Comparative effectiveness of two alkylammonium compounds as wood preservatives

This study describes a laboratory evaluation of the efficacy of two alkylammonium compounds [didecyldimethylammonium tetrafluoroborate (DBF) and didecyldimethylammonium chloride (DDAC)] when applied via vacuum impregnation or superficial treatment. Treated wood specimens were tested for their termite and microbial resistance under controlled laboratory conditions. The higher chemical retentions were needed to suppress the feeding by Coptotermes formosanus ≦3% mass loss in the multichoice test than in the no-choice test. The DBF and DDAC retention levels necessary to meet the performance requirement ≦3% mass loss after 12-week fungal exposure varied with wood species. The retention level of 3 kg/m³ for DBF and DDAC was generally high to keep the nondurable wood species free of decay. Although there was no difference between DBF and DDAC in the efficacy against decay and termite attack, the former slightly outperformed the latter as an antimold and antisapstain agent.     

Serial exposure technique for assessing performance of wood preservatives

Summary The performance of copper-chrome-arsenate (CCA) and two quaternary ammonium compounds as wood preservatives was compared using a serial exposure technique, involving successive 10-week exposures in conventional soil jars. All preservative treatments were successful in preventing decay of Pinus radiata sapwood after the first exposure, but successive 10-week exposures clearly distinguished those treatments likely to offer long-term protection. The progressively increasing times of exposure with test fungi overcame the time lag for decay initiation in wood treated to preservative retentions above the toxic threshold established by conventional laboratory methods. Consequently, an additional and higher toxic threshold could be calculated. Examination of data from field stake tests suggested that a series of toxic thresholds established by a serial exposure technique could be related to preservative retentions which protect wood in the field from decay for increasing periods of time. Results of all tests are discussed in relation to the development of a laboratory procedure which may predict field performance of wood preservatives.     

Anatomical characterization of decayed wood in standing light red meranti and identification of the fungi isolated from the decayed area

To further our understanding of wood decay in living light red meranti (Shorea smithiana) trees, microscopic characteristics of the cell and cell wall degradations of S. smithiana wood in the presence of the decay fungi, the identity of the causal fungi, and the decay potential and pattern by an isolated fungus were investigated. Cell wall degradations, including cell wall thinning, bore holes formation, rounded pit erosion, and eroded channel opening were clearly observed under light and scanning electron microscopy. In transverse view, many large voids resulting from a coalition of degraded wood tissue appeared in the decayed canker zone. All these observations suggest the well-known simultaneous decay pattern caused by white-rot fungi. By phylogenetic analysis based on the sequences of internal transcribed spacer region of ribosomal DNA, a basidiomycete fungus isolated from the decayed wood was identified as Schizophyllum commune. The degradation caused by this fungus on sound S. smithiana wood in an in situ laboratory decay test was classified as the early stage of simultaneous decay, and showed a similar pattern to that observed in the wood samples naturally decayed.     

Comparative study on the durability of heat-treated White Birch (Betula papyrifera) subjected to the attack of brown and white rot fungi

Abstract

The effect of heat treatment on decay resistance of white birch was evaluated for different incubation periods ranging from 2 to 12 weeks using three species of brown rot and one species of white rot fungus. The results of weight loss tests showed that the white rot fungus, Trametes versicolor, effectively degraded the untreated wood (73.5%). While the degradation of untreated wood by brown rot fungi species, Gloephyllum trabeum (11.6%) and Conifora puteana (6.2%), was considerably less compared to T. versicolor, the third brown rot fungi studied, Poria placenta, caused an appreciable degradation of the same species (52.4%). The results clearly showed that the heat treatment reduced the effect of fungi attack on white birch. Increasing the heat treatment temperature from 195 to 215°C resulted in reduction of weight loss, consequently, reduction in fungal attack. As an example, the weight loss reductions due to T. versicolor, P. placenta, G. trabeum and C. puteana attack was 62.2%, 71.3%, 89.6% and 100%, respectively, compared to the weight loss of untreated wood when it is heat treated at 215°C. Thus, these results confirmed that the heat treatment increased the biological resistance of white birch.     

