Pest description and damage Carpenterworms are the larvae of a large mottled gray and black moth. The caterpillars are white to pinkish-red with a dark head and are 1 to 3 inches long when mature. The caterpillars bore in the trunk and main branches. Discolored or bleeding limbs, branch dieback, and lumpy or gnarled trunks may be indications of carpenterworm infestation. Typical symptoms of elm infestation are sawdust-like material (frass) and wood chips mixed with loose webbing on or around infested trees. Trees with severe carpenterworm infestations are susceptible to wind breakage and need to be removed to reduce risk. Infestations may kill trees eventually.
For biology, life history, monitoring and management
See Table 4 in: