INFECTION OF NORWAY SPRUCE (PICEA-ABIES) BY HETEROBASIDION-ANNOSUM INRELATION TO TREE AGE

The presence of H. annosum in stems and roots of young Picea abies of different determined in four heavily infected stands in Southern Germa ny. The frequency of infected trees increased with age (0% in age clas s 1 (1-10 years), 7,5% in class 2 (11-20 years), 33,3% in class 3 (21- 30 years)). Only the S-type was found. An additional investigation of 1-10-year-old trees growing on stumps with H. annosum decay or tightly surrounded by carpophores yielded an infection rate of 20% (mainly S- type). H. annosum was confined to very small regions in the host tissu e in these cases.