Alert: new ash tree disease

Uninfected ash leaves

Chalara dieback has recently been discovered in the UK. It is a serious disease of ash trees, Fraxinus excelsior, and is caused by the Chalara fraxinea ascomycete fungus.

It causes wilting, black-brown discolouration and loss of the leaves. Lesions or necrotic spots appear on the bark and enlarge to form perennial cankers. There is wilting of shoots and branches, causing crown dieback. Ultimately it can lead to tree death, with mortality more common in saplings.

This disease is currently spreading across Europe. In the UK it was identified in a shipment of ash trees from the Netherlands to a nursery in Buckinghamshire in February 2012, the trees were destroyed. Then in June it was found in young ash trees planted in a car park in Leicestershire, the origins of this are still under investigation.

So far the disease has not been located in the UK in the wild, but plant nursery and tree-care sectors are being urged to check the health of any recently obtained/planted ash trees.

Suspected cases can be reported to the Forestry Commission or the Food & Environment Research Agency at the following addresses:

The Forestry Commission’s Forest Research agency is preparing a risk assessment which will provide the necessary evidence to inform future action against this disease. There is also a ‘pest alert’ factsheet on the disease available from the Forestry Commission website.

Kay Haw, Assistant Conservation Adviser


About Kay Haw

Assistant Conservation Adviser, Woodland Trust. Nature is my passion, especially woods and trees which are just amazing elements of life. One day (soon) I hope we humans learn to work in harmony with Mother Earth.
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10 Responses to Alert: new ash tree disease

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  2. These diseases just keep on popping up don’t they? This along with the emerald ash borer still being spread around, this is looking like a pretty deadly set of natural poison.

    -Samudaworth Tree Service

  3. DrHG says:

    Reblogged this on The Culture of Enthusiasm and commented:
    My new research project at UCL will research how citizen scientists might contribute data on and respond to trees diseases. Another scenario where citizens might act as an early-warning system. Great post – thanks!

    • Kay Haw says:

      Brilliant thanks! I think citizen science is becoming an increasingly important tool in the conservation/environmental world. I would be very interested in learning more about your research project.

      • DrHG says:

        Hi Kay, It would be good to talk some more. Perhaps we could chat via Skype? Hilary

        • Kay Haw says:

          Hi Hilary, aplogies for not replying sooner. I was assessing the skype possibilities at work. However, we it is not on our system and I cannot get it added. I am happy to chat over the phone if this is good for you? My email address is if you want to contact me. I look forward to speaking to you. Best wishes, Kay

  4. why are we importing ash trees?!

    • Kay Haw says:

      That is a very good question, when we surely have access to a good supply of ash trees and seeds in the UK.

      • Dr John E Jackson says:

        Ash die back is just the latest of a raft of alien tree pests and diseases that have arrived in Britain in the past decade, associated with imported plants for the horticulture and amenity tree trade. The list includes P.ramorum that has now jumped hosts species into European larch and causing widespread declines in plantations, oak processionary moth, Asian longhorn beetle, P.aust. in native juniper, blights and insetcts in Horse chestnut, acute oak dieback in English oaks and now new for 2012 is Chestnut blight too.
        Take a look at the plant health section of the UKs Governments Forestry Commission website for more;
        The UK imports vast quantities of larger and often container-grown trees to satisfy the gardening and amenity tree trade, mainly from continental Europe where the supply is better quality and cheaper. The well-wooded London Olympic site is clothed with “instant” imported trees even though those may be species native to the UK.
        Until recently, official bodies have been both slow and under resourced to respond to both minimising the risks of importing infected stock int the first place and to erradicate them once here, But then a new tree disease in woodland may only get noticed once it is well-established and too late to erradicate or at least contain.
        Plant and tree biosecurity is now coming up the political agenda but most of the 10 or so major threats to tree health that have arrived in the UK since the turn of this milleniun look set to stay and cause major problems in tree populations here, both native and those that are naturalised.

        • Kay Haw says:

          Thank you for your comment. We certainly need greater levels of control to stop the import of these devastating pests and diseases that are ravaging our natural environment. Some work is being undertaken at national and EU levels, but we need it to progress faster and produce a set of effective regulations/advice.

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