Ash Dieback in the UK: Is It Really as Bad as We Feared?
Ash dieback remains serious, but not every affected tree needs removing. What the latest UK research says and when to book an ash tree assessment.
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For more than a decade, ash dieback has been one of the biggest threats to Britain’s trees. Headlines have warned of enormous losses, and with good reason. Yet the latest research gives us a more complicated picture than the idea that every infected ash tree is destined to die.
The Woodland Trust warns that up to 80% of UK ash trees could be lost to the disease. That is a warning about potential losses, not a count of trees that have already died. Current Forestry Commission guidance is also clear that while many ash will show symptoms, not all of them will die.
For anyone with an ash tree in their garden, on their land or close to a building, that distinction matters. The sensible response is to check the condition of the tree and the risks around it, rather than assume that a few dying branches mean it must be felled.
What is ash dieback?
Ash dieback is caused by a fungus called Hymenoscyphus fraxineus. It particularly affects our native common ash, Fraxinus excelsior. The disease was first officially confirmed in Britain in 2012, although later research suggests it had arrived earlier. It is now widespread.
The fungus grows on fallen ash leaf material and releases spores that can spread on the wind. It can cause leaves to blacken, new shoots to die back and the crown to become thin. As a tree weakens, other problems, including honey fungus, may also affect its structure.
Have eight million ash trees already died in the UK?
You may have seen the figure of eight million trees mentioned in discussions about ash dieback. We could not find an authoritative, current UK-wide count from Forest Research, the Forestry Commission or the studies reviewed that confirms eight million ash trees have already died.
The better-known figure is the Woodland Trust’s projection of up to 80% mortality. That describes the potential severity of ash dieback, not the number already dead. Forecasts, infection rates and recorded deaths are different measures. They should not be used interchangeably.
This is not an argument that the disease has been exaggerated or has gone away. Ash dieback continues to cause serious damage. It simply means we should be careful with the statistics and even more careful about applying a national forecast to one particular tree.
Is ash dieback really as bad as first feared?
It remains a major concern. But the Forestry Commission’s current advice recognises something important: individual ash trees respond differently. Some appear to tolerate infection, while others deteriorate much more severely.
There is also evidence that ash growing in more open, less humid conditions, including some hedgerows and street settings, may decline more slowly than trees in other environments. That pattern is not guaranteed, and it does not make an affected tree automatically safe.
What has changed is our understanding of how varied the outcome can be. Infection alone does not tell us when, or even whether, an individual tree will need to be removed.
Why do some ash trees survive?
Forest Research has been investigating natural tolerance. In one major screening programme, scientists planted almost 155,000 ash seedlings and identified a small number that remained free from symptoms after years of exposure. That work helps researchers understand how more tolerant ash populations might be developed in future. See the Forest Research disease guidance.
There was also a promising result published in Science in 2025, when researchers found evidence of rapid genetic adaptation towards resistance in a wild British ash population. It is an important discovery, but it does not prove that all UK ash trees are becoming resistant or that the disease is under control.
For tree owners, the takeaway is fairly simple. Where a healthier ash can be retained safely, it may be worth keeping. Trees that tolerate the disease could also be valuable to the future of the species.
A word from Tom Howie
Tom Howie - Director of T Howie Tree Specialists
Just because an ash tree shows signs of dieback doesn’t mean the first answer should be to cut it down. We look at how the tree is coping, where it stands and whether there’s a real safety concern. Sometimes monitoring is the right option. If work is needed, we’ll explain why.
What are the signs of ash dieback?
Ash dieback is generally easier to identify during summer, when the tree is in leaf. Ash can naturally come into leaf quite late, so a bare crown in April or early May is not a diagnosis on its own.
Blackened or wilted leaves and shoots during the growing season
Premature leaf loss or thinning in the crown
Dead twigs and branches, sometimes spreading through larger parts of the tree
Dark lesions or discoloured patches on branches or the trunk
Damage or signs of decay near the base, particularly where other fungi are present
These symptoms can also be caused by other problems, including drought or root damage. A single photograph is not always enough to tell what is happening, especially where safety is a concern.
Does an infected ash tree need to be felled?
Not automatically. Forest Research’s management advice is generally to avoid felling living ash just because infection is present, unless there is a justified management or public safety reason. Retaining healthier survivors can matter for future ash populations.
The decision depends on the amount of dieback, the tree’s structure, how it is changing and what is within falling distance. An ash in an open field presents a different situation from a declining tree over a road, playground or house.
In some cases, the answer may be continued monitoring. In others, carefully considered tree pruning may help manage a particular problem. Where the tree is severely weakened and presents an unacceptable risk, tree removal and felling may be necessary.
There is no simple treatment that reliably cures ash dieback in ordinary garden trees. Anyone offering a guaranteed cure should be treated with caution.
When should you arrange a professional tree assessment?
It is worth getting advice if an ash tree is losing a large part of its crown, dropping branches or developing worrying damage around the trunk or base. The urgency increases where the tree stands close to people, a public footpath, buildings, parked cars or a road.
Significant new deadwood above a house, driveway or regularly used area
Large branches breaking or falling
Obvious structural cracks or fresh movement
Extensive crown decline or lesions near the base
A noticeable deterioration since the previous growing season
Do not attempt to climb or dismantle a severely affected ash yourself. If a tree has become immediately dangerous, ask about emergency tree services. For a less urgent concern, a planned assessment is the more sensible first step.
What if your ash tree has a Tree Preservation Order?
Disease does not automatically cancel tree-protection rules. Before pruning or removing an affected ash, check whether it is subject to a Tree Preservation Order, stands in a conservation area or may require other permissions. Different rules and exemptions can apply to dead or genuinely dangerous trees, but the evidence and notification requirements still matter.
Our guide to Tree Preservation Orders in North Yorkshire explains the general process. If a formal opinion or report is needed, ask about our tree surveys and reports.
Ash dieback in Harrogate and North Yorkshire
For homeowners, landowners and property managers around Harrogate, Ripon, Knaresborough and the wider area, there is no benefit in treating every ash tree the same way. A tree with some dieback may be suitable for review, while another with more advanced decline and a busy footpath beneath it may need action.
T. Howie Tree Specialist provides tree services in Harrogate and North Yorkshire. If you are concerned about an ash tree, get in touch. We can discuss what you have noticed, arrange a visit where appropriate and explain whether monitoring, pruning or removal makes sense.
Concerned about an ash tree? Contact T. Howie to arrange a tree assessment or request a quote.
Frequently asked questions
Will every tree infected with ash dieback die?
No. Many ash trees are badly affected, but some have a degree of tolerance and survive for longer. Current UK guidance does not say that every infected tree will die.
Can an ash tree recover from ash dieback?
Some trees remain relatively healthy despite infection, and researchers are investigating tolerance and recovery. That is not a guarantee that an individual tree will improve. Monitor changes and seek advice where there may be a safety concern.
When is the best time to check for ash dieback?
Summer is usually the clearest time to look for leaf symptoms and crown decline. A bare ash in early spring may simply be late coming into leaf. Safety concerns should be checked whenever they arise.
Can you cut down a protected ash tree with dieback?
Not automatically. Tree Preservation Orders, conservation-area controls and other rules may still apply. Check with the local authority or a competent tree professional before non-emergency work.
Research and further reading
Forest Research: Ash dieback biology, symptoms and management
Forestry Commission: Managing ash dieback in England