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Comparison of decay rates of preservative-treated stakes in field and fungus cellar tests
1980 - IRG/WP 2135
With the exception of acid-copper-chromate, zinc-chrome-arsenate, and sodium pentachlorophenoxide, the relative performance of preservatives in the fungus cellar was similar to that in the field.
M E Hedley


Performance of chromated copper arsenate-treated aspen fence posts installed in Forintek's Eastern test plot from 1951 to 1963
1984 - IRG/WP 3272
Aspen poplar fence posts were pressure treated by the full cell process using three formulations of copper chrome arsenate wood preservative. A total of one hundred and fifty nine of the posts were installed in service in Forintek's Chalk River post plot from 1951 to 1962. During the 1982 general inspection of the post plot all 159 posts were still in service. A groundline inspection was carried out on the material to determine the extent to which decay had progressed during this period. Samples were taken from the surface of tanalith C treated posts and subsequent microscopic examination revealed that soft rot attack was present in the outer portion of posts. The groundline area of posts treated with (K 33), CCA type B and (greensalt) CCA type A were in generally good condition after 22 years and 31 years respectively. Rate of decay was highest for CCA-C tanalith treated posts at 0.3 mm per year with a retention of 3.04 kg/m³ oxides.
C D Ralph


Comparison of decay rates of preservative-treated stakes in field and fungus cellar tests. Results after 40 months fungal cellar exposure
1983 - IRG/WP 2200
Decay rates of preservative-treated Pinus radiata stakes during 40 months exposure in the FRI fungus cellar were compared with those of similarly treated material in a field test. Decay rates in the fungus cellar were from 4 to 100 times higher than in the field, although for the majority of preservatives the rate was between 7 and 12 times higher. The lag phase before onset of decay, noticeable with most of the preservatives in the field test, was largely eliminated in the fungus cellar. Possible reasons are given for inconsistencies in relative rates of decay of preservatives in the two tests.
M E Hedley


The influence of gaseous oxygen concentration on fungal growth rates, biomass production and wood decay
1998 - IRG/WP 98-10283
The effects of air and several levels of oxygen balanced with nitrogen (% oxygen (v/v) nitrogen to 100%) on growth rates, biomass production and wood decay were investigated. The best technique for measuring daily growth rates in anaerobic jars was found to be by using 40 mm petri dishes which were attached to the walls of the jars. At the end of the test period the same petri dishes were also used for determining the dry weight of the fungal mycelia. The results showed that 5% oxygen concentration was very favourable for white rot and brown rot fungi (Basidiomycetes). When oxygen levels were reduced from 1% to 0.01%, the growth rates and dry weight of these fungi were steadily decreased. On the other hand, there was a large difference between very low oxygen levels (0.01 to 1%) and other levels (5 to 21% 02). In the case of other fungi there was not a big difference on their growth rates and biomass. Observational and numerical results on Fagus sylvatica (beech) and Pinus sylvestris (Scots pine) degradation by Coriolus versicolor, Coniophora puteana and Chaetomium globosum showed that there was a large difference in the degradation of the wood samples caused by C. puteana and C. versicolor when exposed to air and other levels of oxygen (0.25,1, 5 and 10% 02). Weight losses obtained by C. globosum as a soft rot on timber specimens in air and other oxygen levels were all in same range and below 5%. On the other hand there was a safety point at 5% 02 below which the fungus was unable to degrade beech. This point was 10% 02 for scots pine. At these points, weight losses were under 5%.
S M Kazemi, D J Dickinson, R J Murphy


Factors affecting decay rates in a fungus cellar II
1986 - IRG/WP 2259
Tests were initiated to investigate the influence of various factors on the decay rate in a "Fungus Cellar". Birch and pine stakes treated with chromated copper arsenate and didecyldimethyl ammronium chloride, as well as untreated control stakes, were incubated in two soils in a Fungus Cellar test and installed at two field sites for comparative purposes. The visual rating vs actual stake weight loss relationship was also studied. Preliminary results from the initial Fungus Cellar test indicated differences in decay rates between birch and pine and also between soils. The decay rate observed for pine stakes was generally lower than birch in both soils. The decay rate was greatly accelerated in a Michigan soil with birch and pine over that observed in a Florida soil. Soil type had less impact on the primary decay present in the stakes. Soft rot was the primary decay associated with treated wood in both soils, while soft rot, basidiomycete, or combinations of the two were frequently found in untreated wood. The range of weight loss vs visual rating relationship was similar between wood species, treatment, and soil type. Weight losses tended to "overlap" the visual ratings regardless of the decay type.
P A McKaig


