Understanding Ash Dieback Disease: A Critical Threat to British Trees
Ash dieback disease, caused by the fungus Hymenoscyphus fraxineus (formerly known as Chalara fraxinea), is the most significant tree disease to affect the UK since Dutch elm disease in the 1960s. As a highly destructive fungal pathogen affecting ash trees nationwide, it poses serious challenges for property owners, landowners, and managers of infrastructure.
The disease has spread rapidly across England, Wales, and Scotland since its official recording in 2012, though analysis indicates some UK trees were infected as early as 2004. With ash being the third most common tree species in Britain – approximately 60 million growing outside woodlands and an estimated two billion overall—the impact of this disease is profound.
Research indicates that 70-85% of ash trees may eventually succumb to the disease, though some trees show natural tolerance. This devastating disease supports almost 1,000 species of wildlife, including lichens, invertebrates, and birds, making it ecologically significant as well as culturally important in our rural and urban landscapes.
Update: Responding to the 2025 Ash Dieback Toolkit
At Treetops, we support a wide range of organisations – including Housing Associations, schools, Multi-Academy Trusts, NHS sites and private landowners — to manage tree risk in a safe, practical, and planned way. Ash Dieback continues to be a growing issue across these sites, and with the release of the Tree Council’s Ash Dieback Action Plan Toolkit – Second Edition (2025), there’s now even clearer guidance on what steps to take.
This updated toolkit builds on five years of learning, with new case studies, technical advice and a stronger emphasis on recovery planning. We’re already using it to support clients to:
Identify ash trees across their sites
Assess condition and level of risk
Develop proportionate plans for monitoring, retention or removal
Carry out tree surveys and mapping
Integrate Ash Dieback into wider tree and estate strategies
Importantly, the guidance also reinforces the need to think beyond removals. Replanting, biodiversity, and long-term tree population resilience now form a key part of the recommended approach – and we’re helping clients to plan for that.
Whether you manage a housing estate, school grounds, hospital campus or commercial site, we can help ensure your response to Ash Dieback is structured, proportionate, and aligned with current best practice.
How Treetops Delivers Expert Ash Dieback Solutions
At Treetops, we’ve developed comprehensive expertise in managing ash dieback, helping property owners navigate this complex challenge with professional support and practical solutions across the North West, Yorkshire and North Wales. Our approach combines technical knowledge with specially adapted equipment to address the unique challenges posed by this disease.
Professional Ash Dieback Assessment & Surveys
Our specialist arborists conduct thorough tree health surveys using the established four-class system to accurately assess ash tree condition:
- Ash Health Class 1 – 100%-76% remaining canopy (trees showing minimal symptoms)
- Ash Health Class 2 – 75%-51% remaining canopy (moderate symptoms appearing)
- Ash Health Class 3 – 50%-26% remaining canopy (significant dieback present)
- Ash Health Class 4 – 25%-0% remaining canopy (severe decline)
We also check for dangerous basal lesions that can compromise tree stability even before canopy symptoms appear – a key safety consideration often overlooked in basic assessments.
Conservation-Focused Management Approach
Unlike companies that recommend immediate felling for all affected trees, we recognise that:
- Healthy-looking ash trees should not be felled in anticipation of disease unless there are overriding safety concerns
- Some ash trees show tolerance to the disease and could be valuable for future regeneration
- Each situation requires a customised management plan considering tree health, risk level, conservation value, and your specific needs
Specialised Equipment for Safe Ash Tree Management
With our fleet of specialised forestry and mechanised arboriculture machinery, including MEWPs, long reach excavators and harvesters, we are particularly well equipped for commercial ash dieback projects and large-scale ash tree removal operations. Our extensive experience means we excel at safely and efficiently managing diseased ash trees in both urban and rural environments.
Our Comprehensive Ash Dieback Services Include:
- Expert Ash Health Assessments: Rigorous assessment of ash trees using the established Health Class system, including vital checks for basal lesions that can destabilise trees
- Tailored Ash Dieback Management Plans: Custom strategies for managing affected trees that balance safety considerations with conservation objectives and budget realities
- Safe Ash Tree Removal: When necessary, our qualified tree surgeons provide complete removal services for severely affected trees, including full site clearance
- Deadwood Management: Careful removal of dead branches to reduce risks while preserving trees where possible
- Crown Reduction: Specialised pruning to minimise risk in declining trees that don’t require complete removal
- Replanting Consultation: Expert advice on appropriate replacement species to develop a resilient treescape for the future
Why Choose Treetops for Ash Dieback Management
We are an approved contractor working across the North West, Yorkshire and North Wales. At Treetops we take great pride in providing reliable, quality and safe tree cutting, de-vegetation and forestry solutions regardless of location, size or scope of project.
