The Mischief of the Dry Rot Fungus

The dry rot fungus (Serpula lacrymans (Wulf.: Fr.) Bond.) is one of the fiercest destroyers of wood.

There are over 70 more species similar to it, mostly living in forests, parks and gardens.

However, the dry rot fungus outwits its relatives and settles in more comfortably – in houses, like some benefactor or friend.

Although it does very well in forests, where there is a lot of wood, there are also quite a few competitors there, and moreover it is quickly noticed and destroyed. Under the floors, in hidden corners and under furniture, provided the rooms are unventilated and damp, this fungus feels as if it were in paradise. Not to mention storerooms, cellars, the space under barns and unventilated attics. There it is even safer, because people cast an eye into out-of-the-way corners less often, and sometimes, by cluttering corners or covering ventilation openings, they seem to create comfortable conditions for it on purpose.

Then this fungus, which scientists also call the "weeper", quickly and firmly establishes itself under suitable conditions (30–35 percent moisture, 20–25 °C warmth). Light is not essential for it, not even necessary. The "weepers" even avoid light, because it hinders their development. By way of "thanks" for the shelter, within a few months or years this fungus turns a shed, a storeroom, floors or a corner of a house, and sometimes the whole house, into rotten debris.

It would be futile to try to compile a catalogue of tree species resistant to the dry rot fungus. There are none. Its favourites are resinous conifers, but it successfully gnaws through paper and leather, and even plaster does not stop it.

It is not difficult for this fungus to destroy a masonry wall either, as long as there is damp wood in it. Finding a crack in the wall, a larger or smaller gap and at least a piece of wood, it moves without any trouble to the second or even the third floor, and if conditions are good it climbs even higher, into the attics, where there are usually plenty of wooden structures.

The colourless hyphae of the mycelium spread both vertically and horizontally wherever it is damp, warm and unventilated. Wood turns to dust and plaster crumbles, and it makes no difference at all whether it is winter or summer.

The dry rot fungus does not damage dry, impregnated wood; it dislikes and avoids ventilated rooms. Good ventilation is fatal to the vital activity of this fungus.

The second obstacle is impregnation. There are currently enough products for impregnating wood, only one should not overdo it, because there are cases when not only dry rot fungi but also the owners cannot live in the house. The misdeeds of this fungus are described even in the Bible, where it is called "leprosy of the house". The ancient Greeks and Romans knew how to make impregnating oils whose durability has been proven by time – wooden figurines made almost 500 years before our era, which have even been in a damp environment, survive to this day.

What does this fungus look like? Its fruiting bodies resemble a sponge, 40–50 cm in diameter and 4 cm thick, irregular, most often attached to the underside of the floor, but they also occur along the walls and under the ceiling.

At first the fungus is white, later it turns brown and wrinkles radially into net-like folds, and its surface looks as if it were tearful (with droplets of brown liquid). Because of its villainy, the fungus's "tears" are called "crocodile tears". When the droplets dry and the fungus itself breathes, substances poisonous to humans are released.

So the "weepers" not only destroy the dwelling, but also harm the health of the people living in it. When the "crocodile tears" evaporate, the fungus's spores begin to fall, and they harm the eyes and the respiratory tract. In a single day just 1 cm2 of its fruiting body sheds over 35 million spores. Just imagine how many of them there are in a room. The dry rot fungus also reproduces perfectly well by fragments of vegetative mycelium on the surface of still undamaged wood. The fungus is spread by rats, mice, beetles, cats, and even by people themselves, without sensing or knowing it.

If a sickly, unpleasant smell of mould is felt in a room, or if white or brownish clusters of mycelium are visible somewhere along a wall, this dangerous focus must be destroyed as quickly as possible.

All the damaged wood must be scrupulously replaced, even though the fungus is easily cleaned off or falls off. Good ventilation is essential. Infected wood must be burned. It must not be put with firewood or with building materials, or used for household purposes.

After the plaster has been removed, the wall must be disinfected and plastered anew. Homeowners must take particular care that it is not damp under the floors and that the walls and roof space are dry.

Cellar rooms must be looked after carefully, because it is most often from there that this "benefactor" moves into living quarters. Those who have built small saunas in their homes need to be especially careful.