E x t e n s i o n N o t e # 3 3 M a r c h 2 0 0 1

RESEARCHISSUE GROUPS

Soil Conservation

Wildlife Habitat

Hydrology

Forest Health

Reforestation

Stand Tending

Ecosystem Inventory andClassification

Biodiversity

Silvicultural Systems

Guideline Verification

Extension

n The study results show thatinoculating stumps on cal-careous soils with the com-petitive fungus Hypholomafasciculare is possible.

n Two years after inoculation,the fungus continues to growand shows promise for miti-gating timber losses due toArmillaria root disease.

INTRODUCTIONArmillaria root disease is presentthroughout much of the forestedlandbase in the central and south-eastern parts of British Columbia.In the Nelson Forest Region, withinthe Invermere Forest District alone,Armillaria root disease is consid-ered to be affecting forest produc-tivity on 22 000 ha of the opera-tional landbase; much of this areais on calcareous soils. For moreinformation about calcareous soils,see Kishchuk et al. 1999. The onlyoperational treatment currentlyused to control Armillaria root dis-ease is the removal of tree rootsafter timber harvesting.

Recent research shows that me-chanical root removal techniques,when used on calcareous soils,have the side effect of spreadingconsiderable calcareous material(Quesnel and Curran 1999). Basedon what is known about the rela-tionship between soil calcareous-ness and soil productivity, there isgood reason to suspect that treat-ments that increase calcareous-

ness might decrease soil produc-tivity (Quesnel and Curran 1999).

As part of the Invermere EnhancedForest Management Pilot Project(EFMPP)2, the BC Ministry of For-ests (BCMOF) has been investi-gating the use of a competitivefungus, Hypholoma fasciculare, toreduce timber losses related toArmillaria root disease. It isspeculated that Hypholoma fas-ciculare will reduce Armillaria levelsby outcompeting Armillaria. Inlaboratory experiments, Hypholomafasciculare captured substratemore quickly than Armillaria, grewover top of Armillaria and throughit, and appeared to exude chemi-cals that kill or weaken the Armil-laria (see Chapman and Xiao 2000for more details). These laboratoryresults are now being tested in thefield.

The competitive fungus approachdoes not create any soil distur-bance; if the technique is effective,it might have particular applicationon calcareous soils. An important

USING HYPHOLOMA FASCICULARE INOCULATIONAS A MEANS TO CONTROL ARMILLARIA

ROOT DISEASE ON CALCAREOUS SOILS:TRIAL ESTABLISHMENT AND MONITORING

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1 This document has also been published asExtension Note EN-052 by the Research Sec-tion of the BCMOF’s Nelson Forest Region.2 The goal of the Invermere EFMPP is to de-velop operational forest management strategiesthat focus on the timing, location, and intensityof management practices; the application ofvarious harvesting systems; and forest inventoryand research activities. Emphasis is placed onthe principles of adaptive management.

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question with regard to the com-petitive fungus approach is simplywhether or not the fungus will growwell in calcareous conditions. Inaddition, the theory behind thecompetitive fungus approach isthat after a natural stand-replacingevent, such as a fire, there is aburst of activity by saprophytes asthe large input of fresh woody ma-terial decays. It is thought that thecompetition between saprophytesand root rot fungi after a normalstand-destroying event is what re-duces the vigor of root rot fungi. Totest this theory, and to see if theremight be differences in populationsof saprophytic fungi in differentsoils, a fungus survey has beenestablished in conjunction withcompetitive fungus trials.

The fungus survey focuses oncord-producing fungi because theytend to be mobile in soil and wouldbe the type of fungi that would firstoccupy the roots on stumps. Cordfungi make root-like structures toexplore the soil and to transportnutrients and moisture from onelocation to another. These fungican be identified based on cordmorphology, which makes themeasier to work with than manyother types of fungi.

This portion of the InvermereEFMPP is a cooperative effort ofthe Research Section of the NelsonForest Region, the Invermere For-est District, and the Research Sec-tion of the Cariboo Forest Region.The ultimate goals of the projectare to increase forest productivitythrough better management of Ar-millaria root disease, find alternativesto the potentially soil-productivity-reducing practice of mechanical rootremoval on calcareous soils, andreduce costs by lessening the needfor the costly practice of mechani-cal root removal.

