hosts are discussed. This informationwill aid the user in detection and iden-tification of damage caused by wood-borers, and will also be useful in pre-vention and control. Longhorned bee-tles, metallic woodborers and wood-wasps are emphasized but ambrosiabeetles, shipworms and other wood-borers are also discussed.

Some importantwoodborers relatedto export restrictionsJ. Vallentgoed

F O R E S T

L E A F L E T

holes) which may be caused by poten-tial vectors of the pinewood nematode(Figure 1).

This leaflet describes severalcommon woodborers found in BritishColumbia. The various species orgroups of woodborers are describedand their life histories, habits and

Introduction

Several speciesof woodboringinsects common-ly attack soft-wood logs inBritish Columbia.The larvae(grubs) can rid-dle logs allowedto remain unpro-cessed after cut-ting, causingwormholes (grubholes) whichmay seriouslyreduce the value of the log and allowstain and decay fungi to enter. Inaddition to economic concerns regard-ing woodborer damage, some speciesof woodborers are known or potentialcarriers (vectors) of the pine wiltpathogen, the pinewood nematode,Bursaphelenchus xylophilus, whichcauses mortality of pines in Japan.Pinewood nematode occurs rarely inCanada. Nonetheless, during the past10 years it has become a factor in theexport of lumber to a number ofEuropean countries. Increasingly, theEuropean Economic Community hasdemanded that all imported lumber befree from the type of damage (grub

Figure 1. Typical longhorned beetle woodborer damage in log and lumber.

74

PestPacific Forestry Centre

Natural ResourcesCanada

Ressources naturellesCanada

Canadian ForestService

2

The longhorned beetles,Cerambycidae, the metallic woodbor-ers, Buprestidae, and the horntails orwoodwasps, Siricidae, are the princi-pal agents which bore deeply into thewood of felled, decked, fire-damaged,diseased, insect-damaged, or other-wise recently dead or severelystressed trees. Adult longhorned bee-tles, the only known vector of thepinewood nematode in Canada, arereadily recognized by their long anten-nae (Figure 2); the antennae are oftenlonger than the body, and have beenrecorded up to 12 cm in length. Thelarvae (or grubs) are called round-headed borers because they and theirtunnels (or grub holes) tend to bemore circular in cross section thanthose of metallic woodborers. Adultmetallic woodborers are often brightlycolored and have a metallic sheen.The larvae are referred to as flathead-ed borers because their bodies arenotably flattened and widened at thethorax (immediately behind the head)followed by a long, slender, segment-

ed abdomen. Adult horntails or wood-wasps are large and wasp-like inappearance, have two pairs of clearwings, a cylindrical body, and a horn-like process at the tip of the abdomen.Females have an ovipositor protrudingfrom the tip of the abdomen. The lar-vae are readily distinguished from thelarvae of longhorned beetles by a darkspine at the tail end.

The most commonly encounteredlonghorned or roundheaded woodbor-ers belong to the genus Monochamus(sawyer beetles), especially M. scutel-latus and M. clamator, or the genusTetropium, including primarily T. cin-namopterum parvulum and T.velutinum. The most common metallicwoodborers (family Buprestidae)include Buprestis aurulenta andTrachykele blondeli. The commonspecies of horntails found in BritishColumbia belong to the generaUrocerus and Sirex.

The pinewood nematodefactor

On June 22, 1990 the Plant HealthCommittee of the European EconomicCommunity required kiln drying tobelow 20% moisture content for conif-erous lumber imported into theEuropean Community after Junuary 1,1991, from countries known to havethe pinewood nematode. This regula-tion was enacted purportedly to pro-tect European forests from pinewoodnematode and its insect vector, thesawyer beetle (Monochamus spp.). Aban could threaten British Columbia’slumber exports to Europe, which arevalued to over $600 million. A tempo-rary derogation (exemption) allows thecontinued use of the mill certificationprogram (no bark, no grub holes).Compliance with this program is criti-cal: three violations from Canada mayresult in loss of the derogation, thusmaking kiln drying mandatory. Fieldidentification of the vector involved,

Figure 2. Woodborer adults. From top to bottom, Column 1: Monochamus scutellatus, Buprestis aurulenta, Trachykele blondeli. Column 2:Monochamus notatus, Ergates spiculatus. Column 3: Monochamus clamator, Tetropium velutinum, Semanotus ligneus ampla, Hemicoelusgibbicollis. Column 4: Urocerus albicornis, Asemum striatum, Nacerdes melanura, Trypodendron lineatum.

3

the type of damage caused, and thecontrols available could facilitate fur-ther exemptions and improve theproduct available for export.

