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Degradation of the normal fibre walls of rubberwood (Hevea brasiliensis) by the tropical blue-stain fungus Botryodiplodia theobromae
1998 - IRG/WP 98-10286
Rubberwood was examined by light microscopy and transmission electron microscopy (TEM) after exposure to the common tropical sapstain fungus Botryodiplodia theobromae for four weeks to study hyphal colonisation of wood cells and to determine if this fungus also degraded lignified normal fibre cell walls in addition to the walls of non-lignified elements. Light microscopy revealed relatively large diameter hyphae to be abundantly present in parenchyma cells. The hyphae were also present in other types of wood cells, including fibres. TEM provided evidence of fibre wall degradation in the normal rubberwood in the form of lumen wall erosion (type-2 soft rot decay). These observations suggest that the ability of B. theobromae to degrade lignified wood cells walls should be viewed with concern when utilising rubberwood which has been severely sapstained, particularly after prolonged exposure to this fungus.
A A H Wong, A P Singh


Ultrastructural observations on wood-degrading erosion bacteria
1986 - IRG/WP 1283
G F Daniel, T Nilsson


Ultra-structural observations on the degradation of wood surfaces during weathering
1987 - IRG/WP 2280
Radiata pine (Pinus radiata D. Don) sapwood was converted into blocks with a transverse face about 5 mm square and measuring 8 mm longitudinally. Transverse (T.S.), Radial (R.L.S.) and Tangential (T.L.S.) surfaces were prepared and specimens exposed to the weather inclined at 45° facing equatorially for periods of between 20-60 days. After 30 days exposure erosion of the middle lamella was observed followed after 40 days exposure by extensive separation of individual fibres at the interface of the middle lamella and secondary wall. Degradation of the S2 layer of the cell wall revealed corrugations orientated parallel to the fibre axis suggesting preferential removal of cell wall components. Further degradation proceeded by progressive delamination and checking of the S2 and erosion of the S3 cell wall layer. In addition to the above changes preferential degradation of the rays was observed in radial (R.L.S.) and tangential (T.L.S.) longitudinal surfaces.
P D Evans, S Thein


Evidence for wood cell wall degradation by the blue stain fungus Botryodiplodia theobromae Pat
1994 - IRG/WP 94-10077
Botryodiplodia theobromae Pat., a world wide ubiquitous polyfagus sapstain fungus, was found able to destroy the cell walls of birch fibres (Betula verrucosa Ehrh.) but not Caribbean (Pinus caribaea var. hondurensis Barr. and Golf.) and Scots pine (Pinus sylvestris L.) tracheids. The fungus caused characteristic erosion of fibre cell walls similar to soft rot type 2; destruction of the S1 - S2 interface and delamination and degradation of the S2 layer. No attack of middle lamellar regions or birch vessel walls was noted.
O Encinas, G F Daniel


Formation of soft rot cavities in relation to concentric layers in wood fibre walls
1983 - IRG/WP 1185
A large number of timber species attacked by soft rot have been examined using light microscopy. The S2 layers in a large number of the timbers exhibited special structural features in the form of thin concentric layers. Several observations indicate that these layers may be characterised as "weak" zones by being more easily degradable than the surrounding wall layers. The chemical structure of the concentric layers is not known although some suggestions regarding their composition are given. It was observed that soft rot cavities regularly formed in the thin concentric layers. A hypothesis is put forward suggesting that T-branching occurs as a response to a chemical stimulus, possibly by sugars released by penetrating hyphae when they transverse the thin concentric layers.
T Nilsson, G F Daniel


Microbial decay of an archaeological wood
1994 - IRG/WP 94-10053
A light and transmission electron microscopic investigation of an archaeological wood was undertaken to determine the cause of its deterioration. The wood came from a bulwark constructed in early 1100 in the lake Tingstäde Träsk on the island Gotland in Sweden. The samples of the wood, which was identified as Pinus sylvestris, were taken from a depth of 0.85 m below the bottom level. The wood was found to be heavily deteriorated, and from the micromorphology of decay observed under light and transmission electron microscopes it was concluded that the wood had been largely attacked by erosion bacteria. The degradation of wood components was quite variable, some cell structures/types showing greater resistance than others. The S2 wall layer of axial tracheids, which formed the bulk of the wood, was degraded most. In comparison, ray tracheids appeared completely resistant. Other cell structures/types, such as pit borders of axial tracheids and ray parenchyma cells, displayed features that were intermediate between the extremes noted above. These features are discussed in the light of available information on bacterial erosion of wood cell walls and on chemical composition of these cell structures/types in pine wood.
A P Singh, T Nilsson, G F Daniel


Degradation features of waterlogged archaeological compression wood
1998 - IRG/WP 98-10258
The degradation characteristics of waterlogged archaeological compression wood excavated in South Korea were examined by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Degradation of Pinus compression wood occurred mainly in the inner part of S2 layer. In contrast, the outer part of S2 layer remained relatively intact. CLSM and TEM showed the erosion type of bacterial attack to be dominant in the secondary cell walls of both severe and mild compression wood. However, in some cases middle lamella was also degraded, which suggests that other forms of microbial attacks, such as bacterial tunnelling, were also present. Bacterial erosion in the severe compression wood was mainly confined to the inner part of S2 layer whereas in the mild compression wood it also extended into outer part of S2 and the S1 layer. The extent of erosion correlated to the differences in the amount and distribution of lignin, particularly in the outer S2 layer between the severe and mild compression wood cells. These features are compared with the degradation of normal Pinus wood.
Yoon Soo Kim, A P Singh


Soft rot
1978 - IRG/WP 179
Soft rot decay of treated wood is examined with special reference to hardwoods treated with CCA. Factors which adversely affect the chances of protection of hardwoods against soft rot are discussed. The ratio of the volume of the fibre cell wall to the volume of the fibre lumen is presented as a major factor influencing final preservative concentration in the fibre cell wall, the major strength contributing unit in wood. It is proposed that hardwoods are not necessarily more susceptible to soft rot than are conifers and that 0.2% Cu.wt/wt on gross wood will give control of soft rot in permeable hardwoods. Present and potential soft rot problems of treated conifers in North America are examined.
C R Levy


Ingestion of wood-degrading micro-organisms
1991 - IRG/WP 4169
An ultrastructural study was carried out on the digestive tract contents of Limnoria lignorum, frass, gallery walls and surface structures of the animals. The purpose of the study was to determine whether wood-degrading bacteria, fungi and other microbes and/or wood degraded by these microbes were present in gut regions and therefore could provide indirectly a nutritional source for Limnoria. Both bacterial (tunnelling) and fungal (soft rot) degraded wood fragments as well as lysed microbes, extracellular slime and various other microbes (actinomycetes, diatoms) were found in fore, mid and hind gut regions. The range of microbes associated with wood fragments from gut regions were similar to those recognized either colonizing or degrading surrounding gallery walls or present on the external surfaces of the organism itself. Wood materials in the gut were highly fragmented and showed evidence for either extensive bacterial or soft rot attack, or surface and sub-surface evidence for carbohydrate removal. The major wood degrading bacteria attack noted was tunnelling bacteria as well as a form capable of cell wall dissolution of pine wood. Both bacterial types carried out extensive attack of pine wood fragments present in Limnoria tunnels. Lysed fungal hyphae, and soft rot hyphae associated with residual soft rotted wood fragments were also prominent. Gut regions of Limnoria lignorum lacked a natural resident bacteria flora, although numbers of characteristic Gram-negative active vesicle producing bacteria were represented in all gut regions associated with wood fragments. In hind gut regions a prominence of wood middle lamella regions was noted suggesting that these cell wall regions were more resistant to attack. Results indicate ingestion of bacterial and fungal degraded wood and its associated microflora. It is suggested that ingestion of microbial degraded wood could provide Limnoria with increased substrate assessibility and a greater surface area over which their enzymes could act. Associated bacterial and fungal breakdown products could also provide an important supplimentary source of nitrogen.
G F Daniel, S M Cragg, T Nilsson


Micromorphology of oak wood degraded by brown rot fungus Coniophora puteana
2000 - IRG/WP 00-10356
To characterize the degradation of hardwood by brown rot fungus, Coniophora puteana was incubated on the wood blocks of Quercus accutissima. For comparison, the same fungus was also incubated on the pine wood blocks of Pinus densiflora. In softwood, the shape of the wood cells and thickness of the cell appeared unchanged even the loss of birefringence in the affected areas. In contrast, oak wood decayed by brown rot fungus showed the erosion of wood cell walls from lumen towards the middle lamella. Complete degradation of cell walls including the lignin- rich middle lamella occurred in some areas of the oak wood cells. Degradation modes of brown rot fungus C. puteana in oak wood followed a typical white rot. The production of hydrogen peroxide was confirmed cytochemically by the deposition of cerium chloride in the degraded wood cell walls. However, Bavendamm test was negative to C. puteana. The present work suggested that hydrogen peroxide produced by brown rot fungus might be associated with not only the depolymerization of cellulose in softwood but also the degradation of lignin in hardwood.
Yoon Soo Kim, Seung-Gon Wi, Kwang-Ho Lee


The development of soft rot decay in bamboo fibres
1992 - IRG/WP 92-1572
The development of decay by soft rot fungus Chaetomium globosum was investigated in young and mature culms of bamboo Phyllostachys virideglaucescens. Soft rot decay was influenced both quantitatively and qualitatively by the differing levels of lignification in the material. Weight loss was significantly greater in the younger culm compared with the older, more heavily lignified culm. The distribution of soft rot decay cavities was also highly variable in the young culm, cavities being much more frequent in the lower lignin fibres of the inner layers of the culm wall. In the mature culm a more homogeneous pattern of lignification resulted in a more evenly distributed decay. Studies with light and electron microscopy showed that soft rot cavity morphology was greatly influenced by the degree of cell wall lignification and stratification. Cavities were usually initiated at the boundary between two layers and, in heavily stratified walls, their form was typically restricted being crescent shaped in transverse section. Variable lignification of the wall layers also had a direct influence, with high lignin levels reducing cavity formation. It is considered that the characteristic pattern of lignification which is influence by age and location in the bamboo culm makes this a particularly useful substrate in which to study aspect of soft rot development.
O Sulaiman, R J Murphy


Bacterial degradation of wood cell wall: A review of degradation patterns
1990 - IRG/WP 1460
Information from bacterial degradation studies of 60's and 70's was reviewed by Nilsson in 1982. The application of electron microscopy to this area in recent years has provided much useful information and has eliminated earlier scepticism among workers about the ability of bacteria to degrade lignified wood cell walls. Studies using transmission electron microscopy together with those employing 14C-labelled lignins have confirmed that certain types of bacteria have a capacity to degrade intact wood, including timbers which have high lignin or extractive content and are considered naturally durable. It has not been possible thus far to isolate wood degrading bacteria in pure culture and thus their physiology and taxonomic affiliations remain unknown. Laboratory studies using mixed cultures of these organisms and observations of decaying timbers from natural environments have shown the degradation to be of three main types on the basis of microscopic appearances of degradation patterns. The three types are: cavitation, erosion and tunnelling. These patterns and bacteria which produce them during their attack of wood will be described in detail.
A P Singh, J A Butcher


Soft rot in CCA-treated utility poles in Sweden
1989 - IRG/WP 1398
Soft rot investigations of CCA-treated utility poles (Pinus sylvestris L.) have been conducted throughout large parts of Sweden during 1974-1985. The investigation included 179 utility poles of the State Power Board which had been used for 10-18 years in the different administrative regions from northern to southern Sweden. In addition, 193 telephone poles from the Östersund area and 218 from the Kristianstad area were studied after having been in use for 18-25 years. The soft rot fungi cause two types of attack in wood cells, namely cavities (Type I) and erosion (Type II). In this investigation, soft rot is reported only when cavities of Type I were found. Erosion (Type II) is more difficult to observe, particularly in early stages, and in addition is almost impossible to distinguish from certain other attacks of rot, such as white rot, which may have occurred during storage of the poles before impregnation. In western and central Sweden, minor attacks of soft rot were found after 10-12 years in State Power Board poles embedded in soil in arable land and meadows. Power Board poles in northern Sweden had minor attacks of soft rot after 16-18 years in arable land and also in forest land when embedded in soil. Poles used by the Telecommunications services, all embedded in stone, showed minor and only occasional attacks of soft rot at Östersund (northen Sweden), but considerably more soft rot at Kristianstad (southern Sweden). The Telecommunication poles had been in service up to seven years longer than the poles used by the State Power Board. The localization and spread of soft rot attacks in a pole can vary. There may be many reasons for this, including insufficient impregnation, leaching, etc. The soft rot attacks found in the Power Board poles are always minor and sporadic and none of the investigated poles can be said to imply any safety risk. The same applies to the Telecommunication poles at Östersund whereas those at Kristianstad demonstrated considerably more severe and more frequent attacks. The attacks of soft rot in the Telecommunication poles more frequently occurred internally, more often deeper in the sapwood than in the outermost parts.
H Friis-Hansen, H Lundström


Fungal and bacterial attack of CCA-treated Pinus radiata timbers from a water-cooling tower
1991 - IRG/WP 1488
Transmission electron microscopy of decaying CCA-treated Pinus radiata timbers from an industrial water cooling tower showed presence of a thick biofilm covering some areas of the wood. The biofilm contained various morphologically distinct forms of microorganisms embedded in a slime. The study provided evidence of the activity of soft rot fungi and tunnelling and erosion bacteria in wood cells. The extent of damage to wood cells due to microbial activity varied, combined fungal and bacterial attack having the most damaging impact.
A P Singh, M E Hedley, D R Page, C S Han, K Atisongkroh


The dry rot fungus Serpula lacrymans. Examples of attack and remedial treatment
1988 - IRG/WP 1347
The film deals with several aspects of dry rot attack and eradication in buildings. The detailed biology and morphological charasteristics of the fungus are portrayed. The various forms of mycelial growth, the role of the strands in the nourishment and spread of the fungus, as well as the many types of fruitbody formation are outlined. Environmental and nutritional requirements of the fungus as well as the potential infection danger posed by the basidiospores are discussed. The second part of the film, outlining the main reasons for dry-rot attack and spread in building together with the significant damage caused, shows the full extent of the problem to expert and lay-person alike. The necessity of correct survey and inspection of decayed areas to determine the full range of attack is stressed. Examples of various remedial treatments and the present technological state of eradication techniques, e.g. pressure injection, in Germany are discussed.
G Buchwald, B M Hegarty, W Metzner, R Pospischil, H Siegmund, P Grabow


A short note on fungal decay in K33-treated poles
1982 - IRG/WP 1169
Soft rot cavities and erosion of the lumen have been found in K33-treated Pinus sylvestris poles from the years 1956-66 by microscopic studies. Poor treatment quality has been proved for some of these poles. The microscopy showed an unusual pattern of attack, and pre-treatment decay is suspected but not yet proved. Sounding the poles and using the Pilodyn indicated decay, but poking did not. Quantification of the attacks was possible only by microscopic studies.
H Friis-Hansen


A summary of tests and practical experiences with the Pilodyn wood testing instrument
1980 - IRG/WP 282
This paper presents a summary of the reports, tests and practical experiences with the Pilodyn wood tester not only, however, concerning poles but also in other fields such as standing trees, sawn timber etc. The principle of the Pilodyn is a spring-loaded pin which is fired into the object and the depth to which the pin penetrates is correlated to physical and mechanical properties of the object.
H Friis-Hansen


Micromorphology of the decay caused by Chondrostereum purpureum (Pers.:Fr.) Pouzar and Flammulina velutipes (Curt.:Fr.) Singer
1988 - IRG/WP 1358
Two basidiomycetes, Chondrostereum purpureum and Flammulina velutipes, form typical soft rot cavities in hardwoods and softwoods. Cavity formation is prececed by T-branching or bending of hyphae penetrating the wood cell walls. The two fungi also cause erosion of the wood cell walls.
T Nilsson, G F Daniel


Resistance of Alstonia scholaris vestures to degradation by tunnelling bacteria
1992 - IRG/WP 92-1547
Electron microscopic examination of vessels and fibre-tracheids in the wood of Alstonia scholaris exposed to tunnelling bacteria (TB) in a liquid culture showed degradation of all areas of the secondary wall. The highly lignified middle lamella was also degraded in advanced stages of TB attack. However, vestured pit membranes and vestures appeared to be resistant to degradation by TB even when other wall areas in Alstonia scholaris wood cells were severely degraded. The size comparison indicated vestures to be considerably smaller than TB, and we suspect that this may primarily be the reason why vestures in Alstonia scholaris wood were found to be resistant to degradation by TB.
A P Singh, T Nilsson, G F Daniel


Water-based water repellents for treatment of wood
1987 - IRG/WP 3446
The water uptake by wood can be reduced by treatment with a water repellent. The water repellents most commonly used are solvent based. In the present work a new type of water repellent that is water-based has been investigated. Two different treatments have shown an effect of the same order as a commercial solvent based product. The cellular distribution of the water repellents has been investigated and for one of the formulations a more uniform distribution can be seen at the impregnated surface. Use of water as a solvent would be advantageous due to lower cost and non-toxicity.
I G Svensson, G Hägglund, I Johansson, W B Banks


Laboratory and field evaluation of Plasmite Reticulation System using bifenthrin as a chemical barrier within wall cavities against subterranean termites.
2005 - IRG/WP 05-20307
Laboratory and field bioassays undertaken to demonstrate Plasmite Reticulation system effectively delivers the termiticide (bifenthrin) within a simulated wall cavity at the required concentration. The chemical assay indicated that the amount of bifenthrin sampled at 5, 10, 15, 20, and 25m along the simulated reticulation system tested (30m) exceeded the manufacturer’s minimum recommendation of 0.0044%m/m. Results of the laboratory bioassay, using Coptotermes acinaciformis, indicated that the concentrations of bifenthrin present in the soil core samples at 5, 10, 15, 20, and 25m were extremely toxic and prevented termite penetration of bifenthrin treated soil in laboratory bioassays immediately after field soil treatment. No penetration of any soil core samples was observed in the field test against Coptotermes lacteus.
J R J French, B M Ahmed, J Thorpe, A Anderson


Decay, decayed wood and the Shigometer
1980 - IRG/WP 281
A L Shigo


Durable fibre for durable MDF – testing Tricoya®
2015 - IRG/WP 15-40704
The chemical modification of wood has been a commercial reality for a decade on release of technologies for the modification of solid wood including Accoya®. A challenge and an opportunity for the modification technologies which typically impart dimensional stability, water stability and enhanced biological durability was the adaptation of the technology to wood based panels. This paper presents a summary of the development of Tricoya®, its testing and performance and examples of applications.
E Suttie, J Alexander, M Maes


Importance of bacteria in the deterioration of archaeological woods
1995 - IRG/WP 95-10122
An electron microscopic study of archaeological woods from different sites and of different ages revealed that the woods had been attacked by erosion bacteria, tunnelling bacteria and soft rot fungi. Bacterial erosion appeared to be most widespread, and was present independently as well as together with tunnelling and soft rot attacks. Thus, in many instances bacterial erosion was the only type of microbial attack present. This work recognizes the important role bacteria play generally, and erosion bacteria particularly, in the deterioration of waterlogged archaeological woods.
Yoon Soo Kim, A P Singh, T Nilsson


Ultrastructural aspects of bacterial attacks on an archaeological wood
1993 - IRG/WP 93-10007
Transmission electron microscopy of wood from a Chinese ship submerged in the mud for over 900 years showed bacteria to be the main factor for its deterioration. The micromorphology of degraded wood cell walls was similar to that observed during the attacks of wood by erosion bacteria. Other bacterial forms, previously considered lo be scavenging bacteria, were also abundant in degraded areas of the wall. The observations on the breakdown of the waterlogged archaeological wood are discussed in context with the available information on bacterial degradation of wood under near-anaerobic conditions.
Yoon Soo Kim, A P Singh


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