with identification.
• Remove egg masses by hand where possible.
• Avoid broad-spectrum insecticides unless directed by a professional — these can harm beneficial insects.

6. Wilting or Discolored Leaves Despite Adequate Water

If your tree’s leaves are wilting, yellowing, or browning despite regular watering and no signs of drought, pests could be to blame. Sap-feeding insects can block the flow of water within the tree, mimicking drought stress.

Why it matters: Wilting or discoloration often indicates that the infestation is already interfering with the tree’s vascular system — a serious threat to its survival.

What to do next:

• Rule out environmental factors like compacted soil or root damage first.
• Have a professional test for pest activity and diseases.
• Implement treatment quickly; the longer the infestation persists, the more damage is done.

7. Unusual Growths or Galls

Some pests cause trees to develop abnormal growths called galls. These can appear as bumps, knots, or swellings on leaves, twigs, or branches. While galls themselves don’t always harm the tree directly, they’re a clear sign that pests are feeding or laying eggs.

Why it matters: Galls can indicate an ongoing pest problem that may spread to other parts of the tree or to nearby plants.

What to do next:

• Prune out affected branches if possible.
• Keep the tree healthy with proper watering and mulching to reduce susceptibility.
• Consult an arborist to see if pest management is needed.

The Importance of Early Detection

Catching pest infestations early can make the difference between saving a tree and having to remove it entirely. Healthy trees are naturally better at resisting pests, so proactive care — like proper pruning, mulching, and watering — is just as important as treatment.

Professional vs. DIY Pest Control

While some minor pest problems can be managed by homeowners, many infestations require professional expertise. A certified arborist can:

• Identify the exact pest species.
• Determine the safest and most effective treatment.
• Apply treatments in a way that minimizes harm to beneficial insects and the environment.
• Monitor the tree’s recovery over time.

DIY sprays and treatments often only address the pests you can see, leaving hidden populations to continue causing damage.

How JL Tree Service Can Help

At JL Tree Service, we’ve been protecting trees in Northern Virginia, Maryland, and Washington, DC for nearly 50 years. Our team includes ISA-certified arborists trained to spot pest problems early and recommend the best solutions.

We offer:

• Comprehensive tree inspections to catch issues before they escalate.
• Targeted pest control treatments tailored to your tree species and infestation type.
• Preventive care programs to keep your trees healthy year-round.
• Safe removal services if a tree is too damaged to save.

Protect Your Trees — and Your Investment

Your trees are one of the most valuable features of your property, both aesthetically and financially. Don’t wait for pests to cause irreversible damage.

Call JL Tree Service today at 703-359-4444 for a free consultation or request an inspection online. We’ll help you safeguard your trees so they continue to thrive for years to come.