Ash Dieback Disease (Chalara fraxinea)

Birmingham Trees for Life sometimes gets asked questions about this disease affecting ash trees in Britain. Below you will find some brief information about the disease, and a link to the Forestry Commission’s website to find out more.

This devastating disease affecting all Ash species spread to the UK during 2012 via imported ash plants and by windblown spores.  Hundreds of sites including nurseries and woodlands have already been affected across the country, but especially in eastern coastal counties. Further spread is expected. Some key facts are outlined below:

  • The spores infect the leaves, and as the fungus grows, it blocks the conducting vessels of the tree shoots causing leaf and shoot dieback and discolouration. Young trees usually die quickly but older trees may survive longer, and big ash may not be killed by Chalara but instead may succumb to secondary infections such as honey fungus.
  • The disease is being treated as a quarantine pest and all cases currently must be reported.
  • The disease cannot be eradicated but a control plan should slow its spread and ameliorate its impact. Not all ash will die, as a small percentage of trees will be resistant. In the longer term these trees may be used to breed resistant ash stock for planting. In the meantime there is a ban on all movement of ash plants (not timber) and no new ash trees should be planted.
  • Recent plantings of ash which become infected should be destroyed and replanted with other appropriate species. Where feasible, leaf litter of infected ash in towns and cities should be removed and burned or composted, and dead/dying trees removed. In the countryside and woodlands, selective felling of diseased trees in plantations is recommended, and felling of all ash where more than 50% of ash trees are infected. Infected mature trees should not be felled unless safety is a consideration.
  • Further information on all aspects of the disease, including symptoms and reporting, can be found at
  • A photo guide to identifying affected trees can be downloaded here.
  • A Forestry Commission video on field identification can be found here.

The number and variety of pests and diseases affecting our trees are increasing, and it is more important than ever that we plant new trees to replace those that we will lose to these new threats.  Phytophthora ramorum, which is also known by its common name of ‘sudden oak death’, affects many different species, and hundreds of trees at the Lickey Hills have had to be felled because of it.  You may also have noticed many of the horse chestnuts around our streets are not looking very healthy now too, as they are being affected by a number of problems such as bleeding canker.  We have to act now and every year to continue to replenish the city’s tree stocks for the future.