Factors affecting decay rates in a fungus cellar
1985 - IRG/WP 2242
Birch and pine stakes treated with chromated copper arsenate and didecyldimethylammonium chloride were incubated in two soils in a "Fungus Cellar" test. At three month intervals, sets of stakes were inspected and assigned visual ratings or removed from the soil beds for weight loss determination. Preliminary results after nine months exposure have shown differences in the decay rates between birch and pine and also between soils. Overall, the decay rate for pine, treated and untreated, has been considerably lower than birch in both soils. A Michigan soil accelerated the decay rates up to 3 times that observed for a Florida soil. Soil type also influenced the primary decay present in the stakes. Basidiomycete attack was observed in birch stakes treated with subthreshold retentions of both preservatives in the Michigan soil, while the primary decay in the Florida soil was soft rot. Untreated birch controls failed through basidiomycete attack in both soils. Soft rot was the primary decay in treated and untreated pine for both soils. However, more data is needed to determine if this trend will continue. Weight losses as low as 9.3% caused stake failure (visual ratings of 0). Basidiomycete damage caused stake failure at lower weight losses than soft rot. Regardless of the decay type, threshold retentions selected by weight loss or visual ratings were similar.
P A McKaig


Decay rates and strength and stiffness loss in foundation beams
1992 - IRG/WP 92-1563
The TNO Centre for Timber Research has executed an extensive research programme into the rate of decay in foundation beams, as a result of lowering of ground water tables. The aim of the research was to develop a method, predicting the decrease in strength and stiffness in beams, due to wood decay during drytime of foundation beams. With the calculated extremes in decay, the damage caused by local settlements of the foundation can be estimated. Though this research deals with untreated timber only, the results yield information which may be used for methods of testing treated timber in ground contact. From 1987 to 1989 literature studies and field inspections have been evaluated, and the most important influencing factors were described. In the following laboratory research the aim was, to quantify the influence of these factors (wood species, dimensions, age, soil wetness, temperature, fluctuation of water) on the decay rate. The rate of decay was measured by mass loss after one year of exposure in a wet but aerated soil, using pine and spruce in different dimensions. For part of the specimens, decrease in strength properties was also measured. Results indicate, that for timber with high moisture contents (over 80%), the decay type is dominated by softrot (95%) and is mainly determined by the surface/volume ratio. The relation between mass loss and loss of strength and stiffness was determined. These results will be used for calculating the deformation of foundation.
P Esser, H S Buitenkamp


Comparing microbial colonisation and Decay Rates of Wood from Sound and Aphid-Killed Kenyan-Grown Mexican Cypress (Cupressus lusitanica)
2006 - IRG/WP 06-10599
Samples of wood from 10, 15, and 30-year old trees attacked and killed by the cypress aphid (Cinara cupressi) and sound Kenyan-grown Cupressus lusitanica trees were investigated for variations in moisture content, density and susceptibility to microbial decay. MC varied with tree age, a normal trend, and between samples from aphid-killed and sound trees. In samples from 10, 15 and 20-year old sound trees, MC was higher by 11.1%, 8.6% and 7.8% respectively, than in samples from aphid-killed trees. Similarly density varied with age, to be expected, and between samples from aphid-killed and sound trees, being 3.5%, 2.6% and 2.1% higher in samples from sound trees of the 3 age classes. Exposure to riverwater and soil revealed a pattern of microbial colonisation and degradation normal for each environment. In riverwater, samples were mainly colonised by bacteria, actinomycetes, stain fungi, and softrot fungi, bacteria and softrot fungi being the main wood degraders, but their action on samples were slow and generally moderate in severity of attack. Exposure to soil followed a similar pattern of colonisation, the principal wood decaying organisms being bacteria and softrot fungi, and to a lesser extent brown and white rot fungi. Samples from both aphid-killed and sound trees were colonised and decayed in a similar fashion, but microbial decay in the soil environment was more pronounced than in riverwater. The soil block test recorded low weight losses after 2 weeks exposure, rising to between 29% and 36% after 12 weeks, with no significant differences between weight losses in samples from aphid-killed and sound trees, or tree age. The results of the study revealed that there are no significant differences between microbial decay susceptibility of wood from aphid-killed and sound trees, and that slight differences in MC and density did not influence decay rate. Consequently, wood from aphid-killed cypress trees should not be considered as of inferior quality, in terms of decay susceptibility, by wood processors and consumers.
R Venkatasamy


