Ash dieback

Dieback of ash, a disease caused by the fungus Hymenoscyphus fraxineus (previously called Chalara fraxinea), was identified in the UK in 2012 in a consignment of infected trees from the Netherlands and in woodlands in Norfolk and Suffolk. It is believed that the Chalara fungus may be spread by wind, through the movement of infected ash trees and, to a lesser extent, through the movement of logs and unsawn wood. The disease causes the crown of ash trees to blacken and wither, along with leaf loss and bark lesions and is usually fatal.

In Europe, Chalara has resulted in widespread losses in ash populations since the early 1990s and has the potential to cause extensive damage to the UK’s ash population. Currently there are almost 1,000 confirmed cases of ash dieback, including nursery stock, recently planted sites and established woodland. Modelling published in Defra’s Tree Health Management Plan (2014) suggests that by 2018 over 75% of ash trees in Kent could be infected along with half of ash trees in Essex, Norfolk and Suffolk.

Current initiatives aim to slow the spread of the pathogen, develop treatments, identify resistance and build genetic resilience.

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