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Emerald Ash Borer (EAB)
Agrilus planipennis
Updated Apr 26, 2024
Make a Positive Identification
- Emerald ash borer is an invasive insect that infests all species of ash tree (Fraxinus spp.). It also infests some other members of the olive family, such as olive and fringetree.
- The larvae damage trees by eating plant tissue below the bark.
- Adults emerge from trees through “D”-shaped exit holes in the bark.
- Signs and symptoms of EAB can be seen on the inside and the outside of infested trees.
Identify Emerald Ash Borer
Species: Emerald ash borer
Howard Russell, Michigan State University, Bugwood.org
Emerald ash borer adults are a bright, metallic olive to emerald green. The slender body is pointed at the end, and 1/3-1/2 inches (7.5 to 13.5 mm) long. EAB are active and may be spotted as early as late May through July.
Species: Emerald ash borer
"Agrilus planipennis - Emerald Ash Borer" by Twiztedminds is licensed under CC BY 2.0
When their wings are open a metallic red body is visible.
Species: Emerald ash borer
David Cappaert, Bugwood.org
Larvae can reach 1 to 1 1/3 inches (2.6 to 3.2 cm) long. They are creamy white, with bell-shaped segments. They are found under bark throughout the year. They cause damage to the tree by eating tissue beneath the bark.
Species: Emerald ash borer
Edward Czerwinski, Ontario Ministry of Natural Resources, Bugwood.org
Emerald ash borer larvae feed on the cambium and outer sapwood, under the bark of the tree. They tunnel curving S-shaped galleries. These cut across tissues that transport water and nutrients. This is called "girdling" and kills the tree. They do not burrow very deep into the wood.
Species: Emerald ash borer
"File:Eabexithole.jpg" by Daniel Herms, The Ohio State University, Bugwood.org is licensed under CC BY 3.0
Adults exit the tree in late May / June. They leave D-shaped exit holes about 1/8-inch (3mm) in diameter in the bark. Some emerald ash borer holes can look more oval than D-shaped. Holes will have a smooth edge unlike the messy holes from woodpeckers.
Species: Emerald ash borer
Ryan Armbrust, Kansas Forest Service, Bugwood.org
Early detection of EAB is important for managing it. Adults are the most visible life stage. Find out when adults are likely to emerge in your area. EAB forecasts for Oregon are available at USPest.org. Maps for the entire U.S. are at USA National Phenology Network.
INSECT LOOK-ALIKES: BRONZE BIRCH BORER, GOLDEN BUPRESTID
Species: Bronze birch borer
John .A. Davidson, Univ. Md, College Pk, Bugwood.org
Bronze birch borer (Agrilus anxius) is another invasive boring beetle. It attacks birches instead of ash. Bronze birch borer adults are about the same size and shape as EAB. Their color is metallic olive to coppery brown. They are active May through July. The feeding pattern of the larvae circles the trunk under the bark. The emerald ash borer feeds in a back-and-forth serpentine pattern.
Species: Golden buprestid
"Golden Buprestid" by treegrow is licensed under CC BY 2.0
Golden buprestid (Buprestis aurulenta) is a native wood-boring beetle that is also metallic green. It is twice the size of EAB (about 2/3 inch long). It has ridges and copper or reddish edges around the wing covers.
There are several other species of metallic wood-boring beetles. These can look quite similar to EAB. See this chart of more look-alikes: Emerald Ash Borer Look-Alikes.
Many other wood-boring insects create feeding tunnels and exit holes in ash trees. These signs may be confused with emerald ash borer. These other insects often tunnel more deeply into the wood, and have oval or round exit holes.
Ash Tree Signs and Symptoms
Species: Ash tree
Joseph OBrien, USDA Forest Service, Bugwood.org
Top die-back of ash trees
Three to four years after EAB starts attacking a tree, upper branches will die. The tree crown will look thin. By this time, the insects have bred and spread to other trees. This makes early detection difficult.
Species: Ash tree
Michigan Department of Agriculture, Bugwood.org
Dense suckers on ash trunks
In an effort to stay alive, trees often produce shoots or suckers from the base of the trunk.
Species: Ash tree
Jim Tresouthick, Village of Homewood, Bugwood.org
Woodpecker damage
Woodpeckers shave off the outer bark to search for EAB larvae. Their activity gives the bark a distinct mottled appearance.
