6 Wood Discoloration

8.5 Damage to Structural Timber Indoors 229
Strands: first as vein-like structures in the mycelium, often extending into
soil or masonry, appearing whitish when young, browny-black with age (Eaton
and Hale 1993), 0.3–5.1 cm in diameter, length up to 9 m (Palmer and Eslyn
1980).
Recognition characteristics of S. lacrymans (Fig. 8.21)
Wood: The relatively large cubes of the brown-cubical rot (Fig. 7.1a) are no
reliable characteristic. Painted doorframes or baseboards first show blisters
and fine tears in the lacquer and after longer infestation, wavy surfaces.
Fruit body: The brownish, to 12 mm thick and 2 m size, mostly resupinate
fruit body growing on wood or masonry (Fig. 8.21a) is conspicuous. From
shakes and vertical planes grow pad and bracket-like fruit bodies. The gyrosoreticulate
hymenophore is traditionally named “merulioid” (Fig. 8.21b), which
derives from the former generic name Merulius. The margin is whitish, often
bulging and always with a sharply limited front. Particularly at the margin,
as also with the mycelium, arise liquid drops of neutral pH value due to
guttation, which led to the naming lacrymans (watering). Fresh fruit bodies
have a pleasant smell like fungi, but putrefy after sporulation and then easily
stink (from the ammonia). The old, dry, then black-brown fruit bodies hardly
show the merulioid structure. Fruit bodies develop over the whole year, with
an amassment in the late summer until winter (Nuß et al. 1991).
Affected areas are often widely covered with brown, elliptical, yellow-brown
spores with small, pointed extension at an end and partly with up to five intracellular
oil droplets (Hegarty and Schmitt 1988; Pegler 1991; Nuß et al. 1991).
Falck (1912) calculated the spore release by a 1-m 2 fruitbodyto3×10 9 spores
per hour.
First, however, inconstant fructification in the laboratory culture was obtained
by Falck (1912), Cymorek and Hegarty (1986b) stimulated fructification
by 12 ◦ C incubation and by natural temperature change in the open (cool)
(Hegarty and Seehann 1987; Hegarty 1991). Fruit bodies relatively often developed
in pure cultures, if the mycelium was first incubated for about 4 weeks at
25 ◦ Conmaltagarandthenatabout20 ◦ C and natural daylight (Schmidt and
Moreth-Kebernik 1991b; Fig. 3.1).
Mycelium (Fig. 8.21c) and biology: During initial growth, with sufficient humidity
and standing air, often a white, woolly thick aerial mycelium develops,
which is rapidly interspersed by the typical strands. Yellow to wine-red (also
violet) discolorations (“inhibition colors”) by restraining influences [light,
accumulation of toxic metabolites, increased temperature: Zoberst (1952),
Cartwright and Findlay (1958)] are characteristic and led to the former generic
name Merulius, going back to the yellow beak of the male blackbird Turdus
merula (Coggins 1980). Older mycelium collapses to removable, dirty grey to
silvery skins, in which the branched strand system is embedded. The match-
www.taq.ir