BLOG: North Wales Ash Dieback Toolkit Event. Bangor University

Posted on September 19, 2019 by

In July Jon Burke from Moelyci woodland group attended an event in Bangor hosted by the Tree Council to discuss Ash Die Back and the concern that has been raised by across all sectors in Wales around the environmental and economic impacts this devastating disease is likely to cause. This is his personal view of the event raising some interesting questions about the wider philosophical loss of a tree species not only the initial economic and environmental ones, and,  if there is a deeper  message in the spread of the disease about how we treat our UK trees.



There is real appetite to understand and unpack the complexities and impacts of Ash dieback. The event was oversubscribed and had a good cross section from woodland and tree institutions, contractors, local government, Natural Resources Wales and community groups.  The speakers included representatives from Forest Research Wales, Sara Lon, the CEO of the Tree Council, Welsh Government Forest Policy and local council representatives.

Take Home Message / What are we doing ?

All landowners and land stewards will need an action plan for Ash Die Back. This will help deal with risks, costs, liabilities, insurance, access issues, financial obligations and reputation management.

Action Plan = Awareness + Planning + Action + Recovery


There is a toolkit document to help produced by the Tree Council.

Lots of local councils in the UK have an action plan and are sharing their work. Leicester council (one of the first) also promote making an ‘at risk catalogue’ with ash die back in the red category. This means that the task does not get forgotten or lost in the ‘to do’s’.

Llais y Goedwig has a voice on the new Welsh Government, Wales Ash Dieback Core Group both to express the opinions of community woodlands as well as help disseminate information and developments.  There will be more news on this towards the end of 2019.

‘Awful Opportunity’ – although a national ecological disaster, Ash dieback is also a chance to openly discuss the value that tree species have to us beyond the economic costs and benefits of activity (or lack of it) on, and for, the generations to come.

Enabling vertical conversations within and between organisations is necessary to be effective on the scale demanded for such issues.

The tree council have enabled tree wardens to work with a growing number of tree volunteers to do ‘small steps’ projects on trees. This focussed approach would seem to attract quite a few professionals in the tree world who bring a wealth of knowledge and experience to the projects. One such project is enabling volunteers to use a tablet to gather data about trees using mapping software called QField.

Pathogen Overview

Ash dieback fungus (Hymenoscyphus Fraxineus)

Ash dieback is caused by a fungus that spread from the east across Europe, arriving officially 2012 in Suffolk and Norfolk (evidence on dead wood goes back to 2005).

It is now endemic.

It was first observed on Ash saplings on a newly planted landscaped area of a park and ride scheme. The trees had been imported from Holland. The trees were destroyed but the occurrences escalated to the current estimate of 80% of Wales having locally infected Ash trees. This is high because Wales has a wet and damp climate providing ideal conditions. The fungus lives on the leaves for up to 5 years after defoliation, sporulating millions of spores each year. So it is the leaf litter that carries the highest levels of contagion. The spores are airborne and this is also a probable method of the pathogens entry into the UK as well as imports.

Ash trees in the Far East have evolved to shed their leaves when infected and are tolerant but our UK Ash has not developed any defences against the fungus. Each growing season the disease travels down the rachis (spine) of the leaf, then down the branches and causes diamond shaped lesions or patterns where the branch meets the trunk. This is quite obvious on the small sapling trees but hardly visible on larger more mature trees. The lesion can quickly girdle or kill the living bark, all the way around the sapling trees so they can die quickly (1 – 3 years). Larger more mature trees have the resources to produce new growth and survive longer, maybe up to 7 years. It is a foliar (leaf) disease and re infects the host each year.

There is also a hope that some genetic variants of UK Ash will be able to tolerate the pathogen. It is identifying these Hardy survivors that is the main approach to dealing with the potential irradiation of the native Ash species from our land.

An alternative promoted by some companies is genetic modification to induce tolerance in ash trees. This quick hit, man-made approach was seen to have too many unknown unknowns for most people at the conference.


Ash is 2nd most common tree in Wales (National Forest Inventory Wales). If you are a green woodworker then the Ash is your go to tree. It sustainably provides us with home grown hardwood that is flexible, strong, reasonably durable and beautiful. Lots of our tool handles, stools, benches and even boats will have to be make use of other native trees such as oak or sycamore.

In mythology the Ash has been known as the world tree or Tree of Life going back over 1000 years. And now it has a disease that could potentially wipe it out. Some say it will be replaced with whatever fits the ecological niche and the 1098 associated species that interconnect with it will adapt as well.

For those who have memory of abundant Elm trees, they will know the feelings of loss from the lack of something in the landscape as well as from the psyche. These species are not parts on our machines that can be changed and forgot about. They are an integral part of our living landscape and cultural history. What will we tell our grandchildren’s children about when they ask what the world tree was like?


It is illegal to import or move Ash seeds, saplings or trees.

Ash dieback has spread throughout Europe in a relatively short time. It can travel 30 – 40 Km per year but road transportation has greatly extended its spread.All survey square’s on Forest Research’ Wales Ash Dieback map are recognised to have Ash dieback.

When mapped, it is often the major roads that hold the highest incidents of diseased ash showing the links between transportation and disease expansion.

Trees next to roads and public pathways have a safety priority. Research is showing that standing Ash which has dieback reducing the canopy by more than two thirds, can increase the wind blow chance by 30%. The dieback does not just leave brittle branches, the roots also dieback to substantially reduce the stability of the tree.

There is an increased risk of tree work on advanced dieback trees with the dead branches being more brittle. This increases the ‘shattering’ effect of brash when felled in one go because of brittle dead wood which means more clear up time and cost.

It is not just Ash dieback that can kill the tree, it is often a culmination of other stress factors such as other common fungal pathogens like the widespread honey fungus (Armillaria) which cause a cumulative fatality.

The ‘tree alert’ app is widely used for people to report sightings of tree diseases.

Forest Research estimates that 2 – 10 % of Ash could be disease tolerant. It is these individuals we need to find and support. The resilient strain of Ash that have been identified in experimental plots is called ‘BETTY’.

The pathogen shows susceptibility to fungicide and removal of leaf litter. There is no research into the benefits of sheep grazing of the leaf litter. The fungus on the leaf litter can be destroyed by composting if done well. It will continue to live and spread in poor composting (low temp). Burning is a definite way to destroy the pathogen on leaf litter.


This disease is going to increase costs for most landowners or stewards.

An imperfect estimate of £15 billion pounds UK potential cost but this does not include health and wellbeing impacts. It will take approximately 60 years to regain the benefits ash loss if we start replacement planting now.

We also do not know where all the trees are or exactly how many we have. They have not all been surveyed or even mapped. To make get an accurate economic picture we need to know what is where and how badly affected by the pathogen.

Plantations are easier to count but woodlands without management plans and trees in non-woodland areas add or subtract millions to the estimates. Most landowners do not know how many Ash trees they have, at what age, where they are located and to what extent the fungus has taken.

Some local councils have created an Ash die back action plan involving surveying extent of the population, its location and development of the fungal disease. But the costs involved in dealing effectively with the potential risks are not covered in anyone’s tree management budget. This is expounded because the costs involved increase the longer the problem is incurred and the window to deal with the problem reduces increasing pressure for action.

Is economic rationality the best method for decisions about trees? Are trees an asset or a liability. Average lifetime cost of a street tree is £2-3K, yet the benefits are hard to price – carbon sequestration, pollution reduction, heat index reduction, flood prevention, health & wellbeing etc…


Rough estimates of Ash trees in the UK (millions)

17-34 m         Small woods and plantations

5.4-9.7m         Hedges

4 m                  Highways Agency

3.6 – 4m         Towns & Cities

1.2-2.3m         Wider agriculture

27 – 60m       Non-wooded areas

[400 million seedlings and saplings]


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