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Evaluation of natural durability of solid wood and mixed heartwood-sapwood Cypress (Cupressus sempervirens L.) plywood against Basidiomycete fungi
2008 - IRG/WP 08-10645
The aim of this research was to study the response of mixed plywoods composed of durable heartwood and non-durable sapwood to fungal attack. For this purpose, the species of Cupressus sempervirens (cypress) was chosen for its well-known durable heartwood. The evaluation of durability of plywood panels against fungi was done according to ENV 12038 and the fungi used were Coriolus versicolor (CV) and Coniophora puteana (CP). In order to have the basic data on the wooden element of plywood, the natural durability of cypress sapwood and heartwood in the state of solid wood was also determined against fungi according tothe guidelines of EN 350-1. Plywoods made of pure sapwood and pure heartwood (as controls) allowed a comparison with the mixed ones. 17 different plywoods were laboratory made. The influence of thickness of plies, number of MUF glue line, percentage of heartwood plies integrated to sapwood plies in the mixed plywood, and finally, the way of integration of durable plies in to non-durable plies has been evaluated. In case of solid wood, the heartwood of cypress was found “very durable” against both CV and CP while the sapwood was found “slightly durable”. In the case of plywoods, the evaluation of fungal resistance of pure plywood showed a slight diminution in comparison with the solid wood state. This decrease can be explained by a loss of some extractives molecules during the stage of steaming and peeling. In the mixed plywoods, some of the integrations were found more resistant to the fungal attack. These panels were composed of heartwood layers on the surfaces. It was also found that the criteria of vulnerable surfaces or durable surfaces in plywood is more related to its resistance than the criteria of volume of non durable plies or durable plies that is generally recognized
F Faraji, M F Thévenon, N Lemenager, B Thibaut

Termite resistance of pure and mixed heartwood-sapwood Cypress (Cupressus sempervirens L.) plywoods
2009 - IRG/WP 09-10693
The main objective of this research was to evaluate the ability of different plywoods made of durable heartwood and/or non-durable sapwood to resist termite damage. The well-known durable cypress (Cupressus sempervirens) was chosen for this study. The natural durability of cypress solid wood, divided into sapwood and heartwood, as well as the durability of 17 different laboratory manufactured plywoods, was evaluated towards Reticulitermes santonensis termites. The durability towards termites is discussed by taking into account the influence of composition of the panel (proportion of durable/non durable timber), the ply numbers, the ply thickness, the number of glue lines, and the way of integration of the different plies.
F Faraji, M-F Thévenon, B Thibaut

Highly virulent wood-rotting Basidiomycetes in cooling tower timbers
1995 - IRG/WP 95-10125
Over the past ten years most industrial cooling towers changed their water treatment systems in order to meet environmental requirements. Since this alterations wood rot attack has been reported more frequently. Several Basidiomycete fungi were isolated and determined. Amongst the most important ones are strains of Physisporinus vitreus (Pers.:Fr.) P. Karst., Phellinus contiguus (Fr.) Pat. and Donkioporia expansa (Desm.) Kotl. & Pouz.. In situ total deterioration has been reported of highly durable wood species like azobe (Lophira alata), bangkirai (Shorea leavis) and Californian redwood (Seqouia sempervirens) and of CCA-treated softwood, e.g. Douglas fir. The Donkioporia strain was only recently isolated while on lab-scale research is ongoing to stimulate the growth of Phellinus. The growth under laboratory conditions is not evident for these fungi and different parameters affecting growth were investigated. After altering the malt-agar as medium and improving climatic conditions fungal growth of Physisporinus in laboratory conditions on durable wood has been succesful already. Some preliminary results related to the changes in water treatment are discussed.
J Van Acker, M Stevens, V Rijckaert

Incising to improve penetration and retention of creosote in small-diameter Kenyan-grown Cypress (Cupressus lusitanica)
2003 - IRG/WP 03-40253
Turning small-diameter plantation thinnings into value-added products has remained a challenge in many countries, including Kenya. The present study reports on a feasible technique to effectively treat small-diameter cypress for use in ground contact. Samples of pole-size Cypress (Cupressus lusitanica), 106 mm and 138 mm in average diameter, were sampled from thinnings in 7 and 12 year-old plantations, 2.0 m posts removed from butt-ends, debarked, air-dried to 15% moisture content, subjected to four patterns of incising and pressure-treated with creosote (60:40 creosote/furnace oil mix) at a commercial treatment plant. Un-incised controls were prepared and treated in the same fashion. All samples were then conditioned for 48 days under cover, leached in running tap water for 20 days, air-dried to 15% MC and final retentions calculated on a weight-gain basis. Discs were removed from the middle portions of the samples and average radial penetration measured. The results indicated that the closer the incisions (20 mm x 20 mm), the higher the average retentions (86.3 and 80.8 Kg/m3) and penetration (16.8 and 13.9 mm) in 7 and 12 year-old posts respectively, acceptable for ground exposure situations. Un-incised controls recorded lower average retentions (38.9 and 37.4 kg/m3) and penetration (6.8 and 5.8 mm), sub-standard for poles and posts for ground contact usage. Incising as a technique to obtain the required retention and penetration for cypress small-diameter fencing posts and utility poles is viable, and should be refined and investigated further, together with an appropriate treatment schedule. An effective treatment technique is necessary to allow utilisation of a substantial volume of small-diameter cypress removed as thinnings and normally considered as waste in this country.
R Venkatasamy