Efficacy of radio frequency treatment and its potential for control of sapstain and wood decay fungi on red oak,poplar, and southern yellow pine wood species

The effectiveness of radio frequency (RF) treatment in the control of wood decay fungi (Gloeophyllum trabeum, Ganoderma lucidum, and Irpex lacteus) and sapstain fungus (Ceratocystis fimbriata) in red oak (Quercus spp.), poplar (Populus alba), and southern yellow pine (Pinus spp.) was evaluated in the laboratory as an alternative to methyl bromide (MB) treatment. Wood samples (15.5 x 10 x 10 cm) were inoculated with fungi from a 7-day culture by dipping them to a depth of one face deep (2 cm) into inoculum and incubating them at 25°C for 14 days. Identical wood samples were left uninoculated as controls. Subsequent to incubation, the wood blocks were exposed to RF radiation in an industrial 40-kW dielectric oven at temperatures between 60° and 70°C for 2 min. The test fungi were recovered and reisolated from all of the control wood blocks but not from RF-treated wood blocks. RF treatment resulted in complete inhibition of the fungus in 98%-100% of the wood samples. Moisture content loss (≥1%) was noted after wood had been exposed to RF treatment. Moisture content may be an important factor to consider with RF treatments. RF treatment can, therefore, potentially provide an effective and rapid quarantine treatment as an alternative to MB fumigation for certain pathogen-wood combinations. This article reports the results of research only. Mention of a product does not constitute an endorsement or recommendation by USDA for its use.     

木材厂环境中空气微生物的初步研究

本文采用自然沉降平板法,对哈尔滨市某木材厂空气微生物种类和数量进行测定.结果表明:未经空气净化器处理的木材生产车间中的空气微生物数量(54939 cfu(m-3)是经空气净化器处理(25768 cfu(m-3)的2.1倍.空气净化器虽然能够净化生产车间中的空气微生物,但其净化率为53.1%,净化后的空气未达到洁净空气的标准,因此还应同时采取其他相应净化措施.净化器可以显著降低空气中放线菌的数量,尤其能够完全清除放线菌,如:疮痂类群(Scabies), 烬灰类群(Cinereas)和吸水类群(Hygroscopicas),但对细菌和真菌效果不明显.建议今后采用更有效可行的方法来净化木材生产车间中的空气微生物.     

Mycologg: a new accelerated test method for wood durability above ground

If not properly handled, selected and protected, wood will be degraded by bacteria, fungi and also insects. In order to ensure service life, durability tests are needed. Most accelerated laboratory tests on wood durability are focused either on fungi attacks or the uptake of moisture. Accelerated field tests in ground contact are of limited use since they could be difficult to reproduce and are sensitive to the characteristics of the soil in which the wood is placed. In addition, the results cannot be directly transferred to wood in use above ground because such wood is subjected to different set of conditions. The Mycologg is a new accelerated test method for estimating the durability of wood in above ground applications. The Mycologg allows the test panels to be subjected to the discolouring fungi and different RH (relative humidity) cycles simultaneously. Every 30 min, the temperature, the RH, and the moisture content in each test panel are measured and saved in special software. This allows for a constant update of the moisture patterns during a fungi attack. A trial was made with Scots pine (Pinus sylvestris) heartwood samples, where fungal growth after 6, 8 and 10 weeks in the Mycologg were compared to weather exposure of duplicate samples after 12, 16, and 26 months. The results showed that 10 weeks into the Mycologg accelerated test method corresponds well to real-time weather exposure with respect to fungal discolouration.     

Reduction of ferric chelate caused by various wood-rot fungi

The reduction of ferric chelate caused by various wood-rot fungi was analyzed. Ferric chelate reductive activity was detected in cell-free extracts of seven wood-rot fungi:Phanerochaete chrysosporium, P. sordida YK-624,Ganoderma sp. YK-505,Coriolus versicolor, Bjerkandera adusta, Tyromyces palustris, andGloeophyllum trabeum. These fungi produced NADPH- or NADH-dependent ferric chelate reductive enzymes (or both) of different molecular weight. In the liquid culture ofP. sordida YK-624 andC. versicolor, a positive correlation was observed between extracellular MnP activity and intracellular NADPH-dependent ferric chelate reductive activity.     

