American Wood Protection Association Research Articles

Analysis of Basidiomycete Fungal Communities in Soil and Wood from Contrasting Zones of the AWPA Biodeterioration Hazard Map across the United States

Wood deterioration due to basidiomycetous decay fungi shortens the useful life span of wood and wood-based materials. Prescriptive preservative treatment is the most effective way to reduce the detrimental effects of these microorganisms, particularly in soil contact and areas of critical use (difficult to replace or vital to structure). Current American Wood Protection Association (AWPA) guidelines in the standardized use category system specify 3 zones of severity regarding wood decay fungal hazards but contain very little information on the diversity and abundance of these fungi colonizing soil and wood. In this study, amplicon based sequencing was utilized to compare fungal communities in wood and adjacent soil to provide baseline data on the fungi involved in the process. A thorough understanding of decay hazards is critical for the proper selection and use of wood in soil contact. The goal of this work is to provide baseline data on basidiomycete fungal diversity and species composition in different zones of the existing 3-zone AWPA hazard map as compared to the previous 5-zone hazard map and Scheffer decay indices and discuss the ecological implications for wood decay.

Study on Improving in the Evaluation of Untreated Specimens in the Decay Resistance Effect of Wood Preservatives

This study emphasizes the importance of verifying the vitality of test fungi through the results of untreated specimens in the evaluation of the efficacy of wood preservatives. However, in many cases, the weight loss of the untreated specimens does not meet the criteria in the Korean standard(KS) test method, so we devised an efficient and simplified test method by cross-applying the American Wood Protection Association (AWPA) standard method. The study found that the feeder strip inoculation method specified in the soil block test(AWPA) was more effective than the KS standard, resulting in a higher weight loss (%) of the wood blocks. Among the strains used, <i>Trametes versicolor</i> KACC54448(white rot fungus) showed weight loss rate of 34.1% and <i>Tyromyces palustris</i> and <i>Fomitopsis pinicola</i> KACC53387(brown rot fungi) showed weight loss rates of 63.9%, 58.0%, respectively. Furthermore, we found that maintaining a relative humidity of around 50% by placing distilled water in a low-temperature incubator was sufficient to create an environment in which the test fungi could decay the wood blocks without using expensive equipment such as a constant temperature and humidity chamber. As a result, it was confirmed that the activity of the test fungi can be increased even under conditions of around 50% relative humidity without the shaking cultivation process of the test fungi.

Antifungal properties of lauric arginate (LAE) treated wood

Abstract This study investigated the efficacy of lauric arginate (LAE) as a potential preservative against wood deteriorating fungi. First, the antifungal properties of LAE against two brown rot fungi, Gloeophyllum trabeum (G.t.) and Rhodonia placenta (R.p.), and two white rot fungi, Trametes versicolor (T.v.) and Irpex lacteus (I.l.) were examined using malt-agar media as substrate. Then the biological resistance of LAE-treated wood specimens (10, 20, and 25 % LAE solutions) was tested following American Wood Protection Association (AWPA) E10 soil-block test procedures. The in vitro study showed LAE actively inhibited the growth of all the fungi tested compared to growth in control plates but there were no considerable changes observed in the morphology of fungi hyphae. Wood impregnated with LAE showed increased weight percent gain as a function of treatment concentration. Characterization of LAE-treated wood on a thermogravimetric analyzer showed LAE shifted the thermal degradation temperatures to lower stages but did not significantly improve the thermal stability of the treated specimen. LAE in wood significantly suppressed fungus growth, leading to decreased mass loss but it also leached out from wood specimens during fungi exposure.

Coal Tar Distillate (Creosote)—The First and Still Great Choice to Preserve Utility Poles

Abstract Creosote, a coal tar distillate product, has been used to preserve wooden utility poles for well over 100 years. Such use began in the late 1800s and continues to this day. Creosote’s efficacy in protecting wood from decay, termite attach, and general weathering has been demonstrated by actual performance of poles in utility service and in documented field and laboratory testing. The American Wood Protection Association has standardized and long recognized the efficacy of creosote preservation. With production of pentachlorophenol ending after 2022, preservation may easily convert to creosote preservative. Creosote preservative also is an environmentally sound choice in that used poles can be used as fuel and otherwise, creosote degrades biologically. Wood is sustainable as new trees are grown to replace poles while the poles are sequestered carbon. Utility service life of creosote preserved wooden poles typically lasts for 70 to over 100 years with inspection and maintenance. Utilities can expect new creosote preserved poles to last into the next century.

