Rhodonia Placenta Research Articles

Comparative Copper Resistance Strategies of Rhodonia placenta and Phanerochaete chrysosporium in a Copper/Azole-Treated Wood Microcosm.

Copper-based formulations of wood preservatives are widely used in industry to protect wood materials from degradation caused by fungi. Wood treated with preservatives generate toxic waste that currently cannot be properly recycled. Despite copper being very efficient as an antifungal agent against most fungi, some species are able to cope with these high metal concentrations. This is the case for the brown-rot fungus Rhodonia placenta and the white-rot fungus Phanerochaete chrysosporium, which are able to grow efficiently in pine wood treated with Tanalith E3474. Here, we aimed to test the abilities of the two fungi to cope with copper in this toxic environment and to decontaminate Tanalith E-treated wood. A microcosm allowing the growth of the fungi on industrially treated pine wood was designed, and the distribution of copper between mycelium and wood was analysed within the embedded hyphae and wood particles using coupled X-ray fluorescence spectroscopy and Scanning Electron Microscopy (SEM)/Electron Dispersive Spectroscopy (EDS). The results demonstrate the copper biosorption capacities of P. chrysosporium and the production of copper-oxalate crystals by R. placenta. These data coupled to genomic analysis suggest the involvement of additional mechanisms for copper tolerance in these rot fungi that are likely related to copper transport (import, export, or vacuolar sequestration).

Fungal Degradation of Extractives Plays an Important Role in the Brown Rot Decay of Scots Pine Heartwood.

Scots pine heartwood is known to have resistance to wood decay due to the presence of extractives, namely stilbenes and resin acids. However, previous studies have indicated that these extractives are degradable by wood decaying fungi. This study aimed to investigate the relationship between extractive degradation and heartwood decay in detail and to gain insight into the mechanisms of extractive degradation. Mass losses recorded after a stacked-sample decay test with brown rot fungi showed that the heartwood had substantial decay resistance against Coniophora puteana but little resistance against Rhodonia placenta. Extracts obtained from the decayed heartwood samples revealed extensive degradation of stilbenes by R. placenta in the early stages of decay and a noticeable but statistically insignificant loss of resin acids. The extracts from R. placenta-degraded samples contained new compounds derived from the degraded extractives: hydroxylated stilbene derivatives appeared in the early decay stages and then disappeared, while compounds tentatively identified as hydroxylated derivatives of dehydroabietic acid accumulated in the later stages. The degradation of extractives was further analysed using simple degradation assays where an extract obtained from intact heartwood was incubated with fungal mycelium or extracellular culture fluid from liquid fungal cultures or with neat Fenton reagent. The assays showed that extractives can be eliminated by several fungal degradative systems and revealed differences between the degradative abilities of the two fungi. The results of the study indicate that extractive degradation plays an important role in heartwood decay and highlight the complexity of the fungal degradative systems.

Decay Resistance of Nano-Zinc Oxide, and PEG 6000, and Thermally Modified Wood

In Central Europe, European beech (Fagus sylvatica L.) wood has a high potential for the production of construction and decorative materials, with the aim of replacing Norway spruce, oaks, and other traditionally used tree species. However, the biological resistance of beech wood—to decaying fungi, molds, and insects—is low, and in damp conditions its resistance must be increased with suitable preservatives or modification methods. In the present experiment, beech wood was first treated with water systems of nano-zinc oxide (0.1 to 3.3 wt.% of nano-ZnO) and/or polyethylene glycol 6000 (20 wt.% of PEG 6000), without/with additional thermal modification at 190 °C/2 h. In the presence of nano-ZnO, the decay resistance of beech wood to the brown-rot fungus Rhodonia placenta and the white-rot fungus Trametes versicolor significantly increased, mainly after its additional thermal modification. The presence of nano-ZnO in beech wood—(a) alone, (b) with a subsequent application of PEG 6000, (c) with additional thermal modification—had a more apparent inhibition effect on T. versicolor than on R. placenta. PEG 6000 alone did not improve the resistance of beech wood to rot.

Microscopic characterization of sound and decayed acetylated hornbeam (Carpinus betulus L.)

