Spectator, April 8, 1972 SCIENCE
Tree threats
Rernard Dixon tAatejus;t the moment when Dutch elm dis tan3 OM of the news — dying elms be-intcki,t be distinguished readily from reuaZ'Y ones in winter — a scientific has appeared which explains the of"°n for the sudden increase in severity .tis disease which now afflicts over two land trees in the southern counties of wh'?, Moreover, the journal Nature, in 'Bal'eetile report appears, warns that other species ' of trees in Britain are 4t)te! and suggests that our recent kg. btltr;'kee about the current epidemic of dtne7,, eh disease is symptomatic of a sh-ncY in our plant pathology services. alre2rt, at a time when the landscape is 4Y being plundered of trees for other We have inadequate knowledge of, oulesufficient action to combat, threats AQ.er trees by fungi and other microbes. disea,-!rding to the report on Dutch elm tent-(Nature, vol 236, p 121), the cur pastfeveritY of the disease is due at least Nte-, to the emergence of an unusually Cercit:sive strain of the fungus llitgtrYstis uirni. In laboratory tests, gouths collected from infected trees in the eeffrrl counties proved more virulent in ects than samples of fungi from regions where the disease was at its endemic level — a state where twigs and branches are occasionally affected but trees rarely die. The result of joint research by the Forestry Commission and scientists in the Netherlands and at the University of Massachussetts, this is an ominous finding. It is particularly disquieting because the new strain of fungus attacks even the special clones of elm specifically bred in Holland for their resistance to the disease. And still there is no effective treatment. As with the desperate policy of slaughtering cattle afflicted by foot and mouth disease, ruthless felling and destruction is the only solution. The damage wrought by the microscopic fungus is all too clear from a ground survey conducted last year and about to be published by the Forestry Commission. In an area of 56,000 sq km of southern Britain, including most of England south of a line from Birmingham to Norwich, it is estimated that there are eighteen million elms, of which 4 per cent are dying or dead and another nine per cent have slight to moderate infection. Among the worst affected counties are Essex, with 109,000 trees recently killed by the fungus, Gloucester with 98,000, and Worcestershire with 77,000. Moreover, the rehabilitation of elms in these regions will probably be less successful than it was after the fierce epidemic of Dutch elm disease which occurred in the early 'thirties. The Forestry Commission has estimated that the percentage of saplings in the gen eral population of hedgerow trees in central and southern England fell from 31 per cent in 1951 to 23 per cent in 1965, and that this trend will continue in the future. All the more reason, therefore, why we should nurture and protect the mature trees we already have, of this and other species. Unprecedented, public concern over Dutch elm disease has helped. "Unfortunately," Nature points out, "this interest has been almost entirely confined to elm, and has done little to stress the potentially delicate position of several other amenity tree species already and potentially subject to disease and pest infestations, of threatened by other drastically adverse factors of the environment." The ash, for example, is now in decline throughout Britain, but there appears to be no research in progress to discern the reasons why. And few people outside the professional ranks of plant pathologists know about the epidemic of fungus infection which hit the sycamore trees of north-east London in the late 'forties, leaving the fungus firmly established there. The reason for the lack of scientific activity appears to be an organisational one. The Research Division of the Forestry Commission deals primarily with forest tree species. On the other hand, there are several research establishments in Britain concerned with horticultural crops. Amenity species of tree (including some which also have considerable economic value) fall in the area between the two and are thus neglected. Would some ecologicaly-conscious MP take up the matter?
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