The Canadian position remainsthat the Mill Certification Program issufficient, considering the minimalthreat, and should continue to be so.The push from Canada will be to con-tinue with this program of regulation.Meanwhile, heat treatment (pasteuriz-ing) as a control method is beinginvestigated and exemptions of rarelyattacked host species like hemlockand cedar are being requested.

Hosts, life histories andhabits

Sawyer beetles, Monochamus spp.

The sawyer beetles (Cerambycidae)in British Columbia include thespecies Monochamus scutellatus, M.clamator (which now includes M. mac-ulosus), M. notatus, and M. obtusus(Figure 2). The preferred hosts arepines, Douglas-fir, spruces, and truefirs. Larvae (or grubs) feed for four toeight weeks on the inner bark andcambium, then penetrate the sap-

wood, usually moving downward instanding trees. Their presence andnumbers may be readily determinedby the small piles of excelsior-like bor-ings around each entry hole.Entrance holes into the wood are ovaland average 4 × 9 mm (Figure 3).Mines (grub holes or galleries), whichincrease in size as the larvae mature,are irregular, broad and tightly packedwith bark chips, frass, and shreds ofwood up to 5 cm long. Mines are gen-erally U-shaped back toward the sur-face, but may occasionally extendright through the log (Fig. 4). Larvaeoverwinter; pupation (the inactive

Figure 3. Shapes and sizes of entrance holes, galleries and exit holes of various woodborers in British Columbia (approximate actual size).

4

stage during which the transformationfrom larva to adult takes place) occursin enlarged cavities at the end of thelarval gallery, usually within 8 mm ofthe wood surface. Adults emergefrom May to mid-August; exit holesare circular, and average 8 mm indiameter in cross section (the shapeand size of all woodborer exit holesand galleries may be misleading ifseen at oblique angles). Adults feedon bark and cambium of twigs or nee-dles on living coniferous hosts, andmay live for two and a half months.Eggs are laid in bark niches chewedby adults during early July to mid-August; these hatch in about 10 days.Up to nine eggs may be deposited in aniche and one female may lay up to70 eggs. The life cycle is normallyone to two years although durations ofup to five years have been recorded(Figure 5).

Spruce and western larch borers,Tetropium spp.

Tetropium velutinum (Figure 2)attacks mainly larch and western hem-lock, and while T. c. parvulum prefersspruce, it may also attack pines andtrue firs. The young larva feeds for upto 70 days in the cambium before pen-etrating the sapwood. The entrancehole into the sapwood is elliptical andabout 3 x 7 mm (Figure 3). The larvabores downward and spends the win-ter in the L-shaped gallery which canextend up to 5 cm into the sapwoodand terminates in a plug-sealed pupalchamber (Figure 4). The pupal periodlasts from seven to nine days, and theyoung adult spends a week or more inthe gallery before emerging. Theadults emerge in early summer (possi-bly through the entrance hole), andwithin four to eight weeks the femaledeposits her eggs between and underbark scales. From T. velutinum, thisoccurs from early May to August; forT.c. parvulum, this occurs from theend of June to mid-July. The eggshatch after 10 to 16 days. The lifecycle is usually completed in one year(Figure 5).

BARCAMBIU

SAPWOO

HEARTWOOPIT

Siricidae

Monochamus spp.

Tetropium spp.

Ergates spiculatus spp.

Ambrosia beetles Wharf borer – decaying logs or lumber

Powderpost beetles –cured, processed only

saltwateronly

Shipworm

Gribble }

Golden buprestid

Asemum striatum

Semanotus spp.

Cedar borer

up to 13 mm.

up to

10

cm.

up to 5 cm.

Other roundheaded borers

Other woodborers of the familyCerambycidae that are less commonlyfound include the ponderous borer,Ergates spiculatus, (Figure 2) whichattacks dead Douglas-fir and pon-derosa pine and to a lesser degree,other pines and true firs. Mature lar-vae are up to 70 mm long and areoccasionally found boring deep in theheartwood (Figure 4). Larval galleriescontain fibrous boring dust and exitholes are 20 mm or larger in diameter(Figure 3). Adults are dark brown, upto 65 mm long, thick-bodies andemerge from July to September.Sermanotus (Figure 2) are more com-mon, attack western red cedar, yellowcedar, true firs and other conifers to alesser degree, and they occasionallydegrade lumber. The larvae, up to 18mm in length when mature, feed main-ly in the phloem-cambium area butmay penetrate into the sapwoodthrough oval entrance holes that mea-sure approximately 5 mm (Figures3,4) just prior to pupation which usual-ly occurs in June. The adults are two-

tone dark and medium reddish brownand are generally up to 17 mm long;exit holes are only slightly larger thanentrance holes. The black spruceborer, Asemum striatum, (Figure 2) isabundant in fire-killed Douglas-fir.Larval entrance holes are oval and areabout 4 mm across (Figure 3). Maturelarvae, up to 25 mm long, mine ovaltunnels up to 20 cm in length in bothsapwood and heartwood (Figure 4).Emergence holes are round and about5 mm in diameter. The adult is uni-formly brown or black, up to 18 mmlong, and often it will reattack deadtrees.

