Wpływ czyrenia sosnowego (Phellinus pini (Brot.) Pilat) na przyrosty radialne sosny zwyczajnej (Pinus sylvestris L.)

Scots pine is the most common tree species in Poland with the share in the species structure of Polish forests exceeding 58%. The most dangerous pathogen of this species is Phellinus pini (Brot.) Pilát), which causes the white pocket rot (also called red ring rot) of pine heartwood. It is estimated that as a result of the fungus’s activity, about 8% of annually harvested pine stems is damaged and worthless. As the Ph. pini damages only heartwood, it is often recognized that its occurrence has no influence on the tree’s physiology. As it is still unknown whether the presence of this fungus also does not affect the cambium responsible for the radial growth. We carried out studies in Scots pine stands located in the Radziwiłłów Forest District (central Poland). We investigated trees from 5th and 7th age classes (Biała Góra and Budy Stare forests, respectively). A total of 60 trees were sampled (30 per site). Half of them were specimens showing advanced symptoms of sickness, while the others were healthy specimens with no evidence of infection. From each tree we took one increment core and measured the tree−ring widths. Average tree−ring width was in case of healthy trees significantly higher than for sick trees. The research showed a significant, even of a dozen percent, reduction in the annual increment of infected trees in relation to healthy trees growing on the same site. Presumably, unidentified chemicals secreted to the cambium by the growing mycelium of Ph. pini may be responsible for this. It also seems that this relationship is progressing with the growing age of tree stands and is particularly visible in old stands, for example in reserves. Thus, Ph. pini could be one of the factors limiting the natural age of pine trees and accelerating their dieback. We also found that the growth of trees affected by the disease is influenced by a factor other than climatic, disturbing the natural rhythm of their radial increments. This factor is most likely the presence of mycelium of Ph. pini in the wood.