6 Wood Discoloration

1 Introduction
Wood is damaged by various agents (Table 1.1).
This book addresses wood damage caused by microorganisms (fungi and
bacteria). Wood damage by fungi has also been called “wood diseases” (“Holzkrankheiten”)
and “wood pathology” (“Holzpathologie”). Because it concerns
the substrate “tree” in the majority of dead cells, because all parenchyma cells
in the wood of felled trees are dead after a few weeks, and, thus, because a dead
tissue cannot fall ill, distance was taken to these terms. With regard to the
microbial decomposition of biomass, in the English language there is a welldescribing
differentiation between “biodeterioration”, which means unwanted
biological destruction, and “biodegradation”, which means controlled degradation
by microorganisms or their enzymes and degrading agents. Biodeterioration
corresponds to the German “Holzzerstörung” and “Holzzersetzung”,
and the latter positive aspect of wood biodegradation (“Holzabbau”) belongs
to the area of “biotechnology of lignocelluloses” (Bruce and Palfreyman 1998;
Chap. 9).
Inthefollowingtext,themicrobialdamagetothexylem(wood)ofthetreeis
mainly addressed. Since leaves, bark, and roots are entrance gates for parasites
into the living tree that can lead to reduced tree growth and to lesser wood
quality, some aspects of the area of “forest pathology” are included (Butin
1995; Chaps. 5 and 8.1–8.3). The mechanisms of the decomposition of solid
Table 1.1. Agents for wood damages
– mankind: e.g., paper production, fire for cooking
– conflagrations for agriculture
– weathering, UV light
– acids, bases, corrosion by salts, gases, discoloration by metals
– wood insects: xylophagous beetles, termites, wasps, breeding ambrosia beetles,
wood-colonizing ants
– marine borers
– bacteria: wetwood, discoloration, pit degradation, decay by erosion, tunneling,
cavity bacteria
– fungi:
wood discoloration by molds, blue-stain fungi, red-streaking fungi
wood decay by brown, soft, and white-rot fungi
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