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Conifer Wood Borers (round or flathead)


  • Eggs: Adults lay egg galleries under the bark after mating. Eggs hatch after 2 weeks.
  • Larvae: Legless larvae feed under the bark of the tree, where they over winter. In the spring the larvae continue feeding on the tree. Full-grown larvae have a dirty white or yellowish coloured body with a brown head and can measure between 35 to 50 millimetres in length. Larvae then pupate after a year and emerge as adults.
  • Adult: The adult wood borer emerges from the tree between early June and late July. Adult roundhead borers have long, pronounced antennae. They range from 20 to 25 millimetres in length and may be black or grey in colour. Adult flathead borers are 10 to 25 millimetres in length an have a metallic sheen (exact colour depends on the species.) Adults eat foliage for 10 days before mating.

Identifying infestations:

  • Frass and holes in bark Wood boring larvae produce frass or debris as they eat the cambial surface under the bark. This frass is pushed out of small entry holes in the bark (usually found in and around old cuts or wounds in the tree.)
  • Dead or dying trees Both flathead and roundheaded borers attack dead or dying spruce, pine, true firs, and Douglas fir trees and rarely attack healthy conifers.
  • Wood riddled with feeding tunnels If you split the stem or branches of an infested tree, the wood will be riddled with feeding tunnels.

IPM Toolkit:

  • Preventive tools:
    • Regularly water, fertilize and prune your conifers to keep them as healthy as possible to resist attack from wood borers.
    • Remove dead conifers and conifer firewood from your yard which may harbour wood borers.
  • Physical tools: Not applicable
  • Biological tools:
    • Birds, particularly woodpeckers, can eat up to three-quarters of wood borers found in your tree.
    • Parasitic insects, like parasitic wasps, also feed on wood borers.
  • Least toxic chemical tools: Not applicable