Professionals in the plant nursery and tree-care sectors are being urged to check on the health of recently planted ash trees, and notify any symptoms of Chalara dieback of ash, a destructive disease only recently found in Britain for the first time.
The appeal follows the second discovery in England this year of ash dieback disease caused by the fungus Chalara fraxinea (C. fraxinea), which has the potential to kill millions of ash trees if it spreads into the natural environment. It has already caused widespread losses of ash trees in continental Europe, including the deaths of an estimated 60 to 90 per cent of Denmark’s ash trees.
The disease was discovered in June in young ash trees recently planted at a Leicestershire car park. This followed an interception in February by the Food & Environment Research Agency (Fera) of diseased ash plants in a shipment from a supplier in the Netherlands to a nursery in Buckinghamshire.
Dr John Morgan, Head of the Forestry Commission’s Plant Health Service, said,
“This is a very worrying development. C. fraxinea is an aggressive pathogen which has the potential to inflict considerable damage on Britain’s ash trees. Ash is a much-loved native species which is important for its timber, woodfuel, wildlife, biodiversity and landscape benefits, and it is one of our most numerous tree species.
“We have agreed with Fera to adopt a precautionary approach and to inspect ash plants in nurseries and destroy any material with this disease in order to prevent it from spreading into the natural environment. Because we now know that C. fraxinea is present in the nursery trade we expect there will be more interceptions in the near future.
“We are urging anyone who has received ash trees in the past five years to check their trees’ health and to report any suspicious symptoms to us without delay. This applies principally to professionals working in the nursery and tree sectors, but it is also relevant to anyone who looks after land with ash trees on it."
The disease mostly affects common ash (Fraxinus excelsior), including its ‘Pendula’ ornamental variety, but Fraxinus angustifolia can also be infected. Deaths in continental Europe have been particularly common in very young trees, known as saplings.
Further information, including a “pest alert” factsheet of information about, and pictures of, Chalara dieback of ash symptoms, is available on the Forestry Commission’s website at www.forestry.gov.uk/ashdieback.
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.
NOTES TO EDITOR:
- The ash plants which remained in the Buckinghamshire nursery have been destroyed, and Fera has so far traced almost all of the plants from the shipment which had already been sold on to retail buyers, and ordered their destruction. The origins of the disease in Leicestershire are still being investigated.
- The causal agent of this disease has been only recently been confirmed as an ascomycete fungus. The asexual stage, C. fraxinea, was first formally ‘described’ by scientists in 2006, and the sexual stage, Hymenoscyphus pseudo-albidus, was described in 2010. Trees with symptoms now believed to have been caused by this organism were first reported in Poland in 1992, followed by further reports from many other European countries in subsequent years.
- C. fraxinea is not a “regulated” plant disease in European Union plant health law, which means that the trade in ash plants between Member States is not subject to inspection. Member States may, however, make a case for legislation to control ash imports from areas where the disease is known to be present. In order to do this a Member State must demonstrate that it is still free of it. The pest risk assessment which Forest Research is drafting is the first step towards getting such a case for national legislation.
- Common ash is a deciduous species native to much of Europe, including the British Isles. It is the third most populous native tree in Great Britain after oak and birch.
- Ash timber is a dense, strong but flexible, easily worked hardwood which was traditionally and commonly used for making tool handles and furniture. Usage has declined in these markets due to the advent of other materials, but the good-quality timber is still sought after for flooring and high-end bespoke uses. It also makes excellent firewood, smoking wood and barbecue charcoal.
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