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A study of soft-rot in hardwoods


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Braid, Geoffrey Harold 1982 , 'A study of soft-rot in hardwoods', PhD thesis, University of Tasmania.

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The main aims of this study were to examine the wood
substrate degrading capacities of microorganisms isolated from
soft-rotted CCA-treated Eucalyptus sp. power transmission
poles in ground contact, and to evaluate techniques for
assessment of the degree of wood degradation caused by
microbial attack. The performances of various wood preservatives,
including remedial and ground-line maintenance treatment
systems for poles, were assessed.
The predominant organism isolated from Tasmanian woods
in this study, the Hyphomycete Phialophora mutabiIis, had
demonstrable celIuIase, hemicelIulase, amylase and pectic
enzyme activities as well as a measurable wood-degrading
capacity. Trichoderma viride was a highly cellulolytic fungus
in pure culture, and a dominant early coloniser of untreated
E. obIiqua wood in ground contact. However, it produced minimal
wood degradation in this examination. A small ( < 10 4 cel I s/g wood sawdust) bacterial microflora
was found in untreated and preservative-treated hardwoods.
Bacterial isolates possessed a number of wood-degrading enzymes:
A strain of Bacillus megaterium (S9NC) isolated in this study,
showed cel I ulase, xy I anase, amylase and pectic enzyme activities,
whilst CelIulomonas sp. 8N produced at least one celIuIase,
xyIanase, pectic enzyme and Iaccase. However, no definite
degradation of intact E. obIiqua sapwood cell walls by pure
cultures of bacteria was observed by light microscopy and
scanning electron microscopy.
Fungi (including Basidiomycetes) and bacteria were earl y
colonizers of untreated E. obliqua stakes in the ground. A mutual istic relationship, albeit not a close one, was demonstrated
between propagule counts of fungi and bacteria, isolated from
CCA-treated Eucalyptus sp. sawdusts.
Two techniques for estimating microbial activity in wood
samples were developed in this study, and compared with
other methods for estimating the degree of wood degradation.
The methods were:
i . a Cx-celIuIase assay
i i . a modified and improved chitin assay for estimation
of fungal biomass in wood. Appropriate parameters for both
assay methods were determined. The Cx-celIuIase and chi tin assays were relatively quick
and sensitive methods for assessing the degree of microbial
attack of woods. These assay procedures, plus impaction
determinations using the Pilodyne(R) instrument, and to a
much lesser extent the fungal propaguIe count, were largely
objective procedures. Visual and microscopic estimates of wood
degradation were found to be highly subjective in this study.
Several field trials of wood preservatives were used
to compare the newly developed assay methods with fungal
propagule counts, Pilodyne(R ) impaction determinations, and
visual and microscopic estimates of wood degradation. The
trial s examined were remedial treatments of transmission poles
at Warrane, Tasmania, and bandage treatments of poles at
Grafton, N .S.W . and Coff 's Harbour, N.S.W. In addition, an
E. obliqua preservative-treated sapwood stake trial was emplaced
at Grove, Tasmania.
In this study, the best performed remedial preservative
systems were the Wolman CFB bandage and the CSIRO-developed Busan 30 and Blue 7 (Mark IV) bandages. These bandage
systems show promise as agents for treatment of soft-rot
attack in Australian power transmission poles.

Item Type: Thesis - PhD
Authors/Creators:Braid, Geoffrey Harold
Keywords: Wood-decaying fungi, Wood, Wood poles
Copyright Holders: The Author
Copyright Information:

Copyright 1982 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Bibliography: l. 209-267. Thesis (Ph.D) - University of Tasmania, 1984

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