Picture courtesy of Forestry Commission - Crown copyright

Ash trees threatened

Ash Chalara threatens tree health

Forestry Commission England has warned of the threat posed by the Chalara fraxinea fungus.

A pictorial guide to identifying ash dieback can be found on their website here.

Crispin Thorn, Area Director for Yorkshire and North East, Forestry Commission England, has written to warn the tree sector of the tree health threat posed by “the highly destructive Chalara dieback of ash trees, caused by the Chalara fraxinea fungus.”

He writes, “Chalara fraxinea (C. fraxinea) has caused widespread damage to ash tree populations in continental Europe, especially common ash (Fraxinus excelsior), including its ‘Pendula’ ornamental variety. Fraxinus angustifolia is also susceptible. Chalara dieback of ash is particularly destructive of young ash plants, killing them within one growing season of symptoms becoming visible. Older trees can survive initial attacks, but tend to succumb eventually after several seasons of infection.

“It was unknown in Great Britain until recently, but the first cases were confirmed in a nursery in Buckinghamshire early in 2012, on ash plants which had been imported from the Netherlands. Since then, more infected plants have been confirmed in nurseries in West and South Yorkshire, Surrey, Cambridgeshire and Lincolnshire, and in plantings of young ash trees at four sites: a car park landscaping project in Leicester, a Forestry Commission Scotland woodland near Kilmacolm, west of Glasgow, a college campus in South Yorkshire, and a property in County Durham. Our colleagues in Fera are working to trace forward plants which had already been sold on to retail customers from the infected nursery consignments.”

The Forestry Commission are “treating C. fraxinea as a ‘quarantine’ plant pathogen, which means that (they) may use emergency powers to contain or eradicate it when it is found. This is being done in the form of Statutory Plant Health Notices which we serve on affected owners requiring them to remove and destroy affected plants by burning or deep burial on site.”

Thorn outlines how we can all help fight the spread of this disease, as follows:

1. Be vigilant – Chalara dieback could appear in ash trees anywhere in Britain, especially where young trees imported from continental Europe have been planted. Early action is essential if we are to eradicate this disease from Britain before it becomes established. We have not found any evidence of Chalara dieback in ash trees outside nurseries and recent plantings, that is, we have not found any evidence that it has spread from new plantings into longer-established woodlands and hedgerows etc in the wider natural environment, and this gives cause for hope that it is not too late. They therefore urge you to inspect frequently any ash trees in your care, and especially any which have been planted during the past five or so years. Make yourself familiar with the symptoms of Chalara dieback from the material on our website at www.forestry.gov.uk/chalara. There are other causes of ash dieback, so it is important to distinguish them from Chalara. However, if in doubt, report it.

2. Report it - Report suspicious symptoms to one of the organisations listed at www.forestry.gov.uk/chalara

3. Buy with care – Be careful when buying plants to buy only from reputable suppliers, and specify disease-free stock. A list of countries where C. fraxinea is known to be present is available in the Questions and Answers document on their website at www.forestry.gov.uk/chalara.

4. Be diligent - Practise good plant hygiene and biosecurity in your own gardens and woodlands etc to prevent accidental spread of plant diseases. See the ‘Biosecurity Guidance’ document available at www.forestry.gov.uk/pestsanddiseases for advice on basic hygiene and biosecurity measures you can take.

5. Keep up to date – Check the Forestry Commission website regularly at www.forestry.gov.uk/chalara for updates on developments. ‘Follow’ their Tree Pest News account on Twitter to receive rapid intelligence of new developments, delivered by text or email. (Information about a wide range of other tree pests and diseases can be accessed via www.forestry.gov.uk/pestsanddiseases)

More information can be found at www.forestry.gov.uk/chalara as well as on the EPPO website