Integrated Pest Management

Carpenterworm Moth

Prionoxystus robiniae

carpenterworm moths

Carpenterworm moth (James Solomon, USDA Forest Service,


Carpenterworm moth larva (William H. Hoffard, USDA Forest Service,

carpenterworm moth damage

Scarred bark from carpenterworm moth boring activity (Bob Hammon, Colorado State University,


Pest Description

  • adults: female wingspan ~ 3 inches, length is 1 3/4 inches; males smaller
  • adults: mottled white, gray and black; blend with bark
  • larvae: up to 3 inches long; white to pink; brown head capsule; black dots on abdomen
  • pupae: skins are dark brown with a double row of spines
  • eggs: laid in sticky masses

Host Plants, Diet & Damage

  • ash, aspen, elm, birch, black locust, oak, cottonwood maple and willow; poplar favored
  • larvae feed on sapwood but primarily in the heartwood
  • larval galleries can extend 6-10 inches within the heartwood and are 1/2 inch in diameter
  • boring activity weakens branches and stems
  • bark can become disfigured and scarred
  • frass and pupal skins may be evident in exit holes

Biology, Life Cycle & Damaging Life Stage

  • overwinter as larvae in the wood
  • adults emerge mid-May through July.
  • egg masses are laid on tree bark, usually near wounds
  • larvae spend most of their time in the heartwood
  • one generation every 3 to 4 years
  • larvae are the damaging stage

IPM Recommendations

  • Keep trees healthy with proper cultural practices.
  • Avoid mechanical injury to trees.
  • Monitor trees for irregularly shaped holes with expelled frass or pupal skins.
  • Nematodes (Steinernema carpocapsae or feltiae) may be sprayed into holes to kill larvae within galleries.
  • Apply an insecticide (carbamate; pyrethroid) to the bark in mid-May prior to egg laying.

For more information, see our Carpenterworm fact sheet.