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Ash dieback

The number of invasive non-native tree pests and diseases in the UK is increasing. Ash dieback is one tree disease that is currently having a significant impact on the Derbyshire landscape.

About ash dieback

Ash dieback (Hymenoscyphus fraxineus) is a fungal disease that affects ash trees (Fraxinus species), including our native ash species, European ash (also known as common ash).

Ash dieback is an example of an invasive non-native species, originating from eastern Asia. It is thought to have arrived in the UK in the early 2000s on infected planting stock from continental Europe where it was first recorded in the 1990s.

The impact of ash dieback

The fungus that causes ash dieback blocks the xylem vessels (water transport system) within the leaves and branches of ash trees. This girdles these parts of the tree, causing them to die back. As the fungus spreads through the tree, more and more branches are affected, until eventually the whole tree dies.

Ash dieback is a highly destructive disease and at present there is no cure. It is expected that up to 90% of the UK ash population will eventually be affected by the disease.

Currently there is estimated to be approximately 9 million ash trees throughout Derbyshire, meaning ash dieback will have a significant impact on the county landscape.

How to identify ash dieback

The most common symptoms associated with ash dieback include:

  • blackening and wilting of leaves and small shoots
  • diamond shaped lesions or cankers at the joins between twigs and branches
  • dieback of shoots and branches

A useful photo guide of ash dieback symptoms and disorders often mistaken for ash dieback is available from Forest Research.

What we are doing

We have developed an Ash Dieback Action Plan which sets out how we will manage the progression of ash dieback throughout the county.

This will primarily involve identifying and managing the risks created by the disease to public safety (from falling trees and branches), infrastructure (roads, rail and utilities) and the wider environment (landscape, ecology and ecosystem services). Initially the management of trees posing a risk to public safety and infrastructure will be prioritised, followed by the risks to our wider environment in the medium to long term.

What you can do

If you spot an ash tree displaying symptoms of ash dieback that may pose a risk to people or property, please let us know via our tree management pages:

If you own or manage an individual or a small group of ash trees, or woodlands containing ash trees, you should monitor these for symptoms of ash dieback.

If your trees start to decline and you suspect ash dieback, you need to consider the risks posed by the trees to surrounding people and property and the tree management options available to you.

You should consult a tree professional before carrying out any works on trees affected by ash dieback. Comprehensive guidance on ash dieback management can be found in the following resources:

It's very important to retain ash trees that show any kind of tolerance to the disease as these will have the greatest potential to survive and reproduce to create the next generation of ash trees. A tree professional will be able to advise you of the options available to you regarding removal or retention.

For further information, you can email or Call Derbyshire, tel: 01629 533190.