Chalara dieback of ash

Common ash will be found in the Glen & our other woods. Most of our moorland ash trees are rowan (not common ash) and have naturally seeded locally but it is possible these could be effected too.

The text below is taken directly from the Forestry Commision website here.

If you want to read more there are some links in the article below or try:- Woodland Trust

Chalara dieback of ash (Chalara fraxinea)


Chalara dieback of ash is a serious disease of ash trees caused by a fungus called Chalara fraxinea (C. fraxinea). The disease causes leaf loss and crown dieback in affected trees, and it can lead to tree death.

Outbreak stage

Ash trees suffering with C. fraxinea infection have  been found widely across Europe since trees now believed to have been infected with this newly identified pathogen were reported dying in large numbers in Poland in 1992. These have included forest trees, trees in urban areas such as parks and gardens, and also young trees in nurseries.

In February 2012 it was found in a consignment of infected trees sent from a nursery in the Netherlands to a nursery in Buckinghamshire, England. Since then it has been found in a number of locations and situations in England and Scotland, including a car park in Leicester; a Forestry Commission Scotland woodland at Knockmountain, near Kilmacolm, west of Glasgow; a college campus in South Yorkshire; and a property in County Durham. All these sites had received stocks of young ash plants from nurseries within the past five years. Further cases have also confirmed in the nursery trade.

In October 2012, Fera scientists confirmed a small number of cases in East Anglia in ash trees which do not appear to have any association with recently supplied nursery stock.

C. fraxinea is being treated as a quarantine pest under national emergency measures, and it is important that suspected cases of the disease are reported.


Outbreak map.

Large size map


Our Forest Research agency has produced a practical pictorial guide to recognising the main symptoms, and an exotic pest alert  which gives more information about the disease.

VIDEO: The Food & Environment Research Agency (Fera) has also produced this video presenting and explaining the main symptoms.

Reporting suspected cases

Please report suspected cases of the disease to one of the following:

Forest Research Tree Health Diagnostic and Advisory Service
T: 01420 23000;

Forestry Commission Plant Health Service
T: 0131 314 6414;

Fera Plant Health and Seeds Inspectorate
T: 01904 465625;


Ash trees were first recorded dying in large numbers from what is now believed to be this newly identified form of ash dieback in Poland in 1992, and it spread rapidly to other European countries. However, it was 2006 before the fungus’s asexual stage, C. fraxinea, was first “described” by scientists, and 2010 before its sexual stage, Hymenoscyphus pseudo-albidus, was described. It is believed to have entered Great Britain on plants for planting imported from nurseries in Continental Europe. However, now that we have found infected older trees in East Anglia with no apparent connection with nursery stock, we are also investigating the possibility that it might have entered Britain by natural means. These include being carried on the wind or on birds coming across the North Sea, or on items such as footwear, clothing or vehicles of people who had been in infected sites in Continental Europe.

VIDEO: Our colleagues in Fera have produced this video outlining the history of the pathogen.

Pest risk assessment consultation

A Pest Risk Assessment (PRA) on C. fraxinea  was published, and a formal consultation on its management held by Fera. To read the PRA and find out about the consultation, visit the plant pests and diseases consultation pages of the Fera website.

A new Plant Health Order 2012 (pdf) prohibiting all import of ash trees and all movement of ash material, was subsequently published on 30 October 2012.

Further information

For further information see our page of Questions and Answers about Chalara dieback of ash.

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