Tree Borers: A Homeowner's Guide to Early Detection and Control

Healthy, thriving trees are a valuable part of any landscape. But tree borers, small yet destructive insects, can weaken a tree from the inside out. Learning to identify and manage these pests is crucial for keeping your trees strong and resilient.

What Are Tree Borers?

Tree borers come in many shapes, sizes, and colors, but they all share one thing—they cause serious damage to trees. These insects invade trees by laying eggs on or inside the bark. Once the larvae hatch, they feed on the tree's living tissues, cutting off its water and nutrient supply, leading to dying branches and, in severe cases, tree death.

Factors That Attract Tree Borers

Stress factors such as drought, compacted soil, sun damage, or physical injuries make trees more vulnerable to infestations. Adult borers are drawn to the chemical signals released by weakened trees.

The Life Cycle of Tree Borers

Understanding a borer's life cycle is key to knowing how they operate. While timing varies by species and climate, all borers go through four stages:

• Egg - Adult borers lay eggs on or just beneath the bark, often in cracks or wounds. These eggs hatch within days or weeks.
• Larva - The most destructive stage. Larvae tunnel into the wood, feeding on inner layers and disrupting the tree's ability to transport water and nutrients.
• Pupa - After feeding for months or even years, larvae enter the pupal stage inside the tree or in the soil.
• Adult - Emerging adult beetles or moths leave behind distinct exit holes, mate, and restart the cycle by finding new host trees.

Fact: It can take up to five years for larvae to mature into adult beetles and exit the tree.

What are Borers?

Borer beetles are part of the Anobiidae (order Coleoptera) family. These adult pests are known for burrowing into trees and laying eggs inside the trees. These adult borers find sites for laying eggs by responding to chemicals and signals from stressed trees. Once the larva hatches then they feed on the inside of the tree and create tunnels. This causes additional stress to an already declining tree and can lead to a quicker death if not treated quickly. The tunnel can cut off portions of the vascular system of the tree and deprive it from sending nutrients up the tree.

Common Tree Borers in North Texas

Among the most common types of tree borers in North Texas are clearwing and flatheaded borers. Understanding which borers are prevalent in your area can help you take timely action.

Some of the most dangerous tree borers include:

• Iberia haldemoni

  

• Parelaphidion aspersum

  

• Emerald Ash Borer

Tree Inspection: How to Identify an Infestation

While symptoms vary by species, one of the clearest signs of an infestation is the presence of small, round holes on tree trunks and branches. Other signs include:

• Frass - A fine, sawdust-like material near entry points.
• Leaking sap - A sign of the tree's defense mechanism.
• Discolored foliage - Leaves turning yellow or brown prematurely.
• Weak branches - Limbs that break easily or have cracked bark.

Tip: Woodpecker holes tend to be in a straight row, while borer holes appear randomly spread out.

How to Monitor and Inspect Your Trees for Borers

Borer beetles are most easily identified by the round, oval or D shaped holes that they burrow in the tree trunks. Also keep an eye out for large holes that are leaking sap like the below pictures. You might also see sawdust like material on the ground or in the cracks of the bark.

Some people do misidentify borer holes for woodpecker holes. Just know that woodpeckers also carve a series of holes together, while the borers burrow just one hole in an area. If you have several borer beetles then you could see several holes randomly placed around your tree trunk, but never in a row like the woodpeckers holes.

Preventing Tree Borer Attacks

The best defense against tree borers is prevention. Here are some proactive steps to reduce infestation risk:

• Keep trees healthy - Borers prefer stressed trees. Regular watering, proper fertilization, and care for young trees strengthen their defenses.
• Protect trees from injury - Avoid damaging bark with mowers or pruning tools, as wounds attract borers.
• Remove affected trees and limbs - If a tree is heavily infested, removing it can prevent spread to nearby healthy trees.

How to Treat a Borer Infestation

When to Use Insecticides

For trees with minimal signs of infestation, targeted treatments must be applied multiple times during spring and summer while larvae are actively feeding.

Best Treatment Options

• Once borer beetles have tunneled inside a tree, traditional insecticide sprays are no longer effective. To control them, treatments must be applied in spring or summer while the larvae are actively feeding, this ensures the insecticide is ingested.
• Effective options include systemic insecticides applied through trunk injections (such as azadirachtin, emamectin benzoate, or imidacloprid), as well as bark sprays and soil drenches (like dinotefuran and imidacloprid).
• For flatheaded borers specifically, we often recommend Bayer Advanced 12 Month Tree & Shrub Protect & Feed, a soil drench with imidacloprid as the active ingredient. Multiple treatments are usually necessary, and it’s very important to carefully read and follow all product label directions to ensure safe and effective use.
• If applying treatments feels overwhelming, consider hiring a certified local arborist who can handle the process for you and make sure your trees get the best possible care.

Our favorite product to recommend for flatheaded borers is Bayer Advanced 12 Month Tree & Shrub Protect & Feed. It is a soil drench and the active ingredient is imidacloprid. You will need to treat your trees a couple times, and please make sure to always read and follow label directions for safe use of any pesticides. If you feel overwhelmed with applying these treatments yourself then you can always hire a local arborist to help you.

Final Thoughts

Checking your trees regularly for borer activity is the easiest way to catch an infestation early. Prevention and early treatment are key to keeping your trees healthy and your yard looking its best.

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Pesticide Safety Notice

Always read and follow label instructions when using pesticides. Store them in original containers and keep them out of reach of children. If unsure, consult a local arborist for professional advice.