About 20% of mature spruce stands in Sweden have been hit by root rot, according to the Nordic Forest Owners’ Association.

The problem is estimated to be costing the Swedish forest industry about SKr500m annually. Southern Sweden and coastal regions are most severely hit.

The condition is caused by fungi and bacteria and mainly affects spruce, but sometimes also pine. Contaminated stems are affected from the inside, making the wood useless for timber and pulpwood.

Researchers are blaming forestry industry practices for the spread, with the increase of summer harvesting reckoned to be a contributing factor.