Blue stain fungi associated withIps cembrae (Coleoptera: Scolytidae) in Japanese larch in connection with their brood development

The association between blue stain fungi andIps cembrae Heer (Coleoptera: Scolytidae) was investigated in the Japanese larch,Larix leptolepis Gordon, in the Nagoya University Forest, Aichi Prefecture, central Japan.I. cembrae had one or two generation(s) in a year in this study area. Two blue stain fungi,Ophiostoma piceae andLeptographium sp., were isolated from the body surface of both male adults in mating chambers and female adults in parent galleries, suggesting that this beetle species was a vector of these fungi. Although no blue stain fungi were isolated from non-stained wood, both fungi were isolated from the mating chambers, the center and the uppermost end of the galleries throughout the season. The fact thatO. piceae was consistently isolated with high frequency from adults and from their galleries strongly suggested that this species would be the principal blue stain fungus infecting the beetle-attacked larch trees.     

Weathering durability of CCB-impregnated wood for clear varnish coatings

Outdoor performances of a polyurethane varnish and an alkyd-based synthetic varnish coated over chromium-copper-boron (CCB)-impregnated Scots pine (Pinus sylvestris L.) and chestnut (Castanea sativa Mill.) [10 (R) × 100 (T) × 150 (L) mm] were investigated. These varnishes were also applied to the wood surface as sole coatings or impregnated into wood as water-repellent (WR) solutions. Outdoor exposure was performed in the Black Sea region of northern Turkey (41°N, 39.43°E) where humid weather predominates throughout the year and accelerates decomposition of coated wood surfaces. The wood panels were exposed at 45° south on their tangential surfaces. After 9 months of exposure to summer, autumn, and the following winter season, the color and glossiness changes of the exposed surface, adhesion of the coating layer to the wood surface, water absorption through the coating layers, mass loss, and the hardness of the board surface were studied. CCB impregnation greatly stabilized the surface color of varnish-coated panels of both wood species. Gradual decreases of adhesion between varnished layers and preimpregnated surfaces were attributed to probable weakening of interactions at the interface of the treated wood and the film layer. A superficial cleaning process of treated wood is suggested to improve glossiness and adhesion. The coated wood surface became harder with time on outdoor exposure until a maximum hardness occurred followed by softening, whereas the uncoated surface softened steadily. Polyurethane varnish yielded a harder surface than synthetic varnish. Mass losses of wood panels after 9 months of exposure were negligible for all treatments compared with the untreated controls, which were totally discolored and eroded on the surface. It is concluded that long-term exterior wood protection has been achieved by a successful combination of an appropriate preservative treatment followed by a compatible surface-coating process.     

Microbial population in rotten living body ofSalix matsudana

The microbial population in rotten living body ofSalix matsudana caused byTrametes suaveolens (L.) was researched. 11 bacteria species (1 species ofBacillus, 2 species ofClostridium and 8 species of non-brood-cell bacteria), 1 species ofActinomyces that belongs to Lavendulac, 8 species of fungi and 6 species ofTrichoderma were isolated from rotten trunk. The hyphae ofTrametes suaveolens mainly existed between rotten sections and discoloration sections. In over-rotten section and healthy section the fungi (Trametes suaveolens) were not isolated. The microbes that lived in the discoloration section were the most in kinds and number and they were the pioneer microbes of wood rotting. Only after they dwelled in wood and eliminated its rot-resistance, could wood-rotting fungi invade wood and caused wood-rotting. Responsible editor: Zhu Hong     

Interactions between Scytalidium species and brown- or white-rot basidiomycetes in birch wood

Summary Growth and subsequent decay by seven basidiomycetes in birch wood blocks was inhibited by three Scytalidium isolates. Scytalidium initially colonized the surface of the blocks and gradually overgrew the basidiomycetes. In individual wood blocks from 11 Scytalidium-basidiomycete paired treatment combinations, the basidiomycete was not inhibited throughout the entire wood block. These wood blocks demonstrated interspecific interactions and antagonism between the different fungi. The white-rot fungi responded to isolates of Scytalidium by occluding xylem cells with masses of hyphae, forming pseudosclerotial plates in the zone of initial interaction. Scytalidium appeared to gain access into portions of wood colonized by the basidiomycetes only after substantial decay had resulted by the wood decay fungus.     