Wood preservation research in Tanzania: Priorities and challenges
1988 - IRG/WP 3462
Tanzania provides some of the highest rates of wood deterioration in service leading to alarming economic losses and yet no serious concern is shown in search for solutions to the problem. The paper attempts to point out some of the priority areas in the field of wood preservation research that demand urgent attention if timber is to be used judiciously in this country. An account is given of the major constraints in Tanzania that are hindering progress in the field. The report ends with some suggestions on how to benefit the country by improving this research sector.
K K Murira, R Cockcroft

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

Comparative studies on penetration and retention of CCA (C) and creosote in wood from APHID-killed and sound Kenyan-grown Mexican cypress (Cupressus lusitanica)
2006 - IRG/WP 06-40352
Properties of wood from Kenyan-grown Mexican cypress (Cupressus lusitanica), attacked and killed by the cypress aphid (Cinara cupressi), in terms of density and treatability, were investigated in comparison to the properties of wood from sound trees. Density in small wood samples from aphid-killed trees was found lower than density in samples from sound trees, and reduced with tree age in samples from both. However, differences were slight, being 3.8%, 2.5% and 2.3% lower than density in samples of sound trees aged 10, 12 and 14 years respectively. Conversely, penetration and retention of both CCA and creosote were higher in samples from aphid-killed trees of the 3 age classes. Along the grain penetration of CCA was higher by 3.6%, 4.5% and 6.2%, and across the grain penetration higher by 3.8%, 7.0% and 11.3% in samples from aphid-killed trees of the 3 age classes respectively, compared to penetration achieved in samples from sound trees. Higher penetration of creosote in samples from aphid-killed trees was in the order 3.9%, 5.8%, 7.1% along the grain, and 3.7%, 6.2%, 11.9% across the grain. Along the grain retention of CCA in samples from aphid-killed trees was higher by 1.2%, 1.5%, 2.0%, and across the grain higher by 5.1%, 6.3% and 7.4% for the 3 age classes. Similarly, retention of creosote in samples from aphid-killed trees of the 3 age classes was higher by 3.2%, 4.5%, 5.6% along the grain, and 2.6%, 3.2%, 4.6% across the grain. Differences in density and treatability could not be properly explained, but was assumed associated with extensive sap depletion by aphids, interference with tree growth and normal wood formation, hence lowering of wood cell wall materials and increased cellular spaces within the wood cell wall structure of wood from aphid-killed trees. However, the results revealed that differences between wood from aphid-killed and sound C. lusitanica were minimal, and did not warrant wood from aphid-killed trees being branded as of lower quality, and restricted end uses.
R Venkatasamy, F M Opar

Influence of Grain Direction on Penetration, Retention, and Leaching of CCA(C) in Sapwood and Heartwood of Kenyan-Grown Cupressus lusitanica and Pinus patula
2007 - IRG/WP 07-40384
The influence of grain orientation on penetration, retention, and leaching of CCA (C) was tested on small samples of sapwood and heartwood of Cupressus lusitanica and Pinus patula. Samples measuring 50mm x 50mm, and 200mm in the longitudinal axis were sealed to expose only transverse, or radial, or tangential faces, pressure treated with 6% CCA (C), and penetration, retention and leaching of the preservative measured. Generally, the normal trend of Transverse > Radial > Tangential was observed for penetration, retention and leaching in sapwood and heartwood of both species, and in the three grain directions. Penetration in sapwood samples of both C. lusitanica and P. patula were higher than in heartwood samples, being significantly higher in the transverse grain direction. Both retention and leaching reflected on the depth of penetration of the preservative in samples. Retention was generally lower in the three grain orientations in both sapwood and heartwood of C. lusitanica samples. However, it was noted that retention in the radial and tangential grain directions in sapwood and heartwood of both species were not significantly different. Leaching followed the same patterns as for penetration and retention, that is lower in both sapwood and heartwood samples of C. lusitanica, being high in the transverse grain direction in sapwood and heartwood of both species, low in the radial, and lowest in the tangential grain directions. However, leaching in the radial and tangential grain orientations in heartwood samples of both species were fairly similar. Generally, P. patula samples achieved higher penetration and retention, but amounts of the preservative leached out were also higher. The results of the work clearly shows that sapwood, heartwood, and grain orientation all influence penetration, retention, and leaching of CCA (C) in two species of softwoods tested, and that is likely to be the case with most softwoods. The implications on treatment schedules have to be considered.
R Venkatasamy

