What are the rows of small holes in my tree's bark?

Rows versus random

Ohio State University's BYGL bulletin says sapsucker holes are arranged in orderly rows, either around the trunk or up and down it, while insect exit holes are typically deeper and appear randomly on tree stems. The pattern is the main clue.

A borer hole may also have fine sawdust, called frass, at the entry or on the ground below, and the tree often shows other signs, such as dieback, oozing or loose bark.

How serious are sapsucker holes?

The bulletin says the effect of sapsuckers on trees has long been debated. Later research found they tend to select stressed or damaged trees, which calls into question their role as a primary threat. So the birds may be a symptom, not the cause.

Very heavy feeding can girdle a limb, so a tree with many rings of holes is worth a look. A healthy tree with a few rows usually carries on.

When to have it checked

Have the tree looked at if the holes are scattered, if there is sawdust or pitch, if the crown is thinning or if a conifer shows reddish needles; see bark beetles in pines. Borers and beetles are about identification and the prune-or-remove decision for us; we do not spray.

Take a close photo of the holes and the bark, a wider one of the tree and one of the crown, and send them with the estimate form, or call 775.232.8243. An arborist visit tells you which it is.

If you see the bird at work, the question is half answered, and an arborist can then judge whether the tree is otherwise sound. A healthy tree with a single band of holes usually needs no work, while a thin crown or scattered holes with sawdust deserve a closer look.