Forestry Commission ARCHIVE Cover Summary of the known positions of the Eurasian (EAN) and North American (NAN) races of the aggressive strain of Ceratocystis ulmi in Europe in 1981. Green, EAN race; red, NAN race. Based on identifications of the fungus in artificial culture from isolations made from over one thousand samples collected by Dr. C. M. Brasier (see pp. 96-104). The distribution of the non-aggressive strain of C. ulm iis not shown. FORESTRY COMMISSION BULLETIN No. 60 Research on Dutch elm disease in Europe PROCEEDINGS OF THE EUROPEAN ECONOMIC COMMUNITY RESEARCH SEMINAR, GUERNSEY, CHANNEL ISLANDS, 30th MARCH — 1st APRIL 1982 Edited by D. A. BURDEKIN, B.A., Dip. Ag. Sci., Chief Research Officer, Forestry Commission, Forest Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH, U.K. LONDON : HER MAJESTY’S STATIONERY OFFICE © Crown copyright 1983 First published 1983 ISBN 0 11 710153 2 Contents ruge INTRODUCTION D. A. Burdekin V DUTCH ELM DISEASE CONTROL 1. Dutch elm disease control campaign in Guernsey, G. F. Riley 1 Channel Islands, 1976-1981 2. Dutch elm disease control campaign in Jersey, G. Journeaux 5 Channel Islands, 1974-1982 3. Control of Dutch elm disease in Britain B. J. W. Greig and J. N. Gibbs 10 4. Dutch elm disease control in the Netherlands J. K. Water 17 5. Dutch elm disease in Denmark A. Yde-Andersen 19 6. Evaluation of the trap tree technique for the control D. P. O’Callaghan and 23 of Dutch elm disease in northwest England C. P. Fairhurst ENTOMOLOGICAL ASPECTS OF DUTCH ELM DISEASE 7. The ecology of elm bark beetles in northern S. G. Kirby and C. P. Fairhurst 29 Britain 8. The effect of climatic factors on the dispersal C. P. Fairhurst and C. J. King 40 of elm bark beetles 9. Host feeding preference ofScolytus scolytus J. F. Webber and S. G. Kirby 47 10. Scolytid pheromone research in West Germany D. Klimetzek and H.-P. Kopp 50 11. Biochemical investigations related to Dutch J. F. Grove 59 elm disease carried out at the Agricultural Research Council Unit of Invertebrate Chemistry and Physiology, University of Sussex, 1973-1982 12. Trap design and experimental layout in C. J. King and N. J. Fielding 67 pheromone research in Britain iii MYCOLOGICAL ASPECTS OF DUTCH ELM DISEASE 13. Pseudomonas fluorescens and Ceratocystis ulmi A. Yde-Andersen 72 in wych elm 14. Biological control of Dutch elm disease by R. J. Scheffer 75 Pseudomonas species 15. Host-parasite interactions in Dutch elm disease D. M. Elgersma 78 16. Toxins in Dutch elm disease R. J. Scheffer 82 17. Studies onCeratocystis ulmi in Belgium M. Meulemans and 86 C. Parmentier RESISTANCE TO DUTCH ELM DISEASE 18. The future of Dutch elm disease in Europe C. M. Brasier 96 19. Dutch elm disease in Italy L. Mittempergher 105 20. Resistant elms for Europe H. M. Heybroek 108 Introduction D. A. BURDEKIN Forest Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH, U.K. Dutch elm disease is one of the most important tree scientists involved in research on Dutch elm disease diseases that has been found in the northern hemi­ where research results and control methods could sphere. It was first recognised in 1919 in Picardy in be freely discussed. A series of remarkably successful France and during the following two decades it meetings have been held since that time in Britain, became epidemic throughout Europe and North Holland, Germany and the Channel Island of America. It was called ‘Dutch’ elm disease as a Guernsey. The papers in this Bulletin are those tribute to the intensive research programme under­ presented at the 1982 meeting held in Guernsey and taken by Dutch scientists at that time. It was soon they represent a unique collection of papers on many established that the disease was caused by a fungus, aspects of this complex problem. Ceratocystis ulmi, and was transmitted from diseased In addition to providing support for the co­ to healthy elms by the elm bark beetles Scolytus ordination of research programmes in Europe, the scolytus an d Scolytus multistriatus. It is perhaps EEC has also made a very important contribution interesting to note that there is still some argument to the European research programme. Funds were about the ‘correct’ scientific name for the fungus and made available for the employment of additional the Dutch prefer to use the name Ophiostoma ulmi. scientists to work on the project. Two were employed This is not the place to argue the pros and cons of in Britain to work on various aspects of the fungus fungal nomenclature, merely to note that scientists and the insect, one in Holland to work on fungal/ cannot always agree! host relationships and one in West Germany to The epidemic of Dutch elm disease in the first study the bark beetle. half of this century was very damaging