6 Wood Discoloration

8.5 Damage to Structural Timber Indoors 223
comparable with that one of the Dry rot fungus and can even exceed it. A fresh
floorboard can be completely destroyed in 1 year, so the danger exists that
furniture or persons can fall through. These types of damages occurred in
Germany frequently during the building boom in the postwar years, if insufficiently
dried wood were used, or the homes had not sufficiently dried before
they were moved into and drying was prevented by humidity-impermeable
painting, linoleum, or carpet.
The cellar fungi belong to the fast-growing house-rot fungi and reached on
agar at 23 ◦ C up to 11 mm radial increase per day (Table 3.11). The optimum
temperature (Table 3.8) was between 20 and 27.5 ◦ C, whereby C. marmorata
preferred the warmer range, and the maximum was between 25 and about
37.5 ◦ C. Isolate Ebw. 1 of C. puteana survived 15 min. at 60 ◦ C(Miričand
Willeitner 1984) and 3 h at 55 ◦ C (Table 3.8). In slowly dried wood samples,
even 4 h at about 70 ◦ C were withstood (Huckfeldt 2003). The data concerning
a possible dryness resistance of the fungus vary: after observations from practice,
it dies when drying; up to 7 years were however survived in dry wood in
the laboratory (Theden 1972). There was isolate variation with regard to the
sensitivity to wood preservatives (Gersonde 1958).
Recognition characteristics (Fig. 8.20): The diagnosis is not always easy,
since fruit bodies are rare and colonized wood shows frequently no or only meager
surface mycelium (Käärik 1981). The few centimeters to several decimeters
wide, resupinate, brownish fruit bodies resemble those of the Dry rot fungus,
are however thinner. The species C. puteana is easy to recognize of the warty
knots on the hymenophore (name: “carrying cones”). Characteristic on agar
are double and multiple clamps. The initial stages of the rot are frequently
ignored, since hardly infection signs become visible on exposed wood exterior
surfaces, e.g., on baseboards, while the wood at the backside is already
completely rotten and overgrown by thread-thin, radiate to root-like, brown
to black strands (Fig. 8.20d,e). Early signs of rot are often dark discolorations
under the paints.
8.5.3.4
Dry-rot fungi: Serpula species, Leucogyrophana species, Meruliporia incrassata
This chapter deals with the brown-rot causing dry-rot fungi, namely Serpula
lacrymans and S. himantioides,andtheLeucogyrophana species, L. mollusca,
L. pinastri and L. pulverulenta (Fig. 8.21). Due to its economic relevance in
Europe, emphasis is laid on S. lacrymans, however, the American pendant, the
American dry rot fungus, Meruliporia incrassata,isconsidered.
The way of spelling of the epithet “lacrimans”, which can be attributed to
Fries (1821), is linguistically correct, however illegal, since the original spelling
by Wulfen in 1781 was with “y” (Pegler 1991).
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