Ash Dieback UK 2026 — What Arborists Need to Know

Why Ash Dieback Matters to Arborists

In short: ash dieback is now in most parts of the UK, and Natural England says it's predicted to kill up to 80% of ash trees. A declining ash loses strength quickly and is prone to structural failure, so industry guidance is to work from the ground first, then a MEWP, and climb only if neither is possible. In England, woodland ash needs a felling licence unless an exception applies, and ash dieback alone isn't one; and a dead ash under a TPO or in a conservation area still needs 5 working days' written notice to the council.

Ash dieback — caused by the fungus Hymenoscyphus fraxineus (formerly Chalara fraxinea) — is now present in most parts of the UK (Forest Research). Natural England says the disease is predicted to kill up to 80% of ash trees across the UK, and in many places the dying trees are already standing over roads, paths and gardens.

For arborists, this creates an unusual combination: a genuine ecological crisis and a large, long-running source of felling work. Understanding the disease, the legal framework, and the practical dangers of working on infected trees is now a core professional competency.

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What Is Ash Dieback?

Hymenoscyphus fraxineus is an ascomycete fungus originating in East Asia. It was first confirmed in the UK in 2012 at a nursery in Buckinghamshire. Later in 2012 it was found in the wider environment, including established woodland (Forest Research).

The fungus overwinters in leaf litter (mainly the leaf stalks, called rachises) and releases airborne spores in summer. These spores infect leaves, then the fungus colonises the bark and wood, cutting off the vascular system.

Key Identification Signs

Foliage:

• Wilting, blackened, or dark brown leaves in summer that do not drop cleanly
• Dieback starting at shoot tips, progressing toward larger branches

Bark and stems:

• Dark, diamond-shaped lesions (cankers) in the bark
• White, stalk-like fruiting bodies (apothecia) on blackened rachises in the leaf litter in summer

Crown:

• Dead or bare branches in what should be full leaf — "stagheading"
• Dead epicormic shoots on the main trunk (the tree trying to compensate for lost crown)

Important caveat: Ash can also suffer from other causes of dieback (honey fungus, Phytophthora, mechanical damage). For trees near roads, infrastructure, or with TPOs, always consider professional diagnosis before attributing symptoms solely to H. fraxineus.

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The Scale: Why Every UK Arborist Will Be Working on This for 20 Years

Forestry Commission guidance says that as an ash declines, "it appears to more rapidly lose timber strength and integrity and is prone to structural failure", and "mortality has been observed in as little as two growing seasons" (Operations Note 46a).

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Legal Obligations: What Arborists Must Know

Felling Licences

These are England's rules (Forestry Commission). Wales uses the same Act through Natural Resources Wales. Scotland (Scottish Forestry) and Northern Ireland (DAERA) have their own rules, so check there. Trees in a garden, orchard, churchyard or public open space don't need a felling licence. Elsewhere the occupier can fell up to 5m³ per calendar quarter on land they occupy without one (no more than 2m³ of it sold); that allowance is the occupier's, not each contractor's. Trees 8cm or less in diameter at 1.3m (15cm or less for coppice) are also exempt (Forestry Act 1967 s.9). However:

• Woodland ash needs a felling licence unless an exception applies. GOV.UK names trees that are dead or "pose a real and immediate danger" (GOV.UK). The Forestry Commission says ash dieback "does not in itself provide the authority to fell trees without a felling licence", and treats danger as an exception only in clear cases (Operations Note 46a). Keep photos, maps and surveys that prove the exception. Being in a grant scheme doesn't remove the need for a licence.
• Roadside ash in highway authority ownership — the highway authority has its own powers but contracted arborists must follow their client's documented permissions
• Estate and forestry settings — check whether there's an approved Woodland Management Plan; if so, check that its linked felling licence covers the trees (Tree felling: getting permission)

If in doubt, check the Forestry Commission's list of exceptions or ask your local Forestry Commission office.

Tree Preservation Orders (TPOs)

A TPO does not expire when a tree dies, and it does not automatically permit felling. If the ash is in woodland and needs a felling licence, apply to the Forestry Commission instead: it consults the council (Operations Note 46a §8.2). In England you don't need consent from the Local Planning Authority (LPA) to remove a TPO'd ash that is dead, but you must give the LPA written notice at least five working days before (or as soon as practicable for urgent work to remove an immediate risk of serious harm) (TPO Regulations 2012 reg 14). A dying ash still needs LPA consent, unless the work is urgently necessary to remove an immediate risk of serious harm, and then only as much work as that needs, with written notice to the LPA as soon as practicable.

The administrative step must still be completed. Work without consent is an offence that can bring an unlimited fine, and the landowner must normally plant a replacement tree (Town and Country Planning Act 1990 s.206 and s.210).

Practical tip: For ash with TPOs, submit the application with photographic evidence of dieback symptoms.

Conservation Areas

In England, trees in conservation areas with a trunk diameter over 7.5cm at 1.5m need 6 weeks' notice to the LPA before work. A dead tree doesn't need the 6 weeks, but you must still give at least 5 working days' notice. For urgent work to remove an immediate risk of serious harm, give written notice as soon as practicable (GOV.UK). A dying ash isn't a dead one. Elsewhere in the UK, check with the council.

Bats and other protected species

Ash trees matter to many protected species, especially bats. The law protects their breeding sites and resting places, such as a bat roost in a tree. Check before you fell. You may need a wildlife licence (Operations Note 46a).

