6 Wood Discoloration

226 8 Habitat of Wood Fungi
alive mycelia can lead to re-infections in the case of careless or inappropriate
remedial treatments (Bravery et al. 2003). Thick mats of surface mycelium may
cover the attacked timber assumably preventing the wood from drying.
Serpula lacrymans occurs predominantly in older buildings and in the cellar
and ground floor area (Schultze-Dewitz 1985, 1990; Koch 1990). Uninhabited
and poorly ventilated houses and all buildings with high relative air humidity in
connection with damages to the structural fabric are particularly endangered.
Importantcausesofdryrotinfectionsarebuildingdefectsthataffectincreased
wood moisture content (e.g., Paajanen and Viitanen 1989). The mycelium reacts
sensitively to draught and humidity removal, generally to climatic changes, so
that it often develops in false ceilings and false soil areas under floors and
behind wall coverings, from where it spreads. Because of this hidden way of
life, often only fruit bodies on masonry, baseboards, doorframes or stairway
steps show that the higher floors are already infected. In extreme cases, e.g.,
during the refurbishment of listed buildings, all timbers as well as large parts
of the masonry have to be removed. A survey of houses in northern Germany
indicated that old buildings are particularly at risk, which had insulating
windows as the only measure of heat insulation. Now, the moisture in the
building condenses on other weak spots like empty spaces of the brickwork at
the back of heaters (Huckfeldt et al. 2005).
Except in homes, the fungus occurs on mine timber and rarely in the open
(poles, sleepers), but in the boreal climate not in the forest. However, according
to Pegler (1991), the species occurs outdoors in Central Europe and North
America, and according to Bech-Andersen (1995), in the Himalayas in conifers
forests. Phylogenetic trees based on the rDNA-ITS sequence showed that the
outdoor isolates from the Himalaya and from California belong to the species
S. lacrymans (Chap. 2.4.2.2). Phylogenetic analyses indicate that the indoor
isolates of S. lacrymans may have originated from an ancient lineage closely
related to the Californian outdoor isolates (Kauserud et al. 2004b).
In the open, the Wild merulius S. himantioides (Fig. 8.21e) is common, in
Europe frequently on spruce wood, stumps, structural timber in outdoor use,
and rarely on living trees. Occasionally, it is also found in buildings (Falck
1927; Harmsen 1978; Grosser 1985; Seehann 1986; Pegler 1991).
As further dry-rot fungi occur three Leucogyrophana species (Fig. 8.21f–o)
in the forest on fallen stems and branches, and on wood in indoor use: L. mollusca,
L. pinastri (Schulze and Theden 1948; Siepmann 1970) and L. pulverulenta
(Harmsen 1953). They differ from Serpula by smaller spores (Ginns 1978;
Pegler 1991; Breitenbach and Kränzlin 1986). Leucogyrophana pulverulenta is
rather common in Denmark. The three fungi need a higher wood moisture
content than S. lacrymans (cf. Table 8.7).
Whereas S. lacrymans is restricted in North America to the northern parts
of the USA and Canada, the American dry rot fungus Meruliporia incrassata
(first reported in the USA in 1913) occurs particularly in the southern states
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