Surrey County Council is responsible for dealing with highway trees which have the potential to cause harm to pedestrians, other non-motorised users or vehicles. We are currently experiencing a number of pests and diseases that are increasingly affecting the trees in Surrey.
Page contents
- Ash Dieback (Hymenoscyphus fraxineus) and felling trees adjacent to the highway
- Our approach to monitoring and dealing with Ash Die Back
- Replanting trees
- Oak Processionary Moth
- Our approach to dealing with Oak Processionary Moth
Ash Dieback (Hymenoscyphus fraxineus) and felling trees adjacent to the highway
Ash Dieback is a disease caused by a fungus called Hymenoscyphus fraxineus. The disease causes leaf loss and crown dieback in affected trees, and it may lead to trees losing large limbs or the death of the tree. More information can be found on the Ash Dieback webpage.
Our approach to monitoring and dealing with Ash Dieback
We survey annually all large groups of ash trees along the highway which have been identified as suffering from Ash Dieback.
The surveys verify if the trees have deteriorated further over the last 12 months or stayed the same. The tree groups are then prioritised in alignment with how we maintain our trees.
We aim to fell large groups of trees outside the bird nesting season, although occasionally we will fell trees within that period if the safety of the highway is at risk. Works carried out during the bird nesting season require our contractors to undertake a good physical check of the trees and surrounding area to ensure that nesting birds are not disturbed.
Due to the way that trees are affected by Ash Dieback, traditional methods of felling the trees are not always possible. This may mean that large machinery is used to fell the trees. Timber from the felled trees is sometimes left, in rural areas, to provide a natural habitat for the existing wildlife.
Additionally, dead hedging can be created to provide shelter for small mammals, insects and birds. The material will eventually rot away in ways which are good for ecosystems but this takes quite a few years as the branches are largely off the ground.
Replanting trees
Where we have had to remove large areas of trees, we will monitor the site and consider for replanting in future years. Any replanting will be subject to funds being available, the site being assessed as suitable, and not having statutory undertaker plant under ground which could be affected by any new trees,
Additional information on other highway trees planting is available on the planting trees on the highway webpage.
Oak Processionary Moth (Thaumetopoea processionea)
Oak processionary moth (OPM) (Thaumetopoea processionea) is a non-native pest of oak trees whose caterpillars can pose risks to human and animal health. The species was first identified in Surrey in 2017 and has since become established in parts of the county. The caterpillars feed on oak leaves and develop nests on trunks and branches, and their tiny hairs can cause irritation to the skin, eyes and respiratory system of people and animals who come in contact with them. More information can be found on the advice about processionary moth webpage.
Our approach to dealing with Oak Processionary Moth (OPM)
Surrey County Council takes a risk-based and proportionate approach to managing OPM on the public highway. We focus our resources on locations with higher public use and interaction, while recognising that OPM is now established across parts of the county and cannot be fully eradicated. We do not use chemical insecticide sprays on infected trees; instead, we remove nests by hand where action is required. This is because insecticides would affect all caterpillars, not just OPM, and their use would be disproportionate to the level of control needed. Our approach balances public safety, environmental considerations and the practicalities of large-scale management.
When we will take action on OPM
We prioritise managing OPM where there is a higher risk to public health or frequent contact with people. We will normally take action where:
There is a high likelihood of interaction with the public on the highway, for example:
- Nests located within arm’s reach of pedestrians on a footway
- Trees adjacent to benches, or frequently used crossings, or bus stops
The location has a high concentration of people, and therefore an increased risk of contact, such as:
- Schools, nurseries and playgrounds
- Shops, town centres and public facilities
- Health centres and similar community buildings
When we may not take action on OPM
We may decide not to intervene where the risk to the public is low or where action would have limited benefit. This may include cases where:
- OPM is present but the likelihood of public interaction is low
- The area does not experience high footfall or regular public use, such as locations away from schools, shops or community facilities
- The nests are unlikely to pose a hazard due to their location, for example where they are out of reach or not near pedestrian routes
- Branches from highway trees overhang private property; we do not remove OPM solely for this reason