Ash Dieback disease

Worcester City Council manages trees on 290 parks and green spaces.

Trees are managed for public safety and the environmental benefits they provide.

Ash trees are found in woodland, urban and rural settings.

As well as being an attractive part of the landscape ash trees provide several other benefits, including providing a habitat for other species.

Ash Dieback is caused by a fungus called Hymenoscyphus fraxineus (formerly known as Chalara fraxinea), which is native to eastern Asia.

The disease is now widespread in Europe, where it has been observed damaging ash trees since the 1990s.

It was first observed in the UK in 2012, although subsequent research found sites where it has been present since at least 2005.

The spread can be caused by spores from the fungus travelling in the wind or via other contamination and infect the foliage of other trees.

Ash Dieback leads to leaf loss, dead branches and can cause lesions at the base of the tree, while also making it more prone to secondary infections.

When trees become infected as the disease advances, the trees can become brittle.

With younger trees, the progress of the disease can be rapid and lead to entire tree death within one or two years.

With older trees, decline may be slower, but the safety of the trees needs to be managed.

pdf You can find an Ash Dieback Disease Guide for tree owners here. (1.44 MB)

How to identify ash dieback

The best time to inspect trees for Ash Dieback is in the summer, when the symptoms are more obvious.

There is a range of signs that can help identify infected trees:

• Dead or dying tops of trees and abnormal clusters of twigs resulting from re-growth.
• Wilting leaves are visible in summer. 
• Lesions or wounds on the branches/stalks and sometimes at the base of trees.
• Dieback of leaves, which become dry and blackened.
• Small white fruiting bodies growing on ash leaf stalks.
• Staining of the wood under the bark.

It can be difficult to identify the symptoms in larger trees.

A Forestry Commission video to help identify Ash Dieback is available here.

What can be done by the public to help prevent and minimise spread

There are simple steps that everybody can do to help reduce the spread of Ash Dieback.

These include:

• Clean your shoes before and after visiting a wooded area or areas where there ash trees are located.
• Think twice about taking plants or leaves from the countryside, as this may result in the spread of Ash Dieback.
• Wash your car or bike wheels to remove mud, plants and leaves.
• Stick to footpaths in areas where you think Ash Dieback might be present, to prevent accidentally the fungus to other areas.
• Gardeners with ash trees can help stop the Ash Dieback spread by collecting fallen ash leaves and burning, burying or deep composting them.

If you spot a tree which you believe has Ash Dieback, you can inform the City Council on the Report It section of our website under the ‘Trees - Dangerous/diseased or fallen tree’ section

What measures the Council is taking to manage the disease

Any trees whether ash or other species are subject to failures.

The Council accesses trees and manages them using a risk-based system.

When trees become hazardous and are a risk to public safety, necessary works are considered and implemented.

Only trees that are high risk are either reduced or removed. Trees that pose a low risk to public safety are retained.

Our findings so far

During 2024-25, the Council has carried out visual surveying of its ash trees to compare up to date assessments against existing data/partial data recorded in 2022-24.

To date, 269 sites have been surveyed, with only 12 remaining. The remaining 12 sites are not anticipated to contain significant numbers of ash trees given their size and site characteristics.

The work to plot and zone prominent ash trees has also been carried out.

Plotting has mapped the location of ash trees whilst zoning will record which tree(s) could present a high risk to public safety.

The information gathered will inform the regularity of future inspections to monitor and manage the progression of ash dieback disease.

Tree data recorded in 2022/23 identified 21 ash trees for removal. A number of these trees have been re-assessed in July and August 2025, when signs of ash dieback could be observed.

Due to their low-risk value, removal is no longer considered necessary. The remainder of these trees will be managed during the next 12 months as part of the tree safety works programme, prioritised according to risk

Of the 269 sites surveyed in 2025 (approximately 95% of sites), a total of 50 individual trees and five groups of ash trees require works. While some work is attributed to Ash Dieback (ADB), most of the recommended interventions are essential Remedial Tree Safety Works.

Tree inspections will continue throughout 2025/26 to complete the remainder of sites.