Climate change is making Finnish weather conditions more favourable for the spruce bark beetle. Drier and hotter summers cause stress to trees, while winters without a frozen ground especially expose shallow-rooted spruce to storm damage.
In Finland, spruce has been used predominantly in forest regeneration, but its share in cultivation has levelled off in recent years. Because of the risk the spruce bark beetle poses, spruce trees should not be planted in very barren areas. However, a mixed forest may offer protection against the spruce bark beetle, as it diversifies the range of tree species, helping prevent the dominant role of individual species.
However, climate change may also improve the living conditions of the spruce bark beetle’s natural enemies. Many already live in dead spruce trees, which is why individual dry standing spruce trees should be left in the forest.
How to identify spruce bark beetle damage
During a cool summer, it’s enough to inspect the trees for spruce bark beetle damage at the beginning of the summer, but if the summer is warm and dry, it’s best to observe the spruce stand throughout the growing season. Focus your attention on the base of spruce trees and look for small, round holes, sawdust of a light coffee colour and resin leaks.
Areas susceptible to damage include:
- Sunlit forest edges bordering regeneration areas, where trees suffer from light stress.
- Areas with windblown trees or storm damage.
- Areas in which drought, the site type, or root rot disease causes stress to spruce trees, making them susceptible to spruce bark beetle attacks.
To identify insect-damage-prone sites, you can use the map content in the Metsäverkko mobile app, which detects damage early, even before it is visible to the human eye. If the mobile application displays a red warning of forest damage, you should visit the site to check the situation and contact your own forest specialist if necessary.
The condition of spruce tops is a good indicator for assessing the risk of spruce bark beetle. If top growth is good and the needles are generally dense, the forest is fine.