Improvement of fungicidal properties and copper fixation of copper-ethanolamine wood preservatives using octanoic acid and boron compounds

Copper ethanolamine preservatives are one of the most important solutions for wood preservation. As copper itself can not ensure sufficient protection against wood destroying organisms we combine it with other co-biocides like quaternary ammonium compounds, azoles and/or boron. Influence of different boron compounds and octanoic acid on copper fixation as well as performance of spruce wood impregnated with different copper/ethanolamine/boron based aqueous solutions is described in this paper. Copper fixation was determined according to the modified ENV 1250 (1994) standard method, while performance against Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor was tested according to the mini block procedure. The results showed that addition of boron increases copper leaching, but on the contrary improves performance against wood decay fungi. On the other hand, addition of octanoic acid improves copper fixation, and slightly decreases resistance against copper tolerant fungi.     

Changes of the pH value of impregnated wood during exposure to wood-rotting fungi

and Schizophyllum commune). The third species was the brown-rot fungi Antrodia vaillantii, using three different strains of this species. Antrodia vaillantii substantially decreased the pH-value of impregnated and unimpregnated wood before any mass loss appeared. On the other hand, the white-rot fungus T. versicolor and S. commune caused a slight increase of the pH of impregnated and unimpregnated wood. It is suggested that a decrease of pH of wood may indicate early stages of decay by brown rot fungi.     

Changes of the pH value of impregnated wood during exposure to wood-rotting fungi

Trametes versicolor and Schizophyllum commune). The third species was the brown-rot fungi Antrodia vaillantii, using three different strains of this species. Antrodia vaillantii substantially decreased the pH-value of impregnated and unimpregnated wood before any mass loss appeared. On the other hand, the white-rot fungus T. versicolor and S. commune caused a slight increase of the pH of impregnated and unimpregnated wood. It is suggested that a decrease of pH of wood may indicate early stages of decay by brown rot fungi.

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Trametes versicolor und Schizophyllum commune). Die dritte Art war vom Braunf?uletyp (Antrodia vaillantii), wovon drei verschiedene St?mme eingesetzt wurden. Antrodia vaillantii senkte den pH deutlich in impr?gnierten und unbehandelten Proben, noch bevor ein Massenverlust auftrat. Die beiden Weissf?uleerreger T. versicolor und Sch. commune lie?en den pH dagegen ansteigen. Anhand des pH-Abfalls konnte man schon frühe Stadien eines Braunf?uleabbaus erkennen.

     

Fungal and termite resistance of wood treated with 4-methoxytrityl tetrafluoroborate

This study evaluates the decay and termite resistance of Scots pine (Pinus sylvestris L.) treated with 4-methoxytrityl tetrafluoroborate (MTFB). Decay resistance tests of unleached samples showed that 2%, 1.5% and 1% concentrations of MTFB (15.4 kg/m³, 11.1 kg/m³, and 7.4 kg/m³, retention levels, respectively) gave less than 2% decay of Postia placenta and concentrations of 2% and 1.5% less than 2% decay of Coniophora puteana. Wood specimens treated with 4-methoxytrityl tetrafluoroborate solutions were not protected against the brown rot fungi after a 14-day severe leaching process, suggesting excessive leaching of the chemical from wood. Treatment with 2% concentration protected against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens in comparison with lower concentration levels. These results suggest that 4-methoxytrityl tetrafluoroborate might be promising to protect wood being used outdoors against termite attack. However, 4-methoxytrityl tetrafluoroborate did not protect wood against fungal decay. Field tests are needed to observe the performance of 4-methoxytrityl tetrafluoroborate treated wood in ground contact.     

Influence of fungal decay by different basidiomycetes on the structural integrity of Norway spruce wood

The potential influence of diverse decay patterns caused by different brown rot causing basidiomycetes on the structural integrity of wood was investigated. Therefore, decayed Norway spruce (Picea abies Karst.) specimens representing a wide range of mass loss, caused by four different brown-rot fungi and one white-rot fungus, were applied to a high-energy multiple impact (HEMI)-test series. The relationship between the resistance to impact milling (RIM) and the mass loss by fungal decay could be subdivided into three areas: 1. Prior to measurable mass loss, a strength reduction was detectable due to the depolymerisation of wood cell wall components. 2. Between 0 and 25–30% mass loss, RIM decreased with increasing mass loss. 3. Above 30% mass loss, RIM increased again due to gluing effects of the fungal mycelium. The influence of the different brown rot fungi on the structural integrity of the wood differed slightly, but partly significantly.     

