Incidence of Gremmeniella abietina in planted seedlings of Picea abies and Pinus sylvestris in northern Finland

The ascomycete Gremmeniella abietina causes a disease (scleroderris canker) on conifers. The pathogen kills terminal shoots and branches of Pinus sylvestris and Picea abies, sporulates on host shoots and causes leader changes (i.e. dieback). Damage caused by G. abietina was investigated in young P. abies and P. sylvestris plantations in northern Finland. Side branches from seedlings of both species and the main stems of P. sylvestris were collected from three sites in two locations (Poksa 1 and 2, Kivalo) in northern Finland. The number of cankers and leader changes was counted in branches of each age (i.e. year) in a total of ca. 6300 shoots of P. abies and 1200 shoots of P. sylvestris. Cankers were common on both P. abies and P. sylvestris in Poksa 1 (2002–2008) and on P. abies in Poksa 2 (1998–2001). In Kivalo, cankers occurred only sporadically on P. sylvestris. Leader changes were most frequent in 1999–2009 in Poksa 1, in 2001–2009 in Poksa 2 and in 2003 in Kivalo. Cankers and other symptoms of infection were more obscure on P. abies than on P. sylvestris. According to both conidial morphology and molecular analysis, the strain of G. abietina infecting both P. abies and P. sylvestris was small‐tree type (STT). This is the first report of G. abietina, STT or B type, injuring P. abies in plantations.