A comparison of rates of decay and loss in stiffness of radiata pine and Douglas fir framing lumber
2008 - IRG/WP 08-20378
Stiffness loss with time was recorded for untreated radiata pine and Douglas fir framing size lumber and preservative treated radiata pine which dad been pre-inoculated with Oligoporus placenta, a brown rot decay fungus isolated from decaying untreated radiata pine framing. Between stiffness measurements, samples were contained in a plastic tank located outside at ambient temperature. Index of Condition (sensu AWPA Standard E7-93) was assessed for all samples at the time stiffness testing was undertaken. Substantial loss of Index of Condition was recorded for all untreated samples before there was any significant loss in stiffness. Decreasing order of stiffness loss (and weeks to first measurable loss) was: untreated radiata pine sapwood (24), radiata pine heartwood (48), Douglas fir sapwood (65), Douglas fir heartwood >106), treated radiata pine sapwood (>106). The results indicate that for untreated Douglas fir in particular, the presence of observable decay - the main criterion for replacement of framing when a "leaky building" is rehabilitated - may not truly reflect residual stiffness, which would be retained when leaks were rectified and the framing dried.
M Hedley, D Page, J van der Waals


Comparison of rates of wood decay from four different field test protocols following 4-5 years exposure at a site in New Zealand
2011 - IRG/WP 11-30565
The rate of decay of Pinus radiata was evaluated using four different field test protocols at a site near New Plymouth, New Zealand. The average Scheffer index was 86 over the five year period of testing. The field tests were an in-ground stake test (AWPA Std E7-01) and three above ground tests – lap-joint (AWPA Std E16-98), decking (AWPC protocol) and ground proximity tests (AWPA Std E18-06) Two wood preservatives were used, ACQ and an experimental formulation containing the azole propiconazole. Each preservative was tested at three retentions, a full retention or rate and then ½ and ¼ this retention. All trials included untreated Pinus radiata control samples. The most graphic differences among tests were observed in untreated samples. The in-ground stake test displayed the greatest initial rate of decay with untreated stakes failing after 2 years. However the most reliable early indicator of decay was observed in the decking test where samples were laid on untreated bearers. In a parallel decking test where samples were laid on treated bearers they remained sound for 3 years then declined rapidly in years 4 and 5. Based on untreated and preservative treated Pinus radiata the results in the present study indicate a ranking for most rapid to least rapid for above ground protocols of: decking test on untreated wood > ground proximity > lap-joint = decking on treated wood.
P Lobb, K Day, A Siraa


Modelling decay rates of timber exposed above ground on four different continents
2020 - IRG/WP 20-20670
Durability performance data from an international decking trial were analysed to explore relationships with climate variables, particularly those related to temperature and rainfall. Matched decking samples of slash pine (Pinus elliottii) sapwood and heartwood, spotted gum (Corymbia citriodora), Norway spruce (Picea abies) and Scots pine sapwood (Pinus sylvestris) were exposed to the weather above ground in Australia, Malaysia, Germany, Denmark and the United States. Boards were assessed periodically detect decay, which was rated using a common assessment scale. Preliminary exploration of relationships between decay assessment scores and decay indices – the Scheffer Climate Index and a dose-response model based solely on macroclimate variables – is presented in this paper. Shifting from a time-dependent analysis to one based upon cumulative macroclimate variables helped to better explain variations in performance among sites, although there were still some inconsistencies. Results are being further examined to help develop more precise predictive systems.
L P Francis, J J Morrell, C Brischke, P B Van Niekerk, J Norton


Assessing the risk of marine borer attack of the timber trestles and decay of timber above the intertidal zone of the Barmouth Viaduct
2021 - IRG/WP 21-10974
The Barmouth Viaduct is a Grade II* listed structure which carries the single track of the Dovey Junction to Pwllheli line and footway over the Mawddach estuary. It is in a marine environment where timber below the high tide mark is at most risk in Use Class 5 and all timber above in Use Class 3.2, permanently exposed to the risk of wetting. The structure consists of a timber trestle viaduct of 113 timber spans with 5 steel spans over the deep-water channel. It is of historic importance and is the longest functioning timber viaduct in the UK and is a vital link on the Cambrian line. However, the structure is ageing and under attack from a number of biological agents. Within the intertidal zone, the structure is at risk of attack by shipworm. Above the intertidal zone, the structure is permanently at risk of attack by wood decaying fungi. The structure is undergoing a £20 million refit with much of the work focussing on the renewal of timber that has been attacked by biological agents. The combination of an ageing infrastructure and stressed maintenance budgets provides the impetus to develop innovative methods to support the asset management plan of the structure. Understanding the performance of materials and their rates of deterioration may inform design choices. Moreover, understanding the impact of climate change and local environmental factors and how this can change the distribution of marine borers and affect the risk of decay can also support the long-term asset management of the viaduct.
J R Williams


Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh


Effect of acetylation on decay resistance of wood against brown-rot, white-rot and soft-rot fungi
1989 - IRG/WP 3540
Effect of acetylation on decay resistance of wood was investigated using wood blocks of Cryptomeria japonica, Pinus densiflora, Albizia falcata and Fagus crenata. Blocks were treated with uncatalyzed acetic anhydride for different lengths of time and exposed to Tyromyces palustris, Serpula lacrymans, Coriolus versicolor and unsterilized soil. The action of OH-radical on acetylated wood was also examined using Fenton's reagent. The enhancement of decay resistance by acetylation was revealed clearly for all cases of exposures but varying with fungal and wood species used. For a brown-rot fungus Tyromyces palustris, the weight loss reached almost nil in all woods at 20 WPG (weight percent gain) of acetylation, after the striking decrease from 10 to 15 WPG. For a white-rot fungus Coriolus versicolor, it was counted until 12-15 WPG in the perishable hardwoods used, but not in a softwood Cryptomeria japonica, even at 6 WPG. In cases of another brown-rotter Serpula lacrymans and soil burial, effect of acetylation was intermediate between Tyromyces palustris and Coriolus versicolor. Anti-degradation mechanism by acetylation was discussed, from these weight loss - weight gain relationships, and the IR-and 13C-NMR spectral analyses of fungus-exposed wood.
M Takahashi, Y Imamura, M Tanahashi


Field trial with poles of Scots pine treated with six different creosotes
1996 - IRG/WP 96-30115
In the middle of the 50's field trials with creosote-treated poles were started in France, Germany and Sweden. The trials were initiated by WEI (Western-European Institute for Wood Preservation). Six different creosotes were used and 40 poles per creosote were installed at each test field. Results after 39 years of exposure in Simlangsdalen, Sweden are reported. Poles treated with a heavy creosote were less decayed than poles treated with medium-heavy creosotes. Poles treated with a light creosote were most decayed.
Ö Bergman


Questionnaire - Fungal decay types
1985 - IRG/WP 1265
T Nilsson


JWPA method for testing effectiveness of surface coatings with preservatives against decay fungi
1981 - IRG/WP 2164
In 1979 JWPA established a new method for testing effectiveness of surface coatings in accordance with practical use of preservative-treated lumber. Comparing the new testing method with JIS A 9302, a few new trials - size of wood specimen, weathering procedure, and decay-test procedure - are incorporated.
K Tsunoda


Utilization of curcumin for detection of presence of boron in wood
1982 - IRG/WP 3191
It has been shown that curcumin is not a reliable reagent for detecting boron in wood that has been attacked by fungi
M-L Edlund


Co-operative studies on determining toxic values against wood-destroying Basidiomycetes: Progress report to May 1989
1989 - IRG/WP 2339
This document reports progress on the co-operative study between nine laboratories set up following the proposals contained in Document IRG/WP/2316. Results have been received from two laboratories. Toxic values data have been established successfully using the test fungus Coniophora puteana but problems have been encountered with the other test fungi.
A F Bravery, J K Carey


Monographic cards for wood-destroying fungi. [Fiches monographiques pour les champignons lignivores]
1970 - IRG/WP I 5B
C Jacquiot


On Donkioporia expansa (Desm.) Kotl. & Pouzar
1986 - IRG/WP 1285
Donkioporia expansa is found more often in houses than realised until now. Virulence tests according to EN 113 show not only an attack of oak, but also of other hardwoods and even soft-woods.
G Buchwald