Performance of wood impregnated with N-methylol and copper based aqueous solutions

The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (c_Cu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (c_Cu=0.5%).     

Performance of wood impregnated with N-methylol and copper based aqueous solutions

The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (c_Cu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (c_Cu=0.5%).     

Laboratory evaluation of boron-containing quaternary ammonia compound, didecyl dimethyl ammonium tetrafluoroborate (DBF) for control of decay and termite attack and fungal staining of wood

This study evaluates the decay and termite resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound containing boron. Laboratory decay resistance tests were performed using brown-rot fungus, Fomitopsis palustris and white-rot fungus, Trametes versicolor. Treated wood specimens were also subjected a 3-week-termite resistance test using subterranean termites, Coptotermes formosanus. Decay resistance tests showed that wood specimens treated with 0.5 and 1.0% DBF solutions were well protected against both fungi even after a 10-day severe leaching process, suggesting the adequate fixation of DBF in wood. DBF treatment at 0.1% concentration was efficient against subterranean termites, Coptotermes formosanus Shiraki based on mass losses in both leached and unleached wood specimens. The ability of DBF to inhibit discolorations by selected mold and stain fungi was also screened in laboratory conditions. DBF at the highest concentration level (1%) provided limited protection against mold and staining fungi tested, however, it was effective for only short-term protection (1 or 2 weeks) at lower concentrations. These results suggest that DBF is promising to protect wood to be used outdoors against both fungal decay and termite attack however field tests are needed to observe the performance of DBF-treated wood in ground contact.     

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

Heat treatment is an effective method to improve biological resistance of low natural durability wood species. The aim of this study was to enhance the decay resistance of Pinus patula, an African low natural durability softwood species, via wood thermal modification technique. Heat treatment was performed on wood specimens under inert conditions at different heat treatment intensities to reach mass losses of 5, 10 and 15%. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta. The wood chemical and elemental composition was determined as well as extractives toxicity before and after wood thermal modification to understand the reasons of durability improvement. The treated specimens exhibited a significant increase in their durability against wood decay in line with the severity of the treatment. Wood holocellulose was found to be distinctly more sensitive to the heating process than the lignin constituent. In addition, obvious correlations were observed between weight losses recorded after fungal exposure and both holocellulose decrease and lignin ratio increase. The same correlations were observed with the elemental composition changes allowing using the observed differences for predicting of wood durability conferred by heat treatment. Furthermore, no significant differences were observed between the toxicity of Pinus patula wood extractives before and after its thermal modification.     

Efficacy of water-borne emulsion of copper naphthenate as preservative for northern red oak (Quercus rubra) and soft maple (Acer rubrum)

Northern red oak (Quercus rubra) and red maple (Acer rubrum) cubes pressure treated with water brone formulation of copper naphthenate were evaluated for resistance to attack by brown fungiGloeophylleum trabeum (Pers. Ex Fr.) Murr. (Madison 617 ATCC 11539) andPoria placenta (Fr.) Cooke (Madison 698, ATCC 11538), white rot fungiTrametes versicolor (L. Ex FR.) Pilat (R-105 from Jeff Morrell),Irpex lacteus Fries (FP-105915 from Jeff Morrell) andPleurotus ostreatus (Jacq. Ex Fr.) Kummer (ATCC 32237), and soft rot fungiChaetomium globosum (ATCC 34152) andPhialophoria Sp. Wood samples measuring 19 by 19 by 19 mm were pressure treated to target copper retentions of 12.48 kg/m³ (0.78 pcf), 9.77 kg/m³ (0.61 pcf), 5.6 kg/m³ (0.35 pcf), 4.5 kg/m³ (0.30 pcf), 2.56 kg/m³ (0.16 pcf), 1.2 kg/m³ (0.075 pcf), 0.48 kg/m³ (0.03 pcf). Data from laboratory soil block tests indicate that at 2.0 ± 0.5 kg/m³ (0.13 pcf) copper retention from water borne copper naphthenate, the protection is similar to that from a 1.6 kg/m³ (0.10 pcf) elemental copper from oil borne copper nathenate or 7.2 kg/m³ (0.45 pcf) total oxide from CCA-C. Higher copper levels (3.0 ± 0.2 kg/m³) are needed to protect against copper tolerant brown rot fungusP. placenta. Results from an American Wood Preserver’s Association standard leaching test indicate that waterborne copper naphthenate treated samples retained 80 to 90% the copper initially absorbed. The amount of leached copper increases with the pH of the leaching solution.     

