Dry Rot - Effects

and Control

'Dry rot' (Serpula lacrymans) is a wood destroying fungi, which requires the presence of moisture in timbers during its initial stages of growth.

Water that penetrates the wood allows bacteria and micro fungi to colonise. These break down the cell structure of the timber and the wood becomes more porous which allows it to absorb more moisture. Dry rot can begin by a minute spore landing on the damp timber. The spore grows and forms hyphae (fine filaments), which secrete enzymes and break down the wood. The breaking down of the wood releases sugars which, when respired with air produce carbon dioxide, water and energy for the growth of the fungus. When the wood is broken down and utilised for food, shrinkage, loss of weight, loss of strength and cracking will occur. It is the shrinkage, which causes the typical cuboidal cracking of the timber, often associated with the presence of dry rot. As the dry rot fungus grows the hyphae develops into a large mass, known as mycelium. The mycelium is white and cotton wool like, although in some conditions it may be silky grey and tinged with yellow and lilac patches. Within the mycelium, strands will form. These strands can penetrate brickwork, pass over inert substances and colonise other timber in the vicinity. It is the ability for the fungus to travel away from the food source, which makes dry rot so destructive. Advanced growth of the fungus will create a fruiting body, which resembles a fleshy pancake. Large numbers of spores frequently collect around the fruiting body and form a red ‘dust’. The ‘dust’ (spores) can often be visible in areas where there is no significant attack of dry rot.