Numerous other species of thisfamily occur in British Columbia.Some species bore into wood butoccur infrequently, some mine exten-sively under the bark and have larvaesimilar in appearance in metallicwoodborer larvae, some feed in rootswhile others prefer long-dead or rot-ting wood, and still others feed onbrush species or hardwoods.

Figure 4. Approximate depths to which woodborers penetrate standing trees, logs and lumber.

Horntails or woodwasps,Siricidae

Woodwasps (Figure 2) attack weak-ened, dying, or recently dead trees ofalmost all conifer species. The larvalmines are generally U-shaped and arefrom 5 to 20 cm in length; they some-times penetrate into the heartwood,and terminate in a pupal chambernear the surface. Siricids overwinteras larvae and pupation occurs in latespring and early summer. Youngadults may spend several weeks inthe pupal chamber before emergingthrough round, exit holes about 5 mmin diameter (Figure 3, 4). Eggs arelaid from mid-July until August andsome large females may lay up to 500eggs. Eggs and spores of a symbioticfungus, Amylostereum, which the lar-vae are reported to eat, are depositedthrough a long ovipositor (25 mm inlength) directly into the wood. Theeggs hatch after 14 to 28 days.

In the two-year cycle (a life cyclemay take one to three years), larvaeoverwinter and go into diapause in thespring after the first winter; the adultsemerge at the end of the second year(Figure 5). Adults attack scars on liv-ing trees, trees of low vigor, fire-killedtrees, and freshly felled trees.

Western cedar borer, T. blondeli,and golden buprestid, B. aurulenta

While the western cedar borer (Figure2) primarily attacks western red cedar,it has also been recorded in yellowcypress and incense cedar,Trachykele blondeli larvae bore fromthe branches into the bole where theyprefer heartwood; larval mines are upto 25 mm wide. Gallery entranceholes in branches are small and gener-ally not noted. Mines are oval or flat-tened in cross section and are tightlypacked with fine, light-colored frass.After two or more years, mature larvaepupate at the end of the larval galleriesduring late summer. About 20 dayslater, they transform to adults in the falland then overwinter in the galleries.The following spring, the adult beetleschew through to the surface, leavingemergence holes that are typicallyabout 8 mm in diameter (Figures 3,4).Adult beetles feed inermittently oncedar foliage for several days beforemating. The life cycle is generally twoor more years (Figure 5).

The golden buprestid (Figure 2)prefers Douglas-fir but also attacksspruces, true firs, pines and westernred cedar. Unlike several otherspecies of buprestids which first minethe inner bark, newly emerged larvaeof B. aurulenta bore directly into the

sapwood usually penetrating 1 to 2 cmbelow the surface where they exca-vate mines which enlarge as the lar-vae grow in size; occasionally, heart-wood is penetrated. Entrance holesare minute and are not easily seen.Galleries are oval in cross section andare tightly packed with fine, light-col-ored frass (Figure 3,4). Mature larvaepupate during late summer and trans-form to adults in the fall; the adultsoverwinter in the galleries. In thespring, newly emerged adults requirea period of feeding on Douglas-firfoliage before they mature and mate.In the late spring or summer, thefemales lay eggs in bark crevices andscars. The eggs, laid singly or inmasses, hatch soon afterwards. Thelarval stage lasts two to four yearsunder normal conditions, however, inseasoned wood under low humidity(wood in structures), larvae may liveup to 60 years and adults may emergeat any season in such cases (Figure5).

Numerous other woodborerspecies of the family Buprestidaeoccur in British Columbia, some arewoodborers in softwoods but occurinfrequently; some limit activity to theinner bark; some feed in cones, othersare leafminers, while still others feedexclusively in hardwoods.

5

Descriptions

Sawyer beetles Monochamus spp.

Egg: 1 × 4 mm, elongate, curved, smooth, white and leathery, one end slightly flattened and the other some-what pointed.

Larva: at maturity 25 to 50 mm long, whitish grub, legless and markedly segmented.

Pupa: About 20 mm long, creamy white, and resembles the adult.