Our team includes professionals with specialised qualifications in tree inspection and arboricultural expertise, ensuring we can address the diverse challenges ash dieback presents. We balance safety concerns with conservation objectives, avoiding unnecessary tree removal while ensuring appropriate risk management.
Take a look at our work and team in action!
“Onward Homes has been using TreeTops for several years. Their service and ability to react quickly to the needs of the business are excellent and they often exceed our expectations. Their work demonstrates an in depth understanding of BS3998, where we are safe in the knowledge that our trees are being managed to industry standard. Treetops are very easy to work with, friendly and will always do what they can to meet our needs. They are efficient, polite, tidy, and actively look for opportunities to add value to their service. It is refreshing to work with such a reliable and professional contractor who hold high standards for tree work, Health and Safety and contract management. It is essential for us as a business to know that we have a strong and high performing supplier for tree works behind us who clearly understand the concept of managing trees for the future”.
George Peters, Arboricultural Manager – Onward Homes
Take Proactive Action Against Ash Dieback
If you have ash trees on your property showing signs of ash dieback disease, don’t wait until they pose a serious safety risk. Early assessment and proactive management are key to navigating this disease successfully.
Contact Treetops today to arrange a professional ash tree survey and discuss how our ash dieback specialists can help you manage this challenging situation.
FAQs: Ash Dieback – Advice and Services from Treetops
What is ash dieback?
Ash dieback is a fungal disease caused by Hymenoscyphus fraxineus that attacks the tree’s vascular system. This weakens the tree, leading to leaf loss, dead branches, and structural instability. Over time, affected trees become brittle and more prone to collapse. It’s now one of the biggest threats to the UK’s ash population. You can also view Government guidance.
Can you burn wood from trees with ash dieback?
Yes, wood from infected trees can be burned safely. The disease does not affect the burning properties of the timber. However, to prevent spreading spores, it’s important to follow local regulations on felling and transportation, or speak to us for advice.
What should I do if I have ash trees on my land?
The first step is to assess their condition. Some ash trees show resistance to the disease and don’t need immediate action, while others pose a risk and may require intervention. We provide professional tree surveys to determine the best approach – whether that’s ongoing monitoring, selective pruning, or removal where necessary.
What does ash dieback look like?
Early symptoms include dark lesions on branches and stems, wilting leaves that turn black, and crown dieback. In more advanced cases, the bark may crack, and new shoots may appear lower down the trunk. If you’re unsure, a professional inspection can confirm whether a tree is affected.
How does ash dieback spread?
The disease spreads through tiny airborne spores released from fallen leaves. These spores can travel for miles, infecting new trees. The fungus thrives in cool, damp conditions and spreads particularly fast in woodland settings. Human activity, such as moving infected logs or using contaminated tools, can also contribute.
How can I tell if a tree has ash dieback?
It’s not always obvious at first. Symptoms tend to appear in late summer when leaves should be healthy and full. If an ash tree has dead branches at the top, blackened leaves, or dark patches on the bark, it’s a strong indicator. Regular monitoring is essential, as some trees deteriorate quickly while others remain stable for years.
Does ash dieback affect other trees?
No, this disease only affects ash trees. Other species are not vulnerable to Hymenoscyphus fraxineus, but trees weakened by environmental stress can be susceptible to different infections and pests.
Where did ash dieback come from?
The disease originated in Asia, where local ash species have developed resistance over time. It was first detected in Europe in the 1990s and arrived in the UK in 2012, although evidence suggests it may have been present even earlier. With no natural resistance in British ash trees, the disease has spread rapidly.
What causes ash dieback?
Ash dieback is caused by fungal spores that infect trees through their leaves. The fungus then spreads through the tree’s system, blocking its ability to transport water and nutrients. Over time, this leads to branch dieback and, in many cases, complete failure of the tree.
What services do you provide to manage ash dieback?
We offer a full range of ash dieback management services, tailored to different environments, from housing estates and schools to woodlands and commercial sites. Our services include:
- Tree surveys and reports – Assessing tree health, identifying infection, and providing risk assessments.
- Management plans – Developing tailored strategies for landowners, councils, and businesses.
- Tree pruning and maintenance – Removing infected branches to improve safety and tree health.
- Felling and clearance – Safely removing trees that are structurally compromised or pose a risk.
- Ongoing monitoring – Regular checks to track disease progression and adjust management strategies.
If you’re concerned about ash dieback and need professional advice, get in touch to discuss the best approach for your trees.
