Identifying an ash tree
Ash has opposite branching — two twigs emerging across from each other at the same point, which is unusual in our native trees. The leaves are compound, with five to nine leaflets. The bark on mature trees forms a distinctive diamond pattern.
The most common ash in Westchester yards is white ash, with green ash in wetter spots. Both are susceptible.
Signs of emerald ash borer
The earliest sign is usually woodpecker activity: ash borer larvae live just under the bark, and woodpeckers flake the bark off to reach them, leaving pale patches. Look for D-shaped exit holes about an eighth of an inch across on the trunk, vertical bark splits, and thinning in the top of the canopy.
Epicormic sprouts — clusters of leaves pushing directly out of the lower trunk — appear as the tree tries to compensate for a dying crown. It is a sign of a tree in serious trouble, not a sign of recovery.
Why ash removals are more dangerous than they look
Ash killed by the borer becomes brittle faster than almost any other species here. Limbs that look solid snap without warning, and the trunk itself can fail at the base while the crown still holds leaves.
That changes the removal method: more rigging, less shock loading, and sometimes a crane where we would otherwise climb. It also changes the timeline — an ash with advanced decline near a house is not a tree to leave standing while you collect three more opinions.
Treatment or removal
Systemic treatment can protect a healthy ash if it starts before significant infestation and continues on a regular cycle. It is worth considering for a specimen tree in a good location.
For a tree that is already showing canopy thinning and bark symptoms, treatment is unlikely to restore it, and the structural risk remains. On a property with several ash, the practical plan is usually to remove the declining ones and treat the healthiest one if it has landscape value.