Pest description and damage Carpenterworms are the larvae of a large mottled gray and black moth. The caterpillars are greenish-white to pinkish-white with a dark head and are one to three inches long when mature. The caterpillars bore into the trunk and main branches of cottonwood, ash, birch, black locust, elm, oak, maple, pear, poplar, willow, locust, and occasionally other fruit trees, shrubs and deciduous trees. Discolored or bleeding limbs, branch dieback, and lumpy or gnarled trunks may be indications of carpenterworm infestation. Sawdust-like material (frass) and wood chips mixed with loose webbing on or around infested trees is typical. Trees with severe carpenterworm infestations are susceptible to wind breakage and may need to be removed. Infestations may kill trees eventually.
For biology, life history, monitoring and management