Ash Dieback: A growing problem

Chalara dieback of ash (Chalara fraxinea)
Chalara dieback of ash (Chalara fraxinea)

Ash trees suffering with C. fraxinea infection has been found widely across Europe with 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 and variety of locations in Great Britain, including a car park, newly planted woodland and a college campus. All these sites had received stocks of young ash plants from nurseries within the past five years.

In October 2012, scientists from The Food and Environment Research Agency (FERA) confirming a small number of cases in East Anglia in ash trees at sites in the wider natural environment, including established woodland, which do not appear to have any association with recently supplied nursery stock. Further similar finds have been confirmed in Kent, Essex and other counties in early November 2012 with movement of the disease expected to spread to Sussex and Hampshire.

Based on Government scientist’s most up-to-date understanding of the disease, the following information is relevant to the management of the disease:

  • the spores are unlikely to survive for more than a few days;
  • spore dispersal on the wind is possible from mainland Europe;
  • trees need a high dose of spores to become infected;
  • the spores are produced from infected dead leaves during the months of June to September;
  • there is a low probability of dispersal on clothing or animals and birds;
  • the disease will attack any species of ash;
  • the disease becomes obvious in trees within months rather than years;
  • wood products would not spread the disease if treated properly;
  • once infected, trees can’t be cured; and
  • not all trees die of the infection, and some are likely to have genetic resistance.

C. fraxinea is being treated as a quarantine pest under national emergency measures and is, now, covered by new legislation: The Plant Health (Forestry) (Amendment) Order 2012 (SI 2012 No. 2707). This legal requirement does not need to be incorporated into your Legal Register unless you are importing ash trees, its wood or seeds.

The Forestry Commission has provided a guide to spotting the disease, which causes leaf loss and crown dieback in affected trees, and usually leads to tree death.

Any cases of the disease should be reported to one of the following organisations:

Forest Research Tree Health Diagnostic and Advisory Service         01420 23000
Forestry Commission Plant Health Service                                           0131 314 6414
Fera Plant Health and Seeds Inspectorate                                             01904 465625

A copy of the guide can be found at:, an update page on the Forestry Commission website at: & the The Plant Health (England) (Amendment) Order 2012 at:

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