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Trees - arboriculture and preservation orders

Ash dieback disease

What is ash dieback disease?

Ash dieback is the most significant tree disease to affect broadleaved trees in the UK since Dutch Elm Disease. The disease is caused by the fungus Hymenoscyphus fraxineus, the spores of which are carried and spread by the wind.

The disease was first recorded in Britain in 2012 in south-east England and has since spread across the country. Affected ash trees are now found in most parts of Scotland.

How does ash dieback spread?

The fungus Hymenoscyphus fraxineus overwinters in leaf litter on the ground and produces small white fruiting bodes during summer months which release spores into the atmosphere. The spores are carried by the wind allowing the disease to spread quickly across large distances. The spores land on and attach to the leaves of ash trees from where the fungus can spread through the tree. The fungus blocks the water transport systems of the tree causing leaf loss, lesions in the wood and on the bark. The crown of the tree suffers from gradual dieback and the branches of the tree become brittle and prone to breaking.

How serious is ash dieback?

Ash dieback is the most significant tree disease to affect broadleaved trees in the UK since Dutch Elm Disease. There is no known cure and no practical way to prevent the disease from spreading. 

Evidence from Europe, where the disease has been established for longer, suggests at least 50-75% of Scotland's 11 million Ash trees will be lost to the disease over the next 20 years. 

Dead and diseased ash trees can pose real risks to human safety. 

How do I identify a tree affected by ash dieback?

It is easiest to identify the disease in the summer months when leaves are on the tree. The disease can look different on young and old trees and the condition of an affected tree is likely to visibly decline year on year. 

In young ash trees affected by the disease, the leaves are likely to have wilted, blackened or begun to die and there may be diamond shaped lesions on the trunk of the tree.

Mature ash trees affected by the disease have bare twigs at the end of their branches which, as the name suggests, gives the appearance of the canopy dying back. The tree may also have visible discolouration and/or cracking on the trunk.

Whose responsibility is it for dealing with trees affected by ash dieback?

The owner of the land on which a tree is growing is responsible for the tree. Landowners have a legal duty of care to ensure that, as far as is reasonably practical, public safety is not compromised by the failure of tree branches or the whole tree. 

To help you understand the issues around tree safety and come to a balanced conclusion: one that ensures that trees, essential for the ecosystem and common good, can thrive in Scotland, uncompromised by unnecessary safety management please see ‘Common sense risk management of trees’.

If you have an ash tree on your property it is your responsibility to manage it appropriately. If you have any concerns about the health of your ash tree you should contact a tree professional for advice.

The Tree Council has provided a useful Guide for tree owners in Scotland which provides detailed information to help you understand your responsibilities and guidance for taking action.

Officers from the Roads Service regularly inspect the public road network to ensure there is no risk from overhanging trees or vegetation to road users. If you have an affected tree on land adjacent to a public road that is posing a risk to road users, you may be contacted by the Roads Service and instructed to take action to remove or prune the tree to reduce the risk to a more acceptable level. 

Do all ash trees have to be felled?

No, not all ash trees will need to be felled. Ash is an important tree species; it is a key feature of our landscape and provides habitat for a wide range of other plant and animal species. Some ash trees will be tolerant to ash dieback disease, and it is important that these are retained.

Trees affected by the disease can provide valuable habitats for fungi and invertebrates, birds and small mammals and therefore, where it is safe to do so, consideration should be given to retaining declining trees for as long as possible.

I have an affected ash tree on my land, what do I need to do?

It is advisable to get a tree professional to assess the tree(s) and advise on a suitable course of action. Trees affected by ash dieback can become very brittle and can be unpredictable and dangerous to prune or fell. Trees that show advanced signs of the disease should only be worked on by a qualified and experienced Arborist (tree surgeon). 

If the tree is protected by a Tree Preservation Order or is situated within a Conservation Area it will be necessary to notify South Lanarkshire Council and apply for the work in the normal manner. Details of how to apply for permission to carry out work to protected trees is available on the council’s website: Protected Trees

If the affected trees are growing on land which is not in a garden or area of public open space it may be necessary to first secure a Felling Permission from Scottish Forestry before undertaking felling work. Further information about what permission is required and details of work which is exempt is available from Scottish Forestry.

If the affected trees are growing on land adjacent to a public road or footpath it may be necessary for the road to be closed or traffic management to be put in place which felling is taking place and a permit will be required. Details about the type of permit and how to apply for one can be found on the council’s website: Roads permits and permissions - South Lanarkshire Council

How is South Lanarkshire Council managing ash dieback on council land?

We are in the process of developing a staged Ash Dieback Action Plan for responding to the challenges of ash dieback disease on council owned trees and woodlands.

The initial stage of this plan, to complete a baseline ash tree survey of all council owned and managed land, is making considerable progress. A systematic approach to monitoring the spread of the disease and a risk profile scoring system is being developed along with a protocol for retention of low risk and resistant trees.

Affected trees will be felled (or pruned) in line with identified health and safety priorities and we will liaise with landowners to ensure risk to members of the public from privately owned ash trees is monitored and managed.

We are committed to delivering a scheme of replacement planting as part of an ash dieback recovery plan. We are also committed to the CCF - Clyde Climate Forest that will see 18 million trees planted across the region over the next decade as a response to the Climate and Ecological Emergencies.

South Lanarkshire Council is also developing a Tree Canopy Cover Strategy to ‘protect, enhance and manage’ a benefit-generating canopy cover. At the centre is a shared vision to build greater ecological value and resilience into its canopy cover for future generations that is in tune with their needs and aspirations and responds to the challenges of our times. Furthermore, the strategic approach will help better understand and address significant threats to its tree cover, such as ash dieback, while maximising the diverse benefits tree cover brings to its community. Whilst the developing strategy will aim to reduce the risks of new pests and diseases affecting its tree population, it equally recognises it can never eliminate them. The strategic approach will therefore provide a framework to work with a wide range of partners to ensure that South Lanarkshire’s canopy cover and economy are more resilient to the new pests that will inevitably arrive from time to time.

Will new trees be planted?

Trees are vitally important asset to our towns and villages and we are committed to replacing felled trees with new planting. Where trees are removed on health and safety grounds, new trees of a suitable species will be planted as close to the same location as possible. 

If permission is granted to remove a protected ash tree that is affected by ash dieback it will normally be necessary to plant a replacement tree of suitable species within the same area. 

Where can I find further information?

National Guidance:

Scottish Forestry - Ash dieback in Scotland

Woodland Trust - Ash Dieback

Tree Council - Ash Dieback in Scotland

Forest Research – Ash Dieback

Information on landowner’s duty of care:

National Tree Safety Group’s Common Sense Management for Tree Safety

Information for tree managers, contractors and consultants:

Arboricultural Association Ash Dieback Practice Guidance

Forest Industry Safety Accord Essential information on the felling of diseased ash

Information on how to get involved in the Clyde Climate Forest:

CCF - Clyde Climate Forest