Fungi Causing Above-Ground Wood Decay in Structures in California W

FUNGI CAUSING ABOVE-GROUND WOOD DECAY IN STRUCTURES IN CALIFORNIA W. Wayne Wilcox Professor

and Mark Dietz Former Graduate Student Researcher Forest Products Laboratory University of California Richmond, CA 94804-4698 (Received September 1996)

ABSTRACT

Decay. funei- were isolated and identified from decaved wood above-eround" in structures in Cali- fornia. It was an opportunistic sample made available by a number of individuals dealing with decay nroblems throuehout- the state. An attemnt was made to isolate as lareeu a number of different decav fungi as possible from the limited sample material available. The total number of fungi involved in above-ground decay appeared to be small, and the list of fungi was almost identical with the list of fungi isolated from green lumber prior to use. This suggested the possibility that most of the fungi responsible for structure decay were present in the green lumber when the structure was built. Effects on distribution of decay by type of structure, location in structure, structure age, sub-structure construction and type of siding are reported, along with the frequency of structural defects and moisture problems promoting decay. Smctures with slab-on-grade and stucco siding appeared to be the most vulnerable to decay. These data suggest an explanation for why California, with a low calculated Scheffer Climate Index, has decay problems of far greater severity than predicted by the Index. Keywords: Wood decay, structures, above-ground, basidiomycetes.

INTRODUCTION studies has been ~rimarilvu~on wood in . A ground contact, where the perceived decay California imports over half of the framing hazard is greatest, little is known about the lumber it uses (McWilliams and Goldman fungi that cause decay specifically in above- all 1994). Because nearly framing lumber is ground locations in the United States (Cow- used green on the West Coast, the opportunity ling 1957; Duncan and Lombard 1965). exists to import decay fungi not endemic to The following questions formed the basis the region of the building and build them into for the research reported here: a structure bv using meinfected lumber with- out benefit 0; the s2lization that should ac- 1. Is the number of fungi responsible for de- company kiln-drying. Although decay fungi, cay above-ground in California structures presumably, would become inactive upon air- large or small? drying of the infected lumber, the fungi would 2. Are they, generally, the same fungi as those be expected to become dormant, rather than causing decay in ground contact? dying (Cartwright and Findlay 1958; Zabel 3. Does the distribution of fungi in above- and Morrell 1992). and be available to resume ground decay appear related more to the growth whenever the lumber again became geographic location of the structure or the wet. Because historically the focus of decay source of the lumber?

Worxl and Ffhihpr S.lenre. 29(31. 1997. pp. 291-298 0 1W7 hy the Suclely of Wual Scienrs and Technology 292 WOOD AND FIBER SCIENCE. JULY 1997, V. 29(3)

4. What similarity exists between the fungi cific Northwest and survival through the pres- primarily responsible for above-ground de- sure-treatment process. cay and those decay fungi encountered in green lumber in transit? MATERIALS AND METHODS 5. What are the fungi primarily responsible for decay above-ground in structures in Pest control operators, contractors, home- California? owners calling for help with problems, and neighborhood observation were the primary sources of decayed wood, making this more LITERATURE REVIEW of an opportunistic, than systematic, sample. Two of the most comprehensive lists of fun- Although an attempt was made to secure sam- gi associated with decay in wood in use offer ples from a variety of geographic and envi- little information on which fungi may cause ronmental sites, given the meager resources decay out of ground contact (Cowling 1957; and the size of the problem, it was impossible Duncan and Lombard 1965). The species most to organize the sampling in either a systematic associated with structures by Duncan and or randomized manner. Nevertheless, samples Lombard were Meruliporia incrassata, Gloeo- were obtained from 32 of California's 58 phyllum trabeum, Paxillus panuoides, and An- counties. When fresh (still moist) decayed trodia vaillantii. Research on Douglas-fir wood was available, samples were taken and poles in the Pacific Northwest found decay information about their location and condi- fungi present even in freshly felled trees, with tions of service was recorded. In addition, re- Antrodia carbonica and Postia placenta tail lumber yards and construction sites where among the most frequent isolates (Graham and lumber had recently been delivered were vis- Corden 1982; Morrell et al. 1987, 1988; Przy- ited, and samples were taken from green lum- bylowicz et al. 1987). Gilbertson and Neuhau- ber showing obvious decay. ser (1981) isolated 10 fungi, all brown-rotters, Sampling for decay fungi was performed ei- from Douglas-fir timbers deep in a Nevada ther in the laboratory or in the field. A number mine tunnel and suggested that the fungi may of locations were sampled in each piece of de- have come with the timbers in the form of cayed wood available. The laboratory proce- resistant spores or mycelium. Their most fre- dure consisted of selecting areas that con- quent isolates were Paxillus panuoides and tained the boundary between apparently sound Antrodia carbonica. Morrell et al. (in press), and obviously decayed wood, swabbing the in a study of decay fungi present in Douglas- surface with 70% ethanol, raising a surface fir poles during air-seasoning, reported isolat- chip with a flamed chisel, removing several ing most frequently Postia placenta, Penio- small wood chips from the underneath surface phora spp., Stereum hirsutum, Phanerochaete with a flamed wood-carver's gouge, and plat- sordida, and Sistotrema brinkmanii, after a ing the chips on 2% malt agar. For sampling 3-month exposure; after 6 months, Postia pla- in the field, the sampling site was swabbed centa and Stereum hirsutum were the only with 70% ethanol, and a core was removed identifiable decay fungi isolated in large num- with a flamed increment borer and flamed ex- bers. Zabel et al. (1980) reported that the most tractor directly into a sterile plastic bag. Upon frequently isolated decay fungi from preser- return to the laboratory, pieces of the core vative-treated Douglas-fir utility poles in the were sliced with a flamed razor blade, flamed northeastern U.S., Antrodia carbonica and lightly, and aseptically plated on 2% malt agar. Postia placenta, were not common to the area Some plates also contained 20 ppm benomyl, of use. The presence of these fungi was attrib- to favor decay fungi over mold and stain fun- uted to successful colonization during the air- gi. Isolates that appeared to be possible decay seasoning process at the pole origin in the Pa- fungi were transferred to malt agar tubes, or- Wilcm and Dier:-ABOVE-GROUND DECAY IN STRUCTURES 293