Re-evaluation of fungicidal properties of boric acid

Minimal inhibitory fungicidal concentrations of one of the most important biocides were determined in nutrient medium and on impregnated wood specimens. The results showed, that brown rot fungi are more sensitive to boric acid than white rot ones. To inhibit growth of wood decay fungi, lower minimal effective retentions have been determined than reported in previous publications.     

Correlation between brown rot decay and Pilodyn measurements

Assessment of brown rot decay is one of the most important issues within remedial treatment of attacked wood constructions. Pilodyn is a well-established tool for the assessment of density of several commercially important plantation species, therefore the authors were interested in its suitability to evaluate rate of decay as well. The Pilodyn measurements performed on Norway spruce wood exposed to several brown rot fungi clearly indicate correlations between needle penetration and mass loss.     

Use of wax emulsions for improvement of wood durability and sorption properties

Waxes are used for treatment of wood surfaces for several decades predominately as surface treatments because they weakly penetrate into the wood. In order to overcome this issue, water emulsions were applied in the present experiment. Five water emulsions of various concentrations were used, namely montan wax, polyethylene, ethylene copolymer and oxidized polyethylene wax. Performance of wax treated beech (Fagus sylvatica) and Norway spruce (Picea abies) against white rot, brown rot and blue stain fungi was tested. In parallel, sorption properties of wax treated wood were determined. The treated specimens were more resistant to wood decay fungi. Polyethylene and oxidized polyethylene wax were found to be particularly efficient. Although this treatment does not improve resistance to blue stain fungi, it reduces the sorption of water.     

Genetic studies on house rot fungi and a rapid diagnosis

The paper describes genetic studies on house rot fungi and a rapid identification technique for them, viz. the true dry rot fungus Serpula lacrymans, the wild merulius S. himantioides, the cellar fungus Coniophora puteana and the pore house fungi Antrodia vaillantii and Tyromyces placenta. The method ARDRA-ITS uses the internal transcribed spacer (ITS) of the ribosomal DNA (rDNA) which is amplified by the polymerase chain reaction (PCR). Amplifications were directly performed from agar plate mycelium and even from fungal tissue taken from infected substrate in a building without preceding fungal pure cultures and DNA preparation. For fungal differentiation, the amplified rDNA-ITS region was digested with the restriction endonucleases Haelll and Taql and the obtained ITS fragments separated by agarose gel electrophoresis. The specific DNA-fragment fingerprint allowed the identification of an unknown fungal sample by comparison of its pattern with those of control fungi within one day from sampling to diagnosis.     

Potential of near infrared spectroscopy to assess hot-water-soluble extractive content and decay resistance of a tropical hardwood

The ability to identify both low- and high-durability samples in a population of naturally durable samples would allow more rational use of these materials, for example, using samples in the lower ranges of durability in non-soil contact. One possible method for rapidly assessing differences in heartwood characteristics related to durability is near infrared spectroscopy (NIR) coupled with multivariate statistical methods. A number of recent studies suggest that NIR can be related to a variety of wood properties, including extractive content. There are, however, few data on the ability of this technique to assess decay resistance, especially in hardwoods or species with high natural durability. In this report, the ability of NIR to predict both extractive content and resistance to fungal attack in Goncalo alves (Astronium graveolens) was assessed. NIR spectra accurately predicted hot-water-soluble extractive content of A. graveolens and its susceptibility to the white rot fungus Trametes versicolor. A. graveolens was very resistant to attack by the brown rot fungus Gloeophyllum trabeum and NIR spectra were not useful predictors of weight loss. NIR spectroscopy may be a useful tool for rapidly assessing the extractive content and decay resistance of naturally durable wood.     

Light microscopic analysis of Tectona grandis L.f. wood inoculated with Irpex lacteus and Phanerochaete chrysosporium

Felling of immature teak (Tectona grandis L.f.) trees or delay in transport of wood logs from felling sites provide platform to microbial attack. Among them, white rot fungi are central driving force that degrades wood and causes severe economic loss. In contrast, Phanerochaete chrysosporium and Irpex lacteus are more extensively studied for their ability to degrade synthetic dyes and poly-aromatic compounds. Therefore, in the present study, both the fungi collected from the Gujarat forest were utilised for in vitro decay test to assess their potential in lignin degradation, extent of cell wall damage and pattern of wood decay in sound blocks of teak. In the early stage of fungal inoculation, there was a negligible amount of weight loss; after 1 month it became rapid and highest weight loss (30.05 % by P. chrysosporium and 27.97 % by I. lacteus) was observed at the end of 120 days. Mycelial invasion occurred through vessels, from vessels to axial and ray parenchyma and subsequently into xylem fibres. Both the strains showed selective delignification and the first symptom of degradation was defibration, separation of rays, and formation of boreholes on ray cell walls at an advanced stage. Xylem fibres and parenchyma cells lost their integrity and collapsed completely. Among all the cell types, parenchyma cells and fibres were more vulnerable to fungal attack, while vessels were resistant to the activity of lignolytic enzymes.     

