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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 you to decide what action to take if they are infested with OPM.
Three distinct geographical zones - Core, Control and Protected - have been defined for OPM management purposes (see maps below). The response, and any assistance available to deal with OPM, will depend on which of these zones your trees are in. They are:

  1. the Core Zone - the central part of the London outbreak area, coloured orange on the first map below;
  2. the Control  Zone - this is a buffer area, coloured yellow, surrounding the Core Zone. Work in the Control Zone aims to prevent or minimise outward spread into the Protected Zone. Whole local council areas - including ones where OPM has not been found - are included in the Control Zone if any part of them is within 20 kilometres (12.4 miles) of a confirmed OPM infestation; 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 to act to eradicate them if they do occur.

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. This manual provides advice on the action you can and should take, although you will not usually be legally required to do any work. However, we reserve the right to issue Statutory Plant Health Notices (SPHNs) requiring the removal of infestations in the Core Zone.

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 weaken trees and make them vulnerable to other pests and diseases, and to stresses such as drought.

Control and Protected Zones

The Protected Zone is recognised by the European Union. This means the government has a statutory duty to prevent the spread of OPM into the Protected Zone, and to take action to eradicate it if it is found there. Therefore the focus of government-funded activity must be on taking action in the Control Zone aimed at preventing spread into the Protected Zone, and minimising the population, spread and impacts within the Control Zone.

These aims are most likely to be achieved by a combination of:

  • surveying trees for evidence of OPM presence;
  • correctly timed applications of bio-pesticide which treat the whole of the canopy of affected and, on the precautionary principle, nearby trees; and
  • removal and destruction of nests, preferably while the caterpillars are inside them, thereby preventing them from reaching maturity and breeding.

In most cases, Forestry Commission England will take charge of bio-pesticide treatment of infested trees on private land in the Control and Protected Zones, at no cost to the owners. The Forestry Commission needs to know about OPM-infested trees which might not have been detected in its own surveys, especially in the Control and Protected Zones. Without these, it cannot help with control, so reporting sightings is important.  

However, where it finds nests in the Control and Protected Zones, the Forestry Commission issues SPHNs to the trees' owners or managers requiring them to have the infestations removed. The costs will be the owners' responsibility.

Note that SPHNs are primarily a management and monitoring tool for. Receipt of one is not an indication that you have committed an offence or are in any trouble. Nor does it imply that you are at fault for the infestation. However, the Forestry Commission may take enforcement action and prosecution for non-compliance with an SPHN.

There are other considerations which must be taken into account if you do any other work on trees in the Core or Control Zones, especially if it involves cutting branches and moving them off your land. (See section 10 - Other work on oak trees.)

See also the ‘Good practice guide for handling oak material in areas affected by OPM’.

The remainder of this manual gives you information to help you to help the Forestry Commission and its partners prevent OPM spread into the Protected Zone, and to minimise the pest's population, spread and impacts in the Core and Control Zones.

Last updated: 6th September 2018