Ash dieback in Swansea and South Wales: how to spot it and what to do

Published 2 November 2026

Ash dieback in South Wales: where things stand

Ash dieback is a fungal disease (Hymenoscyphus fraxineus, sometimes still called Chalara) that affects all ash species. It was first identified in Great Britain in 2012, and the Welsh Government now describes it as endemic and found throughout Wales. Its spores are released between June and September and can travel tens of kilometres on the wind, so there is no part of Swansea, Gower or the valleys that is out of reach.

Swansea Council expects around 90% of ash trees in the UK to be killed by the disease. On its own land (parks, schools and roadsides) the council has identified around 2,800 ash trees that need removal, and says the final figure could be higher. Back in 2019, Neath Port Talbot Council estimated there were about 140,000 ash trees in the county borough, most of them on private land.

Once an infected tree starts to decline, the timber becomes brittle. Swansea Council warns that affected trees can collapse without warning, which is why the disease is a safety issue for owners as well as a loss for the landscape.

Our ash dieback management page covers the work our teams do on infected trees. This guide is about what you, as the owner, need to know first.

How to tell if your ash is affected

Carmarthenshire County Council’s advice note lists four signs to look for:

• Leaves turning black and dropping in late summer rather than colouring and falling in autumn.
• Lesions on the bark, visible above and below the points where branches join the trunk.
• Dieback in the crown, with dead, bare or brittle branches, usually starting at the tips.
• Cavities or fungi at the base of the trunk, which point to weakness lower down.

That last sign matters more than it looks. Natural Resources Wales notes that honey fungus often gets into the lesions caused by ash dieback and is frequently what finally kills the tree, especially older ones. Fungus at the base of an infected ash should be taken as a reason to get it looked at soon.

Late summer, while the tree is in leaf, is the easiest time to judge how much of the crown has been lost. In winter, bare dead twigs at the top of the crown are still visible against the sky. For the wider set of warning signs that apply to any tree, see our guide to signs a tree in your garden could be dangerous.

Your responsibilities as a tree owner in Wales

There is no plant health rule that says you must remove an ash tree, and the Welsh Government’s ash dieback policy (2024 to 2029) starts from a presumption in favour of leaving trees standing. What you do have is a duty of care for the trees on your land.

Swansea Council’s ash dieback page points private owners to their duty of care under common law, the Occupiers’ Liability Acts and the Highways Act. Carmarthenshire’s note goes further, saying landowners are “highly likely” to be liable if a tree with obvious defects causes damage when it or its branches fall.

In practice the risk depends on what the tree could hit. The Welsh Government and NRW both ask owners to prioritise ash near roads, buildings, power or broadband lines and paths the public uses. An infected ash in the middle of a large garden, well away from the house and the road, is a very different case from one leaning over the A4118 or a neighbour’s conservatory.

How the councils decide when an ash should come down

The three councils covering our area approach this in slightly different ways, and their thresholds are a useful guide for homeowners too.

Swansea. The council grades its own ash on a scale of 1 to 4, with 4 the most severe, and fells category 4 trees first. Its page says affected trees typically lose 10–15% of their canopy each year, and that trees with only 0–25% of their canopy left should be felled if they are near people or property. Trees that show good resistance are kept. Highways inspectors have been trained to recognise the disease and can issue notices to private owners whose ash overhang the highway.

Carmarthenshire (Llanelli and Burry Port). The council surveys trees next to the highway, including privately owned ones. If a tree shows at least 50% dieback, the owner gets an advisory letter recommending felling, followed by a formal letter if nothing is done within a year. Above 75% dieback, or where the risk is more immediate, the council starts a formal process under the Highways Act. It advises owners to remove trees on busy main roads that have lost half their canopy or more, or show failure at the base, if they are within falling distance of the road.

Neath Port Talbot (Neath, Port Talbot and Pontardawe). The council’s 2019 report set out an action plan built on surveys, felling based on risk, and working with private owners who have ash near highways, footpaths and council property.

If you get a letter or notice from the council about an ash on your land, read it carefully: a Highways Act notice only covers the specific trees it names.

Do you need permission to fell an infected ash?

This is where Wales differs from England, so it’s worth checking before any work is booked.

• Felling licence. Trees in gardens are exempt from needing a felling licence from Natural Resources Wales. Outside gardens, NRW says ash with dieback may still need a licence, unless the tree is dangerous. Its definition is strict: “a real and immediate danger, rather than a perceived danger”. A council letter warning that trees may be diseased is not enough on its own to count as an exemption. Our felling licence guide has the full list of exemptions.
• Tree Preservation Orders and conservation areas. Disease doesn’t remove TPO or conservation-area protection. Swansea Council’s page notes that dead and dangerous protected trees need five days’ written notice to the council before the exempt work. Anything short of that needs consent or notice in the usual way; see do I need permission to cut down a tree in Swansea? and our protected trees page.
• Wildlife. Old ash trees often have cavities used by bats, and nesting birds are protected whatever the tree’s condition. NRW also asks owners to keep the bottom three metres of ash with rare lichens where possible. See our bird nesting season guide.

Why infected ash needs experienced hands

NRW’s guidance is clear that the disease can severely weaken a tree’s structure, so felling is hazardous, and only trained, experienced tree surgeons or forestry workers should work on ash with obvious symptoms. It recommends a precautionary approach, noting that machinery protects operators better than working with a chainsaw where it can be used. Both NRW and the Welsh Government advise owners to use a fully insured tree management professional.

It’s also why it pays to plan early: once decay sets in, an infected ash becomes more dangerous to climb and take apart.

What to plant instead

The Welsh Government does not advise planting ash at the moment, as young trees may already be infected and no guaranteed disease-tolerant ash is on sale in the UK. NRW asks owners to plan replacements whenever trees are removed and to choose species that suit the soil and site. Neath Port Talbot’s report suggested oak, birch, alder and sycamore for its own replanting. On exposed Gower and coastal plots, our coastal gardens guide covers trees that cope with salt and wind.

If you have an ash that is still healthy while others around it are dying, it could be tolerant. The Welsh Government’s policy mentions the Living Ash Project, which collects reports of possibly tolerant trees.

How our teams can help

Our teams across Swansea, Gower, Neath and Llanelli can look at your ash, tell you how far the disease has gone, and agree whether to monitor, reduce or fell. Where a tree does need to come down, we’ll check the permission and wildlife questions first. Ask for a free quote.