Behaviour of an Armillaria in some Eucalyptus obliqua – Eucalyptus regnans forests in Tasmania and its role in their decline

An undescribed but native species of Armillaria is a secondary pathogen in declining stands of Eucalyptus obliqua and Eucalyptus regnans in southern Tasmania. The fungus is almost ubiquitous in healthy and diseased forest and occurred epiphytically or parasitically in local lesions on the roots of 74 % of eucalypts partially excavated in 15 forest stands, 25–75 years of age. The fungus infected 85 % of logging stumps and 64 % of fire killed trees. Although the fungus only infected the sapwood of the eucalypts, it survived in infected stumps for at least 70 years. Rhizomorphs initiated most infections but did not grow freely through the soil. Pathogenicity tests confirmed that the Armillaria is a weak pathogen.