Tree safety | Oxfordshire County Council

Tree safety

Things to look out for in your trees.

Woodland in The Chiltern Hills

Trees like any living thing can become ill (through disease or infestations) or be injured (through cracking or physical damage), and like us when we grow old they may not be as strong and supple as they once were.

Most trees will live for a long time and are perfectly healthy with little or no maintenance but others, depending upon their location, may need some attention from time to time.

We are keen to promote the maintenance of the trees that are located in private properties within Oxfordshire to keep them in a safe and healthy condition for those living around them and also make sure that wherever possible trees on adjoining land and properties do not present a hazard to our staff, visitors or others who attend our sites.

We encourage managers responsible for council sites, as well as members of staff, to keep an eye on the state of the trees in and around their properties, and to report any tree defects that they are concerned about. This may include trees that are located within a private property that could affect a county council site. However if a tree is located on your land, you have a duty of care to make sure that your tree(s) are kept in a safe manner.

Things to look out for to in an unsafe tree

Damage or injury

  • Splits or cracks in the trunk or branches.
  • Branches that are broken, hanging or that have dropped.
  • Sections of bark damaged or stripped to show the wood beneath (remember that some trees such as Plane or Eucalyptus naturally shed their bark).
  • Soil movement around the base of the tree in strong winds.

Ill health, disease or infestation

  • Sections showing signs of rotting.
  • Growth of fungi on the bark, wood or around the base of the tree.
  • Sections of infestations showing holes and damaged material.
  • Foliage dying back or going brown for no apparent reason on evergreen trees, or out of season for deciduous trees.

Common pests and diseases found within Oxfordshire

Tree pests

  • Horse chestnut leaf miner – this affects the photosynthetic capabilities of the trees and causes the tree to look unsightly. Rake up the leaves that have fallen and compost or dispose of them away from the affected tree or other horse chestnut trees.
  • Oak Processionary Moth – this is an insect that has the potential to cause serious damage, financially, sociologically and environmentally to Oxfordshire. At the moment it has only been found just south of the county in Berkshire. The caterpillars defoliate oak trees and can cause respiratory issues in humans and animals. If you think you have seen this insect please contact the tree team immediately and do not under any circumstances touch the caterpillars or nests on the trees.

Tree diseases

  • Acute Oak Decline - this very aggressive bacterial disease affects our native oak trees. Symptoms include bleeding lesions on the stems of trees and results in the rapid death of the tree.  Debris from remedial operations undertaken on dead trees should not be openly transported and all tools must be sterilized prior to their next use.  The County Council’s tree team can advise you on this matter.

Bleeding Canker – this is a bacterial disease caused by the Pseudomonas syringae pv aesculi. It affects the trees' ability to move water and nutrients around and can cause death to the whole or part of a tree. Not all trees affected will die as there are five different forms of the disease, each with their own level of aggressiveness.

Further information can be found about any of the tree pests and diseases above on the Forestry Commission website .

Various fungal diseases

The most common of these are:

  • Ganoderma spp. - a root decaying fungi, visible by a fungal bracket at the base of the tree.
  • Kretzschmaria deusta- a root rotting fungi, present as a black or grey patch at the base of a tree.
  • Inonotus hispidus - a black fungal bracket affecting the trunks and branches of ash trees in hedgerows, causing a brittle fracture and tree failure.

Further information regarding any of the above fungal diseases can be found on the Internet via most search engines.

Weather damage

Trees are sometimes damaged during heavy storms and may be struck by lightening. They can be affected by heavy snow-falls in winter and unseasonal strong winds if their leaves are still retained. Therefore it is good practice to check their structural condition after such events.

Choosing an arboricultural contractor/consultant

If you feel that your tree(s) may be unsafe then you should obtain the advice from a qualified person. This person must have undertaken relevant arboricultural training that will allow them to clearly identify any defects that may be present in your trees. This individual must also hold appropriate insurance for the works that they are undertaking and you should ask to see this prior to instructing them to undertake works.

If you require further information about choosing an appropriate contractor you can either contact the Arboricultural Association for a list of their approved members,

Last reviewed
11 January 2016
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