thorax. The abdomen is much nar-rower than the thorax and consists of10 subcylindrical segments. Thelarva is cream coloured except fordark 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, taperedposteriorly, slightly convex and is bril-liant bronzy green.

WesternCedar BorerR.W. Duncan

C a n a d a - B r i t i s h C o l u m b i a P a r t n e r s h i p A g r e e m e n t o n F o r e s t R e s o u r c e D e v e l o p m e n t : F R D A I I

sites having warm, sunny aspects andparticularly at exposed locations suchas shorelines, selectively loggedareas or borders of clearcuts.

Description

Egg: Oblong, about 2.5 mm longand 1.75 mm in diameter, off whiteashy gray.

Larva: A young larva is about 2.75mm long and 1 mm wide across thethorax; a mature larva is 30-40 mmlong and 6.8 mm wide. The smallhead is retracted into the broad flat

Introduction

The western cedar borer, Trachykeleblondeli Marseul (Coleoptera:Buprestidae), is a common woodborer of western red cedar (Thuja pli-cata Donn) in south coastal BritishColumbia.

Damage caused by the tunnelingactivity of this insect often results inthe culling of logs cut for poles and inthe degrade or culling of lumber, shin-gles and other products requiringsound wood.

Hosts and distribution

Western red cedar and rarely yellowcypress are attacked in BritishColumbia.

The western cedar borer occursfrom southwest British Columbia toCalifornia and New Mexico; distribu-tion in British Columbia includesVancouver Island, the Gulf Islandsand the mainland coast from DruryInlet south, including the Fraser Riverdrainage east to Harrison Lake.Western cedar borer activity is restrict-ed to areas below 250 m elevation.Infestations are most common on

ISBN 0-662-23214-3 Cat. No. Fo 29-6/66-1995E

Western cedar borer larva

L E A F L E TPest

66F O R E S T

Pacific Forestry Centre

Life history and habits

Female beetles seek out suitable egglaying sites in the crowns of livingcedar or cypress trees during May andJune. These sites are usually thin-barked areas on the upper side ofsouth-facing branches within 1 m ofthe bole. Adults lay approximately 15eggs, one or more per site, under barkscales or in crevices. The eggs hatchin 12-18 days. Each larva then tunnelsinto the limb and along the branch intothe bole. There the larva mines trans-versely or vertically between the annu-al rings but occasionally cuts straightor obliquely across the grain. Tunnelsaverage less than 6 m in lengthalthough they may be as long as 13m. The flattened tunnels are 10-30mm wide, 3-4 mm deep and are close-ly packed with frass and borings. Thetunnel surface is marked with curvedgrooves made by the larva’smandibles as it feeds. The larvarequires at least 2 years to reachmaturity. Pupation occurs in anenlarged pupal cell located either inthe sapwood near a scar or in abranch. The pupal period lastsapproximately 20 days, and occurs atsome point between July andSeptember. After pupation the adultremains in the pupal cell until the fol-lowing May or June, when it bores tothe surface. The adult beetle feedsintermittently on cedar foliage for sev-eral days before mating.

Damage and detection

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

Felled trees are not attacked andonce cedar products cut from infestedtrees are seasoned the larvae in themare killed.

Damage is primarily restricted toheartwood in the upper part of thebole but occasionally extends downthe bole as far as the butt.

Most cedar poles mined by thecedar borer showed no significantreduction in strength when tested.However, occasionally a borer will cutshort galleries side by side until, inextreme instances, the tree is almostsevered.

Present grading standards withinthe pole industry cull all borer dam-aged poles. Lumber sawn from infest-ed logs may be culled or degradedaccording to the amount of damagefound. Degrade is greater when dam-aged logs are processed into dressedlumber. Also there is no export marketfor cedar products damaged by the

borer. Financial losses have beenincurred by both pole operators andsawmills handling cedar cut frominfested stands.

As the western cedar borerattacks living host trees without visiblyinjuring or killing the tree, detection ofinfestations in standing timber is diffi-cult. Any area with favorable site char-acteristics, i.e., exposed southerlyaspects and low elevation, within thegeographic range of the borer shouldbe considered suspect in any loggingoperation. Infested trees are readilydetermined once they have beenfelled and limbed as the larval tunnelsare exposed in the knot faces.

2

Western cedar borer adult

Control

Since the larvae are mostly found inthe heartwood it is difficult to applyany form of direct control againstthem. Burning slash would kill anyadults or pupae left in the debris onthe site and would reduce the breed-ing population attacking trees alongthe margin of the logged area. Polesize or larger cedar should not be leftstanding in the clearcut as these treesare especially vulnerable to attack.Seasoning of infested poles or lumberwill kill any larvae present.

Cedar borers are known to beparasitized by Ondontaulacus editusCresson, a parasitic wasp whoseeffect on borer populations has notbeen studied.

References

Bright, D.E. 1987. The insects andarachnids of Canada. Part 15. Themetallic wood-boring beetles ofCanada and Alaska (Coleoptera:Buprestidae). Can. Dept. Agric.,Ottawa, Ont. Publ. 1810.

Burke, H.E. 1925. Western cedar poleborer. Timberman 26(10): 96.

Burke, H.E. 1928. The western cedarpole borer or powder worm.U.S.D.A. Tech. Bull. No. 40.

Chamberlin, W.J. 1953. Insects affect-ing forest products and othermaterials. Oregon State CollegeCooperative Assoc., Corvallis,Oregon. 159 p.

Chrystal, R.N. 1917. The westerncedar borer, Trachykele sp. Agric.Gaz. Canada 4: 946-949.

Dyer, E.D.A. 1959. The western cedarborer in coastal British Columbia.Can. For. Serv., Victoria.Unnumbered pest leaflet. 4 p.

Furniss, R.L.; Carolin, V.M. 1977.Western forest insects. USDAMisc. Publ. 1339. 654 pp.

3

Cross section of larval tunnels packed with frass and borings

Tangential section of larval tunnels

Hopping, G.R. 1927. Studies in the lifehistory of Trachykele blondeliMars. (Coleoptera). Can. Entomol.59(9): 201-204.

Hopping, G.R. 1928. The westerncedar borer (Trachykele blondeliMars.): the life history, distributionand means of control, with a reporton the strength of infested poles.Can. Dept. Agric. Pamphlet (N.S.)No. 94.

Hopping, G.R. 1932. Studies in the lifehistory of Trachykele blondeliMarseul. Can. Entomol. 64(8):189-191.

4

Additional InformationAdditional copies of this and other leaflets in this Forest Pest Leaflets series,

as well as additional scientific details and information about identification services,are available by writing to:

Natural Resources CanadaCanadian Forest ServicePacific Forestry Centre

506 West Burnside RoadVictoria, B.C. V8Z 1M5w

Phone: (250) 363-0600

© Her Majesty the Queenin Right of Canada, April 1995

PDF created January 2001

Adults in sapwood pupal cells

Larval tunnel exposed in knot face

Natural ResourcesCanada

Ressources naturellesCanada

Canadian ForestService

Service canadiendes forêts