Ash Dieback Surveying & Risk Management
Ash dieback — caused by the fungal pathogen Hymenoscyphus fraxineus, formerly known as Chalara — is the most significant tree disease affecting the United Kingdom's ash population. It is estimated that the disease will eventually kill the majority of the country's 150 million ash trees, and landowners with ash trees on their property have a legal duty of care to survey for the disease, assess the risk posed by affected trees, and respond proportionately to protect public safety.
Urban Tree Management provides ash dieback surveys, risk assessments, and management plans for landowners, local authorities, highways departments, housing associations, and estate managers across Greater Manchester, Lancashire, Cheshire, Merseyside, and nationwide.
What is ash dieback?
Ash dieback is a highly contagious fungal disease that infiltrates the vascular system of ash trees — the network of vessels responsible for transporting water, nutrients, and gases through the tree. Once established, the fungus causes vessel obstruction, branch girdling, crown dieback, and ultimately the death of affected parts. Most infected trees will eventually die either from the disease itself or from secondary infections such as honey fungus, which exploit the tree's compromised and weakened defences.
A small proportion of ash trees appear to show some degree of genetic resistance to the disease, and research into identifying and propagating these resistant individuals is ongoing. However, the overwhelming majority of infected trees will continue to decline and will eventually need to be managed for safety as their structural integrity deteriorates. The rate of decline varies significantly between individual trees, sites, and growing conditions, making regular monitoring an essential part of any ash dieback management strategy.
Surveys should ideally take place between July and September when trees are in full leaf, as the characteristic symptoms of ash dieback — wilting and blackening of leaves, diamond-shaped lesions on stems, and dieback of shoots from the tips — are most clearly visible at this time of year.
Ash Dieback Surveys — Phase 1 and Phase 2
Urban Tree Management carries out ash dieback surveys using a two-phase process that allows the extent and severity of infection across a site to be assessed efficiently and systematically before detailed individual tree assessments are commissioned.
Phase 1 surveys identify the areas of significance across the site, establish the overall levels of infection present, assess the potential clearance impact of removing affected trees, and classify the percentage dieback recorded in each tree or group. The clearance impact assessment is a critical element — removing a single tree in a dense woodland has a very different landscape and ecological consequence to removing a lone ash in an open field, and this distinction must inform the management response.
Phase 2 surveys build on the Phase 1 findings and identify the specific number of stems that need to be removed, produce a phased management plan for the affected trees, and establish the restocking levels required to replace the trees that will be lost. Depending on the size of the site and the level of infection found at Phase 1, Phase 2 data can sometimes be captured during the same visit. Following each survey phase, Urban Tree Management provides a full written report of findings, risk ratings, and management recommendations.
Specialist Ash Dieback Inspections
Some ash dieback assessments require a higher level of inspection than a standard ground-level walkover survey. Where trees are of significant size, amenity value, or are located in high-target areas such as roads, footpaths, or play areas, more detailed investigations may be required to establish the extent of structural deterioration before a management decision is made.
Urban Tree Management can carry out aerial climbing inspections where detailed examination of the upper crown is required, and drone surveys for larger sites and woodland blocks where the extent of infection across the canopy needs to be assessed quickly and accurately from above. Where structural decay is suspected — a common secondary consequence of ash dieback as the tree's defences weaken — Resistograph and sonic tomography testing can be carried out to assess internal condition and inform the most proportionate management recommendation.
All Urban Tree Management inspectors carrying out ash dieback surveys are qualified to QCF Level 6 in Arboriculture — significantly above the Level 3 or Level 4 minimum accepted by many organisations — and are experienced in working with large ash populations across a wide range of site types across the North West and nationally.
Your Legal Responsibilities as a Landowner
As a landowner, if you have ash trees on your property you have a duty of care under the Occupiers' Liability Acts and Health and Safety legislation to ensure they do not pose an unacceptable risk to people or property. Where ash dieback is present, this obligation intensifies as the disease progresses, because structurally compromised trees are significantly more likely to shed branches or fail than healthy trees of the same species and size.
Regular surveys that are documented, acted upon, and reviewed provide the most robust evidence that you are meeting your duty of care proportionately and responsibly. Urban Tree Management produces ash dieback survey reports in a format that supports this audit trail, and we are experienced in advising landowners on the most cost-effective and proportionate management approach for ash populations of all sizes.
Ash Dieback Guidance & Management by experts
Our expert tree consultants will recommend suitable management recommendations following surveys and reports to tackle ash dieback disease