Thermogravimetric analysis for wood decay characterisation

The paper focuses on the use of thermogravimetric analysis (TGA) as a fast method for estimating the change of lignocellulosic materials during fungal degradation in laboratory trials. Traditionally, evaluations of durability tests are based on mass loss. However, to gain more knowledge of the reasons for differences in durability and strength between wooden materials, information on the chemical changes is needed. Pinus sylvestris sapwood was incubated with the brown rot fungus Gloeophyllum trabeum and the white rot fungus Trametes versicolor. The TGA approach used was found to be reproducible between laboratories. The TGA method did not prove useful for wood deteriorated by white rot, but the TGA showed to be a convenient tool for fast estimation of lignocellulosic components both in sound wood and wood decayed by brown rot.     

Effect of essential oil compounds and plant extracts on decay and termite resistance of wood

Essential oils and their derivatives have a long history of safe usage as antimicrobial agents in food industry. In this study various essential oils and extracts from plants were screened for their ability to inhibit wood decay and termite attack in laboratory decay and termite resistance tests using treated wood specimens. In the laboratory decay resistance tests, wood specimens treated with essential oil compounds were subjected to brown-rot fungus, Tyromyces palustris, and white-rot fungus, Trametes versicolor for three months. The specimens were also subjected to termite attack by subterranean termites, Coptotermes formosanus for three weeks in laboratory conditions. The formulation with cinnamaldehyde (DF3) was found to be effective against both the brown-rot and white-rot fungi used in the study. However, the formulation with cinnamic acid (DF8) was able to protect wood specimens against only the white rot fungus and about 50% mass loss occurred in the specimens subjected to the brown-rot fungus. The mass losses in the wood specimens treated with cassia oil containing formulation (DF4) showed that cassia oil was effective against both fungi. The wood tar oil and dodecanal compounds also inhibited fungal decay in the specimens. The wood specimens treated with the formulations used in termite resistance tests were more resistant against the termites when compared to specimens treated with the formulations in decay resistance tests. Even after severe weathering process, treated wood specimens showed resistance against the subterranean termites. Results suggest that essential oils and plant extracts might be important to develop new wood preservatives that are less harmful to the environment and humans than recently available ones.     

Boron effect on decay resistance of some fire-retardant coatings applied on plywood surface

Boron effect on decay resistance of some fire-retardant coatings applied on plywood surface was studied. Boric acid (B) was mixed into aqueous trimethylol melamine (TM) solution to increase the fixation in wood. To reveal the decay resistance of boric acid-added formulations, coatings were applied over radiata pine plywood surface as 100 g/m² amounts. Phosphoric acid (P) and dicyandiamide (D) were also used alone or in mixtures as reference coatings for comparison. Coated specimens were exposed to weathering according to Japanese Industrial Standard JIS A 9201 (1991) as severe leaching for 10 cycles, prior to decay-test. Non-leached and leached specimens, then, were inoculated with a brown-rot fungus Tyromyces palustris and a white-rot fungus Coriolus versicolor. Extent of the fungal attack was determined by mass loss of the specimens after 12 weeks incubation and microscopic examinations by 6 × magnification. Results indicated that TMB and TMDB coatings imparted the panels complete decay resistance despite severe weathering conditions and were proved superior over all other alone and mixture coatings. Although other combinations and alone treatments used in the study were also effective to inhibit the fungal damage before weathering, leaching greatly reduced their protective efficacy. Surface characteristics of decayed specimens were consistent with the determined values of mass losses caused by fungal attack. TMB and TMDB coatings were remarkably effective in maintaining sound surface properties after exposure to weathering and decay fungi.     

Resistance of thermally modified ash (<Emphasis Type="Italic">Fraxinus excelsior</Emphasis> L.) wood under steam pressure against rot fungi,soil-inhabiting micro-organisms and termites

Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood^® treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 °C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 °C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation.