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Chalara

Chalara Ash Dieback at Westonbirt Arboretum

Chalara ash dieback is a serious disease of ash trees, caused by a fungus called Hymenoscyphus fraxineus, which is infecting ash trees across Europe and the UK. The disease affects ash trees by blocking the water transport systems, causing leaf loss, lesions in the wood and on the bark. This leads to the dieback of the crown of the tree. Trees become brittle over time with branches breaking away from the main body of the tree. If they are not dealt with, trees are at risk of collapsing, presenting an immediate danger to the surrounding area.

It was first identified at Westonbirt Arboretum in 2015, and since then we have been working with colleagues in Forest Research carefully to monitor the impact of the disease on our trees. The disease is likely to cause significant damage to the UK’s ash population.

Chalara ash dieback at Westonbirt Arboretum video

Chalara ash dieback has now infected ash trees throughout Silk Wood at Westonbirt Arboretum, and in order to ensure the future health of this ancient woodland, Forestry England is now faced with having to respond to this threat to maintain the health of Silk Wood for future generations. This will involve removing infected ash trees to make way for new plantings of various species, which will help to create a resilient woodland.

Video credit: Heliexperts The Drone Company

Heliexpert The Drone Company

The Silk Wood Project video

In 2019 some initial work was done to remove infected ash trees from main pathways in the arboretum, to ensure the safety of visitors and staff. In early 2021 work will begin to remove infected ash trees from Silk Wood. This will mean that there will be significant changes to Silk Wood over the coming years as we work to ensure the continuing health and resilience of the whole woodland. In some areas, we may be removing large numbers of trees, and replanting different species. In other areas, we may try a non-intervention approach.

Monitoring tolerance to Chalara ash dieback video

This does not mean that the ash tree will be disappearing from Silk Wood all together – in some areas Fraxinus excelsior (known as European ash or common ash – which is the disease most affected by Chalara ash dieback) will be retained to monitor the progression of the disease. We have 23 other exotic species of ash which will remain and be carefully monitored for tolerance to the disease. We’ll also monitor native ash specimens that show signs of tolerance.

We all have a part to play in the prevention of the spread of pests and diseases. Though Chalara ash dieback spreads on the wind-borne spores of the fungus Hymenoscyphus fraxineus, and so there is little we can do to prevent the spread of the disease, the spread of other threats can be slowed or stopped by:  

  • Keep it clean! Pests and diseases can spread in the mud and debris on shoes, paws and tyres, so simple measures such as cleaning your boots and car wheels after a walk in the Forest can help to limit the spread of diseases.
  • Don’t risk it! Don’t bring any plant or tree products back from trips abroad, because these might be carrying harmful non-native tree pests or pathogens.
  • Be vigilant! Report any trees that you suspect are in ill-health to the Forestry Commission using Tree Alert
  • Join us! You can help us to protect Silk Wood against the threat of pests and diseases by joining the Friends of Westonbirt Arboretum. Your membership donation goes directly back into maintaining Silk Wood and Westonbirt Arboretum for future generations.