The spring warmth has awakened the spruce bark beetles from their winter hibernation and now both fallen and standing spruces in the south of the country are under attack, according to The Forestry Commission and forestry swarm monitoring. A hot and dry summer can cause widespread damage and millions in losses.
- If the meteorologists' long-term forecast of a summer as dry and hot as 2018 comes true, it would be a disaster for many forest owners with spruce plantations. We risk a new massive wave of spruce bark beetle," says Mattias Sparf, spruce bark beetle specialist at the Swedish Forest Agency.
Monitoring traps from the Swedish Forest Agency and forestry have caught thousands of spruce bark beetles, indicating that the swarming has begun in the southern parts of the country. The largest catches are seen in Svealand, with a peak in Västerås where over 9000 spruce bark beetles have been caught. Further north, the spruce bark beetles are starting to wake up from their winter hibernation but have not yet started to swarm.
- "As a forest owner, it is important to be vigilant when the spruce bark beetles start to swarm so that new infestations can be detected early. If we cut down the infected spruce trees early, we get the best control effect and can save most of the timber value," says Magnus Sääf, forest manager at Mellanskog.
Since the extremely dry summer of 2018, around 32 million cubic metres of spruce have died due to the spruce bark beetle, with a value of around SEK 14 billion. This compares to the large forest fires in summer 2018, which destroyed around 2 million cubic metres of forest.
How to tell if a tree has been attacked
Early infestations of spruce bark beetle can be difficult to spot because the spruce still looks healthy from a distance. But a week or two after swarming has started, you can see up close:
- Brown crumbs around the base of the tree, in bark folds and in spider webs. After rain, however, it may be more difficult to see the crumbs as they may have been washed away.
- Small insertion holes in the bark where the spruce bark beetle has bored its way in.
- Green needles on the ground around the tree (usually a little later in the summer)
Forest owners are advised to check their forests regularly and look for these signs at least every four weeks until the end of August. The greatest risk of new infestations is in sunny areas and where there have been infestations in previous years. It is also important to take care of spruce trees that have been blown down or damaged by snow during the winter, as otherwise spruce bark beetles can breed there in large numbers.
