Affecting trees, these rots cause unsightly wounds and eventual branch drop.
Hosts
All trees - especially beech, sycamore and ash.
Symptoms
Crowns thin, branches die back, bark falls exposing decayed wood, fungal ‘brackets’ appear and branches break and fall.
Fistulina hepatica (beefsteak fungus) causes brown rot of oak, sweet chestnut and other broadleaved trees. The fruiting body is the shape of a liver, red and fleshy; it ‘bleeds’ when cut.
Fomes fomentarius (tinder fungus) mainly affects beech but is common on birch in northern England. The brackets are hoof-shaped, with a brown to grey upper surface.
Laetiporus sulphureus (chicken of the woods) affects many trees, including oak, sweet chestnut and yew. The brackets are orange-yellow, ageing white and crumbly.
Biology
Top rots develop in branches. Airborne spores of decay fungi from many genera, including Inonotus, Polyporus, Fomes and Ganoderma, infect 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 decay advances, fungal fruiting bodies form on the bark of affected branches.
Control
Prune little and often to minimise the size of pruning wounds; make sure pruning is carried out at the right time of year for the species involved. 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. Gardeners are responsible for the state of their trees and are legally liable for any damage or injury arising from neglect.