Signs and symptoms
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.
Sparse leaves and/or branches dying in the upper part of the tree
New sprouts on the roots, lower trunk or lower branches
Short (3 to 5 inches) vertical splits in the bark
Excessive wood pecker activity in the upper part of the tree
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.
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.
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.
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."
D-shaped emergence holes
As adults emerge from under the bark they create an emergence hole; 1/8 inch in diameter and D-shaped.
S-shaped larval galleries
As 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.