Be Aware of the Carpenterworm

A hole in a tree where a carpenterworm has exited. 

Have your trees dropped branches that seemingly look healthy? Have you sawdust around the base of your trees? This might be due to feeding by carpenterworm. Carpenterworms can be a serious pest of trees in Iowa. Commonly infested trees include ash, birch, cottonwood, oak, maple, and fruit trees.

Carpenterworm larvae (caterpillars) are wood-boring and feed on wood.  The feeding damage weakens branches making them prone too breakage and disruption to the trees nutrient flow can cause dieback and decline.

An emerging carpenterworm pupa. 

The adult female moth often lays her eggs in a damaged portion of a tree, like a split in its trunk or branches. When the caterpillars hatch, albeit tiny to begin with, as they grow, they eat into the tree leaving large tunnels in the heartwood. Dark sap spots on the outside of the tree can be another sign of a carpenterworm infestation. Holes also might be visible on the outside of the tree along with sawdust from the hole. The sawdust is actually the caterpillars frass, which since their diet consists of wood, is small wood particles that look like sawdust. Empty pupal cases halfway out of the tree are another sign of a carpenterworm infestation.  The caterpillar pupates inside the tunnel, but the pupa pushes itself out of the tree before the adult moth emerges.

While not as common a pest as some of the woodboring insects, and tree owners should be aware of and watch for the signs of a carpenterworm infestation. Cultural practices that promote tree vigor and preventing bark damage will help prevent a carpenterworm infestation.

Check out the informative video on carpenterworms below, and for more videos on IPM techniques, plant health and more, check out the IPM Youtube Page as well. 

An adult male carpenterworm moth. 



Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on April 23, 2021. The information contained within may not be the most current and accurate depending on when it is accessed.