Can plant passports raise our trees from the ashes?

Britain has already had twice as many tree plagues in this century as it did in the whole of the last

Click to follow
The Independent Online

Universal “plant passports” could be needed to combat imported diseases such as the fungus set to ravage Britain's 80 million ash trees, senior Government scientists said yesterday.

Speaking as the Environment Secretary, Owen Paterson, convened a meeting of the Cobra crisis committee to discuss how to tackle one of the biggest-ever threats to the British countryside, scientists suggested that in future all plants sold in Britain for planting out might have to have a "passport" that would enable their origin to be traced.

The scheme is a potential response to the growing threat to our native trees and plants from foreign pathogens imported into the UK, such as the ash dieback fungus Chalara fraxinea, which has swept across Europe and now arrived in Britain.

It is feared that the disease will be as devastating to Britain's woodlands as Dutch elm disease was in the 1960s and 1970s, and Cobra was assembled yesterday to plan concerted, cross- departmental action to combat it.

However, a briefing by some of Britain's leading plant health researchers in London yesterday made it look increasingly likely that the deadly fungus, first detected in young trees in February and in mature woodland trees last month, is already firmly established here and eradication will be virtually impossible.

The future of the ash, "the lady of the woods" and one of the best loved elements of Britain's landscape, as well as its third most numerous tree, now looks bleak.

Depressing facts highlighted by the briefing included:

* Chalara may be present in mature ash trees in Kent, as well as in East Anglia, where it was first found;

* The disease is likely to have been carried to Britain by fungal spores blown across the Channel from the Continent, as well as by imports of saplings – which was the pathway first identified – and thus further outbreaks can be expected in south-east coastal counties. It may spread naturally at a rate of 30km a year;

* Tackling the disease in mature woodland trees by spraying with fungicide or by burning is likely to be impracticable, and trees cannot be vaccinated; once infected, they cannot be cured.

Most alarming of all yesterday's disclosures by the plant health experts was the massive jump in imported tree pathogens in Britain over the past decade. Dr Joan Webber, head of the Forestry Commission's Tree Health Research Group, said that during the whole 20th century, Britain had five major pest and pathogen outbreaks affecting its trees, two of which were outbreaks of Dutch elm disease.

However, in the past 12 years there have been more than double that number, all of which were "introduced organisms" coming from abroad. The Chalara fungus, first detected in Poland in 1992, was from Japan, she said, where it exists harmlessly alongside Asian ash species. But once it got to Europe, it changed and became harmful to European ash trees – a process that could be replicated with other pathogens. Chalara may have arrived in Europe through imported seeds, she said.

Dr Steve Woodward, of the University of Aberdeen, listed a whole series of new tree diseases in the UK, including pathogens affecting Scots pine and juniper, two of the only three native conifer species found in Britain, as well as others badly affecting the larch, alder and cypress.

It is thought most of these have come in with plant imports. No one knows exactly how many plants are imported into Britain every year, though the total runs into billions. One known figure is more than 5.2 million ash saplings brought in for forestry between 2003 and 2011.

Chalara was first detected on ash saplings imported from the Netherlands.

It is in this context that plant passports, in practice individual labels with tracing details, may be needed in future, said Dr David Slawson, of the Food and Environment Research Agency. "What can we do to prevent future tree pest and disease incursion?" he said. "I think all plants for planting that move within the community could have a plant passport, which at the moment only certain plants have."

Plant health in Britain is governed by the European Union plant health regime, which has not been revised since the 1970s and is widely regarded as unsatisfactory. The legislation is being reviewed, and Britain will suggest that plant passports could be part of a new arrangement.

The immediate action that the Government will take to combat ash dieback is likely to be outlined at a "Tree Summit" being convened by Mr Paterson next Wednesday.

In practice, its strategy will depend on whether or not Chalara can be contained in the south-east corner of England. Containment may be possible, but eradication looks unlikely.

The disease can spread at a rate of 30km per year