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Oak Processionary Moth FAQ

Author:  Defra
Last Updated:  08/08/2019

FAQ – Oak processionary moth interceptions and strengthened national measures

July 2019


What is the current situation?

The government’s Plant Health Service is dealing with findings of oak processionary moth caterpillars on recently imported oak trees. Around 60 interceptions have been made at recent planting sites in the UK Protected Zone. Swift action is being taken by Forestry Commission, APHA and the Devolved Administrations to eradicate recent findings, including tracing recent imports of oak trees, on the ground surveillance and the destruction of caterpillars and infested trees. Landscapers, nurseries, landowners and woodland managers are being urged to check any imported oak trees and to report any findings through TreeAlert and their local plant health inspector.

Where did the trees come from?

OPM has been found on a number of recently planted trees imported from the Netherlands and Germany.

How many oak trees are affected?

A number of infested trees have been found at around 60 planting sites in the UK Protected Zone. All oak trees on these sites have been rapidly surveyed, and will be monitored as a precaution.

Where are the sites?

In England, infested trees have been found in Bedfordshire, Berkshire, Buckinghamshire, Birmingham, Cambridgeshire, County Durham, Devon, Dorset, Essex, Gloucestershire, Greater Manchester, Hampshire, Hertfordshire, Kent, Lancashire, Leicestershire, Lincolnshire, London, Merseyside, Middlesex, Nottinghamshire, Oxfordshire, Southampton, Staffordshire, Suffolk, Surrey, Warwickshire, West Midlands, Wiltshire and Yorkshire.

In Scotland, infested trees have been found in Angus, Edinburgh, Fife, Inverness and Lanarkshire.

In Wales, infested trees have been found in Deeside and Glamorgan.

A 10km map is available on the Forest Research website.

What has happened to these trees?

Swift action has and is being taken to eradicate recent findings in the Protected Zone including tracing recent imports of oak trees, on the ground surveillance and the destruction of caterpillars and trees.

How did you find out?

Through TreeAlert reports, and the work of the government’s Plant Health Service. Anyone who has planted larger oaks (defined below) imported from the Netherlands or Germany, should urgently check the trees for signs of OPM and report any findings to TreeAlert. It is vital that these trees are checked now to minimise the risk of spread of OPM, and protect the health of our oaks.

Are any other trees/areas affected?

We are continuing to investigate the wider situation through tracing work and surveillance activities, and will take swift and appropriate action.

Whose fault is this?

The Plant Health Service has received reports of an exceptional expansion of the OPM population in parts of Europe, due to the weather conditions experienced last year. This is likely to have contributed to the pest pressure around supplying nurseries. The recent interceptions have highlighted that the import requirements were not providing an adequate degree of assurance about pest freedom, which meant that we had to review aspects of the National Measures for this pest introduced in 2018. In particular it is clear that the requirements for nurseries in the open air in infested areas, including to confirm vicinity freedom, were not working and so we have taken action to revoke that option. Details on our strengthened national measures can be found below.

How are you going to stop this from happening in the future?

We have urgently reviewed legislation to strengthen measures further in England. Similar legislation is in place in Northern Ireland, Scotland and Wales to ensure UK-wide protection.

I think I have found trees affected by OPM. What do I do next?

Please report any findings to TreeAlert. If you trade in oak trees and have found infested trees on your site, please contact your local APHA Plant Health Inspector.

What happens after I report my trees?

The Forestry Commission and APHA will assess the situation and advise on what appropriate action should be taken.

Will I be compensated?

It has been the policy of successive Governments not to pay compensation for plant health interception measures, as we believe that resources are better directed at the detection of pests and diseases, risk management and research.

The cost of eradication for interceptions is the responsibility of the landowner. Eradication can be arranged via the Forestry Commission, or by the landowner as per the terms in the Statutory Plant Health Notice.

Owners of infested trees should retain any official documents and contact their supplier.


The Plant Health (Amendment) (England) Order 2019

Legislation available at: http://www.legislation.gov.uk/uksi/2019/1128/contents/made

What has been introduced?

On Monday 15th July, Defra introduced strengthened national legislation to protect oak trees against OPM through movement and import. The legislation builds on measures introduced in August 2018 and prohibits the movement of certain oak trees into the OPM Protected Zone unless specific conditions are met.