The main objectives of the com-petitive fungus survey are:

1. Determine if a fungus competi-tive with Armillaria ostoyae canbe inoculated into stumps on cal-careous soils.

2. Determine if inoculation with acompetitive fungus will reducethe incidence of Armillaria rootdisease.

3. Determine if there are differ-ences in the populations of cordfungi in areas where Armillariaroot disease is a problem versusthose areas where it is not aproblem.

TRIAL DESIGN AND METHODSSeveral competitive fungus trialshave been established in the In-vermere area.

Four of the trials were establishedin cooperation with CrestbrookForest Industries (now Tembec).Two of the trials are located in up-per Dry Creek at different eleva-tions (IDFdm2 and MSdk1), andtwo trials are located along theKootenay River (IDFdm2). Othertrials have been established in theNelson Forest Region in conjunc-tion with other research work goingon at Whitetail Brook (IDFdm2)and Nine Mile Creek (MSdk1), andone trial has been located in aSmall Business Forest EnterpriseProject (SBFEP) block at LemonCreek (IDFdm2). All trials are con-trolled and replicated, and some ofthe trials also include root removalas another treatment.

In the competitive fungus trials,stumps were inoculated with Hy-pholoma fasciculare by burying a~1.3-kg piece of inoculum adjacentto each stump (Figure 1), just un-der the forest floor and adjacent toa large root and the base of thebole. Inoculum is heavy and bulky;horses were an effective means todistribute the inoculum throughoutthe plots (Figure 2).

For the fungus survey part of thestudy, pine stakes, ~45 cm longand ~8-10 cm in diameter, wereused as “traps” to lure fungi so thatwhen the stakes are pulled, thefungi occupying them can be de-scribed. Most of the stakes wereinstalled in fall 1998, with someadditional stakes added in fall1999. Using line intersect sam-pling, the “traplines” were estab-lished by pounding 100 stakes intothe ground at 2-m intervals. Thestakes were pounded into the min-eral soil to a depth of approxi-mately 15 cm, and usually at least30 cm of the stake remained abovethe ground so the stake could befound again later and pulled up.

Figure 1. Inoculum was buried atthe base of the bole.

Figure 2. Horse carrying inoculum.

“Traplines” were placed in a varietyof scenarios including clearcuts,clearcuts with stumping, partialcuts, and uncut forested areas,both with and without Armillariaroot disease—all on calcareoussoil. Plots were also established innon-calcareous clearcuts, clearcutswith stumping, Armillaria-infecteduncut forests, and uninfected uncutforests. In addition, stakes will beplaced in the Long-Term Soil Pro-ductivity (LTSP) trial which is beingestablished in the Mud Creek Area.3

The proof of whether or not thetreatment with Hypholoma fascicu-lare will mitigate timber losses fromArmillaria root disease will not beevident for several years. Seedlingdeaths caused by contact with rhi-zomorphs of Armillaria stumpstypically do not start appearinguntil four or five years after har-vesting (Morrison et al 1991). Fouryears after distributing the inocu-lum, seedlings and trees closest tothe 100 stumps located in the coreof each plot will be monitored forsigns and symptoms of Armillaria

3 The LTSP is an international soil research trial;one replicate of the trial has been installed at theMud Creek site under the auspices of the In-vermere EFMPP, and two more are under way,to make a complete installation of three repli-cates.

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infection, including seedling mortality.

So far it has been practical tomonitor the stumps to see if thecompetitive fungus is established.This is done by using an excavatorto pull stumps, or by digging upindividual roots. A certain amountcan be discerned by peeling thebark away from around the stumpand the upper roots. In somecases, the Hypholoma producesfruiting bodies (mushrooms). How-ever, it is not possible to predictwhen the fruiting bodies willemerge, so to find them, the visit tothe site has to be fortuitouslytimed. Hypholoma growing onwood can be identified in the fieldby its pattern of rot, abundantwhitish cords, and distinctive smell.

In both 1998 and 1999, severalstumps from the Upper Dry Creekinstallations were examined to de-termine if they had become in-fected with Hypholoma fasciculare.

Also, in the fall of 1999, forty trapstakes were removed, ten each fromfour different treatments: the partialcut area with high Armillaria rootdisease and not inoculated with Hy-pholoma; same as above exceptinoculated with Hypholoma; an uncutforest with high Armillaria root rot;and a clearcut in which there was nosign of Armillaria root disease.

