Wednesday, 21 November 2012

Ash dieback

It’s not often that countryside issues make the headlines, but a recent disease affecting ash trees has triggered widespread media coverage. The extent of publicity this epidemic has received is encouraging in the sense that it is a demonstration of the high regard in which we hold our trees here in Britain. However, this is the silver lining on what could potentially be a bleak cloud looming over the future of our countryside. 

A mature ash tree

So what is ash dieback? And why should we be concerned?

Ash dieback, or Chalara fraxinea, is a damaging fungal disease that has recently been discovered in Britain. It has infected up to 90% of ash trees in Denmark, and 80% in Poland, and the potential for establishment in the UK is classed as “very high”. According to the Forestry Commission, “The disease causes leaf loss and crown dieback in affected trees, and usually leads to tree death.” Dr Simon Pryor, Director of Natural Environment at the National Trust, said: “This disease poses a major threat to special places throughout the country and is potentially more devastating to the landscape than the loss of Elm in the 1970s.”

To give the importance of ash (or Fraxinea excelsior if you’re feeling ambitious) as a species some context; there are an estimated 80 million ash trees in the UK, making up around 30% of our tree population. Ash is an extremely important species in terms of its wildlife and timber value. It’s for these reasons that a serious outbreak of Chalara fraxinea could have devastating consequences both environmentally and economically.

As I write this, there have been no reports of ash dieback at Lyme Park. However, we are keeping a close eye on our ash trees for any symptoms of this disease.  

So if you see any ash trees while you’re walking around Lyme Park with any of the following symptoms, please get in touch with the ranger team by emailing:
  • Dead branches
  • Blackening of leaves which often hang off the tree
  • Discoloured stems in a diamond shape where a leaf was attached
Unfortunately, some of the symptoms above are easier to see when the trees are in leaf, which makes identifying infected trees over the winter more difficult. However, lesions (such as in the photographs below) centred on dead side shoots are the best indicator of ash dieback at this time of year.

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