During last 50 years, Norway spruce stands in the Polish mountains have been affected by several outbreaks of bark beetles, mainly Ips typographus with accompanying scolytids. This paper describes the most significant outbreaks, based on data collected continuously by the Forest Research Institute for the annual assessment and forecasting of threats to Polish forests, as well as existing publications on individual cases. Six areas with the most notable outbreaks were selected: two in the Sudety Mountains and Foothills – western and eastern – and four in the Carpathians: Beskidy, Tatry, Gorce, and Radziejowa. According to Manion’s concept, the predisposing, inciting, and contributing factors are specified for each outbreak. The main predisposing factor in all cases was the proportion and age of spruce, further influenced in some cases by long−term industrial stress or root diseases. In some areas the main inciting factor was defoliation caused by foliophagous insects (Zeiraphera griseana, Cephalcia spp.), while in others abiotic factors such as wind or drought were primarily responsible for the initiation and development of the outbreaks. Root rot caused by fungal pathogens was also an important contributing factor (Beskidy). The total volume of Norway spruce trees harvested in mountainous forest districts due to bark beetle infestation between 1976 and 2024 reached 16.1 million m3, with more in the eastern region (Carpathians) – 9.9 million m3 than in the western region (Sudety) – 6.2 million m3. During the largest outbreaks in the western Sudety (1981−1988) and in the western Carpathians (2003−2014), the volume of processed trees infested by bark beetles was 0.9 and 4.3 million m3, respectively, but the consequences of spruce decline differed in each case (the need for forest cover restitution versus conversion to more resistant stands). Stands in protected areas, including national parks, were also affected by the outbreaks, the causes and consequences of which are also presented.
W. Grodzki (Thu,) studied this question.