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Published 12th Nov 2012

Horticulture Week's update on Chalara Ash Dieback

Thanks to Horticulture Week for this update about Chalara Ash Dieback:

Defra's new ash dieback plan relies on mobilising the general public and focuses attention on trees which show resistance to the disease.

The Government has issued the plan this week after bringing together scientists, campaigners, charitable groups and woodland agencies to discuss what action should be taken on the disease.

The immediate plan of action was agreed at the Government's emergency committee COBR, which Defra minister Paterson chaired on Friday.

The Government's objectives for tackling Chalara are 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 and associated industries.

Paterson set out an immediate plan of action to meet those objectives, building on the ideas discussed at the Chalara and tree health summit on 7 November. The advice of stakeholders, scientists and other experts at that discussion, agreed at the COBR meeting, was that in the short term:

  • newly-planted diseased trees and diseased trees in nurseries will be traced and destroyed, because once young trees are infected they succumb quickly;
  • mature trees will not currently be removed, because they are valuable to wildlife, take longer to die, and can help us learn more about genetic strains which might be resistant to the disease. Infection does not occur directly from tree to tree;
  • better understanding of the disease will be built through research and surveys, which will look not only for diseased trees, but also for those which show signs of genetic resistance to Chalara fraxinea infection, to help identify genetic strains resistant to the disease;
  • the search for the disease will include trees in towns and cities as well as the countryside, building partnerships with a range of organisations beyond Government;
  • foresters, land managers, environmental groups and the public will be informed about how to identify diseased trees and those likely to be resistant to the disease, and know what to do if they find a diseased tree.

A ban on imports of ash trees and movement of ash trees and plants around the country remains in place. Immediate action is being taken to remove and destroy infected trees found in nurseries or in recently planted sites.

Where infection is found in mature trees, the scientific advice is to leave them where they are, because infection does not spread directly between trees, but only via the leaf litter.

Paterson said:

"The scientific advice is that it won't be possible to eradicate this disease now that we have discovered it in mature trees in Great Britain. However, that does not necessarily mean the end of the British ash. If we can slow its spread and minimise its impact, we will gain time to find those trees with genetic resistance to the disease and to restructure our woodlands to make them more resilient.

"The groups that put such a lot of effort into looking after our wildlife and our countryside will play a major role in minimising the impact of Chalara, and so will the general public, especially when it comes to spotting other areas where the disease has taken hold.

"Our plans have been developed through bringing together Britain's top experts and listening seriously to their advice. We now have a window of opportunity for action because the disease only spreads in the summer."

Over the coming weeks the Government will work with scientific experts and other interested groups to further develop and implement the measures in the plan, and to set a longer-term approach to tackling Chalara. COBR agreed that this approach will also consider:

  • designating protected zones, to free up trade in ash from areas free of the disease through authorising businesses to issue "plant passports";
  • establishing a tree health early warning network to provide advice, screening and initial diagnostics;
  • developing advice on protecting saplings and responding rapidly if the disease is found;
  • developing advice on sustainable management of mature trees on sites affected by Chalara;
  • what additional equipment is needed to diagnose tree disease;
  • improved biosecurity including import controls; and
  • more public engagement in helping to diagnose and tackle disease through "citizen science", including an OPAL (Open Air Laboratories) citizen science project.

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