Forestry News writes that a new study from SLU shows that the expected major outbreak of spruce bark beetle in southern and central Sweden will continue this year. The Swedish Forest Agency recommends that forest owners with forests in risk areas should prepare now.
Several factors influence the extent of spruce bark beetle damage next summer, including the number of spruce bark beetles in the forest, the health and resistance of spruce trees, and the summer weather.
Fewer spruce bark beetles expected this year
To predict the number of spruce bark beetles, the Swedish University of Agricultural Sciences (SLU) has investigated their reproduction during the summer of 2022. The study shows that the reproductive success remained at about the same level as in previous years in Småland, but decreased in Värmland and Uppland/Västmanland. This suggests that we expect fewer spruce bark beetles in the forest next season, which may reduce the risk of damage. But even if the risk is reduced, forest owners in southern and central Sweden should expect major damage again this year.
"Because the damage was so great last year, and the spruce bark beetle is still very numerous, we expect that a number of million cubic metres of spruce forest are at risk of being killed even in 2023," said Martin Schroeder, professor at SLU and responsible for the study, according to a press release.
The weather decides
Weather is the most important factor in determining the extent of damage. A cool and wet summer reduces the risk of damage because the spruce bark beetle becomes less active and the resistance of spruces increases. However, a hot and dry summer increases the risk of damage.
"If you have had spruce bark beetle infestations in the past or have forests in risk areas, you should already prepare now for damage this summer," says Kerstin Ström, forestry consultant at the Swedish Forest Agency.