Influence of extractives on durability of Cupressus lusitanica heartwood
2010 - IRG/WP 10-10716
Identification of extractives present in Cupressus lusitanica heartwood has been conducted using GC-MS analyses. The chromatogram of toluene/ethanol extracts indicated the presence of high amounts of benzaldehyde and numerous of terpenic compounds such as cedrol, agathadiol, epimanool, bornyl acetate, -cedrene and -cedrene. Effect of extractives on cypress natural durability has been investigated on wood blocks extracted or unextracted and then exposed to pure culture of Poria placenta in a laboratory test. Mass losses revealed severe degradation for the extracted specimens compared to a significant decay inhibition in the cypress control unextracted blocks.Efficacy of heartwood extractives on the growth of Poria placenta was evaluated. The results showed a strong inhibition of the fungal development. Heat treatment was investigated to improve cypress durability due to the conflicting literature reports describing the wood as resistant to non resistant to decay. Evaporation of the volatile extractives during the first stage of heat treatment caused a decrease of durability, while with a longer heating time, an increase of conferred durability was observed. This study suggests that extractives content, which may be modified during drying processes or wood weathering, could be the origin of the conflicting data described in the literatures on cypress durability.
A Mohareb, P Sirmah, L Desharnais, S Dumarçay, M Pétrissans, P Gérardin

Use of the durable species Coast Redwood as a reference system for field testing of Wood Protection systems
2012 - IRG/WP 12-20486
Data is provided and discussed for a number of field exposure tests where the naturally durable wood species Coast redwood, Sequoia sempervirens, was included along with untreated pine and standard preservative treatments. In general, there is potential for higher variability of results with this naturally durable species, but it does suggest that redwood can be a useful reference material for testing systems for above ground applications, especially where long-term decay performance may not be as critical as overall product quality. Comparative performance of products to redwood heartwood at test sites with different climate indices and with different test methods may provide additional useful data on the relative performance of systems than when compared to only untreated pine sapwood and standardized preservative systems.
A Zahora, A Preston, L Jin

Natural durability of plantation-grown coast redwood (Sequoia sempervirens) in New Zealand
2014 - IRG/WP 14-10817
There is wide variation in the wood properties of plantation-grown coast redwood in New Zealand. Contributing factors are the seed source, silviculture, growth and age of the trees in the plantation forests. Little is known about how these factors affect the variation of wood properties among and within the trees of New Zealand’s coast redwood forests. Heartwood of plantation-grown coast redwood from three forests in the North Island, New Zealand, was evaluated using butt log and breast height discs and cores, for natural durability using in vitro decay tests. The heartwood content of the trees showed a wide range of durability which was strongly influenced by the age and size of the trees rather than the site. Inner heartwood was more susceptible to fungal degrade than outer heartwood with trees from the older forest stands having a higher proportion of durable heartwood. Faster diameter growth is likely to increase the heartwood content, and longer rotations will increase the quantity of durable heartwood. The variation among trees suggests there is potential for genetic improvement.
D O’Callahan, T Jones, C Low, C Chittenden

Redwood Durability in NZ – Can pure culture laboratory tests predict outdoor service life
2017 - IRG/WP 17-20610
Coast Redwood (Sequoia sempervirens) is an alternative species in New Zealand to the large scale Pinus radiata plantations. Redwood is classified as moderately durable but its durability is extremely variable. In order to reduce this variability in future stock, understanding growth conditions, clone, and tree age effects are important however this involves many samples and is not suitable for assessment in field trials where tests take many years to complete. Therefore laboratory trials have been used to assess the multitude of parameters. But how reliable are these in assessing in-service durability? In this study we have compared the data from EN113 laboratory tests with in-ground and above ground data from trees of similar ages and growth sites to understand the correlation between laboratory and field data along with natural durability classification methods. The European standard for natural durability has recently been updated and the method in which durability class is calculated in the laboratory has changed therefore in this paper we have calculated durability class for laboratory samples using both EN350:1994 and EN350:2016 methods as a comparison. For field trials we have used the Australasian standard durability classifications (AS5604:2003) and the European standard classifications (EN350:2016) to calculate durability class. It was found that durability classifications of laboratory samples that were subjected to leaching (EN84:1989) before exposure correlated well with in-ground field tests but that there were differences in durability classification between classification methods with the laboratory classifications being slightly more durable using the new EN350 method compared to the old method. Similarly the Australasian standard gave higher classifications in general than the European standard for in-ground tests. The durability rating of non-leached blocks related well to above ground exposure trials even though above ground tests were subjected to rain and UV exposure. The effect of extractive wash off would need to be studied to get a true correlation. It was deemed important to include leached and non-leached laboratory samples wherever possible to understand the range of durability of each wood species. It is not recommended to rely totally on laboratory data although laboratory tests are beneficial for screening lots of different elements.
D O’Callahan, C Chittenden, J van der Waals, D Meason, T Singh