Why is Ash Dieback Significant?

Ash dieback is the most significant tree disease to affect the UK since Dutch elm disease, which claimed 30 million British elms. Ash dieback has the potential to affect more than 150 million mature trees across the country with many more millions of saplings and seedlings also being impacted.
  • What causes Ash Dieback?

    Sometimes known as ‘Chalara’, Ash dieback affects Ash and other Fraxinus species of trees and is caused by a fungal pathogen. The fungus, Hymenoscyphus fraxineus (anamorph - Chalara fraxinea), is believed to have originated in Asia and was discovered in Europe during the 1990s since which time it has rapidly spread across the continent. It was first officially recorded in the UK in 2012, although evidence now suggests it arrived here as early as 2004.

    This invasive fungus causes a range of symptoms from foliar leaf spots to branch dieback to the death of ash trees. Once infected, most trees will die. A few ash trees may survive the infection because of genetic factors which give them tolerance to the disease.

    The precise speed of decline of any individual tree is currently impossible to predict and will be influenced by other factors including soil type, soil moisture levels and topography. However, in some cases, the decline from infection to a potentially dangerous state can be rapid, sometimes in a matter of 2-3 years. Where basal lesions are observed, these can develop into a butt or root rot and the affected trees can become unstable and dangerous very quickly.

How Do You Identify Ash Dieback?

Recognising the visual symptoms of ash dieback is essential to assess the current health of the ash tree population – a necessary step to understanding the severity of the disease in an area. To help with identification, there are a variety of online resources available.
  • Examples include:
    •        The Observatree ash dieback identification guide
    •        The Tree Council ash dieback symptoms guide
    •        The Tree Council guide to symptoms in large trees

    The disease can affect ash trees of all shapes and size. While the symptoms are easily visible in young trees, they are often harder to recognise in more mature trees.

    Things to watch out for:
    • a,b, Brown/orange lesions on leaves (a) followed by wilting (b).
    • c, Disease progression: lesions on shoots followed by diamond-shaped lesions on the stems.
    • d,e, Wild, sexual reproduction occurs annually on fallen leaf rachises in the leaf litter.
    • f, Dieback of the crown.
    • (McMullan, M., Rafiqi, M., Kaithakottil, G. et al. The ash dieback invasion of Europe was founded by two genetically divergent individuals. Nat Ecol Evol 2, 1000–1008 (2018) doi:10.1038/s41559-018-0548-9).

What are the Implications for People who own or are Responsible for Ash Trees?

  • 1. Health and safety impacts

    • Potential for death or injury as a result of Ash dieback related accidents

    • Increased health and safety issues as a result of declining Ash trees on roadsides, owned and managed land such as in county parks, housing estates, schools, cycleways, bridle paths and footpaths and trees adjacent to utility infrastructure

  • 2. Economic impacts

    • Increased liabilities in cases of death or injury as a result of ash dieback related incidents

    • Increased direct and indirect costs caused by ash dieback such as engaging contractors to carry out works

    • Costs of replanting needed to retain ecosystem services provided by Ash e.g. flood reduction, shading, carbon storage and habitat for biodiversity

  • 3. Reputational impacts

    • Political and reputational risks as a result of negative press and/or public criticism of Ash dieback management

    • Potential for disruption as a result of ash dieback management e.g. widespread road closures to deal with potentially dangerous trees

  • 4. Environmental impacts

    • Landscape changes with impacts on tourism and recreational opportunities.

    • Losses to ecosystem services such as reductions in air quality, potential for increased flooding, biodiversity losses, increases in noise levels adjacent to roads, losses of visual screens

    • Risks to protected species/sites through alteration of habitat structure, stability and composition e.g. loss of bat breeding/feeding sites

    • Losses of carbon storage and sequestration

    • Loss of biodiversity from the decline or extinction of species which are largely or entirely dependent upon ash

What Do You Need to Do?

Quite simply you need to make a plan. Ash dieback is either already in an area or is likely to be in the next few years with potentially serious practical and financial impacts to many individuals and organisations.Quite simply you need to make a plan. Ash dieback is either already in an area or is likely to be in the next few years with potentially serious practical and financial impacts to many individuals and organisations.
  • Ash dieback will lead to changes to our landscape and tree populations, changes to biodiversity and landscape character, and potentially increase effects such as flooding caused by the way water interacts with the environment. The national cost of removing trees with Ash dieback is difficult to calculate but the scale of health and safety risks caused by Ash dieback alone will require significant investment and mean that it will not be ‘business as usual’ for any organisation managing Ash trees. Tree failures could translate into an increase in the number of people harmed by trees and a potential increase in property claims. Organisations and individuals will need to review and, where necessary, make changes to tree safety management regimes and practices.

    Landowners are being encouraged to take urgent action to assess and ultimately fell their infected Ash trees where necessary. Local Authorities cannot bear the cost of inspecting and felling privately owned diseased ash trees. Given the potential risk to life and the insurance claims they may be exposed to as a result of third-party injuries arising from landowners doing nothing about the safety risks posed by ash dieback, it is critical for landowners to understand their responsibilities.

We Are Here to Help

Thompson Tree Services (Midlands) Ltd have a lot of experience in the identification, management and mitigation of the effects of Ash dieback. We can help you or your organisation to identify Ash dieback in your trees, assess the potential impacts of the disease on your particular situation and help develop and implement action plans for dealing with the effects.
    • We can provide:
    • Surveying Services

      Our consultants are able to survey your tree stock with speed and precision, allowing us to identify the presence of the disease in your Ash trees and the current condition of those trees. We can then undertake a risk assessment that will help to identify unreasonable levels of risk across your tree stock and enable you to make more effective use of your budget to address high risk situations as a matter of priority. Using this information, we can help you to develop prioritised work schedules aimed at reducing your potential liabilities.

    • Specialist Contracting

      Trees infected with Ash dieback can be dangerous and technically challenging to deal with. The disease can render trees unstable and prone to failure of branches and whole trees. It is often not possible to employ standard climbing and dismantling techniques due to the danger to the climber. Thompson Tree Services (Midlands) Ltd have a large range of specialist equipment including Mobile Elevated Work Platforms and Tree Shears to enable the safe removal of affected trees. We have developed and recorded specific methods and risk assessments to ensure that dangerous trees can be safely removed with minimal risk to skilled staff, members of the public and property.

    • Replanting

      The loss of Ash in our region and nationally is likely to impact heavily on landscape quality, wildlife dependent on trees, the volume of storm run-off and the summer temperatures of cities and towns. Its loss will also have an impact on soil composition, specialist lichen communities and broadleaved timber products in woodlands.

Thompson Tree Services (Midlands) Ltd can help you to mitigate the loss of Ash trees in several ways:


Supply and plant

We can supply and plant the right replacement trees in the right place using the 3/2/1/ formula: at least 3 new trees for loss of a large tree, 2 for a medium tree and 1 tree for a small tree. All trees will be sourced and grown (UKSG) in Britain


Aftercare and maintenance

We can provide aftercare and maintenance of newly planted trees


Take better care

We can help you to take better care of existing trees through Plant Health Care Programmes

Call us today and find out why we are highly recommended for tree work in Derby, Chesterfield, Ashbourne, Midlands and Nationwide UK