How to Get Rid of Emerald Ash Borer: Treatment, Removal, and Prevention

You probably didn’t notice the problem right away. Maybe the upper branches looked a little thin this spring, or a section of the canopy never quite leafed out. By the time most homeowners identify the emerald ash borer, the infestation has been quietly progressing for a year or more.

Emerald ash borers (Agrilus planipennis) have killed hundreds of millions of ash trees across North America since arriving in the United States in the early 2000s, and the pest does most of its damage out of sight, beneath the bark.

If you’re trying to figure out how to get rid of emerald ash borer on your property, this guide covers how to identify them, what treatment options are available, and what’s at stake if you wait.

A Plus Tree provides emerald ash borer treatments throughout California, Oregon, and Washington for homeowners and property managers dealing with active infestations.

What to Do First If You Suspect Emerald Ash Borer

If something looks off with your ash tree, the most primary question is: can it still be saved?

Trees that have lost 50 percent or less of their canopy are generally still candidates for treatment. Once decline crosses that threshold, the structural integrity of the tree becomes a concern on top of the health question, and removal is usually the more practical path. Over-the-counter products exist for at-home treatment, but they’re inconsistent and rarely effective for mature trees. If you have significant emerald ash borer damage on your trees, it’s best to consult with an arborist before spending on products that may not move the needle.

Signs of an Emerald Ash Borer Infestation

The EAB spends most of its life cycle beneath the bark, which is exactly why infestations are so easy to miss. However, the earlier you catch them, the more options you have.

D-Shaped Exit Holes

When adult beetles emerge in late spring, they leave behind small exit holes in the bark roughly ⅛ inch in diameter with a distinctly flat edge on one side. That D-shape is an indicator of EAB — other boring insects leave round holes.

Canopy Thinning and Dieback

Because EAB larvae feed in tunnels just below the bark, they restrict the tree’s ability to move water and nutrients between the roots and the canopy. The result is dieback that typically starts at the top of the tree and works downward, with leaves that yellow, brown, or simply don’t emerge in spring. By the time the upper canopy is visibly dead, the infestation has usually been active for at least a full season.

Bark Splitting and S-Shaped Galleries

Larval tunneling creates pressure beneath the bark, which eventually causes it to crack and split. Peel back a piece of damaged bark and you’ll find the serpentine S-shaped galleries the larvae carve, packed with frass, a mix of sawdust and larval excrement. Finding these galleries confirms active EAB feeding and indicates that the infestation has been there long enough for larvae to do significant damage.

Increased Woodpecker Activity

Woodpeckers are remarkably good at detecting beetle larvae beneath bark, and they’ll return to the same tree repeatedly once they’ve identified it as a food source. If you’re seeing consistent woodpecker activity on an ash tree, it’s worth checking for other signs of EAB.

Can a Tree Recover From Emerald Ash Borer?

Whether or not a tree can recover from EAB depends on how far the infestation has progressed. Additionally, consistent and long-term treatment is often necessary to successfully treat EAB. Managing an infestation means suppressing the beetle population year after year, for as long as the pest is present in your area.

When Treatment Can Save an Ash Tree

A tree that’s still producing healthy foliage across most of its crown has enough vascular tissue intact to respond well to insecticide and push out new growth. Younger trees tend to respond faster. If your ash is structurally sound, located somewhere you want to keep a tree long-term, and has lost less than half its canopy, treatment is worth pursuing.

Certified arborists can help make a clear and effective EAB treatment plan. A Plus Tree provides emerald ash borer treatments for ash trees throughout California, Oregon, and Washington, including trunk injections and other professional-grade options depending on the tree’s condition and size.

When Removal Is the Safer Choice

A tree that’s lost more than half its canopy isn’t just unhealthy — it’s increasingly brittle and prone to sudden branch failure. Dead ash wood deteriorates faster than most species, which means a heavily infested tree can become a safety hazard within a short period of severe decline. Past that threshold, removal is often the safer and more cost-effective call. Our tree removal team can help safely remove impacted trees and properly handle infested material to prevent EAB from spreading throughout your property.

