Ash Dieback

Ash Dieback is a comparatively new disease to Britain having been first formally identified in 2012. It is a very serious disease. It is caused by a fungus, Hymenoscyphus fraxineus, previously known as Chalara fraxinea. This has been known across Europe for a number of years where it has caused widespread tree losses.

The situation has developed rapidly since 2012. The Forestry Commission continue to undertake surveys to monitor the extent of the disease.

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The Forestry Commission maintain a map that shows the current distribution of the disease. Suspected cases of the disease (or any other) can be reported through Tree Alert

If you would like to learn more about this disease and its impacts then there are several good websites including Observatree

Observatree is a collaborative project between:

  • Forest Research
  • Forestry Commission England
  • Forestry Commission Scotland
  • APHA
  • Defra
  • Fera Science Ltd
  • the National Trust
  • Natural Resources Wales and
  • the Woodland Trust

It aims to encourage citizen science to monitor tree health and improve protection of the trees in the UK.

Ash is a common tree across Cornwall in woodlands, copses, hedgerows, towns and villages. At the last census of trees and woodlands* ash was estimated to represent 3.4% of our broadleaf woodland (however it would also be a major component of the 69.5% classified as 'mixed broadleaves') and 13.5 % of our non-woodland trees (Oak was 8.3%). There were estimated to be over 160,000 ash trees outside of woodlands.  Ash is an important tree ecologically and in considering replacement trees it is important to consider the best ecological match as well as other considerations (such as suitability to site, appearance, size at maturity, etc.) We intend to produce guidance on what tree species might provide good replacements and we will publish it on this webpage.

*National Inventory of Woodland and Trees  - Cornwall, March 1997.

If you are concerned about ash trees and wish to learn more about the disease and its symptoms then a good place to start is with the Observatree Field Identification Guide.

If you have concerns about an ash tree (or concerns with any other tree) that you have responsibility for then you should seek professional advice on that tree. You can find appropriately qualified individuals or firms for example on the Arboricultural Association website and looking at their Find a Professional Page.

The disease in Cornwall is less progressed than in many other parts of the Country and we are monitoring the approaches being explored in different local authorities as well as the development of the disease in Cornwall. 

We are monitoring our own trees for signs of the disease through our normal Tree Risk Management Framework.  In addition we are undertaking awareness training with all competent officers to ensure their familiarity with the disease and the actions to take when identified.  We are preparing  a wider Ash Dieback Action Plan to reflect the growing impact this disease will have on our trees and woodlands.  This action plan will guide our actions on our own estate and appropriate guidance to others and which is not available elsewhere.

The work on our own Action Plan is being jointly led by our Highways and Environment Services who we anticipate taking the lead in our operational response.

We are committed to working in partnership on this disease and have convened a stakeholder group which is contributing to the action plan including communications.  This group will meet regularly and, amongst others, includes the Forestry Commission, Woodland Trust, Cornwall WoodMeet, Highways England and private estate representatives.   

Following a number of enquiries regarding the impact of Ash Dieback on our approach to tree protection and other planning issues, Cornwall council has issued this Ash Dieback and Planning Advice Note.

If you have enquiries relating to the disease that are not addressed elsewhere (i.e. on the lead agency websites or in links above) then please direct your enquiries to . Please note that responses from this inbox are prioritised so please do look at the other links before sending in your email.