Risks associated with the introduction of Pinus contorta in northern Sweden with respect to pathogens

Severe damage by Scleroderris canker, caused by the fungus Gremmeniella abi etina, was recorded in provenance and progeny tests as well as in conventio nal plantings of Pinus contorta in areas with a harsh climate in northern S weden in 1987. Damage was related to a period with extreme weather conditio ns. The Swedish Forestry Act placed restrictions on the planting programme of P. contorta in 1987, 1989 and 1991. The disease situation in northern Sw eden in the mid 1990s is discussed as well as the risks associated with the introduction of exotics in relation to the historical background. Attentio n is also drawn to parasitic fungi, which are infecting P. contorta in its natural range in western Canada, and to the potential threat they represent to the indigenous Pinus sylvestris in Sweden. (C) 2001 Elsevier Science B. V. All rights reserved.