Ash dieback is a fungal disease of ash trees, caused by Hymenoscyphus fraxineus. It was first confirmed in the UK in 2012 and is now found across the country. The Woodland Trust estimates it will kill up to 80% of the UK’s ash trees. Only an estimated 1–5% show reasonable tolerance, and none has proved fully resistant.
The disease isn’t harmful to people or animals. The real risk is safety: infected ash become brittle and shed branches, and diseased trees are more dangerous to fell the longer they are left.
“We are seeing a real decline in the health and stability of our ash trees, which is not helped by summer droughts and waterlogged winters. It’s time to remove and replant a better and more diverse mix of trees.”
Charlie Hunt, Forester, Wessex Woodland Management
Below is how to spot ash dieback, when to act, what permissions you need, and what funding is available, with a real example from a woodland near Newbury.
What is ash dieback?
The fungus spreads through wind-blown spores released from last year’s fallen ash leaves each summer. It can travel tens of miles on the wind. Over longer distances it has spread through the movement of infected plants. Once it infects the leaves, it grows into the shoots and branches and blocks the tree’s water-transport system. Branch by branch, the crown dies back.
Symptoms of ash dieback: how to spot it
The best time to check your trees is July to September, while they’re in full leaf. After leaf fall, symptoms are much harder to read.
- Leaves: dark brown to black patches, wilting, and leaves dropping early in mid to late summer.
- Shoots and branches: dead tips at the top and edges of the crown. Twigs die back from the ends.
- Diamond-shaped lesions: dark, elongated diamond-shaped marks on the bark, often centred where a side shoot joins a branch. This is the classic sign.
- Bushy regrowth: clumps of new shoots sprouting along the trunk and main branches as the tree tries to replace lost foliage.
- Lesions at the base of the trunk: the most serious sign. Basal lesions weaken the tree’s structure and often let honey fungus in, which rots the roots.
The stages of ash dieback
Tree surveyors usually grade infected ash by how much of the crown is still alive:
| Class | Living crown remaining | What it usually means |
|---|---|---|
| 1 | 76–100% | Monitor. May be a tolerant tree worth keeping |
| 2 | 51–75% | Monitor closely, especially near roads, paths or buildings |
| 3 | 26–50% | Plan management. Branches are becoming a hazard |
| 4 | 0–25% | Likely to need felling if near people or property |
How long does ash dieback take to kill a tree?
It depends on the tree’s age. Young trees and coppice regrowth can be killed within a few seasons. Mature trees can hold on for many years, but they often decline steadily, and many are finally killed by secondary infections such as honey fungus rather than the dieback itself. Stress speeds this up: on the sites we manage, summer droughts and waterlogged winters are making stressed ash decline faster. That long decline is why mature ash need regular checking, not a one-off look.
Will all ash trees die?
No, but most will. Current estimates put losses at up to 80% of UK ash. A small minority, around 1–5%, show real tolerance. These trees matter: they are the genetic basis of future ash populations. The Forestry Commission advises keeping ash that stand out as healthier than those around them, as long as it’s safe to do so. We follow the same principle: we don’t recommend felling a healthy-looking ash just because the disease is in the area.
Is ash dieback dangerous?
Not to your health. You can’t catch it, and it doesn’t affect people, pets or livestock. The danger is physical:
- Falling branches. Dead ash wood dries out and becomes brittle quickly, so limbs can drop without warning.
- Whole-tree failure. This is most likely where the base of the trunk is infected or honey fungus has taken hold in the roots.
- Harder, riskier felling. Badly affected ash are often unsafe to climb. They may need a mobile elevated work platform (MEWP) or machinery instead, which usually costs more the longer a tree is left.
As a landowner, you are legally responsible for the safety of people who could be affected by your trees. Ash beside roads, footpaths, railways, buildings or public areas should be risk-assessed and checked regularly. Public rights of way are a common trigger for action. See the Newbury case study below.
Can I leave an ash tree with ash dieback?
Often, yes. An infected ash well away from roads, paths and buildings can be left to decline naturally. Standing and fallen dead wood is valuable habitat for fungi, insects, bats and birds. The question to ask isn’t “is it infected?” but “what could it hit?”
- Away from people and property: monitor it, and keep any trees that appear tolerant.
- Near roads, paths or buildings: get it surveyed, record its condition, and plan felling before it becomes dangerous to do.
Do I need permission to fell ash with ash dieback?
