NOW and then when I visit the European Weather Centre in Reading, I am invited to a colleague's house in Gerard's Cross in Berkshire. And sometimes I have stopped along the way at a little country churchyard quaintly called Stoke Poges. It is the idyllic location that inspired the famous Elegy by Thomas Gray, and his presence there is almost palpable.
The place has changed, however. You may remember Gray describing how
Beneath those rugged elms, that yew trees shade,
Where heaves the turf in many a mouldering heap,
Each in his narrow cell forever laid,
The rude forefathers of the hamlet sleep.
The yew trees are still there, and the undulating ground, but all the elms are gone victims, I suppose, of Dutch elm disease and the long hot summer of 1976
Dutch elm disease, so called because it first appeared in the Netherlands about a decade earlier, was one of the less welcome legacies of that fine summer. During any long drought, trees find water hard to come by, and many find survival difficult but then recover. In the case of the elms, however, summer 1976 was different. It was soon noticed that all over southern England, elm trees that had stood for centuries were wilting, losing their leaves, and showing no signs whatever of rejuvenation. Scientists soon confirmed the worst Dutch elm disease was rampant.
The disease is a fungus, carried from tree to tree by the elm bark beetle, Scolytus scolytus, which lays its eggs beneath the elm bark. Once the fungus takes a hold, little can be done, since it blocks the transport of water up the trunk and chokes the tree to death.
Summers like 1976 favour the spread of the fungus in two ways. Firstly, a long continuous drought weakens any tree, and makes vulnerable to enemies. But such conditions also favour the lifestyle of the vector beetle. Like all cold blooded organisms, the elm bark beetle is very sensitive to warmth, and is capable of flight only when the temperature is above 15 or 160C. Warm weather therefore, particularly in May and June when the beetle lays its eggs, allows it to venture far afield and deposit its infection in many different places.
Over 20 million elms were killed by the dreaded fungus in the south of England in the aftermath of 1976. Here in Ireland the damage was more patchy, but serious nonetheless. Less tropical summers in the intervening years have slowed the progress of the plague, but a resurgence was very noticeable in England after the recent hot summer of 1995.