Why: A new disease causing tree mortality has increasingly been observed in European countries on ash trees (Fraxinus excelsior) during the last ten years. The first studies revealed the presence of a pathogenic fungus which was described as a new species, Chalara fraxinea. Because ash dieback could represent a serious threat to forest, amenity and nursery ash trees, the EPPO Secretariat decided to add C. fraxinea to the EPPO Alert List in 2007. In 2008, studies first concluded that C. fraxinea was the anamorph of an already described species, Hymenoscyphus albidus, which is considered as non-pathogenic, native, and widespread in Europe. The emergence of a new disease was thus difficult to explain. However, in 2011 molecular studies concluded that C. fraxinea was in fact the anamorph of a new species called Hymenoscyphus pseudoalbidus (closely related but distinct from H. albidus). In 2012, Zhao et al. considered that a fungus isolated in 1993 from petioles of Fraxinus mandshurica in Japan and initially assigned to Lambertella albida (a synonym of H. albidus) was in fact H. pseudoalbidus. Although further studies are needed, this may indicate that Asia (and possibly Japan) is the area of origin of H. pseudoalbidus.
Pictures were kindly provided by Prof. H. Solheim
and Landscape Institute, Aas), more can be viewed on the EPPO gallery
EPPO region: Austria, Belgium, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Guernsey (under eradication), Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Romania, Russia (Kaliningrad), Slovakia, Slovenia, Sweden, Switzerland, Ukraine, United Kingdom (under eradication).
On which plants: Fraxinus excelsior (European ash) and F. angustifolia (narrow-leafed 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.
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.
Anonymous (2008) La lettre du DSF no. 37 – Décembre 2008. Département de la Santé des Forêts (FR), 12 pp.
Anonymous (2009) La lettre du DSF no. 38 – Juin 2009. Département de la Santé des Forêts (FR), 9 pp.
Anonymous (2009) La lettre du DSF no. 39 – Décembre 2009. Département de la Santé des Forêts (FR), 9 pp.
Barić L, Zupanić M, Pernek M, Diminić D (2012) [First records of Chalara fraxinea in Croatia - a new agent of ash dieback (Fraxinus spp.)]. Šumarski list 9-10, 461-469 (in Croatian).
Chandelier A, Delhaye N, Helson M (2011) First report of the ash dieback pathogen (anamorph Chalara fraxinea) on Fraxinus excelsior in Belgium. Plant Disease 95(2), p 220.
Davydenko K, Vasaitis R, Stenlid J, Menkis A (2013) Fungi in foliage and shoots of Fraxinus excelsior in eastern Ukraine: a first report on Hymenoscyphus pseudoalbidus. Forest Pathology. doi:10.1111/efp.12055.
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
Ioos R, Kowalski T, Husson C, Holdenrieder O (2009) Rapid in planta detection of Chalara fraxinea by a real-time PCR assay using a dual-labelled probe. European Journal of Plant Pathology (in press).
Jankovský L, Holdenrieder O (2009) Chalara fraxinea ash dieback in the Czech Republic. Plant Protection Science 45(2), 74-78 (abst.).
Kirisits T, Matlakova M, Mottinger-Kroupa S, Halmschlager E, Lakatos F (2010) Chalara fraxinea associated with dieback of narrow-leafed ash (Fraxinus angustifolia). Plant Pathology 59(2), p 411.
Kirisits T, Matlakova M, Mottinger-Kroupa S, Cech TL, Halmschlager E (2009) The current situation of ash dieback caused by Chalara fraxinea in Austria. SDÜ Faculty Forestry Journal, Serial A special issue, 97-119.
Kowalski T (2006) Chalara fraxinea sp. nov. associated with dieback of ash (Fraxinus excelsior) in Poland. Forest Pathology 36(4), 264-270.
Kowalski T, Holdenrieder O (2008) Pathogenicity of Chalara fraxinea. Forest Pathology 38(6), 1-7.
Kowalski T, Holdenrieder O (2009) The teleomorph of Chalara fraxinea, the causal agent of ash dieback. Forest Pathology (in press).
Kunca A, Leontovyc R, Zubrik M, Gubka A (2011) Bark beetle outbreak on weakened ash trees and applied control measures. Bulletin OEPP/EPPO Bulletin 41(1), 11-13.
NPPO of Finland (2008-10).
NPPO of Guernsey (2012-11).
NPPO of Italy (2009-11).
NPPO of Lithuania (2010-05).
NPPO of Luxembourg (2014-04).
NPPO of the Netherlands (2010-08).
NPPO of Slovenia (2009-01).
NPPO of the United Kingdom (2012-03).
Personal communication with Dr Bjørn Økland, Norwegian Forest and Landscape Institute, Ås, Norway (2008-08).
Personal communication with Prof. Halvor Solheim, Norwegian Forest and Landscape Institute, Ås, Norway (2008-09).
Ogris N, Hauptman T, Jurc D, Floreancig V, Marsich F, Montecchio L (2010) First report of Chalara fraxinea on common ash in Italy. Plant Disease 94(1), p 133.
Queloz V, Grünig CR, Berndt R, Kowalski T, Sieber TN, Holdenrieder O (2011) Cryptic speciation in Hymenoscyphus albidus. Forest Pathology 41(2), 85-168.
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).
Szabó I (2008) [Dieback of common ash (Fraxinus excelsior) caused by Chalara fraxinea.] Növényvédelem 44(9), 444-446 (in Hungarian).
Timmermann V, Borja I, Hietala AM, Kirisits T, Soldheim S (2011) Ash dieback: pathogen spread and diurnal patterns of ascospore dispersal, with special emphasis on Norway. Bulletin OEPP/EPPO Bulletin 41(1), 14-20.
Zhao YJ, Hosoya T, Baral HO, Hosaka K, Kakishima (2012) Hymenoscyphus pseudoalbidus, the correct name for Lambertella albida reported from Japan. Mycotaxon 122, 25-41.
Department of Agriculture, Food and the Marine of Ireland.
- Chalara disease found in young ash trees. Press release of 2012-10-12. http://www.agriculture.gov.ie/media/migration/forestry/ashdiebackchalara/PR12Oct12.pdf
- Government steps up ash dieback (Chalara) eradication measures. Press release of 2012-12-13. http://www.agriculture.gov.ie/media/migration/forestry/ashdiebackchalara/PR13Dec12.pdf
ETH (Swiss Federal Institute of Technology Zürich). New fungus strikes the ash at its core by Peter Rüegg (2010-04-08). http://www.ethlife.ethz.ch/archive_articles/100408_eschenpilz_per/index_EN
Forest & Landscape Denmark. Ash dieback in Denmark. http://en.sl.life.ku.dk/forskning/fagdatacenterskov/skovsundhed/skader/asketoptoerre.aspx
Institut fédéral de recherches sur la forêt, la neige et le paysage WSL, Birmensdorf (CH). Meier F, Engesser R, Forster B, Odermatt O, Angst A (2008) Protection des forêts – Vue d’ensemble 2007. http://www.wsl.ch/forschung/forschungsunits/walddynamik/waldschutz/wsinfo/fsueb/fsub07f.pdf
Mattilsynet. Regulations of 8 September 2008 concerning measures against Chalara fraxinea. http://www.mattilsynet.no/english/plant_health/regulations_of_8_september_2008_concerning_measures_against_chalara_fraxinea_63077
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
Norwegian Institute of Forestry and landscape. Ash dieback. http://www.skogoglandskap.no/nyheter/2008/askens_endelikt (in Norwegian).
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, 2008/180, 2008/181, 2008/182, 2008/183, 2008/199, 2009/066, 2009/131, 2009/132, 2010/018, 2010/035, 2010/115, 2010/116, 2010/151, 2010/152, 2011/199, 2011/200, 2012/080, 2012/237, 2013/004, 2013/213, 2014/116
|Panel review date 2014-03||
Entry date 2007-09
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