Durability of thermally modified Norway spruce and Scots pine in above-ground conditions

Abstract

One of the main objectives of thermal modification is to increase the biological durability of wood. In this study the fungal resistance of Norway spruce and Scots pine, thermally modified at 195°C and 210°C, was studied with a lap-joint field test. Untreated pine and spruce and pine impregnated with tributyl tin oxide (TBTO) and copper, chromium and arsenic (CCA) were selected as reference materials. The evaluations were carried out after 1, 2 and 9 years of exposure. After 1 and 2 years of exposure mainly discoloration was detected. Only the untreated pine was slightly affected by decay fungi. There were significant differences in the decay ratings of untreated and thermally modified wood materials after 9 years in the field. While the untreated wood materials were severely attacked by decay fungi or reached failure rating, only small areas of incipient decay were detected in the thermally modified samples. Thermally modified pine was slightly more decayed than thermally modified spruce. The only wood material without any signs of decay was CCA-treated pine, since some of the TBTO-treated pine samples were also moderately attacked by fungal decay. The results of the lap-joint test had a good correlation with mass losses in a laboratory test with brown-rot fungi.     

Detection of early stages of wood decay by acoustic emission technique

Acoustic emissions of pine wood samples (Pinus sylvestris L.) previously infected with the soft-rot fungi (Chaetomium globosum Kunze) and brown-rot fungi (Coniophora puteana (Schum. ex Fr.) Karst.) were measured in the perpendicular to grain compression test, in the radial direction. It was found that even a minimum mass loss (below 1%) caused by enzymatic deterioration of the wood substance resulted in an increase in acoustic emission level in the compression test measured perpendicular to grain in the radial direction. A particularly sensitive indicator of wood enzymatic destruction were cumulative counts of acoustic emission related to the value of the applied compression load. Received 4 March 1997     

Micromorphological characteristics of decayed wood and laccase produced by the brown-rot fungus <Emphasis Type="Italic">Coniophora puteana</Emphasis>

Microscopic examination showed the cell wall decay pattern produced by the brown-rot fungus Coniophora puteana to be different from the degradation pattern known to be typical for brown-rot fungi. Erosion and thinning of cell walls in patterns considered to be characteristic of white-rot decay were observed. In particular, the fungal strain COP 20242 degraded secondary cell wall layers extensively, and also degraded lignin-rich middle lamellae. Some strains of C. puteana produced soft-rot type cavities in the S2 layer. All strains of C. puteana employed in the present work showed a positive reaction to tannic acid in the Bavendamm test, indicating the production of laccase. Microscopic and enzymatic studies provided evidence to suggest that the wood decay by C. puteana is unique both in terms of micromorphological and enzymatic patterns of cell wall degradation. This is because brown-rot fungi are not generally known to form cavities in the cell walls or to produce lignin-degrading enzymes. These observations suggest that lignin degradation capacity of brown-rot fungi may be greater than previously considered.     

Dimensional stabilization of wood treated with furfuryl alcohol catalysed by borates

Furfuryl alcohol has a sufficiently small molecular size, which allows impregnation into wood and can be polymerized in the cell walls. Polymerization can be accomplished using a catalyst, heat or penetrating radiation. This research illustrates a natural wood polymer composite (NWPC) that was obtained under the catalytic effect of borates. Furfuryl alcohol (FA) and borates were mixed at different ratios before treatment. When borates alone are used, they were totally leached from wood after cyclic leaching periods. However, this was not encountered with the mixture of furfuryl alcohol and borates. Furfuryl alcohol considerably improved antiswelling efficiency by about 85% for both Japanese cedar ( Cryptomeria japonica) and Scots pine ( Pinus sylvestris L.) wood specimens. Results of the leaching tests of borate indicated that boric acid readily lost its boron content in the early cycles of the leaching periods and the highest leaching rate of boron was observed at the first leaching cycle (512 ppm). When furfuryl alcohol mixed with borates, boron was released to the leaching water at slower amounts, suggesting the possibility of longer protection of treated wood in service.     

Changes in surface properties of tropical wood species exposed to the Indonesian climate in relation to mold colonies

Changes in mold populations and genera on the exposed surfaces of tropical hardwoods — albizia (Paraserianthes falcata), kapur (Dryobalanop lanceolata), mahoni (Switenia macrophylla), nangka (Artocarpus heterophyllus), puspa (Schima wallchii) — were investigated. The wood specimens were exposed to the Indonesian climate for 32 weeks. Properties including mass loss, wettability, mold growth (colony-forming units), and mold genera were evaluated. The change in properties after exposure was significantly affected by the wood species, but there was no clear relation between mass loss and the initial chemical components or between wettability and wood density. The number of mold populations was different by exposure period and wood species, but there was no significant effect of climate conditions, such as rainfall and ultraviolet radiation. Of the genera identified,Aureobasidium, Cladosporium, andPenicillium were dominant molds on the exposed wood surfaces.     