Species: Ash tree
Joseph O’Brien, USDA Forest Service, Bugwood.org
Bark splitting
Splits in the tree bark can be caused by the feeding of EAB larvae.
Correctly identify ash trees
Species: Oregon ash
Walter Breen, Oregon State University
Make sure the suspected tree is an ash tree. Oregon ash (Fraxinus latifolia) is the only ash tree native to Oregon. Many others are grown ornamentally. They are often planted as street trees. They all have compound leaves with many smaller leaflets.
Species: Ash tree
"Opposite branching on black ash" by esagor is licensed under CC BY-NC 2.0
Ash branches grow on opposite sides from each other. The leaf stems grow on opposite sides of their branches. The leaves are compound, with many small leaflets on either side of a central stem.
Species: Ash tree
"Oregon Ash Seeds" by born1945 is licensed under CC BY 2.0
Seeds on female ash trees are canoe‐shaped. They hang on the branches in dense clusters in late summer/early fall.
Species: Oregon ash
Signe Danler, Oregon State University
The bark of ash trees has furrows that become diamond- or lattice-shaped as trees age.
ASH TREE LOOKALIKES
Species: Black walnut
"BW3" by National Park Service Photo/ W. Kaselow is in the public domain.
Black walnut (Juglans nigra) has compound leaves that look similar to ashes. Their stems are arranged alternately along the branches.
Species: Black locust
Gil Wojciech, Polish Forest Research Institute, Bugwood.org
Black locust (Robinia pseudoacacia) has compound leaves that look similar to ash. The leaf stems are arranged alternately along the branch. Young branches are thorny.
Species: European mountain-ash
Robert Vidéki, Doronicum Kft., Bugwood.org
European mountain-ash (Sorbus aucuparia) leaves look similar to ash. The compound leaves are spirally arranged along alternating branches. The leaflets are jagged (serrated) along the edge. Has red or orange berries in clusters.
Species: Tree-of-Heaven
Richard Gardner, Bugwood.org
Tree-of-heaven (Ailanthus altissima) is an invasive tree. Compound leaves are up to 2 feet long and arranged spirally around the main stem. Each leaflet has a pair of "ears" at the base of the leaf.
Species:
Walter Breen, Oregon State University
Sumac (Rhus species) leaves look similar to ash but are arranged alternately along the branch. They have serrated edges. Several species of Sumac are grown in gardens. They are small trees or multi-stemmed shrubs. Red flowers grow in a dense cluster at the end of a branch.
Species:
For more help identifying ash trees, refer to the OSU Extension page "Recognizing ash trees in Oregon, Washington and Northern California".
Emerald Ash Borer (EAB) Benefits
Emerald ash borers are regarded as pests. They don’t have any benefit for people or the environment.
Emerald Ash Borer (EAB) Risks
- Emerald ash borer (EAB) is an invasive wood-boring beetle that infests all species of ash trees (Fraxinus spp).
- White fringetree (Chionanthus virginicus) and olive trees (Olea europaea) are related to ash. They are also at risk.
- EAB can devastate ash tree populations in landscapes and natural areas.
- Ash trees are an important part of natural areas in Oregon. They are also common as street and landscape trees.
- If EAB kills large numbers of Oregon ash trees, it will cause undesirable ecosystem and landscape changes, especially along waterways.
Risk Card
Does it cause harm?
Adults & Children
None
Property
High
Pets
None
Annoyance
Some
Environment
Very High
Action Highly Recommended
TAKE ACTION
Watch for symptoms of emerald ash borer damage on your property and in public spaces.
What damage does emerald ash borer cause?
Larvae damage and kill ash trees
Do I need to take action?
Yes. Emerald ash borer poses a major threat to the Pacific Northwest. It can devastate ash tree populations in yards, public landscapes and natural areas.
NEED HELP?
Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Solutions for Emerald Ash Borer
Early Detection & Rapid Response
- Watch for EAB ash tree damage on property you manage.
- Report any sightings to the Invasive Species Hotline
Protect individual high-value trees
Remove ash trees near infestations
Biological control
Jump To
| Method | Does it work? | Is it safe? | Recommendation |
|---|---|---|---|
A Protect individual high-value trees |
Effective |
Low risk |
Recommended |
B Remove ash trees near infestations |
Somewhat effective |
Low risk |
|
C Biological Control |
Effective |
||
|
D If Using Insecticides, Protect Yourself & Minimize Risks
|
|||
|
E Prevent Emerald Ash Borer Infestations
|
|||
A
Protect individual high-value trees
Chemical Method: Use with caution
"Injecting Tree for EAB Protection" by usfs_Eastern_Region is marked with Public Domain Mark 1.0
Protect individual high-value trees
Recommended
- Individual high-value ash trees can be protected before EAB arrives. There are both stem injected or soil‐drench systemic insecticides.
- This could cost hundreds of dollars.
- Once 30% of the tree canopy has been damaged, it is too late to protect it.
- Consider hiring an ISA-certified arborist. Find one at https://www.treesaregood.org/findanarborist
| Does it work? | Effective Treatment with systemic insecticides can be effective in protecting trees. |
| How much effort? | Moderate effort Treatment must be repeated every few years, requiring a long-term commitment. |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | Using insecticides includes some amount of risk. The lowest risk comes with using alternative methods. You may be exposed to an insecticide if you:
Follow directions closely to reduce risk. |
Several insecticides can be used by homeowners on trees with less than 30% canopy decline.
- Emamectin benzoate (example: ArborMectin)
- Imidacloprid (example: Bonide Systemic Insect Spray)
- Spinosad (example: Captain Jack''s Deadbug Brew)
- Acephate (example: Acecap)
Suggested pesticides are from the Pesticide Information Center Online (PICOL) Database. They are permitted for HOME use in Oregon. Read the label for application directions and effectiveness information.
ONLY professional pesticide applicators can use Restricted-Use Pesticides (RUP) that may be more effective. Contact a licensed pest control company for further support.
B
Remove ash trees near infestations
Non-Chemical Method
"Goodbye, ash trees" by Jim Grey is licensed under CC BY-NC-ND 2.0
Remove ash trees near infestations
- Sometimes it may be advisable to remove healthy ash trees that are in danger of being infested.
- Do this from Oct. 1–March 31 when adults are not active.
- Chip removed ash trees down to one-inch pieces. This will stop the growth of EAB insects inside the tree.
- Cover the chips with thick plastic, or bury them. This will prevent any surviving adults from emerging.
- Re-plant promptly with suitable replacement trees for ash. Don't leave the area for opportunistic species to move in.
| Does it work? | Somewhat effective |
| How much effort? | High effort |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | Using insecticides includes some amount of risk. The lowest risk comes with using alternative methods. You may be exposed to an insecticide if you:
Follow directions closely to reduce risk. |
C
Biological Control
Non-Chemical Method
David Cappaert, Bugwood.org
Biological Control
- There are currently no effective agents against EAB commercially available to the general public.
- Tiny stingless wasps have been released by USDA-APHIS in at least 30 states with EAB infestations.
- They parasitize EAB and reduce populations.
| Does it work? | Effective |
| How much effort? | Moderate effort |
| What's the risk? | |
| Possible risk of exposure or harm from chemicals | NONE |
If Using Insecticides, Protect Yourself & Minimize Risks
Chemical Method: Use with Caution
Weston Miller, Oregon State University
Why Is It Important to Read Insecticide Product Labels?
- They have detailed information on how to use the product correctly and legally.
- They contain information on potential hazards of the product.
- They provide instructions you should follow for poisonings and spills.
- Following label instructions helps you to minimize the risks and maximize the benefits.
Key Insecticide Safety Tips
- Read the entire label front to back.
- Follow the instructions.
- Review the instructions even for brands you know.
- Only apply the product where the label says it can be applied.
- Keep all insecticides in their original container.
The Label is the Law
ALWAYS read the label before using insecticide products. The label is a legal document that provides information on how to safely use the insecticide. This helps avoid harm to human health and the environment. Using an insecticide in off-label ways is illegal. It can result in legal enforcement actions.
READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.
- Labels are different for every product and they often change over time.
- Use a magnifying glass.
- Pay attention to CAUTION, WARNING, and DANGER statements.
- Pay attention to the PRECAUTIONARY STATEMENTS.
- The law states you must read and follow insecticide instructions.
Protect Yourself
Eye, skin, & lung irritants
- Wear gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
- Avoid contact with eyes, skin, or clothing.
- Wash hands after mixing or applying, and before eating or smoking.
