What are councils doing about ash dieback?

Ash dieback has swept across the nation since its first detection in the UK in 2012. A fungal infections that can take decades to strangle even the most steadfast ash trees, it is set to wipe out up to 90 per cent of the European ash woodland at a cost of £15 billion. But this was over a decade ago. Is ash dieback a problem, and what are councils doing about it?

What is ash dieback?

Ash dieback (Hymenoscyphus fraxineus), formerly known as Chalara fraxinea, is a fungal disease that infects ash trees and is the most damaging tree disease since Dutch elm in the 1960s and 70s. Originally native to Asia, its native hosts the Manchurian ash (Fraxinus madschurica) and the Chinese ash (Fraxinus chinesis) were not particularly affected, but the European ash (Fraxinus excelsior), which did not evolve with the fungus, has no natural defence against it. As a result, ash trees across Europe have been ravaged by the fungus, which quickly kills younger trees and takes several years to defeat older ones.

The fungus is incredibly infectious, and produces white fruiting bodies which release spores into the surrounding atmosphere. These spores can blow tens of miles away, landing on leaves of other ash trees and penetrating them, allowing the fungus to grow inside the tree, depriving the tree of water and nutrients.

Younger trees are more vulnerable to the disease, while it can take repeated annual infections to kill older trees.

Ash dieback can affect trees both young and old, though younger trees normally die much quicker. An infected tree will show symptoms in the crown first such as dark patches on the leaves during the summer, which then wilt and drop off in summer rather than in autumn. Dark lesions then develop where branches meet the trunk, and branches can fall off as the tree begins to die. There is no known treatment or cure for a tree once it has been infected with ash dieback.

Although initial findings estimate that one to five per cent of ash trees may show some signs of resistance, none have been found to display complete resistance.

The effects of ash dieback

Ash trees grow tall and often in number, forming a large domed canopy with their leaves which makes up a lot of the UK’s valuable canopy cover. Trees have a huge impact on regions as they filter air, store carbon, reduce flooding, and protect soil – even more so when ash trees also provide a protective canopy.

Ash trees are host to a wide number of different species of wildlife, from wild flowers like dog violet and wild garlic that enjoy the sunlight that reaches through the leaves, to animals that use the trees for nesting, like owls and woodpeckers. The bark is often covered with lichens and mosses which are important food for caterpillars.

It is expected that we will lose up to 90 per cent of our ash populations in the UK, which will have devastating impacts on the landscape and biodiversity of our woodlands, as well as significant losses to hedgerows and street trees. This is a significant number as ash trees are the most common broadleaved tree in Britain.

Research from the University of Oxford, Fera Science, Sylva Foundation and the Woodland Trust estimates that ash dieback could cost the UK £15 billion (2019), with half of this £7 billion to be over the next ten years. The predicted cost is so staggering because it represents the cost of clearing up dead and dying trees, as well as lost benefits that these ash trees provide us, such as water and air purification and carbon sequestration.

Dead trees can be become brittle and weak and at risk of falling, which pose a serious threat to the public, which is why it is paramount to monitor trees in parks, near schools, in car parks, and in public green spaces.

What are councils doing about ash dieback?

A 2022 survey by the Association for Public Service Excellence (APSE) found that 52 per cent of local authorities had in place an ash dieback plan, though seeing as ash dieback isn’t going anywhere and will only worsen as older trees gradually die off, it is expected and recommended that each local authority formulate one based on their own needs and numbers of infected trees.

Local authorities are carrying out tree surveys, paying attention to trees most at risk of falling or injuring people, such as those in parks, in schools, or on roadsides. Highway surveys, detailed databases, and flagging trees that pose a risk are key for councils to stay informed with the changing situation and to ensure dangerous trees are felled before they can pose a problem. Councils have a legal responsibility to ensure that trees on public land are maintained to a reasonably safe condition.

In Carthmenshire County Council, trees showing at least 50 per cent of ash dieback disease are being tagged with orange ribbon or marked with orange spray paint for follow up action.

Worcester City Council, for example, has implemented an Ash Dieback Strategy which has led to 25 per cent of all trees in its parks and green spaces to have been visually inspected thus far, with seven trees identified as needing remedial work.

Councils should hold off from felling trees unless they propose a direct threat to the public such as from falling branches; dead wood is also a vital habitat for wildlife. Where trees are felled, it is important that a diverse species mix of trees are planted to offset this. Exeter City Council announced in October their plans to plant 65 trees during the winter months, with trees to be planted in 11 of the city’s 13 wards to replace trees that have died or been felled as a result of ash dieback.

It is recommended that individuals clean their shoes before and after visiting a woodland, as well as washing car or bike wheels to remove mud or plant matter to slow the spread of infection. The public are advised not to take any cuttings or plant material from the countryside.

The APSE survey also revealed that 86 per cent of respondents did not feel that the government is providing sufficient funding to local authorities to address this problem. Should councils wish to be able to mitigate the disease effectively and safely, critical action needs to be taken as soon as possible to allow councils to carrying out effective management without widescale felling and disposal.