Armillaria

Notes

Spore print white. Caps up to about 10 cm diam., smooth or with small scales on the top, sticky when wet, brownish or yellowish in colour. Stalk very tough, fibrous, darker than cap. Gills covered by a veil when young, the veil persistent as a ring around the stalk when mature, although the ring often becomes flattened against the stalk. Gills attached to stalk.
Typically found in large groups on large pieces of fallen wood and dead stumps. Forms thick, black, bootlace-like ‘rhizomorphs’ beneath the bark of the wood on which it is growing. The rhizomorphs also grow through the soil, allowing the fungus to move through the forest to colonise new pieces of wood.
Apparently saprobic in undisturbed native forest, but can cause disease in some situations. The rhizomorphs can attack and kill living roots, especially of introduced tree species in disturbed sites for example pine trees planted in areas of recently cut native forest. Armillaria also colonises wood from spores dispersed through the air, and it may become established on cut stumps in parks or orchards. From these stumps the rhizomorphs can grow out and kill surrounding trees.
At least three species in New Zealand, all indigenous. The species are distinguished by rather subtle differences in size and colour. The two most common species are A. limonea and A. novaezelandiae.

 

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Images		NZFungi Entry

Armillaria novae-zelandiae

Armillaria limonea