Adult: 15 to 35 mm long, body black to gray-reddish brown, depending on species, elytra (hardened forewings) sparsely covered with black and white scales (short pointed hairs) except for scattered velvetypatches of dense black (brown) scales. Antennae longer than body, those of male, black to gray-brownand longer than those of female, which are alternately banded black and gray (Fig. 2).

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Monochamus spp.

Tetropium velutinum

Tetropium parvulum

Buprestis aurulenta

Trachykele blondeli

SiricidaeLarva Leavescambium, enterssapwood

AdultEggLarvaPupa

Overwinters in gallery / exits in spring

adult in pupal cells until May

gen. 2 - 4 yrs, to 60 yrs in seasoned wood

1 to 3 yrs

in larval stage 1 - 2 yrs

Figure 5. Life cycles of the major British Columbia woodborers.

Spruce and larch borers, Tetropium spp.

Egg: 1 × 0.5 mm, elliptical, white and loosely clustered.

Larva: 10 to 13 mm long, 2.5 to 3.0 mm wide at maturity, yellowish white, cylindrical, slender, three pairs ofthoracic legs, mandibles black, brown head recessed in thorax.

Pupa: gray-white, similar to adult in size and form.

Adult: 10 to 15 mm long, 3 to 4 mm wide. Head black, eyes deeply notiched, antennae medium brown toblack, twice as long as head and thorax, upper surface of thorax shiny black (T. c. parvulum), velvetyblack (T. velutinum), elytra variably pale yellow-brown to black, densely clothed with pale gold-coloredscales, legs medium to dark brown (Fig. 2).

Horntails or woodwasps, Urocerus spp., Sirex spp.

Egg: 1-2 mm, elongate-oval, generally white.

Larva: mature larva to approximately 32 mm in length, whitish, cylindrical with three pairs of vestigial thoraciclegs, head hemispherical with mandibles strongly pigmented and toothed, pigmented terminal abdomi-nal spine. Appears S-shaped from the side.

Pupa: long, slender, similar to adult in size, gray white, within parchmentlike cocoon, distinct adult shape.

Adult: 12 to 50 mm long, elongate, thick-waisted, abdomen black to metallic blue-black, often yellow-banded,two pairs of membranous wings, ovipositor of female one-half or greater body length. Urocerus spp.has yellow patch behind each eye. Size and coloration vary with sex and species (Fig. 2).

Western cedar borer, Trachykele blondeli, and golden buprestid, Buprestis aurulenta.

Egg: 2.5 × 1.75 mm, oblong, off-white ashy gray (pearly white, oval and flattened for the golden buprestid).

Larva: young larva 2-3 mm × 0.5-1 mm, mature larva 30 to 40 mm × 6 to 8 mm, creamy white except for darkbrown mouth parts, small head retracted into broad, flat thorax, abdomen is long and much narrowerthan thorax and consists of 10 subcylindrical segments.

Pupa: 16 to 22 mm × 6 to 8 mm (slightly smaller for golden buprestid), white except for the brown eye spots.

Adult: 12 to 20 mm × 4 to 8 mm, elongate-oval, tapered posteriorly, brilliant bronzy green or blue, elytra longi-tudinally corrugated, antennae short and 11-segmented (borders of grooved wing cases and undersideof body coppery gold on golden buprestid) (Figure 2).

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Distribution and hosts

In British Columbia, some species ofwoodborers occur over limited geo-graphic areas or show a preferencefor a limited number of hosts; manyspecies, however, occur throughoutthe province (Table 1).

Woodborers have historically notpresented major problems as forestpests; consequently, sampling hasbeen limited. Collections and pub-lished records of the Forest Insect andDisease Survey since 1949 providegeneral trends about woodborer distri-bution. The pinewood nematode vec-

tor, Monochamus spp., has beenrecorded throughout the province andcould occur in all forests and millyards where woodborer damage isnoted and to varying degrees in mostconifer species except cedar, cypress,or juniper.

8

Table 1. Distribution and hosts of some woodborers in B.C.

Pest Hosts1 Forest regions2 Remarks2

Monochamus spp. -P,Df,-F,-S, All No samples from QCI

wL,wH(rare) or NW corner of BC

Tetropium c.parvulum wS,eS Kamloops, PG,

Cariboo, PR

Tetropium velutinum wL,Df,eS,wS, All Sparse but occurs

lP,ww,aF,wH throughout BC

Urocerus spp., -F,-S,Df,wH, All All regions except

Sirex spp. -P,wL,yC, wrC NW corner BC

Trachykele blondeli wrC, yC Vancouver Lower coast and S.

