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Forestry Commission and Fera welcome call for moratorium on ash tree imports in bid to control disease

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Chalara dieback of ash - discolouring of ash wood caused by Chalara fraxinea fungus

The Forestry Commission and the Food & Environment Research Agency (Fera) have welcomed a call by the Horticultural Trades Association (HTA) for a voluntary moratorium on importing ash trees. The moratorium call is a bid to help prevent the destructive disease Chalara dieback of ash becoming established in the UK.

Young ash trees infected by the Chalara fraxinea fungus, which causes the disease, have been found this year in six nurseries and four planting sites in England and Scotland. The Forestry Commission and Fera are taking emergency measures to prevent the disease spreading into ash trees in the wider environment.

Fera has also published a Pest Risk Analysis (PRA) drafted by tree health scientists at the Forestry Commission’s Forest Research agency. It has invited views on the analysis by 26 October, with a view to using it to support national legislation to protect the UK from the risk of accidentally importing the disease from continental Europe, where it is widespread.

In a gesture of support, the HTA, which is the trade association for the horticultural industries such as nurseries, garden centres and related activities, this week (Tuesday 18 September) called for a voluntary moratorium by its members on the importation of ash plants. It also called on the plant health authorities to compensate tree owners who are required to destroy diseased plants, and for the Forestry Commission to permit woodland owners who are committed to grant-aided tree-planting schemes which include ash trees to use alternative species without loss of grant.

Dr John Morgan, Head of the Commission’s Plant Health Service, said,

“We welcome this responsible move by the HTA to take a lead for industry by calling for a voluntary moratorium on importing ash plants, and we hope that other sectors will follow suit by adopting their own voluntary moratorium on planting imported ash trees. The season for importing ash trees will begin shortly after the consultation period has ended, and a voluntary moratorium would certainly give us a useful degree of extra protection while further measures are evaluated.”

Dr Morgan said the Commission had considered its response to concerns about already-approved tree-planting schemes in which ash trees were among the species approved for Forestry Commission grant aid. He added,

“We fully understand the concerns of woodland owners who have signed up to plant ash trees in their woodland planting schemes with Forestry Commission grant support or under felling-licence conditions. We will operate a flexible approach for those customers with existing grant or licence agreements.

“However, where those agreements specify ash as a planting species it is essential that owners discuss the situation with their local woodland officer before planting alternatives."

Dr Morgan said there is no provision for compensation for tree owners who were required by Statutory Plant Health Notices served by Fera or the Forestry Commission to destroy infected plants, explaining,

“It has been the position of successive UK Governments that the risks from plant pests and diseases, like other risks, are part of routine business management, and that the risk should therefore be borne by the businesses concerned. As such, compensation from public resources is not appropriate. It is considered that the limited public resources available are better allocated to surveillance, research and management of pests and diseases to help mitigate any impact on businesses associated with the growing and management of trees.”

Dr Morgan encouraged anyone with an interest to study the PRA and contribute their views on an appropriate strategy for managing Chalara dieback in the future. He said all contributions would be considered in any policy decisions which are taken. The PRA is available in the consultations area of the Fera website at , and the deadline for receipt of comments is 26 October.

Further information about Chalara dieback of ash is available from the Forestry Commission’s website at .


  1. The HTA press release calling for the moratorium is available on the HTA website .
  2. Chalara dieback has been found in young ash plants in six nurseries in England, and at four planting sites – a car park in Leicester, a college campus in South Yorkshire, a Forestry Commission Scotland woodland near Kilmacolm, west of Glasgow, and a property in County Durham. All the infected plants are being destroyed, and other plants from the same consignments are being traced forward to their eventual buyers, who are being required to destroy them by burning on site or deep burial.
  3. Monitoring of ash trees in the neighbourhoods of the affected nurseries and planting sites has so far not found any evidence that the disease has spread into ash trees in the wider environment.
  4. Ash trees with disease symptoms now believed to have been caused by C. fraxinea were first reported in Poland in 1992, followed by further reports from many other European countries in subsequent years. The causal agent of this disease is an ascomycete fungus which is characterised by two stages. The asexual stage, C. fraxinea, was first formally 'described' by scientists in 2006 and is not thought to be involved in its reproduction. The sexual stage, Hymenoscyphus pseudoalbidus (H. pseudoalbidus), was only described and confirmed as a new species in 2010. It is the spores from this stage which are thought to be responsible for its reproduction and dispersal.
  5. For a time, scientific evidence indicated that the sexual stage of the fungus was the native European species Hymenoscyphus albidus (H. albidus), and one suggested reason for the outbreak of disease in Europe was that environmental changes might have caused this previously benign organism to become damaging to its host plant, ash.  H. albidus is endemic and widespread throughout continental Europe and the British Isles and therefore, during the period when it was implicated as the pathogen associated with ash dieback, it was not feasible to tackle the disease by means of EU or national regulation. The origin of the new species H. pseudoalbidus, which is now recognised as the sexual stage of the C. fraxinea pathogen, is not yet known.
  6. Because, until now, ash trees have not been of concern in terms of the pests and diseases they might carry, the trade in ash plants between Member States is not subject to plant health controls. Member States may, however, consider a case for legislation to control ash imports from areas where pests and diseases of concern are known to be present. To do this, a Member State must show that a given pest or disease is not established in all or part of its territory. The PRA which Forest Research has drafted is the first step towards making a case for legislation to protect the UK from further imports of ash trees which might introduce Chalara fraxinea.
  7. Common ash (Fraxinus excelsior) is a deciduous species native to much of Europe, including the British Isles. After oak and birch, it is the third most common native broadleaf tree in Great Britain. Ash timber is a dense, strong but flexible, easily worked hardwood which was traditionally used for making tool handles and furniture. Usage has declined in these markets because of the advent of other materials, but the timber is still sought after for flooring and high-end, bespoke uses. It also makes excellent firewood, smoking wood and barbecue charcoal.
  8. Government departments and agencies from across the UK, working with partners in the private and third sectors, have drawn up a Tree Health and Plant Biosecurity Action Plan to ensure that the UK's defences against tree and plant pests and diseases are as robust as possible. Separately, the European Union is reviewing its plant health regime to ensure that it is fit for purpose in the 21st-century global trading environment.

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