Flatworms - Preventing the Spread of Non-indigenous Flatworms

Code of Practice to Prevent the Spread of Non-indigenous Flatworms


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This Code of Practice is issued by DEFRA but is recognised by the Scottish Executive and the Welsh Assembly.


About this Code 

This Code is a practical guide to help producers and traders of nursery stock to detect and thereby to limit the spread of non-indigenous flatworms, notably the 'New Zealand' flatworm, Arthurdendyus triangulatus, and the 'Australian' flatworm, Australoplana sanguinea.

Under the Wildlife and Countryside Act 1981, it is an offence to release or allow to escape into the wild any animal which is included in Part I of Schedule 9 of the Act. This includes the New Zealand flatworm.

Although this Code of Practice has no legal force, demonstration of adherence to its provisions could be taken into account in the event of a case arising.

The need for a Code

  • Non-indigenous flatworms prey on earthworms and so pose a potential threat to our native earthworm populations.
  • Further spread of non-indigenous flatworms could have an impact on wildlife species dependent on earthworms and could have a deleterious effect locally on soil structure.
  • Findings in some parts of the United Kingdom, suggest that non-indigenous flatworms are becoming more widespread and action is needed to restrict their further spread to other parts of the country.
  • The principal means of spread is considered to be through movement of plant material and soil. By following hygienic practices and undertaking careful inspections of their stock of plants, nursery stock producers, garden centres and traders can help to limit the spread of flatworms.

In addition, because the New Zealand flatworm is known to occur in parts of the United Kingdom, certain countries which import UK planting material have expressed concern that they might import the flatworm.


This Code applies to plant producers, nurseries, wholesalers, garden centres and other retailers of plants and is directed at all stages of plant production and marketing.


The New Zealand Flatworm

NZflat.jpg (10616 bytes)

The New Zealand flatworm was probably first introduced to the United Kingdom some 30 years ago and in certain parts, particularly cool and wet regions. It has gradually spread, most notably in southern Scotland and Northern Ireland. In England, it has been found mainly in the North and North West but there have also been sightings in the South East.

The mature stage has a purple/brown upper surface, buff coloured margins and underside. It is usually about l cm wide by 5cm long, appearing longer, 10-15 cm, when it is moving. Large specimens can extend beyond 20 cm. It is flat and has a smooth but very sticky skin.

The Australian Flatworm

NZflat.jpg (10616 bytes)

The Australian flatworm appears to be a more recent introduction and currently has a more limited distribution. It was first recorded in the Isles of Scilly in 1980 and since 1990 has been recorded in Lancashire and Cheshire and the South West of England. it has also been recorded in Wales and is locally well established in the Republic of Ireland.

It is smaller than the New Zealand