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Western cedar borer

  • Latin name: Trachykele blondeli Marseul
  • French name: Bupreste du thuja de l'Ouest
  • Order: Coleoptera
  • Family: Buprestidae


British Columbia

The western cedar borer occurs from southwest British Columbia to California and New Mexico.


Scale, Branch, Trunk, Bark

Damage, symptoms and biology

Damage caused by the tunnelling activity of this insect often results in the culling of logs cut for poles and in the degradation or culling of lumber, shingles and other products requiring sound wood.

Within infested stands, both immature and mature trees may be attacked. Severity of an infestation is variable, and may range from a few trees to nearly all the trees in a stand.

Felled trees are not attacked and once cedar products cut from infested trees are seasoned, the larvae in them are killed.

Damage is primarily restricted to heartwood in the upper part of the bole but occasionally extends down the bole as far as the butt.

Most cedar poles mined by the cedar borer showed no significant reduction in strength when tested. However, occasionally a borer will cut short galleries side by side until, in extreme instances, the tree is almost severed.

As the western cedar borer attacks living host trees without visibly injuring or killing the tree, detection of infestations in standing timber is difficult. Any area with favourable site characteristics, i.e., exposed southerly aspects and low elevation, within the geographic range of the borer, should be considered suspect in any logging operation. Infested trees are readily determined once they have been felled and limbed as the larval tunnels are exposed in the knot faces.

Egg: Oblong, about 2.5 mm long and 1.75 mm in diameter, off-white ashy gray.

Larva: A young larva is about 2.75 mm long and 1 mm wide across the thorax; a mature larva is 30-40 mm long and 6.8 mm wide. The small head is retracted into the broad flat thorax. The abdomen is much narrower than the thorax and consists of 10 subcylindrical segments. The larva is cream coloured except for dark brown mouth parts.

Pupa: 16-22 mm long. 6-8 mm wide; white except for the brown eye-spots.

Adult: 12-20 mm long, 4-6 mm wide. The beetle is elongate-oval, tapered posteriorly, slightly convex and is brilliant bronzy green.

Female beetles seek out suitable egg laying sites in the crowns of living cedar or cypress trees during May and June.

Adults lay approximately 15 eggs, one or more per site, under bark scales or in crevices. The eggs hatch in 12-18 days. Each larva then tunnels into the limb and along the branch into the bole.

The larva requires at least 2 years to reach maturity. Pupation occurs in an enlarged pupal cell located either in the sapwood near a scar or in a branch. The pupal period lasts approximately 20 days, and occurs at some point between July and September. After pupation the adult remains in the pupal cell until the following May or June, when it bores to the surface. The adult beetle feeds intermittently on cedar foliage for several days before mating.

Canadian Forest Service Publications

Western cedar borer

Diet and feeding behaviour

  • Phyllophagous : Feeds on the leaves of plants.
    • Free-living defoliator: Feeds on and moves about freely on foliage.
  • Xylophagous : Feeds on woody tissues (wood).
    • Borer: Bores into and feeds on the woody and non-woody portions of plants.
Information on host(s)

Western redcedar and rarely yellow cypress are attacked in British Columbia.

Main host(s)

Lodgepole pine, western redcedar