Ash Dieback – The Facts

Guides Toolbox Talk

23rd September 2019 | Info

Do you own an Ash tree and have concerns that it has Ash dieback? Or have you had a tree surgeon visit you and tell you that your tree has Ash dieback? 

Ash dieback is present across the United Kingdom and has been in the news a lot over the last few years. We must become aware of the disease and the impact that it is and will continue to have on ash tree populations.

What is Ash dieback?

Ash dieback (also known as Chalara dieback of Ash), is caused by the fungus, Hymenoscyphus fraxineus (H. fraxineus). This fungus infects trees by blocking their water transport systems and causes leaf loss, lesions on the bark and dieback of the Common Ash tree’s crown.

What causes Ash Dieback?

Ash dieback is caused by spores from the fungus that are produced on ash leaves. The wind then carries these spores and disperse naturally to infect trees over a range of distances.

What stages of a tree are most susceptible?

Young trees easily fall into the hands of this disease and die quickly once the disease inhabits them. 

Mature trees are just as affected yet have a slower death rate (typically a year-long bought of infection) as they tend to resist the disease until they can no longer fight it.

Key signs to look out for:

  • Blackening of leaves (looks similar to frost damage)
  • Dieback of the crown of the tree. 
  • A flush of new growth below the dead branches
  • Small, white buds on blackened leaf stocks between summer and autumn.
  • Long and dark diamond-shaped lesions around side shoots
  • Tiny pale fungi growing on damp leaf stalks in early autumn
  • Saplings that have dead tops and side shoots

Final Thoughts

We must report these cases to the Forestry Commission as we are still fighting against this disease, and it’s a race against time. Strands are becoming more resistant, and we must advance our knowledge of the disease to reduce the risk of the Ash tree, one of our most important trees both ecologically and culturally, from ceasing to exist. 

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