Ash dieback

Ash dieback is a serious disease caused by a fungus called Chalara fraxinea.

The fungus infects 60-90% of the trees in its path, causing leaf loss, bark lesions and crown dieback. Young ash trees are killed very rapidly by the disease. Older trees often resist the disease for longer periods but succumb with prolonged exposure.

• The disease is reported to have killed 90% of ash trees in Denmark.
• Ash trees make up around 30% of England’s woodland cover. It is the third most common tree in Britain after oak and birch - there are 80 million ash trees in the UK.
• The disease was first reported in Britain in February 2012 when it was found in a consignment of infected trees sent from a nursery in the Netherlands to a nursery in Buckinghamshire. It has now been confirmed in several other locations in the wider countryside. Knowledge of ash dieback and its spread in the UK is changing on a daily basis.
• At the end of October 2012 the Government introduced a mandatory ban on imports of ash trees, saplings or seeds and restrictions on movement of trees around the country.

Symptoms of ash dieback disease

• Wilting of leaves in summer
• Black/browning leaf, often spreading down the stem
• Black leaf may not drop as quickly as the usual autumn leaf drop
• Lesions, spots and cankers appear on the bark
• Shrivelled, contorted leaf
Images of infected trees can be found on the Forestry Commission webpage.
Do check these images carefully as ash is naturally prone to a range of cankers and bark lesions – if in doubt report suspected cases.

What to do if you suspect a case

Devon Wildlife Trust urge members, supporters and the general public to report potential sightings of infected trees to the Forestry Commission in the hope that the ecological impacts of this devastating disease can be minimised.
If you have a smartphone, you can download the Ashtag app to submit photos and locations of suspected ash dieback and help map the spread of the disease.
Report suspected cases to Forestry Commission: 0131 314 6414 plant.health@forestry.gsi.gov.uk
Suspected cases of ash dieback occurring on Devon Wildlife Trust nature reserves should also be reported to DWT on 01392 279244 contactus@devonwildlifetrust.org

Ash dieback disease Q&A

How does the disease spread?

The way in which the fungus Chalara fraxinea spreads is not fully understood. Evidence suggests that the majority of infections first occur on ash trees' leaves, indicating that the disease's main form of spread is via wind dispersal. Movement of contaminated soil or plant material is also considered to be another possible pathway.

Is the disease widespread elsewhere?

Ash trees suffering with C. fraxinea infection have been found widely across Europe since trees now believed to have been infected with this newly identified pathogen were reported dying in large numbers in Poland in 1992. These have included forest trees, trees in urban areas such as parks and gardens, and also young trees in nurseries.

Where else has the disease been found?

For the most up to date map of cases please visit the Forestry Commission website

How are affected trees dealt with?

In nursery situations Statutory Plant Health Notices are served by the Forestry Commission on affected owners requiring them to remove and destroy affected plants.

Would The Wildlife Trusts support the large scale removal of ash trees from affected areas?

DWT will work with the Forestry Commission to carry out appropriate works that will help halt the spread of this disease. Whilst doing so we will ensure this is carried out in as sensitive manner as possible - reducing the disturbance to wildlife both in the canopy and woodland floor.

Why are ash trees important?

Ash trees are an important and integral part of our native woodland flora.
Because of their loosely-branched structure and compound leaf form, ash trees allow plenty of light through to the woodland floor. This means that a variety of plants can grow beneath them, including wild garlic, dogs mercury, bluebells, wood crane’s-bill and wood avens. Ash woodlands are often accompanied by a hazel understory.


A rich ground layer means plenty of food for insects and birds such as warblers, flycatchers and redstarts. The ash is a very long-lived tree, so can support many specialist deadwood species like the lesser stag beetle and hole-nesting birds such as owls, woodpeckers and the nuthatch. It also provides roosting space for many species of bat.


Ash bark is alkaline and supports a wide range of epiphytic lichens and bryophytes and also attracts snails. At least 60 of the rarest insect species in Britain have an association with ash – mostly rare beetles and flies. The brown hairstreak butterfly uses ash trees due to the honeydew produced by aphids. Young hairstreaks assemble around ash trees shortly after emerging - and this is also where breeding takes place.


Ash trees hold very significant cultural and historical value (veteran ash trees often mark parish boundaries for example) and have been a special feature of our ecological and visual landscape.