Willow: Carpenterworm

Biology

Carpenterworms are the larvae of a mottled gray and black moth. The caterpillars are white or pinkish-red with a dark head and 1″ to 3″ long when mature. They bore in the trunk and main branches of willow, poplar, elm, locust, and other deciduous trees. Discolored or bleeding limbs, branch dieback, and irregular and gnarled trunks are indications of carpenterworm infestation. Sawdust-like material (frass) and wood chips mixed with loose webbing on or around infested trees is typical. Adults emerge from infested trees in early summer. Trees with severe carpenterworm infestations are susceptible to wind breakage and may need to be removed.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• 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 (Neoaplectana carpocapsae or Steinernema 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• None recommended

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