- Never spray directly overhead. Pay attention to wind conditions.
Protect Children & Pets
Keep out of the reach of children.
- Keep children and pets away from the application area.
- Remove toys and pet dishes from the area before applying insecticides. Wait until spray has dried or dust has settled.
Avoid Wet Weather & Keep Insecticides Out of Waterways
Some insecticides are toxic to fish and aquatic invertebrates.
- Don’t spray insecticides in water.
- Insecticides sprayed on plants can wash off with rain and enter waterways.
Protect Pollinators
Many insecticides are extremely toxic to bees.
- Honey bees and other pollinators are harmed by most insecticides.
- Don’t spray on bees or other flying insects.
- Don’t allow spray to contact blooming plants.
Storage & Disposal
- Store out of the reach of children and pets.
- Store in a cool and dry place.
- Never pour down any drain.
- If you mix too much, apply it rather than storing it.
- Don’t put pesticide containers in the trash unless instructed by the label.
- Take unused insecticides to a hazardous waste facility.
Call 1-800-CLEANUP (1-800-253-2687) to find out where to dispose of pesticides.
For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call 503-234-3000, email or visit Metro’s website
More about:
About Using Pesticides on School Grounds in Oregon
If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management (Oregon Department of Agriculture).
NEED HELP?
The National Pesticide Information Center (NPIC) can answer questions about pest control chemicals.
1-800-858-7378 or npic@ace.orst.edu
Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Prevent Emerald Ash Borer Infestations
Kenneth R. Law, USDA APHIS PPQ, Bugwood.org
DO NOT MOVE FIREWOOD!
- Exotic pests like the emerald ash borer can spread when infested firewood is transported to new areas.
- Use local sources of firewood.
- Do not bring firewood from home.
- If you have brought firewood from home, DON’T take it with you, and DON’T leave it–BURN IT!
"IMG_0804 Cascara - Rhamnus purshiana" by Jon. D. Anderson is licensed under CC BY-NC-ND 2.0
Plant Alternatives to Ash Trees
- Replace ash trees with suitable species where appropriate. A native cascara buckthorn (Rhamnus purshiana) is pictured.
- Many Oregon native trees live in similar natural environments to Oregon ash. For a list of alternative trees, see the OSU publication "Alternatives to Ash in Western Oregon".
- In yards and landscapes, non-native ash trees can be replaced with trees suitable for the location.
"Watering bag for planted tree" by Alabama Extension is marked with CC0 1.0
Keep Your Ash Trees Healthy
- If you have ash trees on your property, keep them healthy with proper care.
- Water and mulch both young and mature trees during summer drought.
- Pruning causes the tree to emit chemicals that are attractive to pests. Avoid pruning ash trees during the EAB active season (April through October).
- Pruning cuts cause the tree to send stress signals to pests. Avoid pruning ash trees during the EAB active season (April through October).
Invasive Species Alert
- Invasives are non-native species that spread aggressively and alter the environment.
- Learn about emerald ash borer in Oregon. See Oregon Forest Pest Detector Pest Watch—Emerald ash borer
- If you think you’ve found an infested ash tree in Oregon, please report it to the Oregon Invasive Species Hotline at: 1-866-INVADER (1-888-468-2337) or use their online reporting form
Invasive species data @ 2022, iMapInvasives (NatureServe)
View Larger Map >
If you find signs of emerald ash borer anywhere in Oregon, please report it.
Content provided by Signe Danler and Weston Miller. Pesticide safety information edited by Kaci Buhl.
Peer reviewed by OSU Department of Horticulture.
Emerald Ash Borer References
Emerald Ash Borer Identification (English and Spanish) (pdf)
Oregon State University Extension Service
Oregon Forest Pest Detector Pest Watch—Emerald ash borer (EAB)
Oregon State University Extension Service
Emerald Ash Borer Readiness and Response Plan for Oregon (pdf)
Oregon Dept. of Forestry and Oregon Dept. of Agriculture
What to do about emerald ash borer: Recommendations for tree protection in EAB-infested areas
Oregon State University Extension Service
Emerald Ash Borer Look-Alikes (pdf)
Oregon Dept. of Agriculture
Recognizing ash trees in Oregon, Washington and Northern California
Oregon State University Extension Service
Alternatives to Ash in Western Oregon
Oregon State University Extension Service