Asian Fungus has infected 90% of all ash trees in Switzerland.

Ash are the second most abundant species of leaf-bearing trees in Switzerland (about 5% of all trees in the country). A majority of them will die off in the next few years because of a fungus infection. There is no remedy in sight.

Article by 20min.ch in German. Translation: AbruptEarthChanges

Taking a walk in a Swiss forest now bears the risk of falling branches from ash-trees. Even entire trees may suddenly fall. Heinz Engler, of the Federation of St. Gallen Forest Owners says. „already now occasionally, ash-trees are falling over even in a light breeze.“

The cause is a fungus infection. The so-called „Falsche Weisse Stängerbecherchen“ (Hymenoscyphus pseudoalbidus)  causes branches and shoots to die off. These can then break off easily in a light wind. As a result of this initial weakening the tree is very susceptible to the Hallimasch fungus, that deteriorates the roots of the tree by rotting.

90% of all ash-trees are affected.

Whether a tree is affected or not, shows in the withering leaves. In an advanced stage, tree trunks are deteriorating, the fungus, that originated in East Asia, was first detected in Switzerland in 2008. It spread across the country in a few years.

Around 90 percent of all ash-trees are infected with Hymenoscyphus pseudoalbidus, says Daniel Rigling of the Federal science Unit for Forest, snow, and Landscape. At this point, it is dificult to estimate, what percentage of the inflicted trees will die off.

A study in Latvia, where the fungus has been active as early as the late 1990s, showed that after 10 years, only 4 out of 26 ash-trees were left alive. „We are estimating the losses will be similarly high in Switzerland“, says Rifling.