Written Statement - Chalara Disease of Ash

Ash is the third most widespread broadleaved tree in Great Britain. There are around 15,000 hectares of ash woodland in Wales, representing around 5% of our woodland area and it is a well known tree in gardens, parks and hedgerows across the country. It is important for its timber, firewood, wildlife, bio-diversity and landscape benefits.

Since the early 1990s Chalara fraxinea disease of ash has spread to most parts of northern Europe where it has caused death of young trees and the dieback of mature ash trees in many countries. It has now been found to be present in the UK and poses a serious threat to this important tree species.

The disease was first intercepted at a nursery in southern England in February 2012. Since then, it has been found to be in young ash trees plants in several plant nurseries and is now known to be in over 100 plant nursery and woodland sites, mainly in eastern England. It is thought to have reached the UK through the importation of infected plants and via its spores being blown into eastern England from Europe.

The Welsh Government is taking the threat of this disease very seriously and officials are working closely with our partners in the Forestry Commission (FC), Defra, the Food and Environment Research Agency (FERA) and the devolved administrations in Scotland and Northern Ireland on an UK wide response to the threat it poses. Tree diseases do not respect country boundaries and we need to provide a consistent approach to this threat in order to meet the demands of stakeholders and the public and to ensure that our response is co-ordinated and based on the most up to date scientific evidence.

As soon as there were indications that the disease may be present in the wider environment this partnership instigated a GB wide survey to assess the position.

Through the weekend commencing on 2nd November and the following Monday, 344 FC Wales staff were involved in the survey and visited a total of 970 sites to look for signs of the disease. The survey was based on visiting 4 sites within 259 ten kilometre grid squares across Wales and resulted in samples from 10 locations being sent to FERA for analysis. Nine of the samples were found to have no indications of the disease being present, however one sample was found to be positive.  

This sample was taken from privately owned, broad-leaved woodland containing 25% ash in Carmarthenshire. The site was planted in 2009 so the trees are still quite small and a containment notice has been applied to the site which means that no plant material can be moved from the site. This approach is the correct one as we now have a seasonal window where the disease is not sporulating and any infected leaves have fallen leaving no risk of it spreading from the site.  

As the disease appears to have two main vectors enabling it to spread, through infected plants and being windborne further work is focussed on tracing the location of sites where imported ash trees have been planted in order to identify any further infected sites. As it is unlikely that the disease at the infected site in Wales was caused by wind-blown spores the focus of this further survey is on the trace back of planting sites which we expect to complete within the next week.  

In addition to this rapid action on the ground Welsh Government and Forestry Commission Wales officials attended a summit meeting on tree health in London last week to assist in the development of future plans for managing the disease in the UK. The key objectives of this plan will be to:

• Reduce the rate of spread of the disease;
• Develop resistance to the disease in the native UK ash tree population;
• Encourage citizen, landowner and industry engagement and action in tackling the problem; and build resilience in the UK woodland associated industries.  

More details of how this approach will be implemented will be issued over the coming weeks but in the short term legislation has been introduced to stop the importation of ash transplants as they are considered to be a major source of spreading the infection in the wild. Until now, ash trees have not been of concern in terms of the pests and diseases they might carry.  The trade in ash trees between EU Member States was not subject to plant health controls.

It is known that the short lived spores that are produced from ash leaves are a main cause of infection so initial control measures have been focussed on preventing the movement of ash plants whilst a longer term approach is agreed. In order to restrict the spread from fallen leaves our advice is that people should clean their shoes carefully after walking in woodland to lessen the risk of transferring infected leaves to new locations.  

Although research has demonstrated that Chalara can be transported in the sapwood and heartwood of ash it is not established that new infections can then arise from this material and we are therefore not currently recommending the large scale felling of mature trees nor restrictions on the transport of ash timber.

As the disease largely spreads in summer (typically during July and August), there is now time in which to obtain best scientific advice on the appropriate action to take, including how best to deal with infected sites. However, now that we have the first case of the disease in Wales, it is possible that more infected sites could be discovered.

There is no need to restrict public access to woodlands but people are asked to behave responsibly to ensure that they do not inadvertently carry ash leaves from one woodland area to another. We are therefore asking woodland managers and the public to be vigilant and to report suspected cases.  Chalara poses no risk to human or animal health.

I believe the action we have taken to date is the proportionate response at this stage although this is a rapidly developing situation and I therefore intend to keep the position under review in order to respond quickly to any new information that might require us to adopt a different approach.

Further information, including a ‘pest alert’ factsheet showing pictures of the symptoms of Chalara dieback of ash, is available on the Forestry Commission’s website at www.forestry.gov.uk/ashdieback.