Importance of site type and tree species on disease incidence of Gremmeniella abietina in areas with a harsh climate in northern Sweden

The importance of site type and tree species on disease incidence of Gremme niella abietina was investigated. Blocks of four conventional regenerations of Pinus contorta and Pinus sylvestris, situated on sites formerly support ing pure stands of P. sylvestris and Picea abies respectively, were examine d for the occurrence of G. abietina. Trees planted on spruce sites were fou nd to be more severely diseased by G. abietina than trees planted on pine s ites. Pinus contorta was more severely attacked by G. abietina than P. sylv estris on both site types. The results show that plantations of P. contorta and P. sylvestris in areas originally covered with pure spruce forests run a high risk of damage by G. abietina.