“Dry rot” in the UK, refers to outbreaks of wood decay. Caused by the fungus Serpula Lacrymans. Unlike wet rot for which relatively simple procedures are adequate for control. The successful remedial treatment of dry rot may require elaborate and sometimes very expensive control measures. It is important that an outbreak is identified correctly in the first instance.
There are a number of diagnostic features. But sometimes the presence of several of them may be required for positive identification;
Moisture requirements – Serpula Lacrymans requires wood (hardwood or softwood) or other cellulosic materials as a food source. The fungus grows most rapidly on wood that has a moisture content of above 30% though not saturated. It is unable to colonise wood which has a moisture content of below 20%. But the fungus has the ability to cause localised wetting of previously dry timber
Drier conditions – Even when established dry rot remains sensitive to the effects of low moisture content in timber, of infected wood is dried to a moisture content of about 20% or lower, the fungus will stops growing and will eventually die.
Ability to spread – Besides an ability on wood and other cellulosic materials, the dry rot fungus can also grow on the surface and within other substances such as wood and plaster
Recognition – usual effects on the wood – wood becomes light in weight, crumbles under fingers and has a dull brown colour. It shrinks and splits into cuboidal pieces
Strands – Grey or white 2-8mm thick become brittle when dried
Mycelium – In damp dark places, soft white cushions or silky growths, in drier places thick silver/grey sheets or skins usually showing patches of lemon yellow and tinges of lilac
Fruit Bodies – Are fleshy soft, but rather tough. Shaped like pancakes or brackets. Spore bearing surface rusty red with shallow pores or ridges and furrows, margin white.
Spores – Often settle on horizontal surfaces as a layer of rust-colours dust.