ABSTRACT In this work, bright field microscopy and scanning electron microscopy tests were carried out to find the effect of acetylation on the microscopic structure of hornbeam wood, furthermore to analyze the differences between decayed samples at microscopic level. Several methods of sample preparation (water, acetone) and staining (safranin, astra blue, 1% solution of potassium permanganate) were also tested and compared. Native hornbeam wood was successfully acetylated, which was confirmed by the limited staining effect of safranin. Acetylation did not damage the wood microstructure and significantly increased the cell-wall thickness by 7.0%. The pits of acetylated hornbeam were much narrower, probably due to permanent cell-wall swelling. New brown deposits were found in parenchyma cells of acetylated hornbeam. Each cell contained a small amount of an insoluble substance, which led to the hypothesis that the natural content of living cells became insoluble during acetylation. Further investigation is needed to determine what substance was created during acetylation. In the case of samples which were tested for fungi resistance against Coniophora puteana, Rhodonia (Poria) placenta, and Trametes (Coriolus) versicolor, microscopic studies showed that fungi were able to colonize acetylated cell lumina without visible degradation or mass loss (∼1%).

Biological resistance of sandwich particleboard made with sugarcane, thermally-treated Pinus wood and malva fiber

Particleboards produced with other lignocellulosic materials, beyond wood, are promising products for the furniture and building construction components, as doors, lining, floor, partitions, and coverings. However, there is little information about the resistance of them to xylophagous organisms. This is important due the different uses of particleboards, where they will be subject to attacks by decaying organisms, which can affect a structure and put people at risk. The present study aims to determine the biological resistance of particleboard produced with pine, sugarcane bagasse and malva particles to xylophagous organisms. The particleboard was produced with different proportions of pine wood heat treated at 200 °C and malva fiber (outer layers) and sugarcane bagasse core glued with an adhesive based on polyurethane from castor oil. No-choice and choice feeding tests with dry wood (Cryptotermes brevis) and conehead (Nasutitermes corniger) termites were carried out for the resistance test to xylophagous organisms, in addition to a test with rotting fungi which cause brown (Gloeophyllum trabeum and Rhodonia placenta) and white rot (Irpex lacteus and Trametes versicolor). The trial with dry wood termites showed low mass losses, regardless of the proportions applied. The mass losses were accentuated for the test with conehead termite, having the particleboard composed of 100% pine been the most resistant among the boards tested. The greatest mass losses for fungal resistance were caused by Gloeophyllum trabeum. The particleboard produced with 100% pine (outer layer) showed the highest resistance to the tested xylophagous organisms.

Capturing an Early Gene Induction Event during Wood Decay by the Brown Rot Fungus Rhodonia placenta.

ABSTRACTBrown rot fungi dominate wood decomposition in coniferous forests, and their carbohydrate-selective mechanisms are of commercial interest. Brown rot was recently described as a two-step, sequential mechanism orchestrated by fungi using differentially expressed genes (DEGs) and consisting of oxidation via reactive oxygen species (ROS) followed by enzymatic saccharification. There have been indications, however, that the initial oxidation step itself might require induction. To capture this early gene regulation event, here, we integrated fine-scale cryosectioning with whole-transcriptome sequencing to dissect gene expression at the single-hyphal-cell scale (tens of micrometers). This improved the spatial resolution 50-fold, relative to previous work, and we were able to capture the activity of the first 100 μm of hyphal front growth by Rhodonia placenta in aspen wood. This early decay period was dominated by delayed gene expression patterns as the fungus ramped up its mechanism. These delayed DEGs included many genes implicated in ROS pathways (lignocellulose oxidation [LOX]) that were previously and incorrectly assumed to be constitutively expressed. These delayed DEGs, which include those with and without predicted functions, also create a focused subset of target genes for functional genomics. However, this delayed pattern was not universal, with a few genes being upregulated immediately at the hyphal front. Most notably, this included a gene commonly implicated in hydroquinone and iron redox cycling: benzoquinone reductase.IMPORTANCE Earth’s aboveground terrestrial biomass is primarily wood, and fungi dominate wood decomposition. Here, we studied these fungal pathways in a common “brown rot”-type fungus, Rhodonia placenta, that selectively extracts sugars from carbohydrates embedded within wood lignin. Using a space-for-time design to map fungal gene expression at the extreme hyphal front in wood, we made two discoveries. First, we found that many genes long assumed to be “on” (constitutively expressed) from the very beginning of decay were instead “off” before being upregulated, when mapped (via transcriptome sequencing [RNA-seq]) at a high resolution. Second, we found that the gene encoding benzoquinone reductase was “on” in incipient decay and quickly downregulated, implying a key role in “kick-starting” brown rot.

