The carpenterworm can damage cottonwood, elm, oak, maple, and willow trees, among others. The larva get up to 3 inches long and feed on the sapwood of trees. The mature moths deposit eggs on the surface of the tree and the larvae burrow into a "gallery" as they grow.
The carpenterworm leaves a very impressive exuvia behind when it undergoes metamorphosis from a pupa to moth. These will remain behind in the holes after the mature moth has left. The hole in the photo on the left is about the size of a dime.
Chemicals have limited effectiveness against carpenterworms. Read the following bulletins carefully before attempting to use pesticides.