Hymenoscyphus fraxineus

Hymenoscyphus fraxineus
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Leotiomycetes
Order:	Helotiales
Family:	Helotiaceae
Genus:	Hymenoscyphus
Species:	H. fraxineus
Binomial name
Hymenoscyphus fraxineus Baral et al. (2014)[1]
Synonyms
Chalara fraxinea (Kowalski et al., 2006) Hymenoscyphus pseudoalbidus (Queloz et al., 2011)

Hymenoscyphus fraxineus is an ascomycete fungus that causes ash dieback, a chronic fungal disease of ash trees in Europe characterised by leaf loss and crown dieback in infected trees. The fungus was first scientifically described in 2006 under the name Chalara fraxinea. Four years later it was discovered that Chalara fraxinea is the asexual (anamorphic) stage of a fungus that was subsequently named Hymenoscyphus pseudoalbidus and then renamed as Hymenoscyphus fraxineus.

It is now believed that the trees reported to have died in Poland in 1992 were infected with this pathogen. It is now widespread in Europe, with up to 85% mortality rates recorded in plantations and 69% in woodlands.^[2] It is closely related to a native fungus Hymenoscyphus albidus, which is harmless to European ash trees.^[3][4] A 2016 report published in the Journal of Ecology posited that a combination of H. fraxineus and emerald ash borer attacks could result in the extinction of European ash trees.^[5]