Ash dieback, which is cause by the Chalara fraxinea fungus leads to leaf loss and tree death. Photograph: The Forestry Commission

This is intended to help reduce spread of the disease, to develop resistance to it in the native ash tree population and to build resilience in the UK woodland and associated industries.

Building on the advice of stakeholders, scientists and other experts, including representatives from the Landscape Institute, given at a recent Defra Ash Summit, it has been agreed that, in the short term, newlyplanted diseased trees and diseased trees in nurseries will be traced and destroyed, as young trees, once infected, succumb quickly to the disease. 

Mature trees will not currently be removed, says Defra, as they are valuable to wildlife, take longer to die and can help us learn more about genetic strains that might be resistant to the disease, which is cause by the Chalara fraxinea fungus.

“We knew ash dieback was coming; have known it was here since 2009, ignored it and then conveniently blame imported stock,” says Alan Simson, reader in urban forestry and landscape architecture at Leeds Metropolitan University, and a member of the LI’s Biosecurity sub-committee. “In all honesty, while such stock can and is infected, the fungus in all probability blew in, and looks set to invade Ireland within a few years.”

Britain, he adds, has been importing plant material and timber since the seventh century and in all probability will continue so to do. “There are so many million fungi in the world, and they are on every bean we import from Kenya, every cut flower we bring in from the Netherlands, every Christmas tree we order from Denmark or wherever.”

What turns a benign fungus into a rampant problem is unknown, says Simson. “It may be, in fact probably is, partially to do with climate change, but there may well be other things at work of which we know little.”

Don't panic

Jon Heuch, an independent aboricultural consultant and member of the Forestry Commission’s Biosecurity Programme Board, urges landscape architects who have recently planted ash trees to avoid panicking. There is a risk the trees will succumb to the disease, he adds, but no point in assuming they will. “What proportion of the ash population shows resistance we can only wait and see.”

According to Defra, better understanding of the disease will be built through research and surveys, which will look not only for diseased trees but for those that show signs of genetic resistance to the Chalara fraxinea fungus, 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 the government.

Foresters, land managers, environment groups and the general 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.

The government has already introduced a number of control measures to reduce the speed of spread. A ban on import of ash trees and movement of trees 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 as infection does not spread directly between trees, but only via the leaf litter.

“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,” said Environment Secretary Owen Paterson. “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. 

Over the coming weeks the government plans to 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 fraxinea. It 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”.

It is also looking at 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; and developing advice on sustainable management of mature trees on sites affected by the fungus.

Tightening biosecurity

In the longer term a tightening of biosecurity measures coming partly from government, partly from standards and specifiers, and partly through choice of industry to raise the standard is likely, says Heuch, who is also a member of the Trees and Design Action Group (TDAG), adding that a new Britiish Standard is being developed. We may see a need for much better chain of custody information and even third party certification if purchasers demand it, he adds.

The government admits that it needs to improve biosecurity including import controls, and generate more public engagement in helping diagnose and tackle disease through “citizen science” projects such as the AshTag app which is helping members of the public build up a detailed picture of the spread of ash dieback. 

The Chalera fraxinea fungus will inevitably make a difference to our landscape over the next decade or so, says Simson, but hopefully this time – having learned from the lamentable post-Dutch elm disease lack of activity – we might do something about re-planting sooner. “The current EWGS (English Woodland Grant Scheme) runs out at the end of 2013 – how about having something in place to replace it from 2014?”

He too urges tree owners to hold fire on felling all ash trees, as there will be resistant clones, “and we need to identify these, and propagate from them”. The Danes will have resistant seed commercially available in 15-20 years to start replacing their ash, he adds, “why not us too?”