Vancouver Is. only

Buprestis aurulenta Df,-P,wrC, Vancouver S. half of BC only

wH,sS,aF Nelson, Kamloops

Other woodborers of interest

Trypodendron spp., -P,-S,-F,wH, All Distrib. and nos.

Gnathotrichus spp. Df,wL,wrC,yC vary with sp.

Ergates spiculatus pP,Df, Vancouver Nelson Southern one-third

Kamloops Of BC

Semanotus spp. wrC,-F,Df All Scattered, more

common in south

Asemum striatum Df,lP,pP,alF, All Scattered through all

eS,wS other regions

Nacerdes melanura softwood Vancouver Coastal only

and hardwood spp.

1 -F=true firs, aF=amabilis fir, alF=alpine fir, Df=Douglas-fir, -P=pines, lP=lodgepole pine, pP=ponderosa pine, wwP=western white pine,

-S=spruces, eS=Engelmann spruce, sS=Sitka spruce, wS=white spruce, wH=western hemlock, wL=western larch, wrC=western red cedar,

yC=yellow cedar.

2 BC-British Columbia, NW-northwest, S.-south, PG-Prince George, PR-Prince Rupert, QCI- Queen Charlotte Islands.

Damage and detection

Sawyer beetles, Monochamus spp.

The most susceptible logs are thosecut in May or June and left in thewoods. Trees recently killed by fire orweakened by other causes such asroot rot or bark beetles are also sus-ceptible. The extent of damage to thelog depends on the length of time it isleft in the bush or decked. Damage tofire-killed timber depends on the timeand severity of the fire. Only recentlykilled trees which still contain sap inthe inner bark are attacked. The mostsevere attacks occur in areas wherecutting or windfall during the previoustwo years has encouraged the buildupof borer populations in tops, cull logs,and dying trees. External signs ofdamage are egg slits in the bark, pilesof shredded wood on the bark (coars-er than boring dust produced by barkbeetles), and round exit holes 6 to 10mm in diameter (Figure 6). Internaldamage consists initially of flattenedlarval tunnels which score the innersurface of the bark and cambiumlayer and meander randomly. This isfollowed by galleries 4 to 8 mm widepenetrating 5 to 15 cm into the log,often deep into the heartwood andgenerally U-shaped back toward thesurface.

Much of the lumber sawn from heavilyattacked logs is of low grade eventhough a large proportion of the dam-aged wood is removed in the initialslab cut. Damage to attacked logsincreases continually if processing isdelayed. Galleries also provide anentrance to rot and stain fungi, includ-ing spores of some fungi carried bythe borers. Infested logs are less suit-able for pulpwood because of fungalstaining.

Spruce and larch borers, Tetropiumspp.

These borers attack only those weak-ened, felled or fire-damaged treeswhich have fresh cambium betweenthe end of May and to August. The

galleries have a distinctive L-shape,penetrate up to 5 cm, and are denselypacked with shreds of wood and frasswhich are finer than those made byMonochamus spp. (Figure 6).

Horntails and woodwasps, Siricidae

External evidence of attack in the formof emergence holes is found only afterdamage is completed. Damage holesare round and packed with coarseboring dust as compared to shavingsin cerambycid borings. Both sapwoodand heartwood are attacked, and tun-nels can be up to 30 cm in length.When material is cut obliquely, tunnelstake an oval appearance and may bemistaken for longhorn damage. If siri-cid attack is suspected and the tree ischecked immediately, sometimes theovipositor punctures are visible, usual-ly in groups (Figure 6).

Western cedar borer and the goldenbuprestid, T. blondeli, B. aurulenta

Trachykele blondeli attacks standing,healthy trees leaving no visible exter-nal injury and causing no mortality;detection is therefore very difficult.Low-elevation, exposed southerlyaspects within the geographic rangeshould be considered suspect. Larvaltunnels are visible at knot faces afterfelling and limbing. Attack is alsohighly variable in a stand over a broadmaturity range. Damage is found pri-marily in the heartwood of the upperpart of the bole but occasionallyextends as far as the butt (Figure 6).

Oval emergence holes are theonly external evidence of goldenbuprestid damage. Internally, theoval, flattened larval galleries aretightly packed with fine frass and bor-ing dust. Detection of infested lumberbefore use in construction may be dif-ficult as tunnels of early-instar larvaeare only 0.5 to 1.0 mm wide.Structural damage or noticeable wooddestruction are rare.

Prevention and control

Efficient logging and processing man-agement are the best methods of pre-venting and controlling the attack anddevelopment of woodborers. In fire-killed timber, severely burned andmaterial may be too dry to attractlarge sawyer beetle populations, andtrees subjected to only reflected heator root burn may not become infestedtill the second year. Trees felled andleft in the bush, cold-decked, or dam-aged by defoliators or bark beetles, orinfected by root disease, or severelystressed for other reasons are alsosusceptible to attack by cerambycids,buprestids and siricids.

