Ash dieback disease

Ash tree showing signs of Ash dieback at Lower Woods, Norfolk (credit Steve Collin/Norfolk WT)

‘Ash dieback’ is a serious disease of ash trees, caused by the fungus Chalara fraxinea. It has already devastated ash woodlands in other parts of northern Europe, and has now been found in Britain.

Symptoms of Ash dieback 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 Forestry Commission has produced a pictorial guide highlighting the symptoms.

Origins and spread

Ash tree affected by Ash dieback, SuffolkAsh dieback was first observed in Poland in 1992 and has since spread to 21 European countries. It reached Denmark in 2002 and has since affected 90-95% of Danish ash trees.

The disease was first discovered in Britain in February 2012 when it was found in a consignment of infected trees sent from the Netherlands to a nursery in Buckinghamshire. Until recently, all other known cases were linked to plantations and nurseries but ash dieback has now been discovered in the natural environment.

Cases have been confirmed at Norfolk Wildlife Trust’s Lower Wood nature reserve, an ancient woodland and Site of Special Scientific Interest, and also at Hullback’s Grove, one of Suffolk Wildlife Trust’s nature reserves.

Watch short films below with Brendan Joyce (Chief Executive of Norfolk Wildlife Trust) at Lower Wood nature reserve and Will Cranstoun (Suffolk Wildlife Trust) at Hullback's Grove, part of a natural regeneration project at Arger's Fen and Spouses Vale nature reserve in Suffolk.

 

 

The Wildlife Trusts’ position

We are very concerned about the spread of ash dieback and its impact on the natural environment – the plants and animals that depend upon ash trees and their role in wider ecological networks.

Ash trees make up around 30% of England’s woodland cover and the thousands of miles of hedgerows which knit our landscapes together. They are a key component of ecologically unique woodlands that support rare species and their loss would have a dramatic negative impact on our natural environment. Wildlife in the UK is already under huge pressure and this issue emphasises the need to do all we can to ensure that nature is more resilient in the future.

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. The Wildlife Trusts urged the Government to:

  • act quickly and commit the necessary resources to identify how far the disease has spread
  • give guidance and advice on the best way to stop it from spreading further including biosecurity measures
  • set up an emergency task force to coordinate action to halt the spread of the disease and manage the response to it
  • develop a longer-term strategy for the recovery of landscapes and woodland ecosystems affected by the disease
  • invest more in research on tree and woodland disease resilience and strengthen biosecurity controls

The Wildlife Trusts believe that any measures to combat the spread of the disease should be based on evidence, take into account the impact on the natural environment and ensure the potential resilience of ash to recover from this disease is not undermined.

The Wildlife Trusts' Chair René Olivieri sent a letter to the Secretary of State for the Environment, Owen Paterson, on Saturday 28 October 2012 calling for measures to prevent the spread of disease.

On 6 December 2012 the Government published its interim Chalara Control Plan, which sets out actions to tackle Chalara fraxinea over the next few months.  The Wildlife Trusts broadly welcomed the Plan.  The long-term objective of any response to ash dieback must be to promote genetic resistance to this disease so that ash woodlands can naturally regenerate over time.

On 26 March 2013, the Government published an updated Chalara Management Plan, detailing progress made and further action to be taken.  Read our reaction here.
 

How you can help

All our woods are open for visitors. 

Chalara fraxinea is a fungus, whose spores are spread by infected ash leaves. Whilst there is a low probability of carrying the spores on clothing and footwear, Forestry Commission advice is to avoid moving ash leaves around the countryside. You can help by ensuring your boots are clear of leaves when you arrive at and leave a woodland, nature reserve, park or other countryside site.

The Wildlife Trusts urge members and supporters to report potential sightings of infected trees to the Forestry Commission .  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. 

 

The common ash Fraxinus excelsior

An ash tree in full glory

Description/identification

Leaves
Characteristic delicate ‘leaflets’ rather than single leaves. 3-6 pairs of toothed, lance-shaped leaflets arranged along the leaf stalk, which is tipped with a single terminal leaf.

Bark and twigs
Bark is smooth and grey (thought to have given the tree its name), with fissures developing as the tree ages.

Smooth pale grey twigs with opposite pairs of black buds along their length, with a larger black bud at the tip. A coat of tiny black hairs on the buds makes them look and feel like velvet.

Flowers and seeds
Ash flowers in early April, before the leaves have emerged – purplish-green flowers hang like tassels from the bare twigs and are pollinated by the wind.

Once pollinated, the flowers produce fruits known as keys, which are green at first and ripen brown during autumn. Each key consists of a slightly twisted vane attached to a single seed – the twist gives the seed a spinning motion, keeping it airborne as long as possible (and they are also known as spinners.) Seeds may be blown several hundred metres in autumn gales. Bunches of keys last well into winter and are an important food source for wood mice and birds like the bullfinch.

Age and height
Ash trees grow up to 40m tall and can live up to 400 years – but coppiced trees could live even longer.

The ash is one of the last trees to leaf out in spring and first to shed its leaves in autumn.

Distribution

The ash is native to Britain and most of Europe.

It is the third most common tree in Britain after oak and birch - there are 80 million ash trees in the UK (30% of all British woodland trees)

It grows best in deep, moist, well drained and fertile soil - and so grows best on northern and eastern sides of hills – but can also survive on poor soils where few other trees can grow. It can also tolerate smoke and pollution, making it a good street tree.

Ash woodlands often occur on steep limestone hillsides e.g. Mendips, Pennines, Cumbria.  Upland mixed ash woodlands are one of our richest wildlife habitats.

Ash also grows on on limestone pavement – mostly found on the Yorkshire Dales and on the edge of the Lake District. Here, ash forms open woods with rich layers of shrubs (hazel, blackthorn, bird cherry) and wild flowers (red campion, wood anemone, lily of the valley)

Woodland ecology

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 understorey.

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.

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 (source Chris Panter UEA).

The brown hairstreak butterfly uses ash. Young hairstreaks assemble around ash trees shortly after emerging - and this is also where breeding takes place.  There are important populations at Worcestershire Wildlife Trust's Naunton Court Fields reserve, and The Wildlife Trust of South and West Wales' West Williamston reserve in Pembrokeshire. 

Moths that use ash as a food plant

Ash leaves provide food for the following moths:

Lunar Thorn Selenia lunularia
Privet Hawk-moth Sphinx ligustri
Ash Bud Moth Prays fraxinella
Brick Agrochola circellaris
Mottled Beauty Alcis repandata
Lilac Beauty Apeira syringaria
Twin-spotted Quaker Orthosia munda
Brown Oak Tortrix Archips crataegana
Variegated Golden Tortrix Archips xylosteana
Centre-barred Sallow Atethmia centrago
Tawny Pinion Lithophane semibrunnea
Ash-bark Knot-horn Euzophera pinguis
Ash Pug Eupithecia innotata f. fraxinata
November Moth Epirrita dilutata
Dusky Thorn Ennomos fuscantaria (see right)
Coronet Craniophora ligustri
Privet Twist Clepsis consimilana
Common Slender Caloptilia syringella
Feathered Slender Caloptilia cuculipennella
Brown Ash Ermel Zelleria hepariella