Forster, B.; Knizek, M.; Grodzki, W. (eds.) 1999: Methodology of Forest Insect and Disease Survey in Central Europe.
Proceedings ofthe Second Workshop ofthe IUFRO WP 7.03.10, April20-23, 1999, Siort-Chateauneuf, Switzerland.
Birmensdorf, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) 187-188.
INVESTIGATIONS IN THE DISTRIBUTION OF
PHYTOPHTHORA
SPECIES IN GERMAN ALDER SITESSabine WERRES, Federal Biological Research Center for Agriculture and Forestry, Institute for Plant Protection in Horticulture, Messeweg 11/12, D- 38104 Braunschweig
INTRODUCTION
During the last years alder decline has become a serious problem in many european countries. (GIBBS 1995, BRASIER, ROSE and J.N. GIBBS 1995, GIBBS and LONSDALE 1996, MATHIEU 1996, TIDNGGAARD 1996, CECH 1997). Characterstic symptoms of the disease are crown thinning and tarry or rusty spots on the stems, starting at the ground level, which can develop into a bleeding cancer. Under the bark the tissue is dark brown to reddish brown and can be clearly distingished from the healthy tissue.
From diseased alders species of the fungal like microorganisms of the genus Phytophthora could be isolated. The most important species seem to be a homothallic variation of
Phytophthora cambivora.
In GermanyP. cambivora
and otherPhytophthora
species could also be isolated from dieseased alder trees (HARTMANN 1995, WERRES 1997, 1998). But up to now there has been only little information on the distribution of these pathogens in German alder sites and on the intensitivity of the decline. Therefore in 1998 a project was started to collect data on diseased alder stands and to screen soil samples of these stands forPhytophthora
spp ..MATERIAL AND METHODS
With the help of a questionnaire data such as the occurance of characteristic symptoms, water profile and soil typ were collected. Those foresters who had problems with diseased or dying alders was asked to send soil samples according to a detailed guideline. At the laboratory the soil samples were screened for Phytophthora with the Rhododendron leaf test (WERRES
et al.
1997;THEMANN & WERRES 1998,
www.bba.de/phytoph/diagnose.htm).
In this test Rhododendron leaves are used as a bait to detect Phytophthora propagules. The test had been developed for routine screening of a high number of water, soil and root samples forPhytophthora
spp. and for large samples. The test system baits a wide range ofPhytophthora
species and is highly sensitive. Furthermore it is very easy to handle.RESULTS
As the project has not yet been finished only the first results can be presented.
a - Character of the alder sites, the soil samples had been sent from Soil samples from 45 different sites from all over Germany were sent.
In most of the alder sites:
- the size is below 5 hectars
- the alder trees are of the same age
- the alder trees are aged between 31 and 50 - the alder trees are cultivated (planted)
- Alnus glutinosa
is the main alder species187
- water is close by
-there is temporary stagnant moisture or flooding (mainly winter/spring) -the pH value in the soil samples ranged from 3.3 to 7.9
-between 1-50% ofthe alder trees were diseased - there were only low numbers of dead trees
b - Presence of Phytophthora spp.
In 60 % of the soil samples one or more Phytophthora species could be detected. The taxonomical work to determine the species has not yet been finished.
c - Correlation between the presence of Phytophthora spp. and factors like soil pH
There was a strong correlation between the pH-value of the soil samples and the occurance of Phytophthora spp.
REFERENCES
BRASIER C.M., ROSE J. and J.N. GffiBS (1995): An unusual Phytophthora associated with widespread alder mortality in Britain. Plant Pathology 44: 999-1007.
CECH Th.L. (1997): Phytophthora- Krankheit der Erie in Osterreich. Forstschutz Aktuel119/20:14-16 GffiBS J.N. (1994): Phytophthora root disease of Common alder. Research Information Note 258.
Forestry Authority, Research Division, Alice Halt Lodge, Wrecclesham, Farnham, Surrey: 4 S.
GffiBS J.N. (1995): Phytophthora root disease of alder in Britain. EP PO Bulletin 25: 661-664.
GffiBS J.N. & LONSDALE D. (1996): Phytophthora disease of alder: The situation in 1995. Research Information Note 277. Forestry Commission, EdinbUrgh: 1-4.
HARTMANN G. (1995): Wurzelhalsfaule der Schwarzerle (Alnus glutinosa)- eine bisher unbekannte Pilzkrankheit durch Phytophthora cambivora. Forst und Holz. 18: 555-557.
MATHIEU D. (1996): Resultats de l'enquete ,deperissement de l'aune" de l'automne 1996. La sante des Forets, Bilan 1996: 13.
THINGGAARD K. (1996): Svampen Phytophthora I Elletraeer. Skoven 3: 132-133.
WERRES S. (1996): Phytophthora spp. an Erie, Eiche, Kastanie und anderen Baumen-aktueller Stand in der Bundesrepublik Deutschland. Nachrichtenblatt des Deutschen Pjlanzenschutzdienstes 48(7), 160 WERRES S., HAHN, R. und THEMANN K. (1997): Application of different techniques to detect
Phytophthora spp. in roots of commercial produced Chamaecyparis lawsoniana. Zeitschrift for Pjlanzenkrankheiten und Pjlanzenschutz 104(5), 474-482.
WERRES S. (1998): Mikroorganismen aus der Gattung Phytophthora - Erlensterben. Allgemeine Deutsche Forstzeitschrift 10, 548-549
THEMANN K. und WERRES S. (1998): Verwendung von Rhododendronblattern zum Nachweis van Phytophthora-Arten in Wurzel- und Bodenproben (Use of Rhododendron leaves to detect Phytophthora. species in root and soil samples). Nachrichtenblatt. des Deutschen Pjlanzenschutzdienstes 50(2), 37-45.
Guidlines for the handling of the Rhododendron leaf test to detect Phytophthora spp. in root, soil and water samples (www.bba.de/phytophldiagnose.htm).
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