The traps that have been placed are next to biotope protection, ie protected forests with high nature values where for various reasons you do not want to fell the forest.
- When you can not cut down the trees, you can instead try to catch the spruce bark beetles in this way, says Joel Lindqvist, forest consultant.
This spring, Stockholm County was classified as a control area against the spruce bark drill and the Swedish Forest Agency gives high priority to the control of the drills.
Previously, the border was at Sörmland County.
The traps are one of several methods used by the Swedish Forest Agency during the summer.
Almost 20 million drills caught
How spruce bark beetles are controlled has been a controversial issue and the more prudent control in the protected forests has been criticized for increasing the spread to private landowners.
The proportion of protected forest in Sweden is very small compared with the cultivated forests and therefore does not affect the spruce bark borer outbreak regionally.
But locally, the nearest spruces can be affected, according to Martin Schroeder, professor of forest entomology at the Swedish University of Agricultural Sciences.
The Swedish Forest Agency estimates that they have caught a total of close to 20 million spruce bark beetles in all traps that have been set, from Skåne to Uppland.
It may have saved almost 5,000 spruces.
It is unclear how much effect the traps have
It remains to be seen what the result of the Swedish Forest Agency's new traps in Stockholm County will be.
- You can never catch all the drills, but the traps can catch a certain proportion.
Whether they really reduce the damage is debatable and research on this is ongoing, says Martin Schroeder.
An earlier evaluation of the traps' effectiveness was made after storm Gudrun.
At that time, 940 traps were set up in a damaged nature reserve and only 11 percent of the estimated number of bark borers in the area were caught.