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Phytophthora disease of alder in Europe: potential for damage, opportunities for limitation of pathogen spread, and for management and control

Contract nr: FAIR-CT97-3615
Project nr: 3615
Project type: CA
Starting date: 01/03/1998
Duration: 36 months
Total cost: 181,000 EUR
EC Contribution: 181,000 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health conservation in forest ecosystems

This proposal covers new ground and has not been the subject of any previous proposal to the EU. It concerns a destructive disease of alder and is directly relevant to two areas in the Agriculture and Forestry Work Programme viz. 4.4.1 (Plant Health) and 4.5.3 (Conservation in Forest Ecosystems). Alder (Alnus) is an important genus of trees across Europe. There is an increasing commercial interest in the timber of alder and alders are the dominant species in huge areas of natural woodland. Through a symbiotic association with a microorganism, alder has a remarkable ability to fix atmospheric nitrogen, and this had made it the genus of choice for planting on various types of disturbed soil. In 1993, a lethal new disease of A. glutinosa, affecting the lower stem and roots, was identified in the UK. It soon became clear that thousands of trees, mainly along riversides, had died. The disease is caused by an unusual form of the fungus Phytophthora cambivora - well known as a pathogen of broadleaved trees but not previously recorded on alder. Because of possible quarantine implications, a report was made to the EU Standing Committee of Plant Health in April 1995 and information on the characteristics of the disease was disseminated. In January 1996, an ad hoc working group on the disease was convened in Brussels, under the auspices of the Standing Committee. By that time, it had become clear that the disease was also present in various other EU countries, and it was decided that, before any plant health regulations could be introduced more information was required. To progress matters further an informal meeting was held in the UK in June 1996 involving scientists from 8 European countries. This proposal for a Concerted Action has been developed from that meeting.

The main objectives are:
1) to produce a description of the recently described Phytophthora disease of alder in its various manifestations in different alder species and habitats across Europe, so as to distinguish it from other diseases of alder;
2) to agree methodologies for disease assessment and monitoring, and with these to determine the status of the 'alder Phytophthora' across Europe and the rate of disease intensification in localities where it is present;
3) to evaluate information on the characteristics and relationships of the 'alder Phytophthora' and to determine whether it has the potential to destroy the alder populations of Europe.
4) to evaluate data on the various mechanisms of disease transmission, and in the process to determine if trade pathways, e.g. through the movements of plants and timber, have the potential to contribute to long-distance spread of the pathogen.
5) to determine the likely benefit of various approaches to disease management and control, and to identify research opportunities in this respect.

Description / Current situation:
As a result of progress made during the first year of The Concerted Action, there has been a marked increase in success with the isolation of Phytophthora from alder bark. This year all isolates have been of the 'alder Phytophthora' and it is now evident that this is the only significant cause of 'Phytophthora-like' damage across the EU.
Molecular studies have now produced very strong evidence that the pathogen is a hybrid between Phytophthora cambivora and a fungus close to Phytophthora fragariae. Neither 'parent' fungus can attack alder and the 'alder Phytophthora' cannot attack any other hosts so far tested. The 'alder Phytophthora' exists as 'standard' and 'variant' types and there is evidence that the latter represent a breakdown towards one or other of the two parents. Standard isolates are more damaging to alder than variant types and only variant types have been found in some countries e.g. Sweden.
A critical evaluation has been conducted of the older European literature on alder disease and dieback and so far, no accounts of symptoms resembling those of the Phytophthora disease have been found.
During the year, reports have suggested that the disease is present in Belgium and Ireland but these have yet to be confirmed. Despite some detailed investigations it has not been found in Denmark, Finland or Norway, all countries in which there are sizeable alder populations. Nor is it known to occur in the EU countries of Southern Europe: Greece, Portugal, Spain or Italy.
Riparian alder plots have now been established in Austria, France, Sweden and the UK Some of the worst damage has been recorded in parts of France where up to 40% losses are occurring at some sites. In the UK where plots across the southern half of the country have now been surveyed for six years, cumulative losses have reached 11.4%.
Some useful progress has been made in understanding the processes of disease transmission, but much remains unclear. Some additional, but mainly indirect evidence has been obtained implicating the movement of infected planting material in the spread of the pathogen. Research on disease control is remains focused on the search for natural resistance within provenances of the common alder, Alnus glutinosa; and on the fate of the regrowth that occurs from trees which are coppiced at a time when the crowns are showing disease symptoms.
An interim report on the plant health issues raised by the disease has been prepared. This has been written in this form so that it can be brought to the attention of the EU Standing Committee on Plant Health.

Five publications on the disease have appeared since 1 February 1999 (see references below). A considerable number of others are in process of production and all of these have benefited considerably from the opportunities for the diffusion of information offered by the Concerted Action.

