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Seed clumps on ash trees not signs of disease, says Forestry Commission

by Aug 17, 2018News

The Forestry Commission is reassuring the public that unusually large quantities of clumps of seeds hanging on ash trees this autumn do not mean the trees have Chalara ash dieback disease.

Dr John Morgan, Head of the Commission’s Plant Health Service, said the disease can be difficult to recognise in the autumn, when ash leaves are changing colour anyway. He explained,

“What some people are mistaking for symptoms of disease are actually a sign of the exceptionally productive fruiting season, or ‘mast year’, we’ve had. The clumps of seeds, known as keys, can sometimes look like the blackened and shrivelled leaves which are a symptom of the disease, so it is easy to see how the mistake can be made.

“The best way to recognise Chalara in the autumn is by the elongated, diamond-shaped lesions, or discolouring, which it causes in the bark of stems and branches around the points where leaves, twigs and branches are attached. This discoloured bark often has splits in it.”

The disease is caused by the Chalara fraxinea fungus, and Forestry Commission monitoring has indicated that there has been little apparent spread of the disease in 2013. Most observed spread has been over short distances in local areas which have higher levels of the fungus in ‘wider-environment’ situations such as mature woodland. This means that new cases are more likely to appear in counties such as Norfolk, Suffolk, Essex, Kent and a small number of other areas.

Dr Morgan added…

“We welcome reports of suspected cases, especially in new areas. However, we do encourage people to check first that the tree really is an ash tree and the symptoms are Chalara symptoms, and we have published identification guides on our website at www.forestry.gov.uk/chalara.”

Suspected cases can be reported with the Forestry Commission’s Tree Alert smartphone app or on-line form, which are available from the above web page.

Dr Morgan reminded park managers and garden owners in affected areas that they can help to slow the spread of the disease locally by burning (where permitted), burying or composting fallen ash leaves to break the fungus’s lifecycle.

  • Chalara fraxinea will be one of about 650 plant pests and pathogens categorised for a risk register which the Forestry Commission, Defra and other stakeholders are developing. This register will help to strengthen biosecurity and reduce risks to tree and plant health at the border and within the UK. Other measures under way to tackle the disease are outlined below.

If you want further information or want to report a suspected case please visit www.forestry.gov.uk/chalara