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Survey reveals ash disease in six more counties

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Ash dieback disease (Chalara fraxinea) - developing lesions associated with leaf scars

Issued jointly with Defra

Further cases of the tree disease Chalara dieback of ash have been confirmed in woodland in Sussex, Berkshire, Bedfordshire, Lincolnshire, Yorkshire and Northumberland after an unprecedented survey of Britain’s established woodlands.

The disease has now been confirmed in 115 sites: 15 nurseries, 39 planting sites and 61 locations in the wider environment (forests and woodland).

These instances of Chalara dieback are being discovered as a result of a rapid and intensive surveying operation carried out over the course of last weekend and the beginning of this week.

The discovery of the disease in these counties does not mean the disease is spreading rapidly. It is likely that the disease has been present in these areas for a number of years, originally caused by spores blown in from mainland Europe.

Plant health experts, in conjunction with volunteers from groups such as the National Trust and Woodland Trust, have been examining about 2500 blocks of land, each 10 kilometres square, where mature ash trees are known to be present in order to seek out traces of the disease in established trees.

At the same time, plant health experts have been undertaking an urgent check of 220 prioritised sites which have received saplings from nurseries where Chalara was found to be present.  Taken together, these surveys will give a much better picture of the extent of Chalara throughout the country, but will not have identified all cases of the disease; it is likely that more cases will emerge as checks continue.

Martin Ward, Chief Plant Health Officer, said:

“We have thrown all possible resources at this surveying exercise, which has given us a much clearer picture of the distribution of the disease to inform our evidence base. 

“The science on Chalara is still emerging, and the more evidence we have, the greater our knowledge and understanding of this disease and the better we are able to tackle it.

“I’d like to thank everyone involved in this survey.  Together we’ve surveyed more than 92 per cent of England and all of Scotland and Wales so far – a tremendous achievement, especially in such a short time, which shows our combined determination to deal with Chalara.”

Common ash (Fraxinus exclesior) is a species of broadleaf tree native to Great Britain, providing about five per cent of all woodland cover. Chalara dieback is a serious disease that has affected a high proportion of ash trees in northern Europe, and it was first confirmed as present in the UK in nursery stock in March.

A map showing all locations with confirmed cases of Chalara, and further information, is available at


  • Chalara dieback is caused by the Chalara fraxinea fungus.

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