Symptoms

Ganoderma species are common on broadleaved trees and occasionally found on conifers. Causing vigorous rots this fungus is capable of killing trees outright. Ganoderma is a white rot bracket fungus which grows on living and dead trees; it is very common in the UK.

Ganoderma bracket fungus infects wood exposed by wounds, which may be caused by pruning, wind or animal damage. The fungi grow into and decay the wood, weakening branches and causing them to fall. As the decay advances, fungal fruiting bodies form on the bark of affected branches.

Ganoderma are wood-decaying fungi that can grow on both coniferous and hardwood species. The fungus appears on the outside of the tree as a semicircular mushroom head without a stalk, usually brown or grey, pitted on top and perhaps a little shiny. There are many different types and variations of Ganoderma and most are a white rot fungus which means that it attacks the lignin or cellulose in the trees molecular structure, causing a crumbling of wood tissues and thus is very dangerous.

It is easy to diagnose once a fruiting body appears and we usually recommend removal as the tree can become unsafe fairly rapidly. Fruiting bodies should be destroyed (i.e. burnt) to prevent is spreading, although one should leave the fungus attached until an expert has been consulted. If you think your tree has a Ganoderma fungus, then call an expert to inspect it immediately.

Control of Dangerous Fungi

Avoid damage to the bark and wounding. Healthy trees are able to block the entry of fungi. If bracket fungi are seen on a tree, it may be in poor condition. Felling may be required to avoid injury.

Prune little and often to minimise the size of pruning wounds, infection is prevented once wounds have callused over; this happens quickly with small wounds. Investigate all signs of decay promptly and be prepared to call on professional help.

Fruiting bodies should be destroyed (i.e. burnt) to prevent it spreading, although one should leave the fungus attached until an expert has been consulted. As gardeners are responsible in law for damage or injury their trees may cause.

Unfortunately, there is no prevention or control once a root system is colonised. The positive aspect is that after investigation, immediate removal is not always necessary. It does give your certified arborist a baseline mark to make appropriate recommendations regarding a potential timeline for removal and replacement.

Interesting Fungi Fact

Ganoderma are poisonous, but some species of ganoderma have been used in Asian medication for thousands of years, for many different applications. They are being investigated to see if they have anti-cancerous properties.