Bracket fungi (Gloeophyllum spp.)

Bracket fungi are found in forests and woodlands, mainly on timbers lying on the ground in locations exposed to sunlight. They also occur in coniferous timbers used for outdoor applications, such as utility poles, bridges, posts, fences, and wooden structures, but also balconies, door and window frames. They are very rarely found in buildings.

Common species are the Gloeophyllum abietinum, the Gloeophyllum sepiarium and the Gloeophyllum trabeum.

What do bracket fungi look like?

The species named above can be identified and distinguished by means of their fruit bodies, the structure of the fruiting tissue layer and the microscopic structure of hyphae and spores. On wood used in building structures, the fruit bodies often take on a variety of different forms, making a determination more difficult.

As a rule, the following description is accurate for bracket fungi growing in woodlands. The young fruiting bodies of the Gloeophyllum sepiarium are often rust coloured or dark brown and have a yellow to orange coloured margin. They have concentric zones, are bracket or console-shaped and often arranged in much the same way as slates on a roof. The brackets are between 3 and 10 cm wide and 2 – 7 cm in depth. The fruiting bodies often grow out of dry cracks in structural timber and have a leathery consistence. The fruit tissue often has lamellae and can also have pores.

The Gloeophyllum abietinum has smaller bracket-shaped fruit bodies, which are reddish to dark brown on the top and have a whitish margin. The fruit tissue layer also has lamellae.

The Gloeophyllum trabeum’s fruiting bodies are bracket-shaped, 2 – 12 cm wide and 1 – 4 cm deep. The upper surface is brownish with a slightly lighter margin and the fruit tissue also has pores.

How ist the wood attacked?

In contrast to dry rot, cellar rot or polypores, bracket fungi do not spread by a growing mycelium, but grow inside the wood. It spreads by means of spores which have formed in the fruiting body. When spores fall on a source of nutrition, let’s say coniferous timber with sufficiently high moisture content, they can germinate and develop a mycelium.

In the wood, they cause individual seats of rot which grow in size over time. As the fungi grow in the wood’s interior and can tolerate relatively high temperatures, they can also attack structural components in areas exposed to sunlight, with surfaces that heat up strongly and dry out again.

What damage can bracket fungi cause?

The bracket fungus is a brown rot fungus which causes the wood to rot from the inside. Fungal mycelia can only be seen rarely on the infested wood’s surface, as the fungus grows inside the wood and forms an extensive substrate mycelium. That’s why bracket fungus infestation is frequently only seen when the fruiting bodies start to grow out of cracks in the wood, or when the outer layers of the affected timbers give way. In the later stages of infestation, the wood tends to split along its annular rings and fall apart.

What can be done to combat bracket fungus?

As this kind of infestation only becomes apparent when the fruiting bodies actually emerge from the wood’s interior or when the component is completely destroyed, the damaged timbers must be removed and any remaining or new ones must be treated preventively with a chemical wood preservative.

Infestation in buildings must be tackled thoroughly. Fungal determination and assessment should be carried out by an expert. The guidelines for curing this kind of infestation are contained in DIN 68800-4.