Ash dieback

Ash Dieback, also known as Chalara, is a fungal disease affecting ash trees. The scientific name for the fungus that causes the disease is Hymenoscyphus fraxineus. Trees are now infected across all of Britain. In North Somerset we must begin to manage the effects of the disease.

Ash Dieback can prove fatal to trees, and it may affect up to 90% of ash trees in Britain. Younger ash trees die very quickly but older trees can survive with the infection for longer.

Trees in woodlands are also affected more than trees in parks due to a high volume of fungal spores from infected leaves. Other environmental conditions can also determine how quickly a tree may decline; the disease can be unpredictable. Unfortunately, there is no way of stopping the disease.

The council manages around 75,000 to 80,000 ash trees.

Identifying ash trees

A close up image of the green leaves of an Ash tree

The Woodland Trust has more information about how to identify Ash trees. Key things to look out for include: 

  • pinnate leaves
  • purple flowers
  • winged fruits or 'keys'

How to identify ash dieback

It is easier to identify Ash Dieback disease in the summertime – when trees are in full leaf.

The Forestry Commission is the best source of information for how to identify Ash Dieback. They have produced detailed guidance below. 

How we manage ash dieback

We carry out surveys to make assessments and monitor the health of infected trees. In many circumstances we may eventually have to remove trees for safety reasons. Where the trees are safe to be left, they can become valuable deadwood habitat in woodlands.

On occasion, it may appear that we are removing healthy trees. Sometimes infected trees are in a difficult position to manage, such as on the side of a busy road. In these cases, where trees are declining due to the disease, we will usually need to remove all the ash trees in the area. Long-term survival rates are low where the infection has taken hold. 

Our action plan

We have produced an Ash Die Back Action Plan which provides details of how we will address the issue in North Somerset.

Protected ash trees

Ash trees under preservation orders or in conservation areas

Ash trees will continue to be protected under existing preservation orders in the usual way.

If you are concerned about ash dieback, we recommend that an assessment is made of your trees by a competent tree professional when the tree is in full leaf. This should be done before applying for any works. 

We will also still consider making new Tree Preservation Orders on ash trees that are not in decline from Ash Dieback. This will make sure we keep valuable trees for as long as possible, and that they are replaced with new trees if they require removal in the future.

More information can be found in our Trees section below. 

Trees on private land

Landowners are responsible for trees on their land so if you are a tree owner and concerned about ash dieback, an assessment by a competent tree professional when the tree is in full leaf is recommended. This should be done before carrying out any works.

Protected ash trees will continue to be protected under existing preservation orders in the usual way. In the case of dead protected ash trees, as for all protected trees, we must still be given five days written notice before dead trees are removed.

Find out more about carrying out works on protected trees

What if I have an ash tree on my property next to the road?

If a tree specialist has advised that you prune or remove your trees and they are near the highway, you must use a tree surgeon. A list of approved surgeons is available on the Arboricultural Association website.

If this work requires the road to be closed or traffic changed you may need to apply for permission. See our road closures and temporary traffic management page for more information.

Dead and dangerous trees

As for all protected trees, we must still be given 5 days written notice before dead trees are removed. 

Trees on development sites

Ash trees should still be assessed as usual as part of any planning application. 

If you are an arboricultural consultant, the following guidelines about ash trees will apply: 

It is not considered appropriate to down-grade the BS5837 category of ash trees on development sites unless the tree is both:

  • infected with ash dieback
  • obviously declining following an assessment of the live canopy percentage.

Replanting and replacing trees

Where possible ash trees should be replaced with an alternative native species.

Please see the below advice note produced by the Devon Ash Dieback Resilience Forum. They worked with The Tree Council to create detailed guidance on replacing diseased ash trees.

More information

Further information on ash dieback can be found below.