Banstead Commons and Banstead Commons Conservators
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Ash Die-Back
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Written for the Banstead Village Residents' Assoc. Newsletter, Summer 2020:

In the 1960/70s, Dutch Elm Disease swept across Europe from North America, devastating Elm trees in its path. The fungus that caused the disease simply blocked the trees’ vascular system so blocking water and nutrient supply. Within 20 years, virtually all English Elms had disappeared from the UK, with only scattered survivors in hedges and woods that start to grow as individual trees but then die back because of chronic disease. 

30/40 years on, a similar disease (this time bacterial) hit the UK, this time affecting Ash trees. The disease was cauised by infected trees imported from Europe, even at the time disease was already destroying Ash all over mainland Europe. The first evidence of disease is the death of terminal shoots, hence “die-back”. When it first appeared, the authorities decided to track and trace, everyone was asked to report any trees that showed symptoms, however, the disease spread rapidly and this approach became overwhelmed. The disease is still ongoing but evidence from Europe suggests that more than 90% of trees are affected with very few showing complete resistance and most dying.

In Banstead, where Ash is a common tree the effect so far has been mixed, nearly all trees show some evidence of die back. It seems younger trees are worse affected than larger specimens, in many places, large stands of saplings 4-8m high are dying or dead.  Larger trees appear to be able to respond to die back early in the season by producing abnormal secondary growth in early summer. Wherever you look however, you will find some completely dead trees, some with dead branches but all will show some dead wood even if only at the tips of branches. Certainly, over the past five years the number of dead large trees has increased annually and it seems certain that our Ash trees are going the same way as the Elm. In a lifetime we will have lost two of our most iconic forest trees. 

Even more worrying is that there are new threats to other tree species, both pests and diseases, such as Oak Processionary Moth. One thing is certain just as with Elms and Ash, these lethal pandemics have the potential to change our native woodlands for ever.