Marta Bosque Fajardo
Senior Engineer
Abstract
In Norway, the spruce bark beetle (Ips typographus) has been monitored for several decades. By tracking beetle population levels, the monitoring program can alert forest owners about rising risks of forest damage so they can take preventive measures. In 2025, trap catches of the spruce bark beetle in southern Norway remained at a moderate level compared to the average for all the years with monitoring. Beetle numbers decreased in five of the 12 counties included in the Norwegian bark beetle monitoring program (Akershus including Oslo, Østfold, Vestfold, Telemark, and Sør-Trøndelag) and remained stable in one county (Buskerud). The six counties with increasing trap catch either showed a moderate increase (Oppland and Hedmark) or an increase from very low levels (Aust-Agder, Vest-Agder, Nord-Trøndelag, and Nordland). The 2025 monitoring season started with slightly warmer and drier conditions than normal in May in Southeastern Norway, favoring early bark beetle flight in this region. In contrast, cool and wet weather in Mid- and Northern Norway delayed beetle flight and led to very low trap catches in the first two trapping periods. In July, temperatures rose across the whole country, with extreme drought developing in parts of Mid- and Northern Norway. This contributed to high trap catches in the third trapping period in the three northernmost counties (Sør-Trøndelag, Nord-Trøndelag and Nordland). The highest trap catches in 2025 were recorded in Telemark, Buskerud, and Oppland, where beetle numbers remained high compared to the long-term average. Several municipalities in these counties exceeded the trap catch threshold for moderate risk of bark beetle damage, and Sør-Aurdal, Etnedal, and Tokke also exceeded the high-risk threshold. As in 2023 and 2024, the highest trap catches were concentrated in regions of Southeastern Norway that were heavily affected by a major windthrow in November 2021. In the two municipalities that were hit the hardest by the 2021 storm, Sør-Aurdal and Etnedal, trap catches continued to increase in 2025 and reached very high levels. A temperature-based development model suggests that by September 30, conditions were warm enough for the beetles to complete two generations in areas along the southeastern coast and in low-lying inland valleys. However, the model results do not necessarily mean that two generations actually occurred in the field.
Abstract
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