6 Wood Discoloration
6 Wood Discoloration
6 Wood Discoloration
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194 8 Habitat of <strong>Wood</strong> Fungi<br />
violet striping), then a “bright hard rot” (light brownish, wood still firm), later<br />
a “dark hard rot” (brownish-red, only wood structure remaining) and finally<br />
a “soft rot” (Fig. 8.14B; Zycha 1964), where the wood is fibrously dissolved<br />
and interspersed with small, white spindle-like nests with a black center of<br />
manganese deposits (Fig. 8.14C) (Hartig 1978; see Chap. 7.2).<br />
Imperiled for H. annosum are first plantings on formerly agriculturally<br />
used pasture soils and arable lands (“field-dying”, German: “Ackersterbe”).<br />
Conifers on base-rich and compacted ground, and on sites with very variable<br />
moisture content suffer more from the disease than those on acidic, more open<br />
soils with a more uniform water supply (Butin 1995; Schönhar 1997; Heinsdorf<br />
and Heydeck 1998). The inhibition of acidophilic, antagonistic mycorrhizas<br />
may play a role. A direct control is difficult, and only preventing measures are<br />
used (Schönhar 1990, 2002b). Rooting out and removing the infected stumps<br />
as well as isolating the infected sites by ditches are difficult and not always<br />
successful (Schönhar 1989). The most effective measure is to perform thinnings<br />
during the wintertime, as spore infection decreases during frost (Korhonen<br />
and Holdenrieder 2005). In not-yet-infected first plantings, the stumps which<br />
are the starting point for a propagation of the fungus via root grafts, have<br />
been coated on the fresh surface with carbolineum, which however delays the<br />
stumpdecomposition.Immediatetreatmentofthefreshsurfacewithasodium<br />
nitrite solution prevented spore germination of H. annosum.Aschemical,also<br />
urea (Schönhar 2002b) and boron compounds are used (Pratt 1996). Originally<br />
in the U.K and later in Scandinavia and further European countries, a spore<br />
solution of the antagonistic fungus Phlebiopsis gigantea is immediately applied<br />
to the fresh stump surface of pines (Meredith 1959; Rishbeth 1963; Schwantes<br />
et al. 1976; Lipponen 1991; Gibbs et al. 2002) and spruce (Korhonen et al. 1994;<br />
Holdenrieder et al. 1997). There are spore preparations, which are specifically<br />
suited for spruce, but generally, P. gigantea is more suitable for pines. The<br />
wood can be automatically inoculated with spores through holes in the saw<br />
blade of the harvester (Metzler et al. 2005). The antagonist overgrows the<br />
stump cross surface, so that H. annosum cannot colonize it by spores. Thus, an<br />
infection of neighboring trees over root grafts is prevented. Further antagonists<br />
to H. annosum are treated by Holdenrieder and Greig (1998) and compiled by<br />
<strong>Wood</strong>ward et al. (1998).<br />
Root graft transmission can be reduced by far planting faces and admixture<br />
of hardwoods. Lesser sensitive hardwoods as well as fir or larch should be<br />
selected for particularly endangered sites instead of spruce and pine. In vitro,<br />
mycelial growth was inhibited by stilbenes, flavonoids and lignans (Zycha et al.<br />
1976; Shain and Hillis 1971; Yamada 1992). Breeding attempts with the aim of<br />
red-rot resistant tree clones were performed, but did yet not reach a practical<br />
use. Recent resistance research mainly deals with the genetic mechanisms of resistance<br />
and the physiology of defense reactions (Korhonen and Holdenrieder<br />
2005). Viruses in the root rot fungus, which are morphologically similar to the<br />
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