Sunday, 28 October 2012

Ash dieback

Publicity concerning Ash dieback has achieved remarkable proportions in a very short space of time. And yet why did it not figure three years ago? Had there been a ban on imports three years ago when the problem became apparent maybe we would not have the problem that is faced today? As it stands, the picture looks bleak and we face the loss of a major part of our landscape and its ecology.

Still, what is done is done. We have got to find a solution. There are obvious implications as Ash is a major element of the landscape. As I drove down to Long Crendon yesterday I found myself scanning the landscape for Ash trees. On the limestone this is really a very important tree both in a landscape and a broader ecological context. Ash woodlands are commonplace on the limestone and many support very rich assemblages of saproxylic hoverflies. So we face a major crisis.

From a hoverfly perspective maybe the way forward is to develop a strategy to provide growing replacements before we loose the Ash? If  so, which species should we use? I am amazed to say that I wonder whether we should be looking at Sycamore? Obviously there is a case to be made against Sycamore but it offers some important advantages:
  • It is fast growing and appears to create dead wood situations similar to those that are offered by Ash.
  • It seems to support sap runs with similar properties to those of Ash.
  • The bark appears to have a pH that is favourable to many lichens.
  • It will grow in many of the locations that can be expected to be vacated by Ash.
  • It is not noted for its pests and is a vigorous, tough and fast growing species.
  • It supports good numbers of aphids and potentially rot hole and dead wood hoverflies.
I never thought I would end up as an advocate for Sycamore, having spent much of the 1980s trying to eliminate it from the woodlands of Mitcham Common! These days I am focused on eliminating invasive bramble from acid grasslands but there is a bigger picture to consider. There is a major conservation debate to be had and we have a lot to think about. Ash is so fundamental to our rural landscape and its ecology that there is an urgent need to do some thinking about how to respond to this crisis.


  1. Hi Roger,
    I have to agree that we should be seriously considering planting a wider range of tree species and not just natives. We don't know what other ecologoical timebombs are coming and what trees they may affect, so it strikes me that it would be wise to hedge our bets and plant a diverese selection of tree species.

    Regarding sycamore I cannot understand the terror with which this splendid tree is regardede in conservation circles. Copared to other alien plants it is positively benign! Certainly for saproxylic Diptera (and I suspect also aphid munching insects)it appears to be provide a very good resource. I had the opportunity to regularly visit a fallen sycamore when I wirked at Attingam PArk. It was postively swarming with various Lonchaeaid speceis, including lots of the scarce Lonchaea peregrina. I bredd out dozens of Solva marginata, collected from under loose bark, saw a number of the scarce Stratiomyid - Neopachygaster meromelas investigating the tree,plus plenty of Xylota and Chalcosyrphus nemorum around the fallen bole. Also some nice craneflies, Drosophilidae and more.

    As a Dipterist, I'm a big fan of large sycamores. Perhaps we should be campaigning to stop the ill-informed vendeta against this much maligned tree.