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pests and diseases

HEADLINE: “THE GREAT CHESTNUT TREES OF EUROPE ARE DYING”

ARAB NEWS, 6th September 2012 (syndicated from Associated Press)

Ever since I was a child in England I have loved conker trees.

I don’t suppose it’s still true in these multi media days, but for lads (and sometimes lasses) of my generation the conker tree was instantly recognized, and in the summer months we passed the time watching conkers grow and trying to coax them from the tree long before those wonderful shining chestnut orbs were fit for combat. I can still remember the joy of summer car journeys interrupted in Dorset lanes so that I could linger for a while to scoop, hook or knock the playground currency from the lumbering bent boughs of the mighty chestnut trees. Later we would pickle them for strength, leaving them in dark dusty jars in the garage for the winter. Of course they were long forgotten by spring. Presumably patient fathers quietly disposed of them while we sat at school desks, or watched Blue Peter on dark chilly spring evenings.

summer quarry

The horse chestnut, Aesculus hippocastanum, is a striking tree. Across Europe it’s a stately favorite in parks and large gardens. In England it was introduced in the late sixteenth century, and by the eighteenth century it was a popular feature as part of the man-made landscape in the parklands of country estates, and also to mark the boundaries of larger properties. It can grow to nearly 40 metres, a large tree by english standards, which once mature sends huge drooping boughs towards the ground for children to swing and climb.

under the greenwood tree

In May its bright white flowers, in the form of panicles up to a foot in length, lift english spirits with early thoughts of summer, and bucolic reminiscences of country cricket matches and cattle ruminating in its shade. It has become part of the very myth of Englishness. As an urban feature its smaller cultivar, the Red Horsechestnut (Aesculus × carnea: crossed with a Red Buckeye, Aesculus pavia) decorates city streets with similar, but red, panicles. This tree is particularly popular in Germany, where it’s been a feature for nearly 200 years. I remember it brightening many business trips to Frankfurt in the 1990s.

red chestnut blossom

The horse chestnut is a foreigner to England, and to most of Europe. It’s a native of the Southern Balkans – Albania, Macedonia and Northern Greece – but its popularity has carried it across the temperate world in the last three hundred years. Although a fairly useless tree in economic and domestic terms (the conkers are slightly poisonous and cause sickness both to people and horses if eaten) the beauty of its form and flowers has sent it far and wide as a shade giver and eye-catcher. In England, at least, it doesn’t easily self propagate, and its height and bulk make it unsuitable for smaller gardens and restricted urban spaces. (Hence the use of the smaller red cultivar in German streets). As I know from personal experience it is relatively easy to grow from the conker, but much more difficult to find good homes for it once it reaches its flower pot limits.

For several years now I’ve noticed how early the chestnut leaves turn brown and shrivel – often by mid July in England. I’ve been compelled to share these observations with my long suffering and (understandably) tree-deaf family, and I had wrongly assumed that Aesculus hippocastanum was an early faller. I had obviously forgotten my long summer holidays seeking the (too young) shining orbs under deep green foliage.

But now, courtesy of Arab News – not usually a source for tree updates – I’ve been shown the error of my assumptions. Those beloved conker trees are under attack from two different aggressors: the leaf mining moth, Cameraria ohridella, whose larvae feed on its leaves; and a nasty bacterium called Pseudomonas syringae pv. aesculi which causes a disfigurement (and ultimately death) by “bleeding canker”.

The moth was first observed in Macedonia in 1984 but apparently took 18 years to reach England – presumably assisted by the increasingly global inter-connectedness of human activity. By destroying its leaves so early the moth robs the tree of essential sunlight time during the summer months, and may also make it more susceptible to the the second attacker.  A UK Forestry Commission survey of the bleeding canker conducted in 2007 concluded that ” All regions [sampled] had some symptomatic trees and overall, 44% of the trees inspected in the rural environment and 55% of the urban trees displayed symptoms of the disease… The level of symptomatic trees were (sic) especially high in south east England”.

I do not know what, if anything, can be done, or is being done, to save the horse chestnut. A BBC web-page offers this rather forlorn long term advice: “General advice includes trying to plant trees of local provenance, as research shows that specimens grown from local seed stock are best adapted to local conditions, and have a better resistance to pests and diseases”.

The accountant in me knows that cash-strapped Europeans have more important priorities right now than saving a few useless conker trees. Ironically, a Western Europe without this beautiful traveller would – in a purely technical sense – be a more natural landscape than one which is dotted with foreign imports.

But somewhere deep within me the child and poet pushes the accountant aside. How could we not lament the passing of these beautiful and iconic trees?

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