The stakes were packaged indi-vidually in clean bags and takenback to the laboratory where theywere kept refrigerated until cordfungi on the trap stakes were de-scribed and cultured. The reasonfor taking stakes from only a fewtreatments at this t ime was towork out the methodology—tobe sure that the fungi could bedescribed and cultured from cords.A larger sample will be taken in2000.

RESULTS

Inoculation EvaluationHypholoma mushrooms werefound growing on a few stumps in1998 (Figure 3). All of the rootsystems excavated in 1998 hadHypholoma cords running over thesurface of the root systems, andthe surface wood was infected bythe fungus. The identity of the Hy-pholoma was confirmed by culturestaken from the cords and from the

surface of the wood in the root. Theroot systems were from 10 to>50% occupied by the Hypholoma.

In 1999, four stumps, heavily in-fected with Armillaria and inocu-lated with Hypholoma, were exca-vated. Hypholoma was still foundon all four stumps, ranging from arelatively small patch near the pointof inoculation, to being widespreadover the root system (especially onpine). At the slightly higher eleva-tion installation at Dry Creek,abundant Hypholoma was found,and in one case Hypholoma fruitingbodies were found on the side of astump. Hypholoma seemed morevigorous in the higher elevationsite.

Fungus TrappingMany of the stakes examined had avariety of cord fungi on them, in-cluding Hypholoma (Figure 4). Thesample size is too small to sayanything definitive about treatmenteffects, but the stakes from theclearcut had fewer types of fungi onthem. Armillaria species have alsobeen isolated from the stakes;based on the appearance of thebranching pattern of the rhizo-morphs, the fungus could be Ar-millaria ostoyae.

Figure 3. Hypholoma growing froman inoculated stump.

Figure 4. Two different kinds ofcord fungi found at the Dry Creek

study sites (unidentified cords fromtrap stakes).

DISCUSSIONSo far, the study has clearly shownthat it is possible to inoculate acompetitive fungus onto stumps oncalcareous soils.

The fungus is continuing to growtwo years after inoculation, andshows promise for mitigating tim-ber losses due to Armillaria rootdisease. Even though the fungushas established wherever it wasinoculated, there seem to be differ-ences in tree species preferenceand site adaptation of isolates.More stump excavations will bedone in 2000 and 2001, to elabo-rate on how the inoculum behavesin different conditions.

The fungus-trapping techniquelooks as if it will be useful formonitoring populations of cordfungi. Additional stakes will besampled from a number of treat-ment replicates in in 2000 and2001.

REFERENCESChapman, W.K. and G. Xiao. 2000. “In-

oculation of Stumps with Hypholomafasciculare as a Possible Means toControl Armillaria Root Disease” in Ca-nadian Journal of Botany 78: 129-134.

Kishchuk, B.; D. Maynard; and M. Curran.1999. Calcareous Soils. TechnologyTransfer Note Number 15. Pacific For-estry Centre, Canadian Forest Service,Natural Resources Canada. Victoria,BC.

Mallett, K.I. and Y. Hiratsuka. 1985. “The‘Trap-Log’ Method to Survey the Distri-bution of Armillaria Mellea in ForestSoils” pp.1191-1193 in Canadian J. ofForest Research, Vol. 15.

Morrison, Duncan; Hadrian Merler; andDon Norris. 1992. Detection, Recogni-tion and Management of Armillaria andPhellinus Root Diseases in the South-ern Interior of British Columbia. FRDAReport 179. Research Branch,BCMOF. Victoria, BC. 25p.

Quesnel, Harry and Mike Curran. 1999.Shelterwood Harvesting in Root Dis-ease Infected Stands in SoutheasternBritish Columbia: Post-Harvest SoilDisturbance—EP 1186. ExtensionNote EN-043. Nelson Forest Region,BCMOF. Nelson, BC. 6pp.

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ACKNOWLEDGEMENTSThe authors acknowledge the In-vermere Forest District (fundingprovided by the calcareous soilscomponent of the Enhanced ForestManagement Pilot Project,) andCrestbrook Forest Industries (nowTembec) for their early and ongo-ing support for these trials.

FOR MORE INFORMATION,CONTACT:Bill Chapman, Soil ScientistCariboo Forest Region250-398-4718Bill.Chapman@gems8.gov.bc.ca

Emile Begin, Forest Health OfficerInvermere Forest District250-342-4316Emile.Begin@gems6.gov.bc.ca

Mike Curran, Soil ScientistNelson Forest Region250-354-6274Mike.Curran@gems5.gov.bc.ca

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