Ash Dieback Disease (Hymenoscyphus fraxineus) 

Ash Dieback Disease is a chronic fungal disease infecting ash trees throughout Europe. It is characterised by leaf loss and crown die-back in those trees that are infected.

The fungus (originally Chalara fraxinea), first detected in the UK in 2012, has spread throughout Somerset and is particularly prevalent in the Mendip area. It is feared that Ash Dieback Disease will kill up to 95% of ash trees across the UK at a cost of billions and having a staggering impact on the landscape.

It is therefore important to highlight and be aware of the health and safety issues that should concern all who own and manage ash trees.

The main issues of concern are:

  • Health and safety risks to persons and property. Ash trees infected with Ash Dieback Disease become brittle and consequently the risk of failure increases. It is therefore important to identify affected trees at an early stage and take appropriate action
  • Appropriate management of infected trees. This should be undertaken by a qualified and insured professional arborist
  • Landowners’ awareness of their responsibilities and duty of care in respect of managing their trees
  • The loss of ash trees having a devastating impact on the landscape in terms of landscape character, biodiversity and amenity
  • Replacement tree planting with appropriate species. It will be essential to replace those trees which are felled/removed to mitigate for loss of amenity and biodiversity in the wider response to the effects of climate change

There are landscape and tree professionals based within the County who can provide advice and guidance about Ash Dieback Disease. If you consider that your Ash tree is suffering from Ash dieback, please follow the guidance below.

The Forestry Commission/DEFRA have a dedicated helpline to receive all public reports of Ash Dieback sightings:

Helpline: 0845 933 5577

If you wish to e-mail details, please include your name and address, location of the tree and if possible, photographs of the tree (this will help the forestry commission to get a quicker diagnosis). E-mail:

Acute Oak Decline

Acute Oak Decline can kill a tree in as little as four or five years. It has been found affecting hundreds of trees across central and south-east England and parts of Wales.

Symptoms include dark fluid bleeding from splits in the bark on tree trunks, and as affected trees approach death there is a notable deterioration of the canopy, or treetops, and ‘dieback’ of the branches.

The Forestry Commission has information relating to Acute Oak Decline including area of outbreak, symptoms, advice and guidance and reporting suspected cases on their website Forestry Commission – Acute Oak Decline.

Last reviewed: May 31, 2023 by Sophie

Next review due: December 1, 2023

Back to top