The paper presents recent results of the research on the main causal agent of ash dieback, previously known to occur only in the anamorphic stage as Chalara fraxinea. The presented research enabled to detect the presence of two fungal species on ashes: Hymenoscyphus pseudoalbidus and H. albidus s. str. Their morphological characteristics, life cycle and causal relationship between the fungi and ash dieback were also discussed.

Bakys R., Vasaitis R., Barklund P., Thomsen I. M., Stenlid J. 2009. Occurrence and pathogenicity of fungi in necrotic and non-symptomatic shoots of declining common ash (Fraxinus excelsior) in Sweden. Eur. Journ. Forest Res. 128: 51-60.
Breitenbach J., Kraenzlin F. 1981. Fungi of Switzerland. Vol. 1. Ascomyceten. Mycological Society of Lucerne.
Dennis R. W. G. 1956. A revision of the British Helotiaceae in the Herbarium of the Royal Botanic Gardens, Kew, with notes on related European species. Mycol. Pap. 62: 1-216.
Dennis R. W. G. 1981. British Ascomycetes. Cramer, Vaduz.
Drenkhan R., Hanso M. 2010. New host species for Chalara fraxinea. New Dis. Rep. 22: 16.
Ellis M. B., Ellis J. P. 1985. Microfungi on Land Plants. Richmond Publ.
Grad B., Kowalski T., Kraj W. 2009. Studies on secondary metabolite produced by Chalara fraxinea and its phytotoxic influence on Fraxinus excelsior. Phytopathologia 54: 61-69.
Halmschlager E., Kirisits T. 2008. First report of the ash dieback pathogen Chalara fraxinea on Fraxinus excelsior in Austria. Plant Pathology 57: 1177.
Hietala A. M., Solheim H. 2011. Hymenoscyphus species associated with European ash. Bulletin OEPP/EPPO Bulletin 41: 3-6.
Jankovsky L., Holdenrieder O. 2009. Chalara fraxinea – Ash dieback in the Czech Republic. Plant Protect. Sci. 45: 74-78.
Kirisits T., Matlakova M., Mottinger-Kroupa S., Halmschlager E., Lakatos F. 2009. Chalara fraxinea associated with dieback on narrow-leafed ash (Fraxinus angustifolia). New Dis. Rep. 19.
Kowalski T. 2001. O zamieraniu jesionów. Trybuna Leśnika 4/359: 6-7.
Kowalski T. 2006. Chalara fraxinea sp. nov. associated with dieback of ash (Fraxinus excelsior) in Poland. Forest Pathology 36: 264-270.
Kowalski T. 2007. Chalara fraxinea – nowo opisany gatunek grzyba na zamierających jesionach w Polsce. Sylwan 151 (4): 44-48.
Kowalski T. 2009. Rozprzestrzenienie grzyba Chalara fraxinea w aspekcie procesu chorobowego jesionu w Polsce. Sylwan 153 (10): 668 -674.
Kowalski T., Bartnik C. 2010. Morphological variation in colonies of Chalara fraxinea isolated from ash (Fraxinus excelsior L.) stems with symptoms of dieback and effects of temperature on colony growth and structure. Acta Agrobotanica 63: 99-106.
Kowalski T., Czekaj A. 2010. Symptomy chorobowe i grzyby na zamierających jesionach (Fraxinus excelsior L.) w drzewostanach nadleśnictwa Staszów. Leśne Pr. Bad. 71: 357-368.
Kowalski T., Holdenrieder O. 2009a. Pathogenicity of Chalara fraxinea. Forest Pathology 39: 1-7.
Kowalski T., Holdenrieder O. 2009b. The teleomorph of Chalara fraxinea, the causal agent of ash dieback. Forest Pathology 39: 304-308.
Kraj W., Zarek M, Kowalski T. 2011. Genetic variability of Chalara fraxinea, dieback cause of European Ash (Fraxinus excelsior L.). Mycological Progress DOI: 10.1007/s11557-010-0724-z
Ogris N., Hauptmann T., Jurc D. 2010. First report of Chalara fraxinea on common ash in Italy. Plant Disease 94: 133.
van Opstal N. A. 2011. Introduction to the EPPO Workshop on Chalara fraxinea, a major threat for ash trees in Europe. Bulletin OEPP/EPPO 41: 1-2.
Przybył K. 2002. Fungi associated with necrotic apical parts of Fraxinus excelsior shoots. Forest Pathology 32: 387-394.
Queloz V., Gruenig C. R., Berndt R., Kowalski T., Sieber T. N., Holdenrieder O. 2011. Cryptic speciation in Hymenoscyphus albidus. Forest Pathology 41: 133-142.
Rehm H. 1896. Ascomyceten: Hysteriaceen und Discomyceten. W: Rabenhorst L. [red.]. Kryptogamen-Flora von Deutschland, Oesterreich und der Schweiz. Eduard Kummer, Leipzig.
Schumacher J., Kehr R., Leonhard S. 2010. Mycological and histological investigations of Fraxinus excelsior nursery saplings naturally infected by Chalara fraxinea. Forest Pathology 40: 419-429.
Schumacher J., Wulf A., Leonhard S. 2007. Erster Nachweis von Chalara fraxinea T. Kowalski sp. nov. in Deutschland – ein Verursacher neuartiger Schäden an Eschen. Nachrichtenblatt Deutscher Pflanzenschutzdienst 59: 121-123.
Stocki J. 2001. Przyczyny zamierania drzew i drzewostanów jesionowych w Polsce. Głos Lasu 4, 17-19.
Talgo V., Sletten A., Brurberg M. B., Solheim H., Stensvand A. 2009. Chalara fraxinea isolated from diseased ash in Norway. Plant Disease 93: 548.
Timmermann V., Břrja I., Hietala A. M., Kirisits T., Solheim H. 2011. Ash dieback: pathogen spread and diurnal patterns of ascospore dispersal, with special emphasis on Norway. Bulletin OEPP/EPPO 41: 14-20.
Velenovsky J. 1934. Monographia Discomycetum Bohemiae, Praga.