Red ring rot caused by the fungus Phellinus pini is a serious problem from the point of view of forest economy in Poland, as well as in other countries. The rot attacks the hard part of trunk, it develops unnoticed for several decades of years, frequently, it is not detected before the felling of the tree and it causes enormous economic losses. One can suppose that about 8% of gained pine felling product consists of rotten wood. The main objective of the presented studies was the determination of the occurrence of Scots pine stands threatened by red ring rot on the basis of the presence of fruit bodies of Ph. pini and of red ring rot developed in result of a hollow in the trunk which was settled by Ph. pini mycelium. During observation of disease symptoms on the ten separated areas (2490 trees), sings were detected on 61 trees. A great number of fruit bodies and their locality exert a high influence on the development of rot foci and thereby they cause great economic losses.

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