Armillaria is considered to be a weak pathogen, although it frequently kills trees and sometimes appears in an epidemic form apparently induced by local site conditions. It causes severe damage to young conifers planted on former oak and beech sites after clearcutting. Pinus strobus and Larix spp. are highly susceptible. We observed that the fungus is vigorous only before introduced plants have accommodated to a new environment and the disease lasts only a few years after reforestation. However, recent observations show that Armillaria is one of the causal agents of oak forest decline in polluted areas. All oaks (Quercus petraea) that we examined that were in a state of decline were infected and many had been killed. Some heavily attacked oak stands were felled and replaced with indigenous pine (Pinus sylvestris and Pinus nigra), since we believed these species to be more resistant. Unexpectedly, some of these plantations, established more than 10 years ago, are now dying. A forest decline assessment carried out in 1987 suggests that pollution from local sources is the primary cause of this process but that Armillaria is the final cause of the decline. There is a strong correlation between distribution of local industries and presence of lichens which we used as an additional indicator of pollution. Further investigations of local ecological changes may aid in developing a disease control method.
443.2 (Krankheiten des Samens und der Sämlinge; Umfallkrankheit usw.) 443.3 (Krankheiten in späteren Wachstumsstadien) 425.1 (Gase und Schwebestoffe (Rauchschäden)) [497.15] (Bosnien und Herzegowina) 971 (Kongresse, Konferenzen; Exkursionen)
