A highly infectious fungal disease known as ‘Ash dieback’ (also known as Chalara) is threatening to wipe out our native ash trees, as well as most other non-native members of the ash family. Ash trees are valuable features of Torbay’s landscape and can be found in our native woodlands and hedgerows.
Ash dieback affects ash trees (Fraxinus excelsior) and is caused by the fungus Hymenoscyphus fraxineus (previously known by the names Chalara fraxinea and Hymenoschyphus pseudoalbidus). It blocks the water transport systems in trees causing leaf loss, lesions in the wood and on the bark and ultimately the dieback of the crown of the tree.
The disease has come over from mainland Europe where it was noted in Poland in 1992 and has infected and affected the majority of Ash on the continent. It was first found in the UK in 2012 at sites that had received saplings from nurseries.
Since then the spread of the disease has now reached most areas of the UK. Within Torbay the flush of Ash leaf at the start of the 2019 summer showed indications of a high percentage of infected trees. Some trees do appear more infected than others and there may be some resilience to the disease within some of the specimens.
However, it is widely regarded that once the tree has reached 35%-40% mortality then it’s very unlikely that they will respond positively and will ultimately die due to the disease, or possibly else due to the weakened state of the tree. The rate of decline once a tree is infected can vary with some trees dying quickly and others seemingly able to hang on for a bit longer.
Regrettably, there is no known cure for the disease. Where trees have been shown to have a genetic resistance, and so remain unaffected or are able to tolerate the disease, this will hopefully enable us to understand the mechanics of the resistance and will potentially mean the re-stocking of the Ash.
Identifying the signs and symptoms of Ash dieback
- Dark lesions, often long, thin and diamond-shaped, appear on the trunk at the base of dead side shoots
- The tips of shoots become black and shrivelled
- Blackened, dead leaves - may look a bit like frost damage
- The veins and stalks of leaves, normally pale in colour, turn brown
- Saplings have dead tops and side shoots
- In mature trees, dieback of twigs and branches in the crown, often with bushy growth further down the branches where new shoots have been produced
- In late summer and early autumn (July to October), small white fruiting bodies can be found on blackened leaf stalks.
What are we doing to protect our Ash tree stock?
We will regrettably have to take action should it be shown that infected trees pose a significant risk to people, property or traffic. This though will result in the loss of some of our landmark trees and the general removal of the Ash population throughout Torbay.
To identify the areas where possible intervention might be needed we will assess areas of the Bay that are considered high risk. Where other Ash trees are next to or opposite those that pose a risk they will also be looked at. If it is seen that they are also a significant risk to people, property or traffic action will need to be taken with these as well.
When work on the trees is being carried out, boards will be displayed to show that this is related to Ash dieback.
Ash Trees in Private Ownership
Some of our larger Ash trees are contained within the garden areas of private/residential properties. Household owners, or those responsible for the trees, will have to manage these. However, should the tree be subject to statutory legislation, such as tree preservation orders or within a conservation area, the normal processes still apply. An appropriately qualified person should be employed to correctly identify the disease and make the necessary recommendations for the tree. This is because in some instances an Ash may show signs of decline but the cause may not be Chalara ash dieback.
There will be numerous opportunities for replanting and we are currently looking into the most suitable species to replace the Ash with. The species used is likely to be diverse which will increase resilience within the tree stock and promote greater biodiversity.
Although taking a long time to reach the mature heights of some of the Ash that will inevitably be removed, the replacement trees will provide significant succession planting. These new trees will provide future amenity and biodiversity within Torbay, providing a green environmental legacy for future generations to enjoy.
As part of the ongoing action to mitigate the loss of Ash trees a range of initiatives will take place. Community groups will be encouraged to look after trees, nurseries created to provide replacement tree species, diversity also encouraged, including the potential for fruit tree planting to provide an all year round interest.
This community engagement is seen as a vital part of the process to establish the future tree cover within Torbay, with the potential to use both native and exotic species. One of the many outstanding features of where we live is the benefits accrued from being able to plant exotic species and for them to not only survive but to thrive in our environment. This diverse range of planting will enable Torbay to recover from the loss of the Ash tree from the landscape and provide resilience as we move forward.