Plant Problem Diagnosis Key / Pests

Pest

Emerald ash borer

Agrilus planipennis

An invasive metallic green beetle whose larvae tunnel under ash bark and cut off the tree's water and sugar flow. Large ash trees can die within three years of infestation. It attacks true ash; mountain ash is not an ash and is not attacked.

The D-shaped exit hole an emerald ash borer adult chews out of ash bark
The D-shaped exit hole an emerald ash borer adult chews out of ash bark Photo: Daniel Herms, The Ohio State University, Bugwood.org, CC BY 3.0, via Wikimedia Commons

Signs

What favors it

Ash trees near a known infestation; it travels farthest in moved firewood.

Prevention

Crops it shows up on

Shade & ornamental trees.

Often confused with

PestWood borers DiseaseCanker diseases DiseaseShade tree anthracnose

Sources

Why →

Treatment by crop

Cultural, biological and chemical options in the order to use them, and notes written for each crop.

Identification is free. Treatment is on the Home and Pro plans.

Open in the key See plans

Questions in the key that lead here

  1. Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
    No, only damage or discoloration
  2. Where is the problem?
    A tree or shrub
  3. Which part of the tree or shrub shows the problem?
    Branches dying, or the crown thinning
  4. How is the dieback showing?
    An ash thinning from the top, with sprouts on the trunk

Not a match? Start the key or describe what you see.

More photos

S-shaped larval tunnels under the bark of an ash
S-shaped larval tunnels under the bark of an ash Photo: judygva (back in town and trying to catch up), CC BY 2.0, via Wikimedia Commons

More from university Extension: search Extension pages on emerald ash borer, or find a plant diagnostic lab through your state's Extension.

Other pests

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