The weakening of Polish montane forests is observed for several years, with differences related to local site and stand conditions. In spite of the favourable weather conditions in the vegetation period of 1998, and especially - higher precipitation level and associated better water supply for the plants, the vitality of forest stands and trees remained still reduced. This concerns mainly Norway spruce stands, being actually in the period of the deep health and resistance crisis. The intensification of negative processes in these forests, related strongly with the increase of the activity of fungal pathogens, influences the weakening of trees, resulting in the growing up frequency of the secondary insect pests, finally stimulating the mortality of trees.
The development of the phytosanitary situation in the stands in 1999 will depend, in considerable degree, on the course of the weather conditions during vegetation period. It will be well visible especially in the Norway spruce stands, where the threats from bark beetles will be related with the hydrothermic conditions of its development period. This will be important especially in the period of the spring swarming of the insects, which could influence the situation during all next year.