Nondestructive Evaluation of Oriented Strand Board Exposed to Decay Fungi
2002 - IRG/WP 02-20243
Stress wave nondestructive evaluation (NDE) technologies are being used in our laboratory to evaluate the performance properties of engineered wood. These techniques have proven useful in the inspection of timber structures to locate internal voids and decayed or deteriorated areas in large timbers. But no information exists concerning NDE and important properties of wood composites exposed to decay fungi. For our pilot study on several types of wood composites, we examined the relationship between nondestructive stress wave transmission, decay rate and the bending properties of OSB exposed to the brown-rot fungus, Gloeophyllum trabeum (MAD-617). The following measurements were taken: stress wave transmission time (pulse echo test method), static bending test (ASTM D3043-95), and decay (expressed as percent weight). Stress wave measurements correlated with strength loss and with increasing rate of fungal decay. Stress wave NDE has great potential as a method for inspection of wood composite load-bearing (in-service) structures, detection of decay in laboratory tests, assessment of chemical additives to improve wood composite durability, and prediction of long term composite performance.
B Illman, V W Yang, R J Ross, W J Nelson


Moisture content levels and decay of hemlock
1986 - IRG/WP 1287
As a model of decay conditions of wooden members in wooden houses, a decay test was set up in which samples of western hemlock (Tsuga heterophylla) under 4 moisture levels were examined. Each week the samples were weighed and if the weights indicated that their moisture contents were lower than the expected levels, distilled water was added. Every 8 weeks 3 samples from each condition were oven dried at 60°C for 48 hours, up to 48 weeks. After 48 weeks, 3 samples from each condition were oven dried every 16 weeks. The results obtained were as follows: After examining the samples for 96 weeks at 27°C, the mean weight loss of the hemlock samples kept at about 50-100% moisture content level was larger than those of the other levels. If the samples were dried every 8 weeks, the amount of decay in them was not significant. Decay was also not significant in the samples kept at approximately 20-30% moisture content level.
K Suzuki


Dimensional stability and decay resistance of hot-melt self-bonded particleboard by surface benzylated pine chips
1991 - IRG/WP 3652
Akamatsu (Pinus densiflora Sieb. et Zucc: Japanese red pine) particles were pretreated with 40% NaOH solution and benzylated with benzyl chloride, and the surface of particle was converted into meltable materials. Hot-melt self bonded particleboard having smooth and high glossiness surface was prepared by hot pressing at 150°C and 1.96 MPa without using any conventional adhesives. Dimensional stability and decay resistance of the benzylated particleboard were evaluated. Particleboards made of benzylated particles having more than 38% of weight percent gain (WPG) showed that dimensional stability and decay resistance were superior to the conventional particleboard made by using phenolformaldehyde resin as a binder, because hydroxyl groups of wood were substituted by hydrophobic benzyl groups with benzylation. Though bending strength of the board was a little lower than control board due to the damage of benzylated particles during benzylation, its internal bonding strength was very high, because the hot-melting strengthened the inter-particle bonding.
M Kiguchi, K Yamamoto


How to Document the Performance of Super-Critical Treated Wood in above Ground Situations?
2005 - IRG/WP 05-20316
The paper presents practical experiences from the preparation of a new preservative treated wood product for introduction to the market. The product in question is Superwood™, which is treated with organic biocides using CO2 in a supercritical state as a solvent. The question is how to evaluate the performance of a new product such as Superwood™ in order to get an acceptance on the market and fulfil the formal requirements. In the European Union countries, the EN 599-1 is the standard that needs to be complied when approving a new product for the market, but it only focuses on the toxic limit against representative decay fungi according to EN 113. However, decay test, above ground and other forms of field tests are optional, this is not in line with the traditional test philosophy in the Scandinavian countries. The open question is to which extent treatment to the level of the toxic threshold value also ensures a long service life and expected performance of the treated commodity. Superwood™ is evaluated using a strategy, in which basic laboratory tests are done to get the toxic value (according to EN 599-1) and in addition a number of field tests are done including accelerated testing in the tropics. These tests are focussed on the evaluation of the performance criteria such as durability and service life and maintenance requirements. These questions must be answered by the producer without having a full record of performance test for their new products. A short status on the test performed on super-critical treated wood (Superwood™) is presented. Based on a comparison between field test in Scandinavia and in the tropical Malaysia a service life of more than 25 years for a specific supercritical treated product is estimated. It is stated that the existing European standardisation system is insufficient when it comes to service life prediction. A number of important questions need to be addressed by the European standardisation system as soon as possible because the market and the public opinion change quickly due to environmental concern.
N Morsing, A H H Wong, F Imsgard, O Henriksen


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