Measures available toassist in managementinclude the following:

1. Identify woodborer species knownto occur in your area.

2. Harvest after the completion of theadult egg-laying period. In gener-al, this means after mid-September.

3. Do not leave felled timber in thebush for a full summer.

4. Deck logs compactly (whichreduces penetration of light) tolimit egg deposition to mainly thetop two or three log layers. Uselogs cut in the fall or early winteras the outside layers of decks, asthese are least attractive to sawyerbeetles.

5. Pile logs in shaded areas or coverthem with slash to reduce wood-borer attack (caution-some barkbeetles prefer shaded host).

6. Pond logs to restrict beetle attackto the exposed dry tops of logs;increased moisture content of thewood also reduces larval survival.

7. Overhead sprinkler watering of log

9

Figure 6. Typical damage caused by various woodborers in B.C. including: 1. sawyer beetles, 2. larch and spruce borers, 3. horn-tails, 4. metallic woodborers, 5. ponderous borer, 6. ambrosia beetles, 7. powderpost beetles, 8. shipworms.

1

2

3

5

4

6

7

8

decks (full coverage) to reduce orprevent attack by woodborers.

8. Apply a registered chemical agentto protect logs. Spray the logs lib-erally to cover the tops, sides andends of the logs before egg laying.Sanex (Lindane 10% E.C.) is reg-istered for log decks although usepermits may be restrictive.

9. Promptly debark recently felledtrees exposed to woodborer attackto prevent further attacks.

10. Use good hygiene in log yards andat mill sites to discourage buildupof populations. Rapidly move allinventories from the felling sitethrough the mill yard and thesawmill.

11. Process uninfested logs beforeeggs are laid, or before larvaecomplete their cambial feedingperiod. In general, logs that havebeen cut after mid-Septembershould be processed by early May.

12. Process infested material as soonas possible to reduce the depth ofpenetration by larvae and the sizeof galleries. This will reduce theextent and severity of damage.

13. Identify the woodborer species todetermine the depth to which logshave been penetrated. Maximizelumber recovery by cut controldesigned around penetrationdepth.

14. Remove bark from all green lum-ber; sawyer beetles cannot estab-lish in bark-free material, althoughadults can emerge from suchmaterial if already present.

Other woodborers of inter-est

In addition to the woodborers alreadymentioned, there are several otherspecies of interest, such as shipworms, ambrosia beetles or powder-post beetles. All are relatively com-

mon but are not considered vectors ofthe pinewood nematode; nor is thedamage they cause likely to be con-fused with typical sawyer beetle dam-age.

Ambrosia beetles

Ambrosia beetles, pinhole borers, orpinworms seriously affect the value ofcommercial timber, both from a dam-age and a quarantine perspective. InBritish Columbia, species of the genusTrypodendron are more common inthe interior and species of the genusGnathotrichus are more common onthe coast. Most commercial treespecies are susceptible to attackalthough damage usually occurs inDouglas-fir, western hemlock, true firs,and spruces. The pinholes or gal-leries, in combination with an associ-ated fungus, greatly reduce the valueof timber and veneer. In the past,losses have been estimated as highas $64 million per year.

Adults are stubby (Gnathotrichusspp. are more cylindrical), generallyshiny, dark brown to black, 3 to 4.5mm long with a head and a thoraxrounded in front (Figure 2). Thedevelopment from egg to adultrequires only 6 to 8 weeks. Attacksbegin in March on the coast, peak inMay, and continue to August (and toNovember for Gnathotrichus spp.).Gallery entrances are marked by fine,granular, white boring dust and adultspenetrate to 10 cm. The holes areperfectly round and are 1.3 to 1.5 cmin diameter, and they are stained byfungi a few days after attack (Figures3,4,6). Adults emerge from July toSeptember and hibernate in duff andlitter (Trypodendron spp.) or overwin-ter in the gallery (Gnathotrichus spp.).There is one generation per year.

Logs cut in autumn and early win-ter appear to be most susceptiblealthough Gnathotrichus spp. will alsoattack logs as soon as two weeksafter felling. As with other woodbor-ers, processing prior to attack (in thiscase, May) is the key to preventing

damage; rapid processing even afterattack will help reduce losses.

False powderpost beetles

False powderpost beetles (Anobiidae)attack sawn timber or wood in serviceif high humidity conditions prevail.Fresh logs or recently dead or dyingtrees are not attacked. They are,however, fairly common woodborersand are occasionally found associatedwith areas of decay in some logs.

