Video: Forestry Commission shows how to recognise the symptoms of Chalara ash tree disease
The wild woodlands of East Anglia have become the epicentre of a deadly tree disease outbreak. Rural affairs correspondent CHRIS HILL reports on the efforts being made to define the extent of the infection – and to stop it spreading.
The grim confirmation of a deadly ash tree disease taking root in Norfolk's wild woodlands has thrust the region into the forefront of a national crisis-management effort.
Some conservationists fear Chalara dieback has the capacity to wipe out 80 million trees, and the concerns are great enough to have warranted the attention of the government's Cobra emergency committee.
But at the East Anglian epicentre of the outbreak, a frenzy of forestry activity is under way to confirm the exact extent of the spread – and to work out a battle-plan to contain or destroy it.
The infection, caused by the Chalara fraxinea fungus, was first identified in the UK in February, in recently-planted trees imported from contaminated nurseries in continental Europe, where the disease has already devastated up to 90pc of the species in Denmark.
Since then, it had been restricted to newly-planted imported trees – until last week, when the threat to the wider countryside was exposed by the confirmation of Chalara at four established woodland sites in Norfolk.
Forestry chiefs believe the spread was caused by infected airborne spores carried on the wind from the continent, but the disease can also be carried on boots, tools and plant materials which have been in contact with fungal spores in the leaf litter.
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The number of confirmed cases in Norfolk and Suffolk has now risen to 10, while laboratory samples are also being analysed from symptomatic trees at a further 19 suspected sites. More are being identified by the hour as the initial surveillance effort intensifies.
Geographically, the known spread currently spans an area from Fincham in west Norfolk to Holt in the north, while a coastal site in north Suffolk marks the eastern extremity of the outbreak.
Significant casualties so far include Norfolk Wildlife Trust's (NWT's) Lower Wood at Ashwellthorpe, Holt Country Park, and the Woodland Trust's 90-hectare Pound Farm, near Saxmundham in Suffolk.
But the Foresty Commission's exact action plan will not be known until a detailed diagnosis is complete.
The Forestry Commission's entire field staff, aided by other agencies including Natural England and the Environment Agency, is systematically mapping East Anglia into 10km grid squares, and carrying out four pro-active random checks in each square.
This process, duplicated throughout the country, is due to be completed on Tuesday so the data can be analysed.
Steve Scott, area director for the Forestry Commission in the east of England, said: 'I have been working in forestry for 30 years and the nearest I have got to this level of activity was the 1987 storm,' he said. 'That is the only other time we have had to down tools and react rapidly to an emerging threat on this scale. It is a full-scale mobilisation.
'First, we have banned all movements of ash plants and other materials. Second is a sensible level of biosecurity, particularly for staff working in these woods, who will be expected to clean their equipment and disinfect their boots.
'Clearly, there is no risk to human health and there is nothing stopping people visiting the countryside and visiting their local woodlands. If they are walking routinely at one set of woods then there is no problem. The risk of spreading the disease is if they walk from one woodland to another without cleaning their boots.'
Mr Scott said the impact of the outbreak could not be predicted until all the data had been analysed.
'We will see a structural change to our woodland,' he said. 'If all the ashes were to die it would have a huge impact on these woods. But that's a big 'if'.
'In an ideal world we will be able to contain it within East Anglia. The working hypothesis is that the spores blew over on the wind from Europe, so a lot of it depends on the weather.
'There are also several unknowns. We don't know what the resistance of our native ash is. The Danish ash suffered very badly, but tests have shown it had a very low genetic diversity. Ours might have a high genetic diversity, but we don't know that yet.
'The worst-case scenario is that the native ash tree population is hit very hard. But I would hope that would simply give us a generational gap of ash rather than losing the species forever.'
Chalara fungal spores attack the leaves first, before the disease then moves up the leaf stems and into the branches, eventually blocking the water-carrying 'xylem' vessels, starving them of moisture and killing the tree.
These are the key symptoms to look out for:
1- Brown or blackened leaves, clearly dead but still hanging on the branch.
2- Discolouration of stems and branches, from the normal healthy olive green to a purplish colour.
3- Distinctive diamond-shaped lesions around the leaf stem, where the infection has spread into the branch.
If you spot a suspected case of Chalara in any woodland, hedgerow or garden, it should be reported to the Forest Research Tree Health Diagnostic and Advisory Service on 01420 23000 or via email firstname.lastname@example.org.
-For more on this story, see today's EDP.