Combining mineralisation and thermal modification to improve the fungal durability of selected wood species

The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum, Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis.

Effect of silica bionanoparticles obtained from rice husk for the treatment of wood of Pinus elliottii

Renewable products can ensure environmental sustainability, human health, and reduce the use of traditional products that have toxic compounds in their formulation. Therefore, the research aimed to evaluate the biological resistance of Pinus elliottii wood against xylophagous fungi and termites through impregnation with silica bioparticles (SiO2) obtained from rice husks. To obtain the silica, the material underwent chemical treatment, two cycles of acid leaching with hydrochloric acid, and heat treatment at 500 °C, 550 °C or 600 °C. The purity of the silica obtained was characterized by X-ray fluorescence technique (XRF), and the mean particle size by scanning electron microscopy (SEM). SiO2 was applied to the specimens at concentrations of 0.5%, 1.0%, and 2.0%, and the impregnated samples were subjected to tests with brown rot fungi (Gloeophyllum trabeum, Rhodonia placenta and Neolentinus lepideus), soft rot (taken from natural forest soil) and xylophagous termites (Nasutitermes corniger and Cryptotermes brevis). The thermal treatments promoted the obtainment of high purity bioparticles, with value of approximately 90% and diameter of 263.7 nm. In the termite test, the smallest loss of mass and damage were for the impregnated samples. Termite mortality increased with the concentration of solutions. SiO2 was not effective against xylophagous fungi, with no difference between treatments and controls, indicating that resistance was inherent in the wood itself.

Durability of Thermally Modified Western Hemlock Lumber Against Wood Decay Fungi

The chemical modification of wood is gaining popularity as a treatment to increase wood durability, particularly in jurisdictions where restrictions on the use of chemical impregnation are increasing. This work measures the impact of thermal modification of western hemlock lumber durability against decay fungi. Western hemlock lumber was thermally modified using a cycle with temperatures ranging from 80 to 170°C and was cut into standard 19 mm blocks for testing according to AWPA method E10. Performance of thermally modified wood was measured against two brown rot fungi, Rhodonia placenta and Gloeophyllum trabeum and one white rot fungus, Trametes versicolor over an 8, 12, and 16-week incubation period. Unmodified western hemlock wood, untreated southern pine and copper azole-treated southern pine were included for comparison. Thermal modification resulted in a slight improvement in durability against Gloeophyllum trabeum, but not Rhodonia placenta compared to untreated western hemlock which caused 50.3 and 52.2% mass loss in thermally modified western hemlock after 16 weeks, respectively. T. versicolor caused a 21.2% mass loss after 16 weeks, but this value was not statistically different than untreated western hemlock (p = 0.46). For comparison, copper azole-treated southern pine showed only an average of 0 and 15% mass loss when exposed to G. trabeum or R. placenta for 16 weeks, respectively. Together, these data indicate that while there may be some protective effect of thermally modifying western hemlock, further development of treatment processes are needed to improve the durability of thermally modified western hemlock.

Distinctive carbon repression effects in the carbohydrate-selective wood decay fungus Rhodonia placenta

Brown rot fungi dominate the carbon degradation of northern terrestrial conifers. These fungi adapted unique genetic inventories to degrade lignocellulose and to rapidly release a large quantity of carbohydrates for fungal catabolism. We know that brown rot involves “two-step” gene regulation to delay most hydrolytic enzyme expression until after harsh oxidative pretreatments. This implies the crucial role of concise gene regulation to brown rot efficacy, but the underlying regulatory mechanisms remain uncharacterized. Here, using the combined transcriptomic and enzyme analyses we investigated the roles of carbon catabolites in controlling gene expression in model brown rot fungus Rhodonia placenta. We identified co-regulated gene regulons as shared transcriptional responses to no-carbon controls, glucose, cellobiose, or aspen wood (Populus sp.). We found that cellobiose, a common inducing catabolite for fungi, induced expression of main chain-cleaving cellulases in GH5 and GH12 families (cellobiose vs. no-carbon > 4-fold, Padj < 0.05), whereas complex aspen was a universal inducer for Carbohydrate Active Enzymes (CAZymes) expression. Importantly, we observed the attenuated glucose-mediated repression effects on cellulases expression, but not on hemicellulases and lignin oxidoreductases, suggesting fungi might have adapted diverged regulatory routes to boost cellulase production for the fast carbohydrate release. Using carbon regulons, we further predicted the cis- and trans-regulatory elements and assembled a network model of the distinctive regulatory machinery of brown rot. These results offer mechanistic insights into the energy efficiency traits of a common group of decomposer fungi with enormous influence on the carbon cycle.

