20.11.12
2% of Danish ash trees immune to dieback fungus
Ash dieback from a fungal disease continues to threaten millions of UK trees, but there is a glimmer of hope in suspected natural immunity for a small percentage of trees.
Ash trees in Denmark started dying because of the fungus Charala Fraxinia about 10 years ago, and by 2005, the disease had spread across the entire country. Today at least 95% of Danish ash trees are either dead or dying from the disease.
But around 2% seem to be naturally resistant to the fungus, which could offer hope for Britain, where it has now been accepted that it will be impossible to eradicate or contain the dieback outbreak.
Scientists are collecting seeds from the few healthy trees to determine whether their apparent immunity is passed on to their offspring.
There are 80 million ash trees in the UK, and the Government has stated its approach will focus on developing resistance to the disease and slowing its spread. At the beginning of November, a Cobra crisis meeting was held to discuss measures to prevent the wipe-out of the ash population.
Professor Erik Kjaer, of the University of Copenhagen, warned: “It is a terrible disease and this is the only kind of optimism I can offer the UK – there seems to be some kind of resistance and maybe it can work. But of course this is based on a very pessimistic view that the vast majority of trees seem to be highly susceptible.”
Earlier this month, environment secretary Owen Paterson stated: “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.
“If we are going to really do something radical on the way we handle our forestry in the future and change the priorities, we are going to have to shift resources within Defra. There will be some things we do in Defra now that we are going to have to stop doing.”
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