GardenDrumChalara dieback of ash trees

The UK’s 80 million ash trees are under threat of chalara dieback, a fungal disease that first appeared there earlier this year.

The fungus is believed to have spread from Europe through the importation of diseased young ash plants from several European nurseries. There is no cure for the pathogen and while young, immature ash trees are most at risk, even older trees will eventually succumb. Symptoms include wilting new growth and a blackish discolouration of the leaf base and midrib. Cankers develop on stems and bark and eventually the whole canopy begins to die. Epicormic shoots develop at the base of the tree.

While the appearance of chalara dieback in most of the UK is linked to the movement of infected nursery stock, there are also unconnected infected trees in woodlands in East Anglia, meaning that it may also travel by wind, insects or birds. Movement of logs and mulch from felled infected trees, rain splash of spores onto neighbouring trees and people walking though infected woodlands may also spread the fungus.

UK outbreak map of chalara dieback of ash

The fungus was first identified in Poland back in 1992 and has spread west and north through Europe. It’s estimated that Denmark has lost up to 90% of its ash trees in the past 5 years. There were 309 confirmed sightings in the UK as at 12 Dec 2012.

You can read more details about chalara ash dieback in this UK Forestry Commission publication. If you think you’ve found an ash tree with chalara dieback in the UK, you should first check your identification using the photos and video and then report it using this Tree Alert Form

The video below can assist identification and you can read more about developments in ash dieback management in this very interesting article at Tiger Sheds Garden Resources.

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