Lavender oil as eco-friendly alternative to protect wood against termites without negative effect on wood properties

Timber suffers from various biological damages. Recent efforts aim on nature-friendly sustainable technologies of wood protection to replace classical synthetic agents having usually negative impact on many non-target organisms including man. This research investigated the biocidal effectiveness of lavender oil (LO) in protecting the Norway spruce (Picea abies) wood against the termites Reticulitermes flavipes and the brown-rot fungus Rhodonia placenta. Following, selected physical characteristics of spruce wood treated with LO were evaluated: colour changes, roughness, surface wetting with water and surface free energy (SFE). Experiments showed that LO increased the resistance of spruce wood to termites nearly to the level of its treatment with commercial biocide based on trivalent boron and quaternary ammonium salt. The additional hydrophobic treatment of wood ensured its full termite-resistance even after artificial weathering in Xenotest and leaching in water according to EN 84, respectively. It shows a high potential of LO to protect wood against termites. Adversely, the effectiveness of 5% LO against rot was not sufficient. The colour of the oil-treated wood was preserved, its roughness increased slightly, and wetting and SFE led to a positive change, improving the adhesion of potentially applied coatings or adhesives for exterior exposures.

Fungal resistance and leachability of genipin-crosslinked chitosan treated wood

Chitosan (C) is a natural antimicrobial compound that has been widely explored for wood protection, but its application is limited by its high leachability. Genipin is a biobased crosslinking agent that can crosslink with chitosan under mild conditions. This study aims at examining the decay resistance and leachability of genipin-crosslinked chitosan (GC) treated wood against common wood-decaying fungi. GC formation was confirmed using Fourier transform infrared spectroscopy and Thermogravimetric analysis. The antifungal efficacy of GC 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.) was first determined using malt-gar as substrate, which revealed that GC exhibited similar efficacy as C treatments in inhibiting the growth of all fungi studied. Micrographs of light and fluorescence microscopy showed changes in fungi morphology and nuclei deformation due to the effect of GC. GC-treated wood samples show an increased retention and mass gain as the function of treating concentrations, which were as high as 21 kg/m2 and 3.6%, respectively. However, upon leaching test, the mass gain of 3% GC treated softwood and hardwood was reduced to 1.6% and 0.9%, respectively, indicating cross-linking chitosan with genipin did not reduce the leaching rate of chitosan. In terms of durability testing, GC treated wood samples showed significantly lower mass loss ranging from 11 to 15% than those of the control groups of ≥30% regardless of the leaching test.

Species of fungi recommended for inclusion in the 2nd edition of the Red Data Book of the Oryol Region

Based on the results of the long-term (2008–2020) studies of macromycetes in Oryol Region, a list of 24 fungal species recommended for the second edition of the regional Red Data Book has been compiled. The list includes 4 species of basidial fungi (Clavariadelphus pistillaris, Cortinarius violaceus, Grifola frondosa, and Gyroporus cyanescens) that were included in the first edition of the Red Data Book of Oryol Region (2007) and another 20 species (Aeruginoscyphus sericeus, Bulgaria inquinans, Clavaria zollingeri, Ganoderma lucidum, Gloiodon strigosus, Gyroporus castaneus, Hericium coralloides, Holwaya mucida, Hydnocristella himantia, Metuloidea murashkinskyi, Phellinidium ferrugineofuscum, Polyporus umbellatus, Ramaria fennica, Ramariopsis crocea, Ramariopsis pulchella, Rhizochaete sulphurina, Rhodonia placenta, Rhodotus palmatus, Skeletocutis odora, Triblidium caliciiforme) that are proposed for protection for the first time. Each species is provided with the Latin name, followed by brief characteristics of its current taxonomic position, biology and ecology, population‐limiting factors in the region, data on the range in Russia and on the distribution in Oryol Region, as well as the recommended protection category. The presented species list includes two species (Clavaria zollingeri, Rhodotus palmatus) from the IUCN Red List of Threatened Species and three species (Ganoderma lucidum, Grifola frondosa, Polyporus umbellatus) recorded in the Red Data Book of the Russian Federation (2008). Two species (Aeruginoscyphus sericeus and Rhodotus palmatus) are new to Oryol Region.

