Bracket fungi cause decay and rot in the heartwood of trees and produce bracket-shaped fruiting bodies on the trunk or main branches. These fungi usually lead to the weakening and eventual breakage or fall of affected trees.
What are bracket fungi?
Bracket fungi are the fruiting structures of many different fungi that cause heartwood decay in standing trees. The fungal bodies or brackets appear in spring, summer and autumn, but weakened trees can topple at any time. Note that there are other fungi which also cause decay that are not bracket fungi.
There are many different types of bracket fungi, many which are specific to a particular host and often of little importance in gardens. Important ones that commonly do significant damage to garden trees include:
- Ash heart rot, caused by the bracket fungi, Inonotus hispidus, attacks Fraxinus (ash), Juglans (walnut), Malus (apple), Platanus (plane), Ulmus (elm) and other broad-leaved trees
- Beech heart rots, caused by the bracket fungi Ganoderma applanatum, G. adspersum attack a wide range of broadleaved hosts, especially Fagus (beech)
Although there are many different bracket fungi, they all cause similar symptoms, as mentioned below.
Some of the symptoms you may see:
- External symptoms: the first external symptom of bracket fungus infection is often the appearance of the bracket-shaped fruiting bodies on the trunk or main branches. These can be up to 60cm (2ft) in diameter and may be annual or perennial. This may be preceded by visible crown thinning and die-back, but not always. By the time a bracket appears there will usually have been extensive heartwood decay. Since decay weakens the wood, another symptom may be falling branches
- Internal symptoms: these fungi may cause either white or brown rot in the heartwood; both are structurally weakening. In some cases, the tree becomes hollow and may remain stable, but decay usually leads to weakening and eventual breakage or wind throw. Foresters distinguish top rots which affect upper parts from root or butt rots which affect the roots and base of the tree. The latter, such as Meripilus giganteus, are particularly damaging because the whole tree may fall
- Unfortunately there is little you can do in terms of hygiene or cultural control to prevent bracket fungi
- Removing brackets to prevent spore release will have very little effect on the overall risk
- Trees have some ability to limit the spread of internal infection by responding to the fungus with natural chemical barriers. For this reason, experts no longer recommend painting pruning cuts with wound paints, since as these age they crack, trap water and may actually increase the risk of infection
- Some trees are known to be susceptible to certain bracket fungi: Fagus (beech), Fraxinus (ash) and Prunus are all very susceptible to specific bracket fungi. There is very little information on resistance within cultivars
Gardeners are legally responsible for their trees and may be liable for prosecution if damage or injury results from falling timber. For assessments of tree health, advice on suitable consultants and contractors contact:
The Arboricultural Association
Tel. 01242 522152
The Tree Advice Trust
Tel. 09065 161147
(premium rate phone line charged at £1.50 per minute)
For identification of decay fungi, contact;
Disease Diagnostic Advisory Service
Alice Holt Lodge
Tel 01420 23000
(£50 per specimen)
RHS Advisory Service
(free, but RHS members only)
There are no chemicals for control of bracket fungi.
The brackets release huge quantities of wind blown spores which germinate on wounded wood and penetrate into the heartwood, where the fungus forms an expanding pocket of rot. Any pruning which exposes heartwood will increase the likelihood of infection. Most of the fungi described as ‘brackets’ only live on and decay the heartwood, they do not infect and kill the living parts of the tree.
Honey fungus, a destructive pathogen as well as a decay fungus, is not a bracket fungus.