Ash dieback

Ash dieback disease, or Chalara, is a potentially fatal disease of ash trees. It has spread rapidly throughout the UK and is now firmly established in Midlothian. The disease spreads when spores are dispersed by wind. There is no known cure.

Affected trees will be a potential hazard to residents and property for at least the next decade. The only way to remove the risk posed by badly affected trees in public places is to fell them.

Based on data from European infections, up to 85% of UK ash trees outside woodlands are expected to die from ash dieback. Speed of decline varies, but some trees will succumb to infection within a few growing seasons.

Working on affected trees

Work on ash dieback affected trees is particularly hazardous.

Affected trees become unpredictably brittle as the disease takes hold. They can drop limbs or fail entirely in the later stages of the disease and are dangerous to climb, making felling more difficult and dangerous.

Unqualified people, or contractors who are unaware of the particular dangers, should never carry out this work.

Landowners' responsibilities, and what landowners can do to help

If you have ash trees that could potentially fall on neighbouring land, roads or property, you should check your trees for obvious signs of ill health or dieback. If you are concerned, you should have the trees assessed by a suitably qualified arborist to establish their condition and the level of risk they pose.

Private landowners have a duty of care under common law to ensure they do all that is reasonably practicable to prevent injury or damage to neighbours and anyone visiting their land. The Highways Act also requires them to ensure their trees do not endanger or impede people on roads and footpaths.

Businesses have additional requirements under the Health and Safety at Work Act to ensure their work places are safe.

Larger landowners and businesses should take the following steps:

  • identify how many ash trees you have and where they are
  • assess their current condition - use percentage of canopy cover remaining
  • identify where affected trees pose a risk
  • appoint qualified tree specialists to remove hazardous trees.

It is essential that a qualified professional carries out any tree work.

We recommend that landowners follow the guidance from the Tree Council.

Undertaking work on ash trees

Tree contractors are at the greatest risk of harm from dying ash trees, so it is vital that they are fully qualified and insured and aware of the particular dangers of dealing with Ash Dieback affected trees. Trees can become unpredictably brittle and unsafe to climb even before they are half dead.

Climbing an ash tree that is class 3 or 4 is especially dangerous. (Classifications below)

The Arboricultural Association provides advice for both tree contractors and those employing them.

Advice from the Arboricultural Association

Report a tree of concern

The tree condition score is a useful guide. Any trees at class 3 or 4 are of concern. Those at class 4 may well need removed.

Ash die back - class 1
Class 1
100% - 76% canopy
(100% - 95% would rate as exceptionally healthy)

Ash die back - class 2
Class 2
75% - 51% canopy

Ash die back - class 3
Class 3
50% - 26% canopy

Ash die back - class 4
Class 4
25% - 0% canopy

Report trees of concern in council parks and open spaces:

Report trees of concern next to roads:

If the trees are within the estate you live in and this is maintained by a factor or housing association, please report trees of concern to the factor or housing association.

Resistant trees

Whilst we must fell infected trees before they become a danger, we also need to keep the 10% of trees that may be resistant to the disease, so that a new generation of more resilient ash can establish.

We hope to assess trees on a case-by-case basis in order to identify any with resistance. Tests are ongoing to try to find and propagate resistant specimens.