TABLE1. Basidiomycete fun~iisolated from decay in wood exposed above-ground in structures in Cal(fofomia. .,,...... Fungal eronl Cnmmcrc>rl Multi-family S ~utill Antrodia carbonica (Overh.) Ryv. & Gilbn. 6 1 16 23 Anrrodia sinuosa (Fr.) Karst. I Antrodia vaillantii (Fr.) Ryv. 3 Antrodia xantka (Fr) Ryv. Coniophora puteana (Schum.:Fr.) K~arst. Fomirnpris cajanderi (Karst.) Kotl. et Pouz. Fomiropsir roses (Alb. & Schw.:Fr) Karst. I GIoeophvNum sephrium (I%)Karst. I Gloeoplzyllum trabeum (Fr.) Mum I Pkanerochaete sordida (Karst.) Bun Pleurorus osrrearus (Jacq.:Fr.) Kummer Postia plocento (Fr.) M. Lars. & Lomb. 2 Unknown basidiomvcete 1 Total 16 36 5 1 103

I Tho fungi arc listed alphabstic~llyby nams according to thc cumntly proposed nomenclatvrr. Bccavsc of recent flux in the nomcnclaium md taxonomy of bdridiomycelc ilmgi. rha xclenrific nrme. formerly ~n common usc have not been used. Dictz iIV941 (Appendix A1 conrlinr a rynonymour Itsring nf there fungi with the source iitcnturc. us vcll as other fungi mentioned throughout rhr rexr. 'Commercial ~tmcturerinclude: churches. schoolr. rerrrurrnrs md oxher public gathetins buildings: mulxi-famiiy structures refer\ m eitherapartment building- or condominium cumplcrsr: ringle.hmily xien m single-family home,. ganized into groups based upon cultural char- were: Antrodia carbonica, Gloeophyllum tra- acteristics, and a representative of each group beum, Gloeophyllum sepiarium, Postia pla- was studied following the methods of Nobles centa, and Antrodia vaillantii. There was no (1948, 1965) and Stalpers (1978). Decay ca- evidence of association of any species with pacity of each selected isolate was confirmed any particular geographic region. using a modified agar plate test modeled after Table 2 lists these same fungi with reference the European Standard Method (EN-113, to the part of the structure from which they 1982). After tentative identification was made, were obtained. Expressed as a percentage of isolates were compared with identified cul- the total isolates for each given fungus, the tures from the collections of the U.S. Forest fungi most frequently isolated from exterior Products Laboratory and the Eastern Forest exposure were Gloeophyllum sepiarium Products Laboratory of Forintek. All isolates (88%), Gloeophyllum trabeum (89%), Antro- reported here were either verified or identified dia carbonica (70%), and Postia placenta by the Center for Forest Mycology Research (73%), while those most frequently isolated at the U.S. Forest Products Laboratory. from interior locations were Antrodia vaillantii (54%). Antrodia carbonica (30%). and Pos- RESULTS tia placenta (27%). Table 1 lists the wood-decay fungi isolated The locations in the structure where decay and their frequency of occurrence in various fungi were isolated most frequently were types of structures. Most isolates (65%) were decks (20%) and attics (15%) (Table 3). Based obtained from Douglas-fir lumber. Twelve upon 5-year age groupings, the highest per- identified species of wood-decay fungi and 5 centage of isolates was obtained from build- decay fungi of unknown identity were ob- ings in the 6- to 10-year age class (Table 4). tained from 103 successful isolations of basid- Buildings with slab-on-grade construction iomycete fungi from above-ground decay in (67%) and stucco siding (30%) yielded the structures. Of the twelve, the 5 isolated most greatest number of isolates (Table 5) and, frequently, in decreasing order of occurrence, therefore, appear to be at greatest risk of decay 294 WOOD AND FIBER SCIENCE. JULY 1997, V. 290)