ATR-FTIR Study of Alaska Yellow Cedar Extractives and Relationship with Their Natural Durability

New approaches for assessing wood durability are needed to help categorize decay resistance as timber utilization shifts towards plantations or native forest regrowth that may be less durable than original native forest resources. This study evaluated attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis (PCA) for distinguishing between groups of Alaska yellow cedar (Cupressus nootkatensis) wood for susceptibility to two decay fungi (Gloeophyllum trabeum and Rhodonia placenta) and the eastern subterranean termite (Reticulitermes flavipes). Alaska yellow cedar durability varied with test organisms, but the majority of samples were highly resistant to fungal and termite attack. Weight losses and extractives yield using sequential extractions (toluene:ethanol &gt; ethanol &gt; hot water) showed moderate to weak relationships. PCA analysis revealed limited ability to distinguish amongst levels of wood durability to all tested organisms. The absence of non-resistant samples may have influenced the ability of the chemometric methods to accurately categorize durability.

Radiata Pine Wood Treated with Copper Nanoparticles: Leaching Analysis and Fungal Degradation

Radiata pine is the main wood species used in the Chilean construction industry, but it must be protected due to its low natural durability. Chemical protection of wood by impregnation allows for a more efficient utilization of the forest resources by extending its useful life. The use of nanoparticles in wood protection has garnered great interest during the last decade, due to their unique physicochemical properties, different from those of larger sized materials. In this research, the impregnation of radiata pine wood with copper nanoparticles (CuNP) was studied in terms of retention, penetration, leaching, and its protective effect against wood rot fungi growth according to EN 113, AWPA A3-91, A9-18, and E11-16. Penetration analysis confirmed a uniform distribution across the wood, with total penetration in the impregnated samples with the highest concentration solution of CuNP. Retention values of the impregnated wood increased proportionally with the concentration of nanoparticles evaluated by EDXRF. Leaching analysis showed copper removal during the first hours of the test, with a constant leaching rate up to 144 h. Impregnated wood mass loss (ML) due to exposure to Gloeophyllum trabeum and Rhodonia placenta fungi were significantly reduced regardless of the CuNP concentration or fungi tested, with an ML smaller than 5% and smaller than 14% for leached samples.

Comparative Transcriptomics During Brown Rot Decay in Three Fungi Reveals Strain-Specific Degradative Strategies and Responses to Wood Acetylation.

Brown rot fungi degrade wood in a two-step process in which enzymatic hydrolysis is preceded by an oxidative degradation phase. While a detailed understanding of the molecular processes during brown rot decay is mandatory for being able to better protect wooden products from this type of degradation, the underlying mechanisms are still not fully understood. This is particularly true for wood that has been treated to increase its resistance against rot. In the present study, the two degradation phases were separated to study the impact of wood acetylation on the behavior of three brown rot fungi commonly used in wood durability testing. Transcriptomic data from two strains of Rhodonia placenta (FPRL280 and MAD-698) and Gloeophyllum trabeum were recorded to elucidate differences between the respective decay strategies. Clear differences were found between the two decay stages in all fungi. Moreover, strategies varied not only between species but also between the two strains of the same species. The responses to wood acetylation showed that decay is generally delayed and that parts of the process are attenuated. By hierarchical clustering, we could localize several transcription factors within gene clusters that were heavily affected by acetylation, especially in G. trabeum. The results suggest that regulatory circuits evolve rapidly and are probably the major cause behind the different decay strategies as observed even between the two strains of R. placenta. Identifying key genes in these processes can help in decay detection and identification of the fungi by biomarker selection, and also be informative for other fields, such as fiber modification by biocatalysts and the generation of biochemical platform chemicals for biorefinery applications.

Using MALDI-FTICR-MS Imaging to Track Low-Molecular-Weight Aromatic Derivatives of Fungal Decayed Wood.

Low-molecular-weight (LMW) aromatics are crucial in meditating fungal processes for plant biomass decomposition. Some LMW compounds are employed as electron donors for oxidative degradation in brown rot (BR), an efficient wood-degrading strategy in fungi that selectively degrades carbohydrates but leaves modified lignins. Previous understandings of LMW aromatics were primarily based on “bulk extraction”, an approach that cannot fully reflect their real-time functions during BR. Here, we applied an optimized molecular imaging method that combines matrix-assisted laser desorption ionization (MALDI) with Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) to directly measure the temporal profiles of BR aromatics as Rhodonia placenta decayed a wood wafer. We found that some phenolics were pre-existing in wood, while some (e.g., catechin-methyl ether and dihydroxy-dimethoxyflavan) were generated immediately after fungal activity. These pinpointed aromatics might be recruited to drive early BR oxidative mechanisms by generating Fenton reagents, Fe2+ and H2O2. As BR progressed, ligninolytic products were accumulated and then modified into various aromatic derivatives, confirming that R. placenta depolymerizes lignin. Together, this work confirms aromatic patterns that have been implicated in BR fungi, and it demonstrates the use of MALDI-FTICR-MS imaging as a new approach to monitor the temporal changes of LMW aromatics during wood degradation.

