Artikkelit kirjoittajalta Risto Heikkilä

The occurrence of different types of damaging agent in 9 Scots pine seedling stands established on peatlands and subsequent effect on the initial development of the seedlings was examined in the study. The results concern only those parts of the seedling stands, many of them rather extensive ones, which were in a poor condition. About 36 % of the seedlings had either died or were incapable of further development as a result of damage by various agents. The most commonly occurring insect pests were pine weevils (Pissodes spp., especially P. pint L.), damage being caused by both larvae (in seedlings weakened before) and imagos. Damage caused by Petrova resinella L. which makes grooves in the seedlings that remain unhealed for a long time, was found to some extent. Damage caused by Hylobius-species was very rare. Damage caused by Diprionidae and Cryptocephalus pini L. was found to some extent but it was very slight. Of the fungal deseases, pine stem canker (Scleroderris lagerbergii Gremmen) was found to be a serious damaging agent. Snow blight {Phacidium infestans Karst.) occurred relatively abundantly, but because most of the seedlings had already grown higher than the snow cover, the effect of this fungus was generally only slight. Stems damaged by pine stem rust (Melam-psora pinitorqua Rostr.) were found to some extent, the damage being only slight. Abiotic damage was rather common on the seedlings. Snow had broken branches and pressed the seedlings down, thus weakening them and making them more susceptible to subsequent damage. Rather a lot of the seedlings (22 % of them) were suffering from bark damage (channels, compression, drying out of the bark), which obviously often presupposed damage by pine stem canker and pine weevils. Needle yellowing, symptomatic of nutrient deficency, was also found in part of the areas. Most of the damage noted in this study was of the same kind as that found in Scots pine seedling stands established on mineral soils sites in Northern Finland.

• Heikkilä, Sähköposti: ei.tietoa@nn.oo