TABLE3. Number of deca.y fungi isolnfed from nbove- ground decav in various locutions in smflctrrrer in Cnli- fornia.

~ypcof rrluciurc nnd number ot iv!lnlon\ Comme~ Mulli. Single- cia1 Rmiiv filmlly Total Attic Bathroom Bedroom Deck Glulam beam Garage Kitchen Livinglfamily mom Patio Roof Siding Stairs (Exterior) Trim boards 5 5 10 Total 16 36 51 103

among structure types in California. Decay in Vim the building interior also was highest (48% of isolates from the interior) in stmctures with both slab-on-grade foundation and stucco sid- N N ing. The most common source of moisture associated with decay was direct precipitation in the form of rain, fog, dew, or landscape irri- N gation; the most common moisture-related problem was leakage through roofs or siding. - The most frequent building defects found associated with decay were short roof overhangs allowing runoff onto exposed wood (23 cases), lack of maintenance (17 cases), leaky roofs (15 cases), inadequate ventilation (13 cases), and landscape irrigation wetting (12 cases) (Table 6). Decay fungi also were isolated from lumber

- TABI.E4. Proportion of deco,y fun,& isolates hv rhe ape of rite strucrure. Wiicox and Diet:-ABOVE-GROUND DECAY IN STRUCTURES 295

TABLE5. Number of decay fungi isolated from above-ground decav in buildings associated wirh eurious rypcs qf siding and sub-structure construction.

Type of rub-nrucare

Type of riding Crawl spncc Full basement Pier Slub-on-grdde Spllr levcl h101 Number of isolates Aluminum 1 1 2 Asbestos shingle 1 1 2 Cedar plywood I I Cedar shakes 2 2 4 Douglas-fir plywood 3 12 I I h Hardboard lap 3 I I 14 Hardboard panel h 1 7 Masonry block 1 3 4 Stucco 4 1 2 22 2 3 1 Wood lap 7 1 10 4 22 Total isolations 21 3 2 69 8 103 in storage or recently delivered to construction rence, were Antrodia vaillantii, Postia placen- sites. Ten species of wood-decay fungi and ta, Gloeophyllum trabeum, and Antrodia car- one unidentified decay fungus were isolated bonica (Table 7).Although all of these fungi from 32 specimens of green Douglas-fir lum- appear on the lists of principal fungi from both ber. Of the 10 identified species, the most fre- exterior and interior exposures in structures, quently isolated, in decreasing order of occur- the ranking matches most closely the interior list. Although several white-rot fungi were iso- TABLE6. The rvpe and frequency of structural defects lated from above-ground decay in this study, and moisture-related problems in buildings from which decav fungi were isolated. all of the fungi identified above as being the fungi most frequently isolated are brown-rot fungi.

Bathroom or clothes drier vented into DISCUSSION enclosed spaces 2 Caulking missing or incomplete 5 The results of this study suggest that the Cracks in stucco siding 6 number of fungi causing economically impor- Decks or roofs improperly joined to the tant above-ground decay in structures in Cal- main structure 5 ifornia is small and that the fungi responsible Flashing around penetrations missing or used improperly 8 for building decay are, to a great extent, the Hose or sprinkler wetted wood 12 same fungi present in the green lumber from Lack of general preventive maintenance 17 which the buildings were built. The most fre- Leaks in plumbing 2 quently isolated fungi, Antrodia carbonica, Leaks in roof 15 GloeophyNum trabeum, GloeophyNum sepia- Moisture drainage into the structure 4 Paint failure 2 rium, Postia placenta, and Antrodia vaillantii, Short or no roof overhang, roof runoff 23 accounted for 85% of the total isolates ob- Siding defects: exposed corners, open joints 4 tained from building decay. All of these fungi Untreated, unpainted or nondurable share a reputation, or potential, for being se- lumber in exterior exposures 6 rious wood destroyers. Because of the oppor- Vapor membranes mis-applied or lacking 5 Ventilation insufficient, restricted or lacking 13 tunistic nature of the sampling, and the small size of the sample as compared with the enor- ' Das not add up to 103 bccausc many buildings had more than one type of defect or moilnlm.mla!cd problem. mity of the decay problem in California, this 296 WOOD AND FIBER SCIENCE. JULY 1997. V. 29(3)

TABLE7. Bn~idiom~cerefun~i isolatedfrom new construcfion or lumber invenro? stocks ar retail sales ourlers and cnnstrucrion siter in California.