to the elms The papers which appear in this Bulletin sum­ of Europe and North America but was much less marise the results of recent research undertaken by dramatic than the devastating epidemic which scientists from six members of the European occurred in Europe during the 1970s. An upsurge of Community. It is, of course, impossible to make a the disease started in the late 1960s in Britain and comprehensive review of the achievements of the soon spread to many western European countries. overall research programme in a short introduction. A very active research programme was initiated in However a few highlights can be mentioned and a Britain about this time followed by a resurgence of number of important conclusions can be reached. activity in Holland. Following a classical series of Three main approaches to the control of Dutch studies in Britain it was established that a different elm disease have been investigated during the past strain of the fungus, termed the aggressive strain, decade and these are: had been introduced into Europe from N. America, (a) control of the elm bark beetle probably in the late 1960s. The aggressive strain was considerably more damaging to European elms (b) control of the fungus than the non-aggressive strain which was probably (c) selection and breeding of resistant elms. responsible for the earlier epidemic. By the mid 1970s the aggressive strain of C. ulmi The traditional method of controlling the disease had been found in several European countries and has been by sanitation felling, the cutting and a number of scientists in these countries became destruction of dead or dying elms so that the source involved in research on the disease. It became clear of the breeding beetles is eliminated. This method that a co-ordinated European programme of research of control has been tried in many countries and has was urgently required and that an ideal opportunity met with varying degrees of success. Some examples existed for the European Economic Community in of successful and not so successful sanitation felling Brussels to assist in this goal. Since 1977 the EEC are presented in the first section of this Bulletin. has provided funds for an annual research seminar of Where valuable individual trees are at risk techniques v FORESTRY COMMISSION BULLETIN No. 60 for the injection of chemical fungicides or perhaps decade, the long term selection and breeding prog­ biological agents such as bacteria have been ramme for resistant elms has continued in Holland. developed. Selected new clones at least moderately resistant A number of studies of the elm bark beetles in to the aggressive strain of C. ulm ihave been released Europe has given a much greater insight into the to the nursery trade. A number of promising elm conditions governing the activity of the beetle. clones have been planted in a series of trials in most The means by which the beetle is attracted to dead member states of the European Community. and dying elms is now much better understood. New collections of potentially resistant elms have The chemical nature of the attractants (pheromones) been made in Asia. produced by Scolytus scolytus has been identified. What conclusions can be drawn at this stage in the These chemicals have been used in the field to research programme? monitor beetle populations where control operations In order to safeguard existing elm populations are in progress. from the ravages of Dutch elm disease a vigorous Studies of the fungus have followed two main sanitation felling programme can markedly reduce directions, one towards a better understanding of the impact of the disease. Valuable elms, e.g. in the effects of the fungus on the host tree and the important streets and parks, can be protected from other involving a detailed study of the variability infection by the injection of chemical fungicides and of the fungus. A clearer picture is now emerging perhaps also of biological agents such as bacteria. of the mechanisms by which the fungus can invade A number of factors both climatic and biological and kill the vascular tissues of the host. can affect the rate of progress of the disease and The studies on the variability of the fungus have these factors are now much better understood. considerable implications for the selection and In future plantings of elm, there is an important breeding of elms. As a result of recent studies it is place for elms resistant to the disease. New clones clear that at least two forms of the aggressive strain are being introduced which not only show resistance exist, one invading Europe from the west and the to Dutch elm disease but are also suited to particular other from the east. Until there is a clearer view of environments (e.g.