Increased swarming has been reported from basically all counties in the southern parts of the country, according to the Norwegian Forestry Agency. At the same time, more and more new attacks are being discovered on fir trees, in the vicinity of previously infested trees.
“The recent warm and dry weather favors the insect pest,” says Mattias Sparf, an expert at the Norwegian Forestry Agency, in a press release.
Forest owners are now asked to keep an eye on their forest and remove infested trees as soon as possible.
Spruce trees felled by the wind are easy prey for the bark borers. Trees that are dry or otherwise weakened are also attacked.
Big financial loss
How extensive the damage to the forest will be is impossible to say yet. Last year, roughly eight million cubic meters of forest were attacked by spruce bark beetles. Södermanland, Östergötland and Örebro counties were the worst employed.
The economic loss as a result of the spruce bark borer’s ravages has been calculated at several billion kroner per year, in a national perspective.
Before the hot summer of 2018, it was unusual for spruce bark beetles to reproduce with two new generations during a Swedish summer half-year.