Anrrodio carbonica (Overh.) Ryv. & Gilbn. Anrrodio vaillantii (Fr.) Ryv. Cen'oporiopsis rivu1o.m (Berk. & Cun.) Gilbn. & Ryv. Fomiropsis rosea (Alb. & Schw.:Fr.) Karst. Gloeoph~lhrmsepiarium (Fr.) Karst. Gloeoph~llumrraheam (Fr.) Mum Lentinus lepideus Fr. Postia plncenra (Fr.) M. Lars. & Lomb. Sisturrem brinktnannii (Rrcs.) J. Erikss. Trameres versicolor (L.:Fr.) PilAt Unknown basidiomycete

cannot be construed as an exhaustive list of both recognized wood destroyers, particularly the fungi responsible for all above-ground de- in Douglas-fir, and are found especially in cay in California. However, the consistent na- wood in ground contact (Eslyn 1970; Graham ture of the results argues favorably for their and Corden 1980; Zabel et al. 1980). They significance. have not often been reported as wood destroy- All of the identified isolates have been re- ers in the above-ground portions of buildings. ported previously in association with decay in However, they have been cited as frequent col- structures or various wood products. Two of onizers of Douglas-fir poles in air-seasoning the five isolates found most often, Gloeophyl- yards (Graham and Corden 1982; Morrell et lum sepiarium and GloeophyNum trabeum, are al. 1987; Przybylowicz et al. 1987). Douglas- well-known wood product destroyers. They fir lumber and plywood accounted for 79% of are frequently associated with decay in wood the total decayed samples studied here, and exposed above-ground, frequently associated Antrodia carbonica was the most frequent iso- with decay in a variety of wood species, in- late from Douglas-fir. In addition, 82% of the cluding Douglas-fir (Eslyn 1970; Graham and Antrodia carbonica and Postia placenta iso- Corden 1980; Zabel et al. 1980) and enjoy a lates came from Douglas-fir lumber or plywood. The overall fungal population and dis- ubiquitous distribution (Cartwright and Find- tribution found in this study may have been lay 1958; Duncan and Lombard 1965). These quite different were it not for the preponder- two fungi, which are able to withstand inter- ance of Douglas-fir used for framing in Cali- mittent desiccation and prefer higher temper- fornia. atures (>35"C) for optimum growth than most Others have suggested the role in building other structural wood-destroyers, are most decay played by preinfected lumber (DeGroot likely to be important in the decay of exterior 1976; Lindgren 1955; Verrall 1952, 1956, wood. Furthermore, they have been reported 1957; Viitanen and Ritschkoff 1991), and to survive up to 10 years in air-dry wood careless handling of lumber prior to its being (Cartwright and Findlay 1958). In the present built into the structure (Wilcox 1986; Wilcox study, these two fungi were isolated substan- and Rosenberg 1982), but little documentation tially more often from decay in the externally has been available. exposed wooden members of buildings than from interior locations (Table 21, consistent CONCLUSIONS with many other reports worldwide. This study has presented evidence that, at Antrodia carbonica and Postia placenta are least in a region that depends upon green lum- Wilcox and Die=-ABOVE-GROUND DECAY TN STRUCTURES 297 ber for its framing, the fungi primarily re- which the senior author was committee chair. sponsible for above-ground decay in structures The authors thank the Center for Forest My- are the same species present in the wood used cology Research at the U.S. Forest Products to build the structures. The difference between Laboratory for confirmation of fungal identi- exterior and interior exposure alters the fre- fication. Supported, in part, by the Renewable quency of occurrence, with species able to Resources Extension Mini-grant Project Act withstand higher temperatures and periodic and McIntire-Stennis. desiccation favored in exterior exposure and those requiring high moisture content favored REFERENCES indoors; but exposure appears not to introduce CARTWRIOHT.K. ST. G.. AND W I? K. FINDLAY.1958. new species. These results call into question Decay of timber and its prevention. Her Majesty's Sta- the role played by spores and air-borne hyphal tionery Office. London, UK. 332 pp. fragments in the initiation of above-ground de- COWLMG.E. B. 1957. A panial list of fungi associated cay at the building site. Study of the available with decay of wood products in the United States. Plant fungal flora in areas surrounding various Disease Reporter 41(10):894-896. DEGROOT,R. C. 1976. Wood decay ecosystem in resi- building sites and remote sawmills and log- dential construction. 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