Gremmenialla abietina on Scots Pine in Rikkilehto Stand in Salla, Northern Finland

1993

18 S.

zahlr. Lit. Ang.

Bandaufführung

37334

Several Scots pine (Pinus sylvestris L.) stands damaged by Gremmeniella abietina (Lagerb.) Morelet were found in eastern Lapland during the years 1988-1989. The most severely damaged area 3,6ha in size was a stand in Rikkilehto, Naruska, Salla. The condition of the trees, quality of the site and the history as well as the significance of Gremmeniella abietina in Rikkilehto prior to 1991 is reported. The most important damage agent was Gremmeniella abietina, but also pine shoot beetles (Tomicus spp.) had caused shoot mortality. About 60% of the Scots pines were dead. Their radial increment had started to decrease in the 1960's, and continued to do so in the 1970's and 1980's. No recovery in radial increment was measured after the epidemic until 1990. The most severe damage was concentrated at the very bottom of the area. The pH of the hums correlated positively with the damage degree. According to branch cankers and scars, infections caused by Gremmeniella abietina had occurred regularly since the early 1960's. The disease incidence increased from the late 1960's through to the 1970's with a serious epidemic in 1980's. The infections were very frequent during the period 1981-1987. Shoot mortality was at its highest during the years 1982- 1988. Since 1988, the epidemic has weakened. Attacks by Tomicus spp. increased dramatically in the late 1980's after the Gremmeniella abietina epidemic had ceased. Thus shoot beetles have been the main problem in the Rikkilehto stand between 1988 and 1990. The possible role of air pollutants in the development of the damage is discussed.