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Caption: Carpenterworm larval mine
Photo by: Unknown
Elm : Carpenterworm
(revision date: 4/28/2014)

Carpenterworms are the larvae of a mottled gray and black moth. The caterpillars are white to pinkish-red with a dark head and 1" to 3" long when mature. They bore in the trunk and main branches of elm, poplar, willow, locust, and other 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. Adults emerge in early summer. Trees with severe carpenterworm infestations are susceptible to wind breakage and may need to be removed. Infestations may eventually kill trees.
Management Options

Non-Chemical Management
  • Keep trees healthy to enable them to tolerate some damage.
  • Prevent injuries which may attract carpenterworm moths to trees.
  • Probe tunnels with a sharp wire to kill larvae when practical.
  • Apply beneficial nematodes (Steinernema carpocapsae or S. feltiae) into tunnels to kill larvae. Fill tunnels with nematodes in water, then plug holes and wait about a week. It may be necessary to treat tunnels again if plugged holes are reopened by surviving larvae.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Carpenterworm larval mine
Photo by: Unknown