Treatment vs. Removal Decision Matrix

Ongoing Monitoring and Retreatment Planning

Treatment is a long-term commitment, not a one-time fix. Most options require reapplication every one to three years. A monitoring schedule with your arborist — checking for new exit holes, bark changes, and canopy shifts each spring — keeps you ahead of reinfestation and helps you decide when to continue current treatment or shift course.

Can You Treat Emerald Ash Borer Yourself?

Some products are available without a license, but results are inconsistent. Soil drench treatments containing imidacloprid can provide some protection for trees under 12 inches in trunk diameter, and homeowners can legally apply them in most states. Larger trees require professional-grade equipment and expertise that most homeowners cannot access.

Additionally, timing is often a challenge, because insecticides must be applied before larvae begin feeding each season. An application just a few weeks off can significantly reduce effectiveness. For most ash trees, working with a certified arborist is the safer, more reliable path.

Emerald Ash Borer Treatment Options

There are four main approaches to managing EAB. Each has different effectiveness rates, application requirements, and practical tradeoffs.

Trunk Injection Treatments

Trunk injection is the most effective treatment for EAB control. A licensed applicator injects insecticide directly into the tree’s vascular system, where it moves throughout the canopy. Studies have shown up to 90 percent effectiveness when applied correctly. Depending on the product, a single application can last one to three years. Multi-year formulations cost more upfront, but reduce total applications over time.

Soil Drench Treatments

Soil drenches apply insecticide around the base of the tree, which is absorbed through the roots and carried upward. Homeowners can legally apply it themselves on smaller trees, which makes it the most accessible option. However, results are inconsistent, and the product moves through surrounding soil in ways that can affect nearby plants and insects. Professional application improves outcomes, but soil treatment is generally the least effective treatment method for EAB.

Bark Spray Treatments

Bark spray applies insecticide to the lower five to six feet of the trunk, where it penetrates and moves throughout the tree. It requires annual reapplication and produces results similar to soil drenches — variable, and generally considered a secondary option. Spray drift is also a factor, as surrounding plants and beneficial insects can be affected if application isn’t careful.

Tree Removal and Replacement

When decline has progressed past the point of treatment or the tree poses a safety risk, removal is the right answer. In addition to endangering any nearby property, dead or declining ash left standing continues to produce beetles, which can spread to neighboring trees. Infested wood should be chipped or processed on-site rather than hauled away. Replanting with a non-host species is the best long-term strategy once the ash is gone.

Can You Get Rid of Emerald Ash Borer Naturally?

There’s no natural treatment that meaningfully controls an established EAB infestation at the property level. If you’re researching how to get rid of emerald ash borer naturally, here’s what the evidence actually shows.

Do Natural Repellents Work?

Neem oil, essential oils, and similar products have no meaningful effect on EAB, because the beetle spends most of its lifecycle beneath the bark where surface applications can’t reach it. Biological control agents like parasitic wasps that target EAB larvae exist and are being deployed in some regions, but these are managed at a state and federal level across entire landscapes and are not available to individual property owners.

Non-Chemical Ways to Reduce EAB Spread

You can’t naturally cure an infestation, but you can slow the pest’s spread in meaningful ways:

• Don’t move firewood. This is the single most impactful action an individual can take. EAB larvae survive in cut wood and can travel with it, so try not to move impacted wood.
• Remove infested trees promptly. A dead or dying ash left on the property continues producing beetles each season. Removal eliminates that source.
• Report suspected infestations. In Oregon and other states with active quarantine zones, reporting helps agencies track EAB and coordinate control efforts.

How to Prevent Emerald Ash Borer and Protect Healthy Ash Trees

Monitor Ash Trees Regularly

Walk your ash trees each spring and fall — looking for exit holes, bark changes, or early canopy thinning. The earlier you catch EAB, the more treatment options you have. If you have several ash trees on your property, an annual tree health care visit makes it easier to track changes across the whole site at once.

Avoid Moving Infested Wood and Firewood

EAB larvae can survive in cut wood and firewood long after the source tree has been removed. Never transport ash wood from a property where infestation is confirmed or suspected, and be cautious about bringing firewood in from outside your immediate area.

Know When Preventive Treatment Makes Sense

If EAB has been confirmed within about 15 miles of your property, preventive treatment of healthy ash trees shifts is imperative. Talk to an arborist about whether your trees are worth treating preemptively and what timing makes sense given the local infestation pressure. A tree pest and disease assessment gives you a clear picture of where things stand and what’s worth protecting.

Emerald Ash Borer on the West Coast

Is Emerald Ash Borer in California Yet?

EAB has not been confirmed in California. However, EAB is currently established in Oregon, and California is within its likely expansion path. The California Department of Food and Agriculture monitors for EAB through trapping programs, and tree owners — particularly those with large or high-value ash trees — should know what to look for before the pest arrives.

The Oregon Outbreak and Why It Matters to California

Oregon confirmed its first EAB detection in the Portland area in 2022, and the pest has continued to spread since. Because wood and plant material regularly moves between Oregon and California, it represents a real and proximate threat — urban trees, street trees, and riparian ash corridors included.

Quarantine and Wood-Movement Rules in Oregon

Oregon has established quarantine zones in counties where EAB has been confirmed. Movement of ash wood, chips, bark, and nursery stock out of these zones is restricted. If you’re in Oregon or moving materials from Oregon into another state, check the Oregon Department of Agriculture’s current quarantine map before transporting any ash material.

Safe Timing for Ash Pruning and Removal

EAB adults are most active from between May and August. Pruning during this window can attract egg-laying adults to fresh wounds. When possible, schedule significant ash work in late fall through early spring to avoid this window. Our tree pruning and trimming team works within these seasonal timeframes as part of responsible EAB management.

Protecting Native Western Ash

Oregon ash (Fraxinus latifolia) is the only ash native to the Pacific Coast, playing a critical role in riparian habitats by shading salmon-bearing streams, stabilizing streambanks, and supporting native wildlife. EAB doesn’t distinguish between ornamental and native species; all Fraxinus are susceptible. For more on threats to these trees, see our ash tree diseases resource.

Talk to a Certified Arborist About Your Ash Trees

If you have ash trees and EAB is in your region, the time to get a professional assessment is before the symptoms are obvious — not after. A Plus Tree’s ISA Certified Arborists serve homeowners and property managers throughout California, Oregon, and Washington. We’ll evaluate your trees, recommend the right approach for current local conditions, and build a monitoring plan that keeps you ahead of EAB.

Schedule an emerald ash borer treatment consultation or reach out for arborist consulting to discuss your situation.

Emerald Ash Borer FAQs

How Much Does Emerald Ash Borer Treatment Cost?

EAB treatment cost varies based on tree size, treatment method, and local rates. Trunk injection for a mid-size ash typically runs $100–$300; larger trees cost more. Soil drenches and bark sprays are cheaper per application but require more frequent retreatment. Removal depends on size and site access and can range from a few hundred to several thousand dollars. An arborist visit is the only reliable way to get accurate numbers.

How Long Does Emerald Ash Borer Treatment Last?

Treatment timelines and effectiveness depends on the product. Some trunk injection formulations are designed to remain effective for two to three years; soil drenches and bark sprays typically need to be reapplied annually. No treatment is permanent, and retreatment is an ongoing part of managing EAB for as long as the pest is present in the area.

Does Homeowners Insurance Cover Emerald Ash Borer?

Homeowners insurance usually does not cover EAB treatments. Treatment costs for pest infestations are generally considered a maintenance issue and aren’t covered. Removal may be covered in some circumstances — particularly if a dead tree falls and damages an insured structure — but policies vary significantly. It is best to check with your insurer directly rather than assuming either way.

How Fast Does Emerald Ash Borer Kill Trees?

A small or already-stressed ash can decline and die within one to two years of infestation. Larger, healthy trees may hold on for three to five years, but canopy decline is typically severe by that point. Because visible symptoms lag a year or more behind actual infestation, waiting until the tree looks obviously sick usually means the ideal treatment window has already passed.

For more context on when to act, see our guides on insects that kill trees and when to remove a tree.