The EAB adult is no more than half an inch in length. That and its emerald green coloring make it very hard to spot on the tree. The larvae grows to be one-and-a-half inches long, and has distinctive bell-shaped segments. Nonetheless, it spends its time below the surface of the bark. Consequently, the infestation can remain hidden until the tree is well beyond saving.

Perhaps the most obvious sign of an infestation is canopy dieback, beginning at the top and progressing downward through the year. But this can also be a symptom of Ash Yellows.

A possible indication is sprouting from the base of the tree. Once again, this can be a sign of Ash Yellows instead.

Increased woodpecker activity is yet another potential indication of an EAB infestation.

With a sharp eye, one might be able to spot D-shaped exit holes on the bark. The most telltale sign, however, can't be seen until the bark begins to strip off. That is the S-shaped channels which the larvae leave behind.

The mountain ash, it should be noted, is not actually of the ash species. Therefore, it is not susceptible to the EAB.