First discovered in the UK in 2012, chalara ash dieback is still on the increase in the UK and has now been found among trees in Silk Wood, one of the oldest parts of Westonbirt, The National Arboretum in Gloucestershire.

© Andrew Montgomery

Forestry England is embarking on a major project to try to save the ancient woodland, by replacing many of the older ash trees with a wide variety of tree species that are more resilient to pests and diseases. Chalara ash dieback, which is caused by the fungus Hymenoscyphus fraxineus, thins the tree’s crown, ultimately leading to the death of the tree. Its spread is difficult to prevent as it travels on wind-borne fungus spores. Although the project will mean Silk Wood will look and feel very different, it will eventually result in a healthier woodland.

According to the Woodland Trust, Hymenoscyphus fraxineus will affect 95 per cent of ash trees across the UK. It can affect trees of all ages and symptoms include leaves developing dark patches in summer that wilt and discolour to black, shoots and leaves dying back, which is visible in summer, lesions where branches meet the trunk and new growth from previously dormant buds further down the trunk (a common response to stress in trees).

Another example of struggling trees in the UK is the horse chestnut, which has been added to the The European Red List of Trees and classed as 'vulnerable' following declines caused by the leaf-miner moth (Cameraria ohridella).

The list blames invasive species, unsustainable logging and urban development for the decline in tree health and trees and 58 per cent of Europe’s 454 endemic tree species are on the ‘at risk’ list.

For more information on the new plans for Westonbirt, head to Forestry England.