The Pacific powderpost beetle,Hemicoelus gibbicollis, (Figure 2) isthe most damaging in BritishColumbia, infesting well-seasonedhealthy sapwood of Douglas-fir, truefir, western hemlock, and spruce.Underportions of older buildings with-out basements are most frequentlyinfested and structural timbers may berepeatedly attacked until they areeventually pulverized.

Adults are generally 2 to 7 mm inlength, dark brown to black, elongatedand cylindrical with a hoodlike thoraxover a retractile head. Mature larvaeare white, somewhat curved, andapproximately 5 mm long.

Eggs are laid in cracks and crevices.Larval galleries less than 2 mm indiameter are bored primarily into sap-wood (Figures 3,4). Larvae can beactive for three or more years, oftenreducing wood to flour-like powder(Figure 6). When mature larvaepupate near the wood surface, adultsemerge cutting circular holes throughthe surface; this and the boring dustare usually the first signs of attack.The same material is attacked repeat-edly and infestations may be 20 ormore years old before damagebecomes obvious. Sapwood may becompletely disintegrated, leaving athin veneer; where the sapwood toheartwood ratio is high, structuralweakness may result.

11

Wharf borer

The wharf borer, Nacerdes melanura,a beetle of the family Oedemeridae, isof interest only because typical dam-age can be confused with cerambyciddamage in certain situations, Itattacks both sapwood and heartwoodof partly decayed material, althoughdamage can occasionally penetratefrom decayed wood into adjacentsound wood.

Eggs are laid in cracks and crevicesin summer and larvae are grayishwhite, 12 to 30 mm long and havethree pairs of well developed legs.Adults are 6 to 12 mm, reddish brown,bright or metallic, have the apex ofelytra black, and have relatively longantennae (Figure 2).

The wharf borer is found alongthe coast where it develops in moistrotting wood; it prefers wood wettedwith salt water. Larval tunnels areintermittently plugged with long tornfibres (Figures 3, 4).

Marine borers

Marine borers damage floatedtimber in salt water. When the timberis processed, damage may be con-fused with that caused by woodboringinsects. Two families are represent-ed: the mollusks, including the genusBankia, and members of the genusTeredo, commonly called shipwormsor pileworms; in the crustaceans,members of the genus Limnoria, alsocalled gribbles, are common.

The local species, Bankiasetacea, may reach a size of 60 cmand diameter of 20 mm while Teredonavalis only reaches 15 cm in lengthand a diameter of 10 mm. Bothspecies, as the comon name sug-gests, have a wormlike appearance.Numerous tunnels can be built in ashort time; these start as pin-sizedholes on the periphery of logs and canincrease rapidly in diameter to 2.5 cm(Figures 3,4). Galleries contain noboring dust but are lined by a calcare-

ous material (Figure 6). All hostspecies may be attacked and due tothe minute size of the external hole,serious internal damage may go unde-tected. Shipworms may survive forseveral weeks outside salt water andcan function effectively in 1% salinity,which is approximately one-third ofnormal sea water salinity.

The gribble, Limnoria lignorum, is6 mm long and resembles a wood-louse. It attacks in similar fashion tothe teredo; however, it is unable tosurvive in water below 1-1.5% salinity.The tunnels are shorter and smaller,although very numerous. Damage,which penetrates to only 13 mm withtunnels of 1 mm diameter, is severe(Figure 3,4). Activity is easier todetect because the gribble feeds onthe outside soft tissue just under thesurface and works inward as eachlayer is eroded by salt water and tidalaction.

The pinewood nematode

The pinewood nematode,Bursaphelenchus xylophilus, is amicroscopic worm, approximately1mm long and 0.2 mm in circumfer-ence. While it is a serious pest caus-ing mortality of pines in Japan, there isno record of tree mortality directlyattributable to the nematode inCanada, although it has been found inrecently dead or dying trees. It ismost common on pines, true firs, andspruces where it can be found activeinto the heartwood as well as the sap-wood. The nematode can increasefrom one female to many millions in asingle year. For optimum develop-ment, it requires a temperature of 23-27°C or warmer. Using a retractablestylet, it punctures cells and removesthe contents. This feeding activity,and the great numbers that can occurin the resin canals, disrupts the flow ofwater and eventually causes the deathof the tree. After a period of feedingand development, the dispersal (third)stage nematode larvae accumulatewithin 1 to 2 mm of the vector pupalchamber in the wood; these larvae

molt to fourth stage (dauerlarvae) inlate spring and are adapted to con-taminate the adult beetle just after itemerges from the pupa. In Japan, thevector than carries the nematodes tohealthy trees where the nematodesdrop into branch wounds created bythe beetle during maturation feeding.In contrast, in Canada, transmissionoccurs during oviposition in recentlydead or dying trees (Figure 7).

The nematode in BritishColumbia

Forestry Canada has been involvedwith the pinewood nematode for thelast 10 years. In that period, in BritishColumbia, 2000 samples from trees orlogs, boards and vectors from diverselocations have been inspected for thenematode. The tree species exam-ined were pine, cedar, western hem-lock, true firs, Douglas-fir, and spruce.Nematodes were found in a total ofonly five trees, mostly pine, from verydiverse locations. Out of 645 vectorextractions, the pinewood nematodewas found in a single adult beetle,Monochamus clamator.

Western hemlock and westernred cedar were surveyed in 1990 toconfirm these hosts are seldomattacked by Monochamus beetles.This was done in order to support therequest for exemption of thesespecies from the kiln drying require-ments. Only one adult ofMonochamus scutellatus was found in1000 trees or logs examined.Additionally, in inoculation trials of 22species of conifer seedlings, westernhemlock and western red cedar werenot susceptible to pinewood nema-tode.

Monochamus beetles are theprime vectors of the pinewood nema-tode and in Canada they are the onlyknown vectors. In British Columbia,28 woodboring species other thanMonochamus beetles were reared,primarily from nematode-inoculatedbolts, and found to be free of thepinewood nematode.

12

13

JAPAN(1 year cycle)

CANADA(2-3 year cycle)

sawyer beetlesmaturation feedon branches ofhealthy trees

sawyer beetles emergefrom dead trees or felled

timber carrying PWN

PWN attracted to pupaein logs or dead trees

trees die frompine wilt disease

PWN from sawyerbeetles enterfeeding wounds

PWN multiplyin resin canals

sawyer beetles carryPWNs to stressed trees orfelled timber and lay eggs

sawyer beetle larvae developand PWN feed on introduced

fungi in pine resin canals(longitudinal section shown)

sawyer beetles layeggs in dying trees

fungi-carryingbark beetles

colonizefelled timber

PWN DISEASE CYCLE

Log deck with beetle damage

Figure 7. The pinewood nematode – sawyer beetle disease cycle in Japan and Canada.

REFERENCES

Bletchly, J.D. 1967. Insect and marine borer damage to timber and woodwork. Her Majesty’s Stationary Office. London.

Cerezke, H.F. 1975. White-spotted sawyer beetle in logs. Northern For. Res. Cent. Inf. Rep. NOR-X-129.

Duncan, R.W. 1979. Western Cedar Borer. Can. For. Serv. Pac. For. Res. Cent. For. Pest Leafl. 66.

Duncan, R.W. 1981. The Golden Buprestid. Can. For. Serv. Pac. For. Res. Cent. For. Pest Leafl. 68.

Dwinell, L.D.; Nickle, W.R. 1989. An overview of the pinewood nematode ban in North America. U.S. Dept. Agric. Gen.Tech. Rep. SE-55.

Furniss, R.L.; Carolin, V.M. 1977. Western forest insects. U.S. Dept. Agric. Miscellaneous pub. No. 1339.

Mamiya, Y. 1984. The Pinewood Nematode. Pages 589-626 in W.R. Nickle, editor. Plant insect nematodes. Marcel Dekker,Inc. New York. 925 p.

Ostaff, D. 1977. Protect Your Logs. Eastern Forest Products Laboratory. Bulletin LD8E. Ottawa.

Sutherland, J.R., Ring, F.M. Seed, J.E. 1991. Canadian conifers as Hosts of the Pinewood Nematode (BursaphelenchusXylophilus): Results of Seedling Inoculations. Scand. J. For. Res. (in press).

Shore, T.L. 1985. Ambrosia Beetles. Can. For. Serv. Pac. For. Cent. For. Pest Leafl. 72.

Wingfield, M.J., Blanchette, R.A., Nicholls, T.H. 1984. Is the pinewood nematode an important pathogen in the UnitedStates? J. For. 82: 232-235.

Additional Information

Additional copies of this and other Forest Pest Leaflets,as well as additional scientificdetails and identification services,are available by contacting:

Natural Resouces CanadaCanadian Forest ServicePacific Forestry Centre

506 West Burnside RoadVictoria, B.C. V8Z 1M5

http://www.pfc.cfs.nrcan.gc.caPhone (250) 363-0600

© Her Majesty the Queen in Right of Canada, 1994PDF Version created April 2001

Natural Resources Ressources naturellesCanada Canada

Canadian Forest Service canadienService des forêts