What does this mean in practice?

The strengthened national legislation applies to oak trees (Quercus L), other than Q. suber (cork oak), with a girth at 1.2m above the root collar of 8cm or more. Such trees represent the greatest likelihood of introducing OPM, hence the need for strengthened requirements.

The legislation requires that imports into and movements within the OPM Protected Zone can only take place if the trees concerned:

  • have been grown throughout their life in places of production in countries in which Thaumetopoea processionea L. is not known to occur;
  • have been grown throughout their life in a protected zone which is recognised as such for Thaumetopoea processionea L. or in an area free from Thaumetopoea processionea L., established by the national plant protection organisation in accordance with ISPM No. 4; or
  • have been grown throughout their life in a site with complete physical protection against the introduction of Thaumetopoea processionea L. and have been inspected at appropriate times and found to be free

Most oak tree imports are from within the EU, but the new requirements apply to both third country and EU imports, as well as movements from the infested area in and around London into the Protected Zone.

Why has this been introduced?

OPM is established across many parts of Europe and is regulated in the EU Plant Health Directive. National legislation to strengthen import controls were introduced in 2018. Recent interceptions of OPM on oak trees have highlighted that the import controls for oak trees introduced in 2018 need to be further strengthened. To combat potential threats, this legislation has been strengthened in the UK before the main 2019 import season.

Where did these intercepted trees come from?

Infested trees were intercepted from within the EU. Most of the affected consignments were from the Netherlands.

Who does this apply to?

The legislation applies to all those importing and moving oak trees above the specified girth, including small businesses.

Which countries are classified as OPM-free?

Ireland is the only recognised pest-free country in the EU.

Where is the Protected Zone?

A Protected Zone is an area of the EU designated as free of a particular pest, which is established elsewhere in the EU. Special import and movement requirements apply to prevent infested plants being introduced into zones. The majority of the UK has Protected Zone status for, and is free from, OPM. OPM is only known to be established in parts of London and surrounding areas.

A map is available on the OPM website www.forestresearch.gov.uk/opm.

What about smaller oak trees, surely they pose a risk too?

Larger trees represent the greatest likelihood of introducing OPM, as they are more susceptible to pest populations and more difficult to inspect, hence the need for strengthened requirements for these trees. Existing requirements on OPM freedom will continue to apply for trees with a smaller girth than 8cm. There have been no interceptions involving such smaller trees.

All oak trees moving into and within the Protected Zone must be accompanied by a plant passport, regardless of the size of the consignment.

All landings of oak plants in England must be pre-notified to APHA to facilitate targeted inspections for pests and diseases. There are similar notification schemes in Northern Ireland, Wales and Scotland.

This legislation is England only. What is Northern Ireland, Scotland and Wales doing about it?

The majority of oak tree imports are into England but oak trees can be moved to other parts of the UK after import. Northern Ireland, Scotland and Wales have introduced equivalent legislation to ensure UK-wide protection.

Why are you still allowing movements of oak trees within the UK Protected Zone, when we know that infested trees have been moved in this area?

All the infested trees that have been intercepted have originated from infested areas in other countries. There is no suggestion that UK nurseries within the Protected Zone have grown or supplied such trees. For those nurseries in the Protected Zone that may have imported oak trees earlier in the season and are still holding them on site, we would urge them to visually inspect those stocks for any signs of OPM presence. At this time of year, caterpillars would be present on infested trees, so would be easy to detect visually. Any suspicion of pest presence should be reported to the Plant Health Service or through TreeAlert. Additionally, official inspections will continue to be undertaken as part of plant passporting and routine surveillance activities, as well as in the context of follow up investigations to the current findings. Statutory action would be taken in the event of any findings.

Are you still allowing movements of oak trees within the UK but outside of the UK Protected Zone?

Trading oak within the core and control zones is not affected by this legislation.

However larger oak trees cannot be moved from the core or control zone into the Protected Zone, unless they have been grown under complete physical protection at an official authorised site throughout their lifetime. Smaller oak trees can only be moved from the core and control zone into the Protected Zone if they come from an officially authorised site and are accompanied by a plant passport confirming they are free of OPM.