Husum fells sick ash trees: Fight against ash shoot dieback!

Husum fells sick ash trees: Fight against ash shoot dieback!

In Husum there is currently a bitter battle against ash shoot dieback. The city is forced to cut down diseased ash trees because the safety of its citizens comes first. Martin Boecker, the head of the Husum building yard, leads the measures: “The trees could fall onto the cycle path and pose a danger to passers-by,” he explains. Even if the disease is often not immediately visible, three weeks ago ash trees had to be felled that seemed completely inconspicuous until they suddenly fell into a private garden.

The cause of the big dilemma is the invasive fungusHymenoscyphus fraxineus, which comes from the East Asian region. It was probably introduced to Europe in the 1990s and is already having a devastating impact on ash trees. In Germany, where ash trees make up around three percent of the total tree population, the situation is alarming: between 2012 and 2022, the population fell by around 20 percent. What is particularly worrying is that 90 to 95 percent of ash trees in Switzerland are affected by this disease, highlighting the need for decisive action.

The threat of the fungus

The ash shoot die fungus clogs the ash tree's nutrient pathways, which leads to the tree slowly dying. In Husum there are another 20 ash trees on the list this year that also need to be felled. The symptoms of the infection are diverse: They range from brown spots on the leaves to necrotic changes in the bark that can cause massive death.

The fungus has been observed in Switzerland since 2008, where it first appeared in the canton of Basel, and has been detected nationwide since 2015. Since the fungus has already spread too far, it can no longer be eradicated. The authorities then set up a task force with the aim of developing a comprehensive strategy for the conservation of the ash tree, which was published in 2017 and includes five key areas: quarantine, control, resistance, replacement and monitoring.

Resistance and protective measures

There is hope: around four percent of ash trees show resistance to the fungus. Studies have shown that the trees' genetic makeup and their mycobiome can contribute to resistance. Healthy trees that were tested for higher resistance were also found in Switzerland. Forest owners and forest services play a critical role in removing diseased ash trees and ensuring safety.

Ash trees are of great importance for biodiversity and the furniture industry. Their reduction has far-reaching consequences not only for nature, but also for economic structures. In Schleswig-Holstein, as well as in Switzerland, the preservation of this tree species remains a challenge, where it is urgently advisable to show a good hand. Continued efforts to combat ash shoot dieback are necessary to secure the future of ash trees.

With every tree felled comes a reminder of the dangers that diseased trees bring. A rethink in forest management and deeper research initiatives are now more important than ever to guarantee the survival of the ash tree.

For more information please visit NDR, FOEN and Forest knowledge.