The Effect of Variables on Laboratory Termite Testing: Part 3 - Test Block Density and Moisture Content

The objective of this study was to determine the impact on termite feeding of wood ring count and MC in standard tests. Introduced species (Coptotermes formosanus) were tested in an American Wood Protection Association (AWPA) E1-97 standard laboratory test. Samples with a ring count in the range of 6 – 10 rings per inch (RPI) had a higher, but not significantly different, weight loss than the 4 – 6 RPI specified by E1-97. With respect to the MC, it was determined that a lower level of moisture than that currently specified by AWPA E1 would be preferred over the higher MC achieved in ASTM D3345. Sample placement on top of the sand was recommended over the burial procedure in ASTM D3345.

Aboveground Field Performance of Douglas-Fir Heartwood Subjected to Combinations of Glycerol, Boron, and Thermal Modification

Abstract The effect of pretreatment with either boron or glycerol followed by thermal modification on the durability of Douglas-fir heartwood was evaluated in an American Wood Protection Association ground proximity test in Hilo, Hawaii. Non–thermally modified samples were generally more heavily decayed than any of the modified woods, but there was no consistent effect of different thermal modification conditions on decay resistance. Thermally modified woods tended to perform better than untreated timbers but not as well as copper azole–treated Douglas-fir heartwood lumber in test at the same site. The results are discussed in relation to how the extreme site conditions might have made it difficult for thermally modified materials to perform.

The Effect of Variables on Laboratory Termite Testing: Part I—Worker:Soldier Ratio

Abstract The objective of this study was to determine if the same soldier:worker ratio could be used in the eastern subterranean termite (Reticulitermes flavipes) and the Formosan subterranean termite (Coptotermes formosanus) in standard tests. Native (R. flavipes) and introduced (C. formosanus) subterranean termite species were tested in an American Wood Protection Association E1 standard laboratory test. Statistically equivalent weight losses were found as long as the ratio was within 10 percent of the rate required by the standard.

Statistical Process Control and Related Methods for Improvement of the Treated-Wood Industries

Abstract An approach for implementing statistical process control and other statistical methods as a cost-savings measure in the treated-wood industries is outlined. The purpose of the study is to use industry data to improve understanding of the application of continuous improvement methods. Variation in wood treatment is a cost when higher-than-necessary chemical retention targets are required to meet specifications. The data for this study were obtained in confidence from the American Lumber Standard Committee and were paired, normalized assay retentions for charges inspected by both the treating facility and auditing agencies. Capability analyses were developed from this data for three use categories established by the American Wood Protection Association (AWPA), including UC3B (above ground, exterior), UC4A (ground contact, freshwater, general use), and UC4B (ground contact, freshwater, critical structures, or high decay hazard zones). Agency and industry data indicate that between 4.45 and 9.82 percent of the charges were below the lower confidence limit of the passing standard (LCLAWPA), depending on use category. A Taguchi loss function (TLF), which is quadratic based and decomposes the monetary loss into shift and variation components, was developed to estimate the additional cost due to process variation. For example, if a treatment input cost of $1.00/ft3 is assumed for UC3B, reducing the variation in total retention allows lowering treatment targets, e.g., 1.45 to 1.38, reducing costs to $0.76/ft3. The study provides some important continuous improvement tools for this industry such as control charts, Cpk, Cpm capability indices, and the one-sided TLF.

Biological performance of a formulation containing water-dispersible copper naphthenate and sodium fluoride against decay fungi

ABSTRACTTwo formulations of wood preservative one containing water-dispersible copper naphthenate (CuN) alone and in combination with sodium fluoride (NaF) were used to treat southern pine sapwood blocks to determine the effect of the addition of sodium fluoride in the QNS on the protection against wood decay fungi using laboratory soil block tests following AWPA (American Wood protection Association) standard E10-16 [American Wood Protection Association AWPA-E10. (2016) Laboratory Method for Evaluating the Decay Resistance of Wood-based Materials Against Pure Basidiomycete Cultures: Soil/Block Test]. The standard consists in exposing treated blocks to pure monoculture of white rot (Irpex lacteus (FP-105915) and Trametes versicolor (R-105)) and brown rot fungi (Gloeophyllum trabeum (Madison 617) and Postia placenta (Madison 698) during a specific period. The weight loss (WL) in percentage of treated blocks was used as an indicator of the biological performance of treated blocks against basidiomycetes at specific retentions. Minimum WL was obtained with blocks treated with the formulation containing mixture of QNS and sodium fluoride with the retention of 0.29 kg/m3 Cu and 0.51 kg/m3 of fluorine in treated blocks. A copper retention of 1.65 kg/m3 from blocks treated with formulations containing only QNS was needed to obtain similar WL to blocks containing blocks Cu++ and F− (fluorine). The lower Cu retention is attributed to a combination of the presence of the fluorine with some toxic activities against bacteria and decay and the interaction of anions fluorine and ionic Cu (II) in the aqueous treating solutions to form more soluble biological toxic hydrate of copper fluoride ((H2O Cu (II) F2) in treated blocks compared to copper complexes less biological available in water-dispersible CuN-treated bocks.

