Poplar carpenterworm

  • Latin name: Acossus centerensis [Lint.]
  • French name: Charpentier du peuplier
  • Order: Lepidoptera
  • Family: Cossidae



A northern species occurring from New Jersey west to Illinois and North Dakota and in Canada from Quebec and Ontario west to British Columbia.


Trunk, Bark

Damage, symptoms and biology

There are a number of wood boring insects commonly found in live hardwoods of the Prairie Provinces. These wood boring insects often go unnoticed in the trees they are attacking until severe damage has resulted. When attacked by one or more of these borer species, trees are usually weakened structurally and are susceptible to wind and snow breakage, especially if they are repeatedly attacked. Severe attack can place trees under stress, making them more susceptible to other damage agents such as drought and disease. If a tree is suspected of being attacked by a wood boring insect, careful examination will reveal small entry holes in the bark (often in and around old wounds) where the larvae of the developing moths or beetles extrude frass or debris. In many cases, small amounts of sap bleed from these entry holes. When a tree is severely attacked, large amounts of frass will accumulate at the base of the tree. Splitting the branches or stem of an attacked tree will reveal wood that is riddled with feeding tunnels.

The poplar carpenterworm pupates within its host tree, with adult moths emerging in June and July. These adults have wingspans of 40-50 mm. Adults are similar in appearance to the carpenterworm, with mottled gray wings and bodies. The larvae off-white bodies with brown spots, and dark brown heads and thoracic shields. Life cycle duration is unknown.

Adult description: Moderately large, black and gray-mottled moth. Forewings covered with black reticulations over black-gray scaling, shading darker toward base. Hindwings rounded and translucent with faint reticulation (more conspicuous beneath) in both sexes and blackish hairs at base. Wingspan of males 40 to 50 mm; females 50 to 64 mm. Head, thorax, and abdomen blackish and edged and shaded with gray. Sexes more alike than other cossid moths. Females distinguished from males by their threadlike antennae (feathery antennae in male) and slightly more robust bodies.

Larva description: Creamy white with dark brown head and strong black mandibles. Thoracic shield pale yellowish to blackish brown. Thoracic legs well developed with black claws. Spiracles dark brown and anal shield yellowish. Mature larvae range from 32 to 45 mm long. Pupa description: Narrow, shiny, wrinkled, brownish black, and about 30 mm long.

Other information

A number of biotic agents act as natural controls for wood borers of hardwoods. Studies have shown that birds, particularly woodpeckers, may feed on up to 75% of a population of wood borers and are probably the most effective natural control agent. Parasitic insects, especially parasitic wasps, also feed on wood borers. In the United States, fast-growing wood decay fungi have been documented as trapping pupae within feeding tunnels, thus preventing adult emergence.

Most of the wood borers prefer wounds and scars on trees for oviposition. Care should, therefore, be taken when working on or near ornamental hardwoods, because careless cultivation, pruning, or mowing may cause injury resulting in oviposition sites. Ornamental trees that are healthy and growing well are most resistant to wood borer attacks. During drought, trees should be watered to prevent the drought stress that may predispose trees to wood borer attacks.

Canadian Forest Service Publications

Poplar carpenterworm

Information on host(s)

Quaking aspen is preferred. Balsam poplar also has been casually mentioned as a host.

Main host(s)

Balsam poplar, poplars / aspens / cottonwoods, trembling aspen

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