Highways Act / Network Rail / Utility-Adjacent Trees

Local authorities have powers under the Highways Act 1980 to require landowners to remove dangerous trees. Network Rail and utility operators have their own frameworks. Arborists contracted to these bodies work under their client's permissions but should ensure the paperwork trail is complete.

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Safety: Why Ash Dieback Felling Is Different

Infected ash presents hazards that differ from normal tree work. Treat every significantly infected ash as a high-risk tree regardless of apparent size.

Specific Hazards

1. Unpredictable brittle wood failure

As the disease advances, the vascular system dies in patches. Wood can appear sound but fracture with much less load than expected. This affects both the main stem during felling and branches during climbing operations.

Industry guidance: work from the ground first, then a MEWP, and climb only if neither is possible. Where you can, fell with a harvester or tree shear (Arboricultural Association).

2. Epicormic failure during felling

Epicormic growth on the trunk — a stress response to crown loss — often has weak attachment. It can fail during felling vibration even when not in the fall zone. Exclusion zones should account for this.

3. Root system compromise

On damp sites the fungus can cause lesions at the base of the trunk. These often let in honey fungus and make the tree unstable, even when the crown looks fairly healthy. Check the base before choosing a felling direction.

4. Rapid deterioration

A tree assessed as "manageable" in spring may be significantly more dangerous by autumn. Document inspection dates and re-inspect before work begins if there has been a delay between survey and operation.

PPE and Equipment

Standard chainsaw PPE applies. For significantly infected trees:

• Helmet with visor is non-negotiable (brittle branch failure scatter risk)
• Avoid working alone on moderate-to-advanced infected trees: plan for at least two people on site for felling
• If using a MEWP, ensure ground conditions support outriggers on ground that may be softened by root dieback

For equipment suitable for high-volume ash felling and chipping programmes, browse Kit & machinery on TreeBay.

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Commercial Opportunity: How to Position Your Business

Ash dieback represents a multi-decade revenue stream for arborists who are positioned correctly. Volume felling is only part of it.

Survey Work

Many landowners — estates, local authorities, highway departments, Network Rail contractors — need ash condition surveys before committing to a removal programme. If you hold relevant qualifications (such as Lantra's Professional Tree Inspection, RICS, or ISA Certified) or work under one, this is skilled work you can charge for.

Even without formal consultant status, arborists can provide visual tree assessment (VTA) reports as part of tendering for the removal contract.

Phase Programmes

Large landowners cannot fell everything at once. They need a phased removal programme delivered over several years that balances:

• Tree risk (proximity to people/infrastructure)
• Timber value (accessible, merchantable-size timber first)
• Ecological mitigation (replace felled trees, retain some standing dead wood for habitat)
• Budget

Arborists who can present a credible multi-year programme win longer-term contracts rather than one-off callouts.

Timber and Wood Fuel

Ash is a premium firewood (high calorific value, splits well, burns well once seasoned). Freshly felled ash from the first years of dieback can have commercial value if:

• Volumes are sufficient to interest a timber merchant
• The wood is sound (no secondary rot has established)
• There is vehicle access for extraction

Even small-scale operations can market ash logs or split firewood locally. It offsets tip costs and adds a modest revenue stream.

In England, logs sold for burning in homes in bags or loads under 2 m³ must be certified Ready to Burn (no more than 20% moisture, with the certificate holder's name, the certificate number and the logo). Larger loads must come with the official notice on how to dry the wood (Air Quality (Domestic Solid Fuels Standards) (England) Regulations 2020, regs 3, 4 and 8).

Note: The spores come from infected fallen leaves. Moving wood from infected trees is considered a low risk, and there are no restrictions on moving ash timber, branches or leaves.

Subcontracting Surge

Local authorities and housing associations often go to larger contractors for bulk ash programmes but those contractors need qualified subcontractors. If you're available for subcontract work, keeping your calendar flexible can fill gaps with steady, well-defined work.

Look for subcontract work on TreeBay Jobs. Self-employed and looking for day-rate work? List your day rate in Subcontracting, or post that you’re available, free, in the forum’s Jobs category.

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Resistant Ash: A Qualified Note of Hope

Research by Forest Research (part of the Forestry Commission) and the Living Ash Project has found good evidence that a small proportion of ash trees can tolerate H. fraxineus (Forest Research) — trees that remain relatively symptom-free after years of exposure. A breeding programme is underway.

This won't change the work for years: up to 80% of ash are predicted to die (Natural England), though GOV.UK says "not all will die". So arborists should:

• Retain visually resistant trees where safe to do so (flag them for surveyors)
• Be aware that some landowners and ecologists may specifically request identification of tolerant specimens before clearance

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What to Do with Your Ash-Felling Equipment

If you're kitting out for a long-term ash programme, you'll want saws with anti-vibration systems (sustained chainsaw work is hard on hands and wrists), good quality pull lines, and access to a self-propelled chipper for high-volume site clearance.

See our guides on:

• Buying a used wood chipper in the UK
• NPTC chainsaw certifications — which units you need
• What to charge for tree work in 2026

If you're buying or selling used equipment for ash programmes, see Kit & machinery on TreeBay.

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Summary Checklist for Ash Dieback Work

For any question about TreeBay, how to list equipment, or what category fits your trade, visit our FAQ page.

Official sources

• GOV.UK: Managing ash dieback in England
• GOV.UK: When a felling licence is needed
• GOV.UK: Tree Preservation Orders and trees in conservation areas
• HSE: tree work