Tree pests

EAB signs and symptoms

How to identify an an ash tree


Quick reference guide

  • EAB CSI (PDF)
    Think your ash tree has been attacked by EAB? Use this guide to do some crime scene investigation.

To begin, make sure your tree is an ash tree. To identify an ash tree, first look for the following:

Twig Twig
 

  • Above left, opposite branching pattern; two branches come off the main stem, one on each side and directly opposite each other.
  • Above right, compound leaves (a group of leaflets joined by a stalk to a woody stem) possessing five to nine leaflets; each leaflet with smooth or finely toothed margins.

The visual symptoms associated with emerald ash borer infestations are nearly identical to those we often see on ash trees infested or infected by other ash pests and diseases. For example, crown dieback can result from multiple stressors including drought stress, soil compaction or verticillium wilt just to name a few. Therefore, it is important to look for a combination of at least two or more symptoms or signs (see list directly below) when trying to determine the presence of EAB in your ash tree.

Signs

Adult beetle

A lot of little green insects look like EAB. Know the difference between harmless insects and ash-killing EAB.

Green insects
EAB look-alikes PDF

Bell-shaped larvae

Emerald Ash Borer damageEAB larvae have no legs. They are creamy-white in color and flattened, with distinctive bell-shaped body segments.
 

D-shaped emergence holes

Emerald Ash Borer damageAs adults emerge from under the bark they create an emergence hole; 1/8 inch in diameter and D-shaped.
 

S-shaped larval galleries

Emerald Ash Borer damageAs larvae feed under the bark they wind back and forth, thus creating galleries that are packed with frass and sawdust and follow a serpentine pattern.
 

Symptoms

Thinning canopyCrown dieback

Dieback of the upper and outer crown begins to occur after multiple years of EAB larval feeding. Trees begin to show dead branches throughout the canopy, beginning at the top. Larval feeding disrupts nutrient and water flow to the upper canopy, thus resulting in leaf loss. Foliage in the top of the tree may be thin and discolored.
 

Thinning canopyEpicormic sprouting

Stressed trees will attempt to grow new branches and leaves where they still can. Trees may sucker excessively both at the base of the tree and on the trunk, often just below where the larvae are feeding.
 

Split barkBark splits

Vertical splits in the bark are caused due to callus tissue that develops around larval galleries. Larval galleries can often be seen beneath bark splits.
 

Woodpecker damageWoodpecker feeding

Woodpeckers feed on EAB larvae located under the bark. Feeding is typically evident higher in the tree where the emerald ash borer prefers to attack first. Large numbers of larvae under the bark can lead to woodpecker damage that looks like strips of bark have been pulled off of the tree. This is called "flecking."