Invasive Species: Emerald Ash Borer

Agrilus planipennis

Emerald Ash Borers were brought to North America accidentally in the early 2000s. They were first detected near Detroit, Michigan, but were found in Oregon in 2022.

Why is it important to control?

Emerald Ash Borers (EAB) are highly destructive to any ash trees (Fraxinus spp.) they encounter. While ash trees in EAB’s native range are adapted to the insect, North American ash trees have no defenses. In Michigan, where EAB was first detected, ash trees are all but extinct. Currently there is no known solution for EAB infestation, but there are steps that can be taken to slow the spread of this insect.

Adult emerald ash borer with wings closed.

How can you identify it?

Emerald Ash Borer adult beetle
A person's finger pointing at a larval gallery created by emerald ash borer larvae on an ash tree.
A close up of D-shaped exit holes on an ash tree. They are less than 0.5cm in width.

 

Identifying Signs of the Insect

Tree Damage: EAB typically attacks trees from the top down, so it may be difficult to see damage at first
Larval Galleries: Larvae chew through the inner bark of the tree, creating meandering grooves called larval galleries. These are often undetectable until the tree is dead, but they are very distinctive.
Exit Holes: Adults leave the tree after pupating (the process of going from larva to adult). They leave distinctive D-shaped exit holes in ash trees. These are very small, and most often shaped with the straight line of the D above and the curved part below (like a D rotated to the right).

 

 

Identifying the Insect Itself

Habitat: Anywhere with ash trees
Life Cycle: Females lay 40-90 eggs in ash bark May-September; larvae hatch and begin tunneling into the tree’s inner bark October-March; larvae pupate into adults April-May and begin the cycle again. Some larvae may remain in the bark for two years.
Size: Adults are up to 1/2 inch long; larvae are up to 1.5 inches long
Adult Description: Shiny, dark green wing shell/outer wings; shiny red body underneath, when wings are open; black, oval-shaped eyes
Larvae Description: Cream/white segmented body; small, orange-ish head
Adult Flight Time: May through September

How do you control it?

  • Prevention is the best tactic. Yamhill County is under a quarantine, so it is illegal to move firewood outside of the county. However, we also strongly discourage moving wood within the county, as Emerald Ash Borer has only been detected in the northern part of the county. We can slow the spread of EAB by being conscious of what we move around, even within the county.

  • Emerald Ash Borers are attracted to unhealthy ash trees. If you have any ash trees that are not doing well, consider removing them now before EAB infests them, as a way to delay the insects from getting to your healthy trees.

  • The Oregon Department of Agriculture is actively working to control this insect.

How to report it?

There are various ways you can report this invasive insect.

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