  • Brasier, C.M., Cooke, D.E.L. and Duncan, J.M. (1999). Origin of a new Phytophthora pathogen through interspecific hybridisation.
    Proceedings of the National Academy of Sciences USA 96, 5878-5883.
  • Cech, T.L. and Brandstetter, M. (1999). Phytophthora-erlensterben - actuelle Situation in Österreich. Forstchutz Aktuell23/24: 16-19.
  • de Gruyter, H. and van Dijk, C. (1999).Phytophthora als veroorzaker elzensterfte bij de swarte els.Tuin & Landschap 10: 60-61.
  • Streito, J-C., de Villartay, G. and Tabary, F. (1999).Une nouvelle espèce de Phytophthora s'attaque à l'aulne.Phytoma 519, 38-41.
  • White, J. and Gibbs, J.N. (2000).The value of alders to Britain.Quarterly Journal of Forestry 94, 23-28.

Internet pages describing the Concerted Action, showing the countries involved, and including contact details of the participants from each country and information on the progress of the research are available. The url is: From it links can be made to the other sites listed below:
For Austria a page detailing the symptoms of Phytophthora disease, and requesting records of any sightings is available within the main FBVA web site at:
In France a page of information on the alder Phytophthora is available by accessing the main LNPV web site at and then following the link to 'Le Phytophthora de l'aulne'.

John Newton GIBBS
Forestry Commission Research Agency
Alice Holt Lodge, Wrecclesham
UK-GU10 4LH Farnham
Tel.: +44 142 02 22 55
Fax: +44 142 02 36 53


  • Hugues, Yves CLAESSENS
    Faculté des Sciences Agronomiques de Gembloux
    Passage des Déportés 2
    B-5030 Gembloux
    Tel.: +32 81 62 23 01
    Fax: +32 81 62 23 01

  • Thomas Ludwig CECH
    Federal Forest Research Centre
    Seckendorff - Gudentweg 8
    A-1131 Vienna
    Tel.: +43 1 878 38
    Fax: +43 1 877 59 07

  • Philippe LEGRAND
    Ministry of Agriculture, Fisheries and Food
    Avenue Du Maine 19
    F-75732 Paris
    Tel.: +33 4 73 42 14 97
    Fax: +33 4 73 90 83 70

    Ministry of Agriculture, Nature Management and Fisherie
    Geertjesweg 15
    NL-6700 HC Wageningen
    Tel.: +31 317 49 68 31
    Fax: +31 317 42 17 01

  • Isabella BORJA
    Norwegian Forest Research Institute
    Hoegskoleveien 12
    N-1432 Aas
    Tel.: +47 6 494 90 26
    Fax: +47 6 494 89 71

    Swedish University of Agricultural Sciences
    S-750 07 Uppsala
    Tel.: +46 18 67 18 07
    Fax: +46 18 30 92 45

  • Cecile ROBIN
    Institut National de la Recherche Agronomique
    Rue de l'université 147
    F-75338 Paris
    Tel.: +33 1 55 68 43 210
    Fax: +33 1 55 68 43 222

  • Sabine WERRES
    Federal Biological Research Centre for Agriculture and Forestry
    Biologischebundesanstalt fuer Land- und Forstwirtschaft
    Messeweg 11/12
    D-38104 Braunschweig
    Tel.: +49 53 12 99 44 07
    Fax: +49 53 12 99 30 09

  • Kevin J. CLANCY
    University College Dublin
    IRL-4 Dublin
    Tel.: +353 1 706 77 44
    Fax: +353 1 706 11 02

  • Kirsten THINGGAARD
    Ministry of Food, Agriculture and Fisheries
    Danish Institute of Plant and Soil Science
    DK-8830 Tjele
    Tel.: +45 65 99 17 66
    Fax: +45 65 99 25 66

  • Jean-Claude STREITO
    Unité de Mycologie Agricole et Forestiere
    Rue Sainte Catherine 38
    F-54043 Nancy
    Tel.: +33 38 330 41 51
    Fax: +33 38 332 00 45

  • Cornelis VAN DIJK
    Koninklijke Nederlandse Akademic van Wetenshappen (KNAW)
    Nederlands Instituut voor Oecologisch Onderzoek
    PO Box 40
    NL-6666 ZG Heteren
    Tel.: +31 264 79 13 12
    Fax: +31 264 72 32 27

  • Arja LILJA
    Finnish Forest Research Institute (FFRI)
    Department of Forest Ecology
    PO Box 18
    FIN-01301 Vantaa
    Tel.:+35 89 85 70 54 84
    Fax: +35 89 85 72 575
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