Chalara fraxinea has been wild in Britain for at least two years

After probably the largest-ever rapid survey of Britain’s woodlands, new incidences of Chalara fraxinea, the fungal pathogen that causes ash dieback, have been found in a possible 100 sites across the East and South of England.

After the announcement last week that Chalara fraxinea was in the ‘wild’ in the countryside of East Anglia in England, Forestry Commission staff have undertaken an unprecedented rapid survey. Every 10km square in Britain where ash trees were likely to be found was targeted, selecting four sites in each sampled square. The news is not good, as I predicted (see post).

Chalara fraxinea is present possibly in at least 100 sites, rather than the two where it was originally reported just one week ago. In addition to new confirmed sightings in Kent, possible occurrences extend to the Midlands and even Wales (see Forestry Commission latest map). Note that these are still to be confirmed officially but samples collected from many seem indisputable, even without any scientific analysis.

Today I visited Wayland Wood in south Norfolk as part of a specialist task force convened by Government. We viewed an area where hundreds of coppice stools of ash had succumbed to dieback (see pictures below).

Observing the branches of one more mature tree (with a stem about 30cm dbh) it was clear that this tree had suffered dieback during Summer 2011. This means that the Chalara fraxinea was present in Britain at least one whole year before realised, as indicated from tree physiology alone. When accounting for the life-cycle of Chalara fraxinea, then it is more likely that it was present from Summer 2010 if not even earlier. It is clear that the pathogen arrived in Britain by stealth before anybody recognised it.

Click to enlarge images

A stakeholder meeting is to be held on London today, and more details will emerge about the sightings that I report here. Scientists are working around the clock to confirm observations made in the field, by using sophisticated DNA sampling techniques on collected samples. Further expert groups are being set up and all concerned are working hard to provide practical advice to foresters, arboriculturists, nurseries and others.

Gabriel Hemery


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3 thoughts on “Chalara fraxinea has been wild in Britain for at least two years

  1. If the disease has been here longer than we think, then it must be spreading more slowly than we think, and perhaps our genetically distinct UK trees are more resistant than we think. The growth in sightings is perhaps more a measure of awareness than actual growth in incidence. Could it be possible?

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