Influence of carbon source on wood decay-associated gene expression in sequential hyphal zones of the brown rot fungus Gloeophyllum trabeum.

Brown rot fungi show a two-step wood degradation mechanism comprising oxidative radical-based and enzymatic saccharification systems. Recent studies have demonstrated that the brown rot fungus Rhodonia placenta expresses oxidoreductase genes ahead of glycoside hydrolase genes and spatially protects the saccharification enzymes from oxidative damage of the oxidoreductase reactions. This study aimed to assess the generality of the spatial gene regulation of these genes in other brown rot fungi and examine the effects of carbon source on the gene regulation. Gene expression analysis was performed on 14 oxidoreductase and glycoside hydrolase genes in the brown rot fungus Gloeophyllum trabeum, directionally grown on wood, sawdust-agar, and glucose-agar wafers. In G. trabeum, both oxidoreductase and glycoside hydrolase genes were expressed at higher levels in sections behind the wafers. The upregulation of glycoside hydrolase genes was significantly higher in woody substrates than in glucose, whereas the oxidoreductase gene expression was not affected by substrates.

Modelling the Material Resistance of Wood—Part 1: Utilizing Durability Test Data Based on Different Reference Wood Species

To evaluate the performance of new wood-based products, reference wood species with known performances are included in laboratory and field trials. However, different wood species vary in their durability performance, and there will also be a within-species variation. The primary aim of this paper was to compare the material resistance against decay fungi and moisture performance of three European reference wood species, i.e., Scots pine sapwood (Pinus sylvestris), Norway spruce (Picea abies), and European beech (Fagus sylvatica). Wood material was collected from 43 locations all over Europe and exposed to brown rot (Rhodonia placenta), white rot (Trametes versicolor) or soft rot fungi. In addition, five different moisture performance characteristics were analyzed. The main results were the two factors accounting for the wetting ability (kwa) and the inherent protective properties of wood (kinh), factors for conversion between Norway spruce vs. Scots pine sapwood or European beech for the three decay types and four moisture tests, and material resistance dose (DRd) per wood species. The data illustrate that the differences between the three European reference wood species were minor, both with regard to decay and moisture performance. The results also highlight the importance of defined boundaries for density and annual ring width when comparing materials within and between experiments. It was concluded that with the factors obtained, existing, and future test data, where only one or two of the mentioned reference species were used, can be transferred to models and prediction tools that use another of the reference species.

Caffeine – Perspective natural biocide for wood protection against decaying fungi and termites

The aim of this study was to test caffeine – harmless to health and eco-friendly natural compound – as a potentially effective fungicide and insecticide for wood protection. Caffeine treatment of wood, using simple and cheap long-term dipping technology, was tested against the brown-rot fungus Rhodonia placenta and termite Reticulitermes flavipes. Fungi and insects can cause severe loss of functionality of wooden structures. The current search for of nature-friendly products is understandable in the context of the changing world environment. The experiment with caffeine-treated refractory Norway spruce (Picea abies) wood lasted for 16 weeks against the rot attack according to EN 113, and for 6 weeks against the termite attack according to EN 118. Mass losses of caffeine treated wood samples without ageing, caused by R. placenta and R. flavipes were small, only 1.4% or 0.5%, respectively. Results clearly suggested that caffeine is an alternative to commercial biocides, e.g., to the reference in wood well fixable Bochemit QB, containing boric acid and alkylbenzyldimethylammonium chloride. Caffeine was sensitive for leaching out from wood by water even in the presence of an additional hydrophobic protective layer. Based on the achieved results it is possible to recommend caffeine treatment as an environmentally friendly alternative for wood protection, but only in the interior or outdoor under roof area against termite attack and also against brown-rot fungi. Treatment with caffeine had no negative impact on the compression strength and colour of the spruce wood, while it improved surface wetting important for potentially follow-up coating or adhesive applications.