Chalara fraxinea
Ash dieback
Why: A disease suspected to be caused by a newly described fungus species, Chalara fraxinea, has increasingly been observed in European countries on ash trees (Fraxinus excelsior) in the last ten years. Because ash dieback may represent a serious threat to forest, amenity and nursery ash trees, the EPPO Secretariat decided that C. fraxinea should be added to the EPPO Alert List. However, it is acknowledged that much data is lacking on its pathogenicity (other biotic and abiotic factors could be involved in ash dieback), biology, geographical distribution and economic impact.
Where:
EPPO region: Austria, Germany, Lithuania, Poland, Sweden (C. fraxinea has been identified in these countries). On the basis of symptoms, the disease has also been observed in: Denmark, Estonia, Finland (Åland archipelago but absent on the mainland), Latvia.
On which plants: Fraxinus excelsior (European ash). No data is available on the susceptibility of other Fraxinus species.
Damage: Initially, small necrotic spots (without exudate) appear on stems and branches. These necrotic lesions then enlarge resulting in wilting, dieback of branches and particularly in the death of the top of the crown. The disease is often chronic but can be lethal. Ash dieback has been observed not only on forest trees but also in urban areas (parks and gardens) and in nurseries.
Pictures of the disease can be viewed on the Internet: http://www.plantesygdomme.dk/Asketoptoerre/thumbnails.html
Dissemination: Data is lacking on the biology of C. fraxinea. It was isolated from diseased twigs and branches, as well as in dead roots of living ash trees.
Pathway: Although data is lacking on the biology of the fungus, it seems likely that plants for planting and wood of F. excelsior could be pathways for spreading the disease over long distances.
Possible risks: Fraxinus are widely grown across the EPPO region both for forestry and amenity purposes. Although data is still lacking on the exact role of C. fraxinea in ash dieback, EPPO member countries should be warned that ash dieback is emerging in Europe and that there may be a risk in moving diseased F. excelsior plants across the region without any precaution. Further studies are obviously needed on the etiology of ash dieback, its geographical distribution and economic impact.
Source(s)
Halmschlager E, Kirisits T (2008) First report of the ash dieback pathogen Chalara fraxinea on Fraxinus excelsior in Austria. New Disease Reports, Volume 17, February 2008 - July 2008. http://www.bspp.org.uk/ndr/july2008/2008-25.asp
Kowalski T (2006) Chalara fraxinea sp. nov. associated with dieback of ash (Fraxinus excelsior) in Poland. Forest Pathology 36(4), 264-270.
Schumacher J, Wulf A, Leonhard S (2007) [First record of Chalara fraxinea T. Kowalski sp. nov. in Germany – a new agent of ash decline.] Nachrichtenblatt des Deutschen Pflanzenchutzdienstes 59(6), 121-123 (in German).
INTERNET (last retrieved in 2007-09)
Forest & Landscape Denmark. Ash dieback in Denmark. http://en.sl.life.ku.dk/forskning/fagdatacenterskov/skovsundhed/skader/asketoptoerre.aspx
NAPPO – Pest Alert System. Chalara fraxinea Kowalski - Intensive dieback of European ash in Poland associated with a newly described fungal species, Chalara fraxinea. http://www.pestalert.org/viewNewsAlert.cfm?naid=26
Nordic Forest Research Cooperation Committee. Ash decline in Nordic and Baltic countries. http://www.metla.fi/org/pathcar/ash-decline.htm
Research and Training Centre for Forests, Natural Hazards and Landscape (BFW)
Actual situation of dieback of ash in Austria by TL Cech and U Hoyer-Tomiczek. http://bfw.ac.at/400/pdf/fsaktuell_40_3.pdf
Ash dieback and premature leaf shedding in Austria by TL Cech. http://bfw.ac.at/400/pdf/fsaktuell_37_8.pdf
EPPO RS 2007/179, 2008/128
| Panel review date - | Entry date 2007-09 |
Back to Alert List