Usually, yes. In England, felling trees generally needs a felling licence from the Forestry Commission, and ash dieback doesn’t remove that requirement. The main exceptions are:
- trees that are dead
- trees that pose a real and immediate danger
- small-scale felling of up to 5 cubic metres per calendar quarter (of which no more than 2 cubic metres may be sold), plus some other specific exemptions.
Ash trees are not protected in their own right. But Tree Preservation Orders and conservation-area rules still apply, and a tree with holes, cracks or loose bark may hold roosting bats, which are a protected species. Felling licences commonly come with conditions to restock the land. Check before you start. We handle licence applications as part of our felling work.
Grants for ash dieback
Funding is available in England through the government’s Tree Health Pilot, aimed at dangerous ash along roadsides and public rights of way. As of July 2026 it covers:
- 60% of tree survey costs and of traffic management or road closures during works
- 80% of European protected species surveys
- restocking: up to £4,720 per hectare of woodland (£6,000 in ancient woodland), or per-tree rates for trees outside woodland
- maintenance of the new planting for 3–5 years.
It does not pay for the felling itself. Individual applications need at least 100 metres of road and 20 ash trees. Group applications between neighbouring landowners are preferred and can be worth up to £100,000. Other woodland grants may also help with replanting: on our Newbury project, tree health grant funding contributed £4.15 per tree towards tree shelters. See our woodland grants and subsidies guide, or ask us whether your site qualifies.
Replanting after ash dieback
Ash often makes up a large share of the canopy, so losing it can leave big gaps. Replant with a mix of species suited to your soil and site rather than a single replacement. Diversity is the best insurance against the next pest or disease, and against a changing climate. Where tolerant ash survive, natural regeneration from them is worth encouraging too. We plan and plant new and replacement woodland across the south of England.
Case study: unsafe ash on public footpaths near Newbury, Berkshire
The problem. On an estate north-east of Newbury, a compartment of mixed ash and oak is crossed by two public footpaths with heavy footfall. In the wetter pockets of the wood, the ash was in severe decline and beginning to fall apart, making the footpaths unsafe.
What we did.
- Applied to the Forestry Commission for a felling licence with restocking, then removed the dangerous ash.
- Took out around 600 m³ of ash, all sold locally as firewood.
- Replanted with 1,500 mixed native broadleaves: oak, wild cherry, wild service tree, hazel, field maple and common alder.
- Used tree health grant funding, which paid £4.15 per tree towards shelters, to cut the cost of restocking.
The result. The footpaths are safe again. The felled areas (known as coupes) have been replanted with a much wider mix of species, and the young trees are now establishing among the surrounding mature woodland. That gives the wood a more varied age structure and makes it more diverse and resilient in a changing climate.
Ash dieback in Berkshire, Hampshire and Wiltshire: how we can help
We are based near Hungerford and manage woodland across Berkshire, Hampshire, Wiltshire, Dorset and the wider South West. For owners dealing with ash dieback, we can:
- survey your ash, grade each tree and prioritise the ones near roads, paths and buildings
- handle felling licence applications and any permissions
- carry out felling and timber harvesting, including difficult and dangerous trees
- help you sell the timber. Ash felled before it deteriorates still has value, especially as firewood
- prepare grant applications and replant with a resilient mix of species.
Worried about ash on your land? Contact us or call 01488 685007 to arrange a survey.
Working with diseased ash yourself? Dead and damaged trees are among the most hazardous in forestry. Our chainsaw courses include NPTC training for dealing with windblown, uprooted and interwoven trees.
Ash dieback: frequently asked questions
Is ash dieback harmful to humans?
No. The fungus only affects ash trees. The risk to people comes from brittle, dying branches and trees falling.
How can I tell if my ash tree has ash dieback?
Look in July to September for blackened, wilting leaves, dead shoot tips in the crown, diamond-shaped lesions on the bark and bushy regrowth on the trunk. Lesions at the base of the trunk are the most serious sign.
Do I have to fell an ash tree with ash dieback?
No. There’s no requirement to fell infected ash. But you are responsible for the safety of anyone your trees could affect, so infected ash near roads, paths and buildings should be surveyed and managed.
Do I need a felling licence to remove ash with ash dieback?
Usually. Dead trees, trees posing an immediate danger, and felling within the small-scale 5 m³ per quarter allowance are exempt. Tree Preservation Orders still apply.
Are there grants for removing ash dieback trees?
In England, the Tree Health Pilot funds surveys, traffic management and replanting for dangerous ash along roads and public rights of way, but not the felling itself.
What should I replant after ash dieback?
A mix of native broadleaves suited to your site rather than a single species. Near Newbury we replanted with oak, wild cherry, wild service tree, hazel, field maple and common alder.