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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

Soft rot cavity widening - A consideration of the kinetics
1984 - IRG/WP 1227
Studies on the micromorphology of soft rot cavity formation by Phialophora hoffmannii in birch using time-lapse cinemicrography are briefly outlined. A mathematical model is constructed to describe the cavity widening process, particularly changes in the surface area of a hypothetical cavity during enlargement. On comparison with observed data it is concluded that the rate of cavity widening is determined by wood cell wall characteristics.
M D C Hale, R A Eaton

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

The Relationship of Fiber Cell Wall Ultrastructure to Soft Rot Decay in Kempas (Koompassia malaccensis) Heartwoo
2004 - IRG/WP 04-10541
The ultrastructure of fiber walls in kempas (koompassia malaccensis) heartwood was examined in relation to soft rot cavity formation. The fibers consisted of middle lamella and thick secondary wall. The secondary wall was differentiated in to a S1 layer, and a unique multi-lamellar S2 layer. Two distinct forms of lamellae were recognisable, one type being considerably thicker than the other. They also differed in their electron density, the thin lamellae being much denser than the thick lamellae. It was not possible to determine whether a S3 layer also existed, because of the presence of a dense material coating the lumen wall, which obscured the definition of this region of the fiber wall. The resistance to soft rot varied with different regions of the fiber wall, middle lamella being completely resistant and the thick S2 lamellae least resistant. The observed relationship between the ultrastructure of these fiber wall regions and the degree of their resistance/susceptibility to soft rot cavity formation is discussed.
A P Singh, A H H Wong, Yoon Soo Kim, Seung-Gon Wi

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

Diffuse cavity formation in soft rot of pine
1992 - IRG/WP 92-1541
A new type of soft rot of southern pine longitudinal tracheids is described. In this type, soft rot cavities form by diffuse degradation of the S2 cell wall layer by hyphae growing within the cell wall. Erosion is diffuse and irregular as opposed to the restricted, periodic erosion typical of type 1 soft rot cavity formation. Proboscis hyphae remain small (diameter 0.6 to 0.8 µm) and rapidly autolyze. These proboscis hyphae are not easily recognizable with light microscopy, especially at later decay stages, and require transmission electron microscopy to confirm their presence. This may be an alternative interpretation of the type 2 soft rot of softwoods described previously as being caused by lumenal hyphae through an intact S3.
S E Anagnost, J J Worrall, C J K Wang

An unusual soft-rot decay pattern caused by the Ascomycete Hypoxylon mediterraneum (de Not.) J Miller
1984 - IRG/WP 1222
A distinct pattern of soft-rot decay has been observed for the fungus Hypoxylan mediterraneum (de Not.) J. Miller. This fungus also produced decay patterns typical of brown and white rot decay. The production of characteristic cavities by Hypoxylan mediterraneum was prolific in the hardwoods Eucalyptus maculata and Eucalyptus regnans, but infrequent in the softwoods, Pinus elliottii and Pinus radiata. The chemistry of this decay was investigated using carbon-13 nuclear magnetic resonance (13C-NMR). This technique produced results valuable to the understanding of the timber decay activities of Hypoxylan mediterraneum.
D M Francis, L E Leightley

The First Description of Soft-rot Cavity in Waterlogged Archaeological Woods by a Japanese Wood Anatomist Prof. F. Onaka in 1935
2017 - IRG/WP 17-10885
The term soft rot, which was caused by Ascomycetes and Deuteromycetes, was first used by J G Savory in 1954. Soft rot decay can be characterized by cavities within secondary cell walls align along the cellulose microfibrils. Our recent literature search revealed, however, that Prof. F. Onaka in Kyoto University described the soft rot cavities in the waterlogged archaeological woods in detail from the year of 1935 on, almost 20 years earlier than Savory. Although Dr. Onaka did not use the term of cavity, however, “micro boreholes” matched precisely with the definition of Savory’s soft-rot cavity. He described that the boreholes (= cavities) were developed along the microfibril in the latewood of waterlogged archaeological larch, yew and umbrella pine. Dissemination of his novelty would limited due to the language unfamiliar to Western hemisphere.
Yoon Soo Kim, K Yamamoto