How To Get Rid Of Tree Borers

Recognizing the Enemy: Signs of Tree Borer Infestation

If you suspect tree borers, the first step is to know what to look for. Borers are a broad group of insects whose larvae tunnel into wood or under bark, starving the tree of nutrients and weakening its structure. Early detection makes control realistic; wait too long and the damage is often irreversible.

Look for these telltale signs:

• Small holes in the trunk or branches — shapes vary by species, but round, oval, and D-shaped holes are common.
• Frass — sawdust-like material or fine wood powder at the base of the trunk or around exit holes.
• Galleries — winding, S-shaped tunnels beneath the bark if you peel a small area back.
• Dieback of branches, thinning crown, or epicormic shoots (sprouts from the trunk).
• Wet, gummy sap oozing from wounds or holes on the trunk.

Common types of borers you might meet

• Flatheaded borers — often attack stressed or recently transplanted trees; signs include flattened, oval exit holes and under-bark galleries.
• Roundheaded borers — larger, often leave round holes and can kill branches or the entire tree.
• Bark beetles — smaller, attack stressed trees and often carry fungal pathogens.
• Emerald ash borer — a notorious invasive pest with D-shaped exit holes and S-shaped larval galleries; devastating to ash trees.

Knowing which borer you’re dealing with matters because timing and treatment differ by species.

Step-by-step Plan to Get Rid of Tree Borers

Here’s a practical, gardener-friendly game plan that I use when a tree starts showing borer trouble. Follow these steps in order for the best chance of saving the tree.

Inspect and confirm

• Walk your property and inspect trees up close. Use a flashlight and magnifying glass for small holes and frass.
• If you’re unsure, take clear photos of holes and galleries and contact your county extension office or a certified arborist for identification.

Cultural and mechanical control

Start with the least toxic methods. Healthy trees are the best defense against borers.

• Prune out and destroy heavily infested branches. Cut well below the damage and burn or chip the wood — do not leave it near healthy trees.
• Remove dead or dying trees promptly to reduce the local borer population.
• Avoid injuring trunks with lawnmowers or string trimmers; wounds invite borers.
• Maintain good watering and mulching practices to reduce tree stress. Stressed trees are favorite targets.

Chemical and professional options

When infestation is active or the species is aggressive (like emerald ash borer), chemical measures can be effective if used correctly.

• Systemic insecticides — products containing imidacloprid, dinotefuran, or emamectin benzoate are commonly used. Applied as soil drenches, trunk injections, or bark sprays, these move through the sap and kill feeding larvae. Timing is critical: treat in spring or early summer before larvae cause too much damage.
• Trunk sprays — contact insecticides can reduce adult beetles or newly hatched larvae, but they must be timed to adult flight periods.
• Professional injections — for valuable trees, hire a licensed arborist to administer trunk injections (emamectin treatments are often done this way). These last longer and reduce non-target exposure.
• Follow all label directions, wear protective gear, and consider hiring professionals for injections or large trees.

Important: chemical controls are species- and timing-specific. Consult local experts or extension services for the best product choices in your area.

Biological and organic approaches

If you prefer low-toxicity methods, there are options that can reduce borer populations over time.

• Predators and parasitoids — in some cases, native parasitic wasps and beetles will attack borer larvae. Encourage beneficial insects by providing diverse plantings and avoiding broad-spectrum insecticides.
• Entomopathogenic nematodes — these microscopic worms can be applied into bark crevices or drilled holes to seek out larvae. They work best on certain species and under the right moisture and temperature conditions.
• Sticky or pheromone traps — useful for monitoring adult flight and timing treatments; traps alone rarely control outbreaks but tell you when to act.

Monitoring and Timing: The Secret to Success

Most chemical and biological treatments rely on precise timing. Knowing the life cycle of your borer is crucial.

• Monitor for adult flight with traps or by watching when exit holes appear.
• Treat soil or inject in spring when trees are actively transporting sap and before egg hatch or larval feeding peaks.
• Reapply according to label instructions — some systemic treatments protect for one season, others for multiple years.

Repeat inspections throughout the growing season. Early detection and timely treatment are the difference between control and tree loss.

Prevention and Long-Term Tree Health

Keeping trees vigorous is the best long-term protection against borers.

• Plant the right tree in the right place — species suited to your soil and climate are less stressed and less attractive to borers.
• Water during dry spells, especially young or newly planted trees.
• Fertilize only when needed; overfertilization can make trees more attractive to some pests.
• Practice proper pruning, wound care, and sanitation to minimize entry points and breeding sites.

When to Call an Arborist

Some situations require a pro:

• Large trees with active infestation or structural weakening.
• Confident identification and treatment recommendations are needed (example: emerald ash borer management).
• When trunk injections or commercial-grade pesticides are being considered.

A certified arborist brings diagnostic tools, safe application methods, and experience choosing the right treatment schedule.

Final Thoughts and Personal Experience

“I remember the spring my neighbor’s pear tree started dropping branches. The tiny holes and sawdust told me borers were at work. We pruned out the worst branches, treated the root zone with an approved systemic in early April, and kept the tree watered that season. It wasn’t easy, but the tree recovered its vigor the next year.”

From my own yard and from helping neighbors, I’ve learned that patience, vigilance, and a combination of cultural care and targeted treatments save the most trees. If you catch borers early, clean up the damage, improve tree health, and use properly timed treatments — chemical or biological — you can halt many infestations. When in doubt, reach out to your local extension or a trusted arborist. Trees are worth the extra care.

Ready to protect your trees? Start by walking your property this weekend, look for frass or exit holes, and plan your next steps based on what you find.