Concerned about ash dieback disease?

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What is Ash Dieback?

Ash Dieback (Chalara fraxinea) is a fungal pathogen specific to Ash trees (Fraxinus excelsior) and has infected and killed a large proportion of ash trees in Europe. 

It was first discovered in the UK in nursery stock in 2009 and has recently been discovered in ash trees growing in woods and plantations especially in Eastern England.  It is thought that the fungus spores have been carried on the wind from Europe to infect trees here.

It is potentially a very serious threat to our Ash trees and it is unlikely that the disease can now be eradicated from Britain.  

Ash Dieback is now firmly established in St Albans City and District and also in other local authority areas in Hertfordshire. Council officers are sharing information between authorities so that a well informed and consistent approach can be made in terms of managing the disease on publicly accessible land and also in the provision of advice to the public.


Predicted decline rates in infected trees

The fungus is extremely aggressive and symptoms become obvious in younger trees within months rather than years. 

Trees cannot recover from infection, but larger trees can survive infection for a considerable time and some might have genetic resistance and not die. (Current experience from Denmark). 

In line with national guidance the District Council will retain ash trees where possible. The likelihood of infection with Chalara, is not a justification to undertake works to fell or prune ash trees. This is for three reasons:  


  • to aid identification of trees which may show genetic resistance or other ability to recover;
  • to  retain as much of the biodiversity that is dependent on ash for as long as possible in as wide a population as possible, to allow other species to bridge the biodiversity gap;
  • to allow more time for other replacement species of trees to grow, to give a more gradual transition of dominant landscape species.


Owners should seek advice from a qualified arborist if it is considered that there may be an immediate risk to public safety. The Trees and Woodlands Section has a list of approved arborists.


More detailed information on Chalara can be found on the Forestry Commission website and the following link to the Countryside Management Service.

Infected Ash
Date of last review: 09 May 2017