Managing ash dieback in England

Ash dieback causes widespread decline of ash trees in some areas of England. It is likely that the majority of our native ash trees will exhibit symptoms of ash dieback, but not all will die. Some ash trees will have some tolerance to the disease, and others will exist in locations where they escape the worst impacts.

It is important that the effects of ash dieback are planned for and managed, especially in safety-critical locations.

About ash dieback

Ash dieback is fungal disease affecting the common ash tree (Fraxinus excelsior) and other Fraxinus species. It is caused by a fungus called Hymenoscyphus fraxineus, which is native to eastern Asia. The disease was first identified in England in 2012, although research has shown that it is likely to have been present since at least 2005.

Ash trees are common in woodland and non-woodland settings. They make up 12% of Great Britain’s broadleaved woodland, and are often found in parks, gardens, hedgerows and roadside margins.

The severity of the disease varies locally. Local conditions will determine how ash trees are affected by the disease. Trees in woodlands with high proportions of ash are likely to decline more quickly due to higher inoculation loads.

There is some evidence that ash trees growing in open, less humid locations such as streets and hedgerows may deteriorate more slowly or persist indefinitely, although it is not yet clear whether this will be a consistent pattern. Some trees with few symptoms could survive on these sites for many years.

Identifying ash dieback

Infection leads to leaf loss and dead branches throughout the crown of ash trees, and clumps of new growth towards the centre of the crown.

In areas of high infection, the fungus can cause lesions at the base of the tree, making it more susceptible to secondary infections, such as by Armillaria fungi.

Read Forest Research’s guide on ash dieback signs and symptoms.

Videos on how to identify ash dieback can also be found on the Forestry Commission’s YouTube page.

Guidance for land managers and tree owners

You should consider the effects of ash dieback if you own or manage ash trees, even if you’re dealing with low levels of infection.

Felling diseased ash requires a felling licence, unless the trees are dead or pose a real and immediate danger. Restrictions such as tree preservation orders must also be respected. Your local authority can provide guidance.

Some ash trees may have genetic tolerance to ash dieback, meaning they may survive and reproduce to create the next generation of ash trees. When this happens you should retain ash trees where they stand out as being healthier than those around them, providing it’s safe to do so.

Retaining a proportion of dead, dying or felled trees will provide deadwood habitat and be beneficial for biodiversity.

Guidance for local authorities

Read the Tree Council’s guidance for local authorities on preparing an ash dieback action plan.

Trees on special scientific interest sites or with protected species

If a site is subject to a designation such as Site of Special Scientific Interest (SSSI), or might contain European Protected Species, additional rules apply. See guidance from the Forestry Commission and Natural England:

• Managing woodland SSSIs with ash dieback
• Managing and protecting protected species

Public health and safety

If you manage ash trees near roads, railways, buildings and other publicly accessible land, you must consider the risks posed by infected ash. You should carry out a risk assessment for trees or woodlands in these areas. The owner of land where a tree stands is legally responsible for the health and safety of those who could be affected by that tree.

If you are unsure about health and safety risks, consult a fully insured tree management professional who holds a relevant qualification.

Learn more about risk management of trees on the National Tree Safety Group website.

Dead or dying ash also poses a risk to professionals working on or near them. If you’re a landowner or forestry manager, read more:

• Safety guidance on the felling of diseased ash (UK FISA)
• Ash dieback: practical guidance (Arboriculture Association)

Replacing trees lost to ash dieback

Replacing trees felled due to ash dieback is important for minimising the impact of the disease. The species chosen should be well suited to the current site conditions, and those likely to be seen in the future due to climate change.

If large numbers of trees are being planted, use of a range of appropriate species to help to lower the risk and impact of future disease events.

For guidance on restocking woodland, see:

• Restocking woodland following loss of ash due to ash dieback
• Right trees for a changing climate database (for trees in urban areas) – Forest Research
• Ecological impacts of ash dieback and mitigating methods (Forest Research)

Where a felling licence is granted, you will need to restock the area where trees were removed.

Funding for restoring woodland

There are grants available to help restore your woodland.

Further information

This guidance is summarised in Managing ash dieback in England.

Read the Ash tree research strategy Defra, Forestry Commission and Forest Research.

Read about other tree pests and diseases.