Well, I found the name of the fungi myself but would like to share the
information given:
"Armillaria root rot - (honey fungus, bootlace fungus)
A weak parasite on native trees, this fungus often severely damages newly
planted orchards or garden trees and shrubs. It occurs mainly in areas
recently cleared of bush where the sol is light and sandy. Infection from
one root to another is spread through the soil by means of black strands
called rhizo-morphs. The tree wilts and drops leaves indicating possible.
root problems, and on investigation the root wood is powdery or jelly-like
with a mushroomy smell. On affected trees cut off all affected wood and
bark, smooth the area as much as possible and paint with a bituminous
grafting compound. Leave the root system exposed around the base of the
tree for and indefinite period. Remove badly attacked trees and fumigate
the soil before replanting. Stumps and large roots left in the soil when
clearing land for replanting are a source of infection."

Don