Ash dieback (Hymenoscyphus fraxineus) is a fungus which originated in Asia. It doesn’t cause much damage on its native hosts of the Manchurian ash (Fraxinus mandshurica) and the Chinese ash (Fraxinus chinensis) in its native range. However, its introduction to Europe about 30 years ago has devastated the European ash (Fraxinus excelsior) because our native ash species did not evolve with the fungus and this means it has no natural defence against it.
Ash dieback can affect ash trees of all ages. Younger trees succumb to the disease quicker but in general, all affected trees will have these symptoms:
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.
The tree can fight back, but year-on-year infections will eventually kill it.
Gardeners and managers of parks and other sites with ash trees can help stop the local spread of ash dieback by collecting the fallen ash leaves and burning, burying or deep composting them. This disrupts the fungus's lifecycle.
If you manage a woodland you can find more guidance from the Forestry Commission here.
If you have ash trees on your land that could potentially fall on neighbouring land, roads or property, it is important that the trees are assessed by a suitably qualified or experienced arboriculturalist to establish their health and the level of risk they pose.
What assessment has the Council made of the potential impact of ash dieback (Chalara) in the Pembrokeshire area and what strategy does it have to cope?
Pembrokeshire County Council is addressing the problem of Ash Die-back in its own stock of trees with a view to prepare a ‘Chalara Strategy’ to calculate the number of trees under our responsibility and to evolve a strategy for their treatment.