木材加速腐朽试验方法的研究

采用纸板箱和聚乙烯袋作培养箱,将土壤、试样和腐朽菌均放入聚乙烯袋内进行腐朽试验.SAS分析结果表明,菌种和腐朽时间对木材失重率和力学强度变化的影响显著(0.05水平);而且,腐朽木材失重率与力学强度损失率之间的相关性也非常显著,说明本研究中设计的木材加速腐朽试验方法具有可行性.     

Optimisation of a two-stage heat treatment process: durability aspects

Heat treatment of wood at relatively high temperatures (in the range of 150–280°C) is an effective method to improve biological durability of wood. This study was performed to investigate the effect of heat treatment process optimisation on the resistance against fungal attack, including basidiomycetes, molds and blue stain fungi. An industrially used two-stage heat treatment method under relatively mild conditions (<200°C) was used to treat the boards. Heat treatment of radiata pine sapwood revealed a clear improvement of the resistance against the brown rot fungi Coniophora puteana and Poria placenta. Increasing process temperature and/or effective process time during the first process stage, the hydro thermolysis, appeared to affect the resistance against C. puteana attack, but the effect on the resistance against P. placenta was rather limited. Heat treated radiata pine showed a limited resistance against the white rot fungus Coriolus versicolor and process variations during the hydro thermolysis stage appeared not to affect this resistance. A clear difference between the resistance of heat treated Scots pine sapwood and heartwood against fungal attack is observed. Scots pine heartwood showed a higher resistance against C. puteana and P. placenta but also against the white rot fungus C. versicolor. Similar results were obtained when heat treated birch was exposed to brown and white rot fungi. Heat treatment showed an improved resistance against C. puteana attack, especially at higher temperatures during the hydro thermolysis stage. A clear improvement of the durability was also observed after exposure to the white rot fungus C. versicolor and especially Stereum hirsutum. Increasing the process temperature or process time during the hydro thermolysis stage appeared to have a limited effect on the resistance against C. versicolor attack. Heat treated radiata pine and Norway spruce were still susceptible to mold growth on the wood surface, probably due to the formation of hemicelluloses degradation products (e.g. sugars) during heat treatment. Remarkable is the absence of blue stain fungi on heat treated wood specimen, also because the abandant blue stain fungi were observed on untreated specimen. Molecular reasons for the resistance of heat treated wood against fungal attack are discussed in detail contributing to a better understanding of heat treatment methods.     

Mycorrhizal dependency and growth responses of Acacia nilotica and Albizzia lebbeck to inoculation by indigenous AM fungi as influenced by available soil P levels in a semi-arid Alfisol wasteland

A series of available phosphorus (Olsen) levels ranging from 10 to 40 ppm were achieved in a semi-arid soil. The influence of the levels of phosphorus on the symbiotic interaction between two subtropical tree species, Acacia nilotica and Albizzia lebbeck, and a mixed inoculum of indigenous arbuscular mycorrhizal (AM) fungi was evaluated in a greenhouse study. The extent to which the plant species depended on AM fungi for dry matter production decreased as the levels of soil P increased, but the degree of this decrease differed in the two species tested. Acacia nilotica colonized by AM fungi showed a significant increase in shoot P and dry matter at a soil P level of 10 ppm whereas in Albizzia lebbeck, such increase occurred at 20 ppm. Mycorrhizal inoculation response disappeared beyond soil P levels of 25 ppm in Acacia nilotica and 30 ppm in Albizzia lebbeck. Levels of soil P greater than 25 ppm suppressed AM fungus colonization in both species. Soil P levels of 30 and 40 ppm and 40 ppm caused negative mycorrhizal dependencies (MD) in Acacia nilotica and Albizzia lebbeck respectively. Values of MD for both species were negatively correlated with soil P levels. Based on the MD values, regression equations were developed to predict MD for given levels of available P.