Decay of Thermally Modified Engineered Wood Products

Abstract In this study, rated plywood, oriented strand board, laminated strand lumber, and laminated veneer lumber were thermally modified as a posttreatment at 140°C, 150°C, 160°C, 170°C, and 180°C using a closed, pressurized treatment method. Eastern larch oriented strand board manufactured from heartwood and sapwood was also thermally modified as a posttreatment at 160°C and 180°C. All specimens were subjected to laboratory soil block durability tests according to American Wood Protection Association E10‐12 utilizing Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) fungi. Heat treatment caused a reduction in weight loss for most substrate and fungi combinations.

Amplicon-Based Sequencing of Soil Fungi from Wood Preservative Test Sites.

Soil samples were collected from field sites in two AWPA (American Wood Protection Association) wood decay hazard zones in North America. Two field plots at each site were exposed to differing preservative chemistries via in-ground installations of treated wood stakes for approximately 50 years. The purpose of this study is to characterize soil fungal species and to determine if long term exposure to various wood preservatives impacts soil fungal community composition. Soil fungal communities were compared using amplicon-based DNA sequencing of the internal transcribed spacer 1 (ITS1) region of the rDNA array. Data show that soil fungal community composition differs significantly between the two sites and that long-term exposure to different preservative chemistries is correlated with different species composition of soil fungi. However, chemical analyses using ICP-OES found levels of select residual preservative actives (copper, chromium and arsenic) to be similar to naturally occurring levels in unexposed areas. A list of indicator species was compiled for each treatment-site combination; functional guild analyses indicate that long-term exposure to wood preservatives may have both detrimental and stimulatory effects on soil fungal species composition. Fungi with demonstrated capacity to degrade industrial pollutants were found to be highly correlated with areas that experienced long-term exposure to preservative testing.

Dimensional stabilization of wood treated with tall oil dissolved in different solvents

Many water repellents, such as classic wood preservatives have the disadvantage of being harmful to the environment. Therefore, interest increased even eco-friendly, or of biodegradable material. Natural oils (tallow, linseed oil), appears to be capable of preventing the wood water uptake. However, the total amount of oil required to achieve a high penetration of the sapwood. The aim of this study was to investigate the water repellent efficiency of tall oil dissolved in different solvents. As solvents ethanol, methanol, acetone and tall oil water emulsions were used. Scots pine and Uludag fir sapwood samples were impregnated with tall oil formulations. For this purpose we used tall oil/solvents (W/W) at the concentrations of 10% and 20% respectively. Test samples cut into small sizes (20 x 20 x 10 ± 0,2 mm) for water uptake and tangential swelling tests. The tests were carried out based on American Wood Protection Association (AWPA) standard E4 (2003).

Comparative Study of Resistance and Feeding Preference of 24 Wood Species to Attack by Heterotermes indicola (Wasmann) and Coptotermes heimi (Isoptera: Rhinotermitidae, Termitidae) in Pakistan.

Present study was conducted to evaluate the laboratory and field preference of 24 Pakistani wood species: Azadirachta indica (Neem), Pinus roxberghii (Chir), Dalbergia sissoo (Sheesham), Populus deltoides (Popular), Albizzia lebbeck (Shirin), Abies pindrow(fir), Alstonia scholaris (Alstonia), Erythrina suberosa (Gul-e-nister), Eucalyptus citriodora (safaeda), Ficus religiosa (Bohar), Heterophragma adenophyllum (Beeri Patta), Melia azedarach (Derek), Pinus wallichiana (Chir), Terminalia arjuna (Arjun), Acacia Arabica (Kikar), Betula utilis (Birch) Cedrus deodara (Deodar), Cordia oblique (Lasura), Mangifera indi,a (Aam),Ehretia serrata Moringa oleifera (sohanjana), Putranjiva roxburghii (Lucky bean), Syzygium cumini (Jaman) and Zizyphus jujube (Berry) against attack and damage by termite species Heterotermes indicola and Coptotermes heimi. Two weeks laboratory and four weeks field feeding trials were performed as described in standards of the American Wood Protection Association (AWPA, 1997). Samples of each of the 24 wood species were individually exposed to 100 termites (10% soldiers); and termite mortality, wood mass loss and visual appearance of the samples (on a scale of 0-10) were recorded. Results indicated that by no choice feeding assay, Populus deltoides was the most preferred and Dalbergia sissoo was the least preferred among the 24 wood species tested in laboratory against Heterotermes indicola and Coptotermes heimi. Field studies by no choice feeding test against mixed termites and C. heimi indicated D. sissoo the least palatable and Mangifera indica the most palatable wood. So it is recommended that though all 24 species evaluated in the present study differ in their susceptibility to termite attack, they would require additional protection to avoid termite attack.

An International Termite Field Test of Wood Treated with Insecticides in a Buffered Amine Oxide Carrier

Abstract A buffered amine oxide carrier has shown promise to deeply penetrate dry lumber with insecticides for termite control without using pressure treatment. Pine sapwood from trees attacked by mountain pine beetle (MPB) has increased permeability. In this study, short lengths of heavily blue stained, post-MPB lodgepole pine lumber (Pinus contorta) were treated with the buffered amine oxide carrier to borate levels less than the retentions recommended for protection against attack by the Formosan subterranean termite (average, 0.5% mass/mass boric acid equivalent ), with and without the addition of organic insecticides. Additional samples were pressure treated with alkaline copper quaternary type D carbonate (ACQ-D) and disodium octaborate tetrahydrate (DOT). The boards were installed in field tests in Hawaii and Japan at sites with confirmed populations of Formosan subterranean termites. They were inspected after 2 and 5 years. Dip plus kiln-conditioning treatment with imidacloprid, permethrin plus imidacloprid, and permethrin provided good protection to post-MPB lodgepole pine lumber against termite attack over 5 years in Hawaii and Japan. Dip plus kiln-conditioning treatment with the buffered amine oxide alone provided no protection because of the low loading of borate used as the buffer. Samples that were DOT pressure treated to below the retention required for Formosan termites in American Wood Protection Association standards did not perform as well, possibly as a result of poor heartwood penetration as well as below-standard retentions. Addition of permethrin to DOT pressure treatment improved performance. ACQ pressure-treated samples did not perform as well, with two failures in Hawaii. This was also likely associated with poor penetration in the heartwood because this material was not incised.

Monoethanolamine extraction of copper-preservative-treated wood and reuse of the extract for wood preservation

Remediation of copper-based alkaline copper quat (ACQ) and micronized copper quat (MCQ) wood-preservative-treated weathered southern pine mulch samples by monoethanolamine (Mea) extraction was studied. The potential reuse of Mea extract in ACQ wood preservative application was also evaluated. Continuous column extraction of copper-preservative-treated samples for 32 h, using 12 % Mea removed 66–86 % (between top and bottom of the column) and 65–80 % of Cu, respectively, from ACQ- and MCQ-treated wood. Mea extracts of treated wood could be reused in ACQ-treating solutions that met the American Wood Protection Association standard specifications for ACQ wood preservatives. This was achieved either by mixing the extract with industrial Cu–Mea solution at 1:4 ratio or by adding cupric acetate salt directly into the Mea extract. ACQ-treating solutions reformulated using Mea extracts of ACQ- and MCQ-treated wood performed similarly to wood treated with industrial ACQ solution and freshly prepared solution using cupric acetate. All treated wood had similar penetrations of Cu in wood during preservative treatment, Cu leaching from the treated wood in contact with water, corrosion of nails in contact with treated wood, and ability to protect wood from mold growth.

Wood dimensional stability and extractives as reasons for termite and fungal resistance of the lesser known Albizia malacophylla Kenyan wood species

Studies were carried out on termite and fungal resistance of the lesser known Albizia malacophylla Kenyan wood species. In addition wood dimensional stability, amount and chemical nature of heartwood extractives was also evaluated. Wood resistance against white rot tropical fungi was based on a laboratory soil bed test and subterranean termite resistance in the field according to American Wood Protection Association: E7-93 (1993) standard. Wood extractives were subjected to infra-red analysis using standard laboratory procedures. Albizia malacophylla heartwood is dimensionally stable (5.5 %) with a less dimensionally stable sapwood (9.6 %). Heartwood extractive content is high (9.7 %) in comparison to sapwood (4.6 %). Albizia malacophylla heartwood is resistant to fungi (8.1 %) mass loss and very resistant to termites (4.8 %) mass loss reported after 6 months exposure. Removal of extractives significantly lowered heartwood dimensional stability, termite and fungus resistance. Heartwood extractives were able to inhibit the growth of fungi under laboratory sterile conditions. Infra-red analysis of crude heartwood extractives indicated presence of aldehydes, ketones carbonyl compounds, esters, aromatic, carboxylic acids and aliphatic carbonyl compounds. Put together, the nature, amount of heartwood extractives and wood dimensional stability are at the origin of the found termite and fungus resistance of A. malacophylla wood.

Condition of Chromated Copper Arsenate Treated Hem-Fir Guardrail Posts after 20 Years in Service in Western Washington State

AbstractWood guardrail posts are among the most common wood materials currently used in highway construction. Preservative treated hem-fir is an important species for guardrail applications in the western United States. The service life of treated timber post guardrail systems has been estimated to be between 10 and 20 years. However, there is surprisingly little information on performance of timber guardrails. One aspect of the estimate of service life is wood durability. This study assessed the flexural properties, level of decay, and residual preservative levels in chromated copper arsenate preservative treated hem-fir guardrail posts removed from a project near Bellingham, Washington. Increment cores were removed from each post to assess preservative treatment and fungal colonization. The posts were tested for flexure properties in a three-point bending test. Posts that met the American Wood Protection Association standards for preservative penetration tended to have lower levels of internal decay aft...

Biological performance of Liquidambar orientalis Mill. heartwood

New approaches for wood protection based on green technologies have increased interest in using heartwood portions of certain wood species for the effects (toxic and antioxidant properties, chelate formation, hydrophobicity) of extractives located in heartwood. This study evaluated the biological performance of heartwood of Liquidambar orientalis Mill., trees well-known for production of balsam. Heartwood specimens were subjected to soil-block decay tests based on the American Wood Protection Association standard method using two brown-rot and two white-rot fungi. Specimens were also subjected to two different laboratory termite resistance tests. Additionally, heartwood specimens were tested for mold growth and resistance to furniture beetle larvae. Laboratory fungal decay resistance tests showed that the heartwood of the tree was not resistant against the fungi tested; however, the wood was resistant against termites and furniture beetle larvae in laboratory conditions. Mold tests revealed that the wood also showed resistance to mold growth. Complete biological resistance was not achieved in this study, suggesting that heartwood extractives do not directly correspond to resistance to wood-degrading fungi.

Preference of Formosan Subterranean Termites for Blue-Stained Southern Yellow Pine Sapwood

Little research has been conducted to investigate interactions between the invasive Formosan subterranean termite, Coptotermes formosanus Shiraki, and pine bark beetles native to the southeastern United States. Facilitative interactions between these organisms could alter stand dynamics and impact wood utilization strategies. American Wood Protection Association Standard E1-09 choice tests were carried out to determine the feeding preference of Formosan subterranean termites for blue-stained versus unstained southern yellow pine sapwood. Three separate colonies of Formosan subterranean termites consumed on average twice as much air-dried blue-stained southern yellow pine sapwood over unstained air-dried controls. Additionally, Formosan subterranean termites consumed over five-times more kiln-dried blue-stained sapwood than unstained kiln-dried control wafers. The implications of these results are particularly relevant to pine forest ecology, nutrient cycling, and the utilization of blue-stained southern pine building products in the southeastern United States, where Formosan subterranean termites have become established.

Fungal biodegradation of CCA-treated wood and removal of its metal components

In the present study, 5 isolates of brown-rot fungi were used for fungal bioprocessing (FB) of chromated copper arsenate (CCA)-treated wood wastes: Antrodia vaillantii SEL8501, Fomitopsis palustris TYP0507 and TYP6137, and Crustoderma sp. KUC8065 and KUC8611. The isolates showed notable capacity for the degradation of treated wood and removal of CCA components via the American Wood Protection Association soil block test. Among them, Crustoderma sp. KUC8611 effectively decayed the treated wood, causing a mass loss of up to 60%. F. palustris caused extensive leaching of CrO3 of up to 79% and As2O5 of up to 87%, but only moderate leaching of CuO of up to 50%. This high capacity for removal of CrO3 and As2O5 showed a strong logarithmic relationship with the amount of oxalic acid produced in the decayed wood. The majority of metals removed from treated wood during the decay process were deposited in the soil and feeder strip. Further investigation will be required to establish the capability of selected fungi for FB of full-sized lumber treated with CCA.