chalara die-back of ash

(Chalara fraxinea)

A fungal pathogen of ashes (Fraxinus spp.) discovered in Britain in June 2012. In Europe the disease was first noted in Poland in 1992 and has since caused serious losses, for instance killing up to 90% of Denmark’s ash trees. Chalara fraxinea is the anamorph of the Ascomycete fungus Hymenoscyphus pseudoalbidus, which inhabits ash leaf litter. North American species are more or less susceptible while Asian Fraxinus spp. have high resistance, suggesting that the disease originated from Asia. Die-back in ash has several causes.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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