Spore deposition of Heterobasidion annosum coll. in Picea abies stands of North Karelia, eastern Finland

Abstract

Spore deposition of Heterobasidion annosum coll.was measured with the wood disc method in 20 Norway spruce stands in June, July and September 1999 in North Karelia, eastern Finland. The study area crossed the presently known northern boundary of the distribution area of H. annosum (62°45′N). The spore deposition rate decreased northwards and in the northernmost parts of the study area, deposition was detected only in September. On average 71% of the spore deposition consisted of intersterility group P and 29% of intersterility group S. The proportion of S-type in the deposition increased northwards. Most of the isolated colonies were homokaryons, but the proportion of heterokaryons increased with increasing deposition rate.