Hello Kathleen,

The holes could be left by borer insects that eat on crabapple trees, including the shot hole borer, apple tree borer, and dogwood borer. These insects attack healthy trees and deposit their larvae by boring into the branches and trunk. Apple tree borer holes are found near the base of the tree and are the exit holes when the mature beetles emerge. When insects bore holes into trees, they leave ‘frass’ or sawdust at the openings of the holes. Have you noticed piles of fine sawdust at the base of your tree? Without the frass, this does look like the work of a Yellow-Bellied Sap Sucker who are large birds and resemble a woodpecker.

When the weather warms up in the spring and the sap begins to flow, the birds drill small, round, shallow holes, usually in horizontal rows, on the trunks of trees including, Crabapple trees. These holes create sap wells where they return to drink the sap and eat the occasional insect. Their holes range in size from 1/4- 3/8 of an inch.

To protect the tree from these birds you can wrap a barrier- such as a net, burlap or 1/4 hardware mesh, around the tree trunk. The woodpeckers are active in spring and fall, so you can remove the trunk protection over the summer and winter months.
You could also use fright tactics like hanging shiny, reflective objects that move in the wind—aluminum pie plates, reflective tape or old CDs or DVDs—anything that flashes light.
If you do find frass, please get back to us.

Thank you for contacting Ask Extension.