Ash dieback, tree planting and the plant trade

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Update June 2014 The potential ecological impact of Ash Dieback in the UK is the subject of a commissioned report, published by the JNCC (http://jncc.defra.gov.uk/page-6459)

As one response to ash dieback the Future Trees Trust, working with many organisations including Flora locale, published a Strategy, "A future with broadleaved trees in Britain and Ireland 2013 -2020" - click here to download. Flora locale pressed for the use of direct tree seeding as a priority approach.


The Government has issued a Chalara management plan. Flora locale is, however, concerned that a major part of this is to fund the establishment of ash plantations as a means of detecting disease-resistant trees. We believe this is a flawed idea and that a better approach would be to promote natural regeneration if and when ash dieback disease becomes prevalent. Only after a long time will we then have a good idea about the resistance of trees and their progeny.



The story of the introduction of a deadly disease affecting native Ash (Fraxinus excelsior) in Britain started to unravel in Autumn 2012. The disease is the fungal pathogen Chalara fraxinea, a stage in the life-cycle of a cup-fungus, Hymenoscyphus pseudoalbidus, the latter a species formally identified in 2010 (prior to this C. fraxinea had wrongly been assigned to another species of Hymenoscyphus). It is not known how long the disease has been around, but there is a herbarium specimen of H. pseudoalbidus collected in the 1960s from Switzerland. Ash dieback has been spreading throughout parts of Continental Europe since the 1990s, with Latvia being the first affected country. In Britain, surveys have confirmed its presence in recently planted woodlands in England, Wales and Scotland as well as in established woodlands in south and eastern Britain. For the latest news on where it has been found, and to identify the symptoms of ash dieback, see the Forestry Commission's news updates. The Department for Environment, Food and Rural Affairs issues regular updates and its press release of 7 November 2012 outlines the outcome of a summit held with interest groups and experts.

A ban on the import and movement of ash (seeds, plants and trees) came into force on 29 October 2012.  New requirements for statutory notification of imports of Fraxinus (Ash), Castanea (Sweet chestnut), Platanus (Plane) and Quercus (Oak) came into effect in January 2013. According to FERA, the aims of statutory notification are to (a) raise awareness about the threats to these species; (b) provide intelligence about the level of trade; (c) facilitate tracing in the event of problems; (d) allow targeted inspections to be carried out by Fera and the Forestry Commission; and (e) generate evidence in support of further measures, if needed. It will not be the intention to inspect every consignment notified. Initially these requirements apply in England only, where the vast majority of imports take place.

Role of the plant trade

There is no doubt that C. fraxinea's introduction and spread has been due to the global plant trade. Millions of native tree and shrub species have been imported into Britain over the past 30 years, and planted in farm hedges, to replant woods and create new ones. Over a decade ago, members of the Horticultural Trades Association Tree Seed and Nursery Group and Flora locale were jointly lobbying for this to stop.

Plant pathologist and emeritus mycologist at Forest Research, Clive Brasier, writing in the Plantsman in 2005 also made recommendations to clamp down on the plant trade as a means of protecting Britain's biodiversity, gardens and nurseries from the risks he predicted would occur from imported plant diseases. His warning was stark,

"As I see it we have a choice. We can take steps now to more effectively protect our present natural environment and its constituent species. Alternatively, we must resign ourselves to becoming a global melting pot of imported diseases, resulting in further ecological destabilisation and extinctions."

Clive reckons that the disease could have been in Britain for quite a while, and that its effects could have been mistaken for damage from weather or even squirrels.

It has also become apparent that much of the ash imported was grown from British-collected seed, subsequently sent to the Netherlands for propagation, then returned as saplings to British nurseries. This aspect of the plant trade has very likely been instrumental in facilitating the spread of C. fraxinea. As a result of the import of this disease, nurseries are now facing huge costs associated with destroying their ash stock. The Telegraph (24 November) reports, "Owen Paterson, the Environment Secretary, has attacked the “crazy trade” that sees British seeds sent abroad to be grown into trees and then imported back into the country possibly infected with dangerous new diseases like ash dieback." As Flora locale has pointed out since 1997, many other native species planted in Britain are implicated in this trade, with significant quantities of stock grown from non British seed - from hawthorn sourced from Italy, to oak from Hungary and Beech from Czechoslovakia.

Tree planting needs scrutiny

Some consider our native ash is genetically diverse. It does regenerate very easily from seed. The Botanical Society of the British Isles, suggests that its genetic diversity should protect wild populations, although woodland specialist Keith Kirby disputes this (see his response to the BSBI's coverage). In Denmark, up to 90% of trees are considered susceptible,  in Sweden around 50% of the trees have noticeable damage and 25 percent are severely injured; under this scenario countless millions of trees in Britain will also be affected, with devastating consequences on some of our native woods and landscapes. The precise impact of the disease in Britain is, however, impossible to predict.

The hope is that some disease-resistant trees will survive and regenerate naturally. This is another reason why it is madness to import what may be less genetically and maladapted ash (or indeed any other native species) ecotypes of Continental European origin. The suggestion to breed "disease-resistant" varieties and for these selectively-bred, genetically uniform, varieties to be widely introduced also needs scrutiny. But it has taken this major catastrophe to act as a wake-up call - there now seems to be a consensus among forestry, trade and environmental groups that we must develop a more sustainable approach to the growing and sourcing of native trees and shrubs, with emphasis on the use of British-grown, British-origin stock of local provenance.

The dash to create new woodland and replant existing ones is another aspect of forestry and environmental projects that needs to be subject to proper scrutiny. Most of our native trees will plant themselves, given time. This is especially true of Ash, which will grow practically anywhere where its seeds fall. Are we too impatient? Research and practical projects (that Flora locale has showcased) have also demonstrated that tree seeding is just as effective as tree planting, with the added benefit that some natural selection will take place to weed out individual trees that are unfit to the planted environment. It has been a great disappointment that this approach has not been taken on board by government agencies and those major charities that undertake tree planting and woodland creation. Advice on methods using tree seed are available in Flora locale's practice note on Creating Woodlands Naturally. There are also other practice notes, issued by the Forestry Commission and the now defunct National Urban Forestry Unit - the latter documenting the experimental work in Kent successfully completed by Tom Ladell.

Sourcing planting stock

While it is no longer possible to purchase and plant nursery-grown ash trees, millions of other species of native trees and shrubs will be planted in Britain this winter. Before purchase, check out the nursery. Does it grow its own stock and know the origin of its propagation material (i.e. seed or cuttings)? If not, then buyer beware. Trees and shrubs planted in the countryside should be grown from seed or cuttings collected from wild stock in Britain, and grown by a nursery in Britain. Ideally, use planting stock should be sourced from an appropriate Forestry Commission Seed Zone. For further advice see Flora locale's guidance Go Native! Planting for biodiversity and relevant pages in the Restoration Library.

Wider measures to address the threat from non-native species are urgently needed

The wider issue is that Britain needs a much better early-warning system to protect our environment and economy from the threats associated with non-native invasive species, whether they are microscopic organisms or more obvious plants and animals. Once a risk is identified, then response should be rapid and an action plan put in place - this needs to be pre-emptive action, not a reaction once a threat has arrived (the current situation).

What is the Government saying?

The fact that the Government's COBRA committee has met to consider ash dieback is a first for biodiversity. Flora locale Chairman, Richard Clarke, attended a summit of experts and interest groups convened by Defra Minister Owen Paterson, held on 7 November, and lists some of the collective initial thoughts from the meeting:

In the short term

  • Focus action on newly planted trees.
  • Do not panic or close the countryside
  • Keep surveying disease outbreaks and look for natural resistance.
  • Raise awareness about the importance of leaf litter management (in urban areas)
  • Promote accurate and good information.

In the medium to long term:

  • Research resistant strains
  • Develop a more sustainable approach to the growing and sourcing of plant stock withemphasis on the use of local provenance over imported plant stock; this may be achieved using fiscal measures
  • Improve biosecurity on imports including a biosecurity action plan.

The Minister indicated he was willing to countenance 'radical' solutions. These need to look not just at forestry, but at the major trade pathways that are facilitating the movement of non native invasive species.

Other's commentaries and news on ash dieback

Guest blog on Mark Avery's website, by Peter Marren and Peter's feature It's not neglect, it's our love of planting trees that has caused this disaster (The Independent, 2 November)

Potential consequences of ash dieback in Britain (Dr Keith Kirby, Oxford University)

Ash dieback (a comprehensive collection of curated and analysed summaries of articles on the subjects and issues involved, sponsored by Open Intelligence Ltd)

Information on the Horticultural Trades Association website

Updated news and blog (Leo Hickman) on The Guardian website

Feature by Michael McCarthy (The Independent, 9 November)

What woodland expert Professor Oliver Rackham has to say on ash dieback (Daily Mail, 3 November)

Specifying seed sources for trees (JCLI, 2002)

Compiled by Sue Everett, for Flora locale

Page last modified on Thursday 05 of June, 2014 19:37:03 BST