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Carpenterworm ID, Symptoms, Treatment
Home  > Tree Care  > Tree Insects  > Carpenter Worm Information


Prionoxystus robinae

Carpenter worm borers are the larvae form of a moth. Carpenter worm borers tunnel around and through the trunks of several different tree species. Carpenter worm larvae develop over a two to three year period. As young borers Carpenter worm larvae feed in the cambium layer, just underneath the bark of a tree. As Carpenter worm borers mature they tunnel deep into the heartwood of a tree.


Carpenter worm borers have been found on Ash, Black Locust, Boxelder, Cherry, Chinese Tallow, Cottonwood, Elm, Oak, Pear, Poplar, and Willow trees.

Male and Female Adult Carpenter Worms

Carpenterworm adults

Carpenterworm adults; female (left) and male (right). Photo: James Solomon, USDA Forest Service,

Carpenter Worm Gallery


The initial symptoms of Carpenter worm borer damage is usually the decline or death of individual tree branches. This is usually noticed at the top of the tree or at the tips of tree branches. Other signs of the presence of Carpenter worm borer include piles of sawdust and grass in the cracks and crevices of tree bark.


Adult Carpenter worm moths emerge in the spring, are rather large, and have spotted wings. Mating and egg laying follows soon after adult moth emergence. Newly hatch borer larvae tunnel into the bark of the host tree and continue to feed and grow over a two to three year period.


Like most tree borers, Carpenter worm borers attack trees that are under stress. The best defense against borers is to use quality landscape trees and keep your trees healthy through proper care. Proper tree care includes:

Landscaping with trees that will tolerate local environmental conditions. Consult with an arborist on the best trees for your area.
Choose the proper planting location in your landscape.
Mulch around the base of trees to conserve water and prevent lawn mower and string trimmer damage.
Fertilize trees to encourage healthy growth.
Water your trees during times of drought.
Whenever possible, prune susceptible tree species during the winter months.
Remove trees that have been killed by borers.

Carpenterworm gallery

Carpenterworm gallery. Photo: James Solomon, USDA Forest Service,

Insecticide Options for Borer Control

Most tree services recommend tree spraying to control Carpenter worm borers. Tree spraying will not kill borers that are already inside a tree, but are designed as preventative treatments to keep additional borers from infesting the tree. Thorough coverage of the tree trunk and larger tree branches is necessary and the best control is obtained with multiple tree spraying treatments. Borer treatments are timed to coincide with the emergence of adults and when eggs are hatching.

Damage to Elm Trees from Carpenter Worms

Carpenterworm damage

Carpenterworm damage on Elm trees. Photo: USDA Forest Service,

Biological Options for Borer Control

There are few biological control options for trees infested with Carpenter worm borers. Infested tree branches can be pruned and destroyed and trees killed by Carpenter worm borers should be completely removed. Carpenter worm larvae have been known to exit and reenter the tree as they mature, so it may be possible to physically remove a few borers from an infested tree.
Whether chemical or biological controls are attempted, every effort should be made to improve the overall health and vigor of the tree with proper mulching, watering, and fertilization.

Carpenter Worm Larvae

Carpenterworm larvae

Carpenterworm larvae from an Oak tree. Photo: William H. Hoffard, USDA Forest Service,


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