Artist’s fungus (Ganoderma species)

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Common host(s)                    Mostly deciduous – beech, ash, also oak elm. Sometimes Douglas fir.

Colonisation strategy             Enters via wounds.

Symptoms                              Large, distinct, flat hoof or clam-shell shaped perennial brackets. Can build up into tiered layers. Tops are brown, reddish brown or grey brown and can look as if covered in cocoa powder (spores). White or cream under-surface when new, duller with age. Brackets become hard with time. Show ribbed growth patterns which can reveal age. Thinning crown, yellowing, reduction in leaf size. Bottle butt may result as reaction wood forms.

Type of rot                             White rot. Can break down cellulose and lignin in heartwood, but more efficient with lignin, so white soft rot results. Eventually forms large cavities as cellulose degrades too.

Part(s) of tree affected          Brackets usually on main butt of tree, commonly at trunk/root interface. Rarely high on trunk or lateral branches.

Significance                            Ductile fracture of stem / root plate. Leaves trunk very weak structurally if cavity is large or if ring of sapwood was damaged by initial or subsequent infection. No control known.




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