Bark beetle populations experienced a decline across neighbouring countries in 2025

Outbreaks of subcortical insects affecting Norway spruce in Central Europe (specifically Austria, the Czech Republic, Germany, Poland, and Slovakia) significantly decreased in 2025. A total of 11.5 million cubic meters of infested timber were recorded, compared to nearly double that amount (21 million cubic meters) in 2024.

Photo: Spruce bark beetle infestation site in Slovakia, author A. Gubka

Compared to the previous year, all the countries mentioned experienced a decrease in the volume of bark beetle infestation. The figures are as follows: the Czech Republic saw a drop from approximately 2.1 million m³ to about 1.1 million m³, Slovakia decreased from roughly 3.5 million m³ to 3.1 million m³, Poland went from approximately 2 million m³ to around 1.5 million m³, Austria fell from about 2.6 million m³ to 2 million m³, and Germany dropped from approximately 10.7 million m³ to 3.8 million m³.

The two countries most severely impacted by the bark beetle outbreak in recent years, the Czech Republic and Germany, recorded the largest declines in the volume of bark beetle-infested timber in 2025. In the Czech Republic, the recorded volume fell by half, while in Germany, it dropped to just one-third of the previous year’s level.

In 2025, the damage caused by abiotic factors in Central Europe amounted to approximately 8.5 million m³, a decrease from about 16 million m³ in 2024. This damage primarily affected coniferous timber, with wind (windthrow) and drought being the main causes.

Slovakia

In recent years, the bark beetle outbreak in Slovakia has remained consistently high. In 2025, approximately 3.1 million cubic meters of spruce timber were infested, compared to about 3.5 million cubic meters in 2024.

Photo: Gallery pattern of beech bark beetle, VÚLHM LOS archive

The dynamics of the outbreak are linked to the fact that the remaining spruce stands are now primarily located at higher elevations, where the effects of weather patterns (specifically ongoing warming) are more pronounced.

As 2025 was once again a climatically unfavourable year in Slovakia, the bark beetle situation remains critical. Additionally, effective control of the outbreak of subcortical insects on spruce has long been hampered by strict legal regulations and the stance of nature conservation authorities. As a result, practical forest protection options are severely restricted across vast areas of protected mountain regions.

In 2025, abiotic factors caused damage to approximately 1 million cubic meters of timber, a figure similar to that of 2024. As in the previous year, the primary causes of this damage were windthrow and drought.

Due to the effects of drought, beech trees have continued to be targeted by the secondary pest known as the beech bark beetle. Additionally, the invasive oak lace bug (Corythucha arcuata), which was introduced, continues to spread across the southern half of the country.

Poland

The extent and progression of bark beetle infestation in Poland are currently favourable. In 2025, the total volume of infestation recorded was approximately 1.5 million cubic meters, down from about 2 million cubic meters in 2024. This positive situation regarding forest protection against sub-cortical insects is primarily due to a more consolidated forestry sector, which facilitates the timely and effective implementation of preventive and remedial measures in state forests.

Photo: Alpine longhorn beetle on beech wood in southeastern Poland, VÚLHM-LOS archive

In 2025, abiotic factors caused damage to approximately 2.2 million cubic meters of timber, a slight decrease from about 2.3 million cubic meters in 2024.

Additionally, damage from sub-cortical insects (excluding those affecting spruce trees) amounted to roughly 2.4 million cubic meters, down from approximately 2.6 million cubic meters in 2024. This damage primarily impacted pine stands, with the main species responsible being the metallic wood-boring beetle (Phaenops cyanea) and the pine shoot beetle (Tomicus acuminatus), consistent with the previous year.

Leaf-eating, sap-sucking, and other insects were documented over an area of approximately 130,000 hectares. Control measures were implemented on 60,000 hectares of this area, focusing mainly on the nun moth and cockchafers. In 2024, infestations were reported across about 140,000 hectares, with control measures conducted on around 80,000 hectares.

Additionally, there was a significant increase in the prevalence of the parasitic European mistletoe (Viscum album), which primarily affects pine tree species. It covered an area of approximately 165,000 hectares, up from about 150,000 hectares the previous year.

Austria

According to reports from 2025, the bark beetle situation in Austria improved slightly. Nationwide, approximately 2 million cubic meters of infested timber were recorded, a decrease from roughly 2.6 million cubic meters in 2024. The most critical areas remain the Alpine regions of East Tyrol and Carinthia, where the volume of infested timber had surged in previous years. However, a decline in infestation was also observed in these regions last year.

Photo: A pile of fresh brushwood prepared for burning to prevent infestation by the pine bark beetle (Pityogenes chalcographus), VÚLHM-LOS archive

In 2025, abiotic factors caused damage to approximately 0.9 million cubic meters of timber. This figure was significantly higher in 2024, when it reached around 4.4 million cubic meters.

Concerning invasive species, the spread of the oak lace bug (Corythucha arcuata) continues. After six years of expansion, it has colonised a substantial portion of potentially suitable territory in Austria, with initial damage becoming evident in affected areas. However, 2025 proved to be more favourable than the previous year, likely due to weather conditions during the non-growing season that were unfavourable for the insect.

Germany

In 2025, approximately 3.8 million cubic meters of bark beetle-infested timber were reported across Germany, marking a significant decrease from the 11 million cubic meters recorded in 2024. There were notable regional disparities in the infestation levels. The highest volumes of infested timber were found in Bavaria (1.9 million cubic meters), Baden-Württemberg (about 1 million cubic meters), and Thuringia (around 0.5 million cubic meters).

In 2025, abiotic factors caused damage to approximately 1.6 million cubic meters of timber, a reduction from the roughly 4.7 million cubic meters affected in 2024. Windthrow damage was most severe in Bavaria (0.3 million cubic meters) and Baden-Württemberg (0.2 million cubic meters), while drought damage was highest in Baden-Württemberg (0.4 million cubic meters) and Bavaria (0.3 million cubic meters).

Photo: Poplars infested with mistletoe, VÚLHM-LOS archive

In conclusion, there are no reports of increased occurrences or outbreaks of any harmful forest factors (agents or influences) requiring specific attention in the border regions of neighbouring countries for 2025. The exception is the presence of spruce bark beetles, which, as in 2023 and 2024, primarily affects the border areas of northern Bavaria and western Saxony, and to a lesser extent, the border with Upper Austria. Looking ahead, the focus in all neighbouring countries continues to be on the spruce stand bark beetle outbreak, which is considered the most significant threat to forest protection in the upcoming growing seasons.

Additional information can be found in the “Forest Protection Bulletin (Zpravodaj ochrany lesů) – Supplementum 2026”, which is available for download here.

This information is based on the article titled „Výskyt lesních škodlivých faktorů v roce 2025 v okolních státech“ (Occurrence of harmful forest factors in 2025 in neighbouring countries), author  Jan Liška.

Prepared by Jan Řezáč, VÚLHM, v. v. i., e-mail: rezac@vulhm.cz