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3. Management zones - OPM manual

Your next duty is to check which OPM management zone your oak trees are in, because this will help to inform your decision about what action to take if they are infested with OPM.
Three distinct geographical zones have been defined for OPM management purposes (see map below). The response, and any assistance available to deal with OPM, will depend on which of these zones your trees are in. They are referred to as:

  1. the 'Core Zone' (the central part of the West London outbreak area, coloured orange on the map);
  2. the 'Control' or Buffer Zone (an area surrounding the Core Zone, coloured yellow, where eradication remains the aim to prevent or minimise outward spread from the Core Zone); and
  3. the 'Protected Zone' (the OPM-free area, coloured green. This is effectively the whole of the remainder of the United Kingdom, where we are required to prevent incursions by OPM or, if they do occur, to take action to eradicate them).

Map - OPM management zones

Core Zone

As a simple guide, if your trees are anywhere in the London Boroughs of:

  • Ealing;
  • Hammersmith & Fulham;
  • Hounslow;
  • Kensington & Chelsea;
  • Kingston Upon Thames;
  • Richmond Upon Thames; or
  • the City of Westminster,

they are in the Core Zone, where control action is not compulsory, although we nevertheless strongly advise it.

If they are in the London Boroughs of:

  • Brent;
  • Hillingdon;
  • Merton;
  • Wandsworth; or

  • the Surrey District of Elmbridge,

they could be in the Core Zone or the Control Zone, depending on which part of the borough or district they are in. If your trees are in one of these council areas, the following maps will help you to work out which zone they are in.

In the Core Zone, it is tree owners’ responsibility to check their trees for OPM infestation and to take any necessary action. Although you will not usually be legally required to do any work, we reserve the right to issue statutory Plant Health Notices requiring the removal of infestations in the Core Zone which threaten to spread into, and become established in, the Control Zone. This manual provides advice on the action you can take.

We strongly recommend that you do take action to protect yourself, your family, neighbours, visitors, staff, pets and livestock, and others who have reason to be close to the trees.

Oak processionary moth caterpillars on oak tree, London, showing severe defoliationThis will also protect your oak trees from potentially damaging defoliation by the caterpillars, as in the tree in the picture. Severe defoliation can leave trees weakened and vulnerable to other pests, diseases and environmental stresses such as drought.

Control and Protected Zones

Outbreaks of OPM in the Control and Protected Zones are treated the same for management purposes, and we aim to eradicate them. Eradication is most likely to be achieved by a combination of methods, which include:

  • surveying trees for evidence of OPM presence;
  • correctly timed applications of insecticide which treat the whole of the tree canopy; and
  • removal and destruction of nests.

In general terms, Forestry Commission England will take charge of treating (by spraying with bio-pesticide) privately owned infested trees in the Control and Protected Zones, and there will be no costs for the owner.

If infested trees in the Control and Protected Zones are in public ownership, such as those in public parks and streets, the measures necessary will be mandatory, but will need to be carried out at owners' expense.

These distinctions between the Core and Control/Protected Zones are necessary because European Union legislation was introduced in October 2014 which recognises those parts of the UK that are outside the affected areas as a 'Protected Zone'. The Government now has a statutory duty to prevent infestation of the Protected Zone, and this has to be the focus of government-funded activity. Government policy continues to be to contain the spread of OPM from the West London outbreak, and to eradicate it elsewhere. Accordingly we focus government-funded control effort on the buffer area (the 'Control Zone') and the Protected Zone. The Core Zone has been defined using the best evidence and scientific advice available to us. The government budget has not been reduced, but we need to focus public resources on controlling those populations which most threaten to expand into, or further into, the Protected Zone.

If you do any other work on trees in either zone, especially if it involves cutting branches (tree surgery), there are other considerations which must be taken into account. (See section 9 - Other work on oak trees.) In particular, see also our ‘Good practice guide for handling oak material in areas affected by OPM’.

The rest of this manual gives you information to help you to help us to achieve eradication in the Control and Protected Zones, or to manage the pest as effectively as possible in the Core Zone.

Last updated: 8th June 2018