Scourge of the British Countryside

By “Awake!” correspondent in Great Britain

TWENTY thousand elm trees are dying every day in Britain. It is estimated that 11 million have died since 1968, all casualties of a scourge known as Dutch elm disease.

Although called “Dutch,” the disease did not originate in Holland. Rather, it is so named because much of the early research into the disease was undertaken in that country. It is generally thought that Dutch elm disease reached North America from Central Europe, and the present epidemic probably was introduced into Britain in diseased timber from North America in 1968. But before discussing the disease, let us take a brief look at the elm itself.

Of the six basic species of elms growing in the British Isles, the English elm, also known as the common, or field, elm, and the wych, or broad-leaved, elm, have long predominated. The common elm has a thick rough trunk on which are many gnarled bosses or knobs, and the bark of the tree is very rugged and covered with deep furrows. It is an easily recognizable tree, being clothed right down to the ground with a dense mass of brushwood. The wych elm has no brushwood at the base of the trunk, and its leaves are larger and broader. Being less rugged, the wych elm is the more graceful of the two types.

Elm wood is still valued as timber, the rough bosses that grow on the trunk of the common elm being prized by cabinetmakers who find the wood curiously veined and streaked. Today, though, it is used mainly for pallets, chipboard, pit props and coffins. The most important feature of the English elm, however, has been its unique contribution to the landscape. It stands either in rows or individually, and is one of Britain’s tallest trees.

What Is Dutch Elm Disease?

Dutch elm disease is a fungus disease transmitted by a beetle, Scolytus destructor, which feeds on healthy trees for a week or so before it starts to breed. During this period fungus spores are rubbed off the body of the beetle and enter the wood vessels of the healthy tree. A reaction from the fungus gradually weakens the elm and it dies from loss of foliage and from poisons. When an elm has thoroughly weakened, the beetle enters the bark of its main trunk. There the insect breeds, the young beetles emerging the following spring to start the cycle all over again.

Typical external symptoms of Dutch elm disease are yellowing and browning of once bright green leaves. Sometimes vigorous new shoots bend over, indicating that they are dying. Peeling back the bark of a twig will reveal the outermost wood vessels stained with long dark streaks. Such symptoms can be recognized readily by the layman. But there are two strains of this tree malady, one aggressive and the other nonaggressive. The difference cannot easily be determined. The nonaggressive strain does not usually kill infected trees, but the aggressive strain spreads twice as fast and kills elms by the million. During the 10 years it has been in Britain, this disease has swept through the country, decimating all but the Cornish and Huntingdon elms. By the end of 1977, 11 million of the country’s 23 million elms had died. In at least one county, more than 90 percent of the elm trees are already dead, which amounts to 50 percent of all the trees in that county.

In London there are many beautiful parks where old and particularly fine elms have grown, and these have suffered severely. In Regents Park during 1977 alone, approximately 100 of the remaining 500 or so elms had to be cut down. As in other parts of the country, attempts have been made to inject affected trees. But it appears that these measures have been ineffective in the face of this virulent disease.

Countering the Disease

Until recently the only long-term remedy for Dutch elm disease was to replace dead elms with new resistant varieties. Short-term measures were aimed at preserving as many of the existing elms as possible, the primary means of control being ‘sanitation felling.’ For sanitation felling to work, trees must be cut down as soon as they are infected, and the bark must be burned. A tree that dies should be felled by the following spring, before the beetle can breed and spread the fungus. In the majority of cases, this will not happen, which means that by the following spring a further 1,000,000 elm trees probably will be infected. Unfortunately, sanitation felling has failed because too little was done too late.

A recently introduced antidote is fungicide. This is injected into the base of healthy trees so that sap will distribute it throughout the branches, where it acts against the fungus. Such injections cost about £5 ($10, U.S.) per tree and the treatment must be repeated every year. Results have shown, however, that this method is effective only on trees up to about 40 feet (12 m) in height; and it is more successful on some elms than on others.

On occasion, elm roots join together, enabling the fungus to spread underground from tree to tree. It is possible for a tree to be isolated by means of a chemical barrier established by pouring a soil sterilant into one-inch (2.5 cm) holes, drilled two feet (0.6 m) deep and six inches (15 cm) apart between trees. This treatment will last for several years, but it is very expensive, costing at least £12 ($24, U.S.) per tree. It is practical only in the case of valuable elms.

Efforts to Replant

Today there is a growing awareness that trees are an essential part of the whole ecological balance of life. Will the elms be replaced? And if so, how? In many areas there are schemes for public rather than private planting, but with quick-growing species like limes, not elms. In an area where more than 170,000 new trees were planted by 1975, none of them were elms. So far, the response to the elm tragedy has been as effective as trying to stem a forest fire with a garden hose.

In spite of government grants, there is a natural reluctance on the part of farmers and landowners to plant new trees. Why? Because present laws require that of every four trees planted, three, in effect, must go to the government in the form of taxes. Hence, at least 90 percent of planned replanting schemes were canceled in 1975.

The grounds of the Watch Tower Society’s branch office in London have also felt the effects of tree maladies. Up to 30 trees on these grounds have had to be cut down, including many elms. Gales, too, have taken their toll. Recently, however, a vigorous replanting program has been undertaken. In addition to over 100 conifers forming part of a perimeter fence, more than 200 trees have been planted throughout the grounds. These include silver birch, sycamore, eucalyptus, rowan (mountain ash) and maple. But filling gaps in the landscape is a very slow process.

In recent months ecologists have been heartened at noticing elm suckers springing up from some of the old root systems around the countryside. Perhaps they will eventually grow and help to restore the balance. But at present it is too early to be sure of their ability to mature.

Meanwhile, Dutch elm disease continues its rampant course. The pleasant British countryside, vividly recalled in the classic paintings of Constable, Gainsborough and Turner, has been tragically scourged and destroyed by this disease. The bare boughs of once-proud trees are a reproachful reminder of the failure of any conservation policy.