Mycobionta of birch and birch stump roots and its possible effect on the infection by Armillaria spp. I.

Zygorhynchus moelleri was the dominating species on/in roots of 2 year-old stumps of the 49 year-old birches. Trichoderma viride was more frequently found in the fine roots of living birches than in the fine roots of stumps though its population increased in thick roots of stumps. Occasionally the fungus also occurred on the surface of fine roots of stumps. Z. moelleri is known to produce indole 3-ethanol and indole-3 acetic acid which stimulate the growth of A. ostoyae rhizomorphs and phenoloxidizing enzymes which play an important role in the degradation of the wood. It seems that the accumulation of Z. moelleri and absence of bigger populations of T. viride on/in roots of 2-year-old stumps of the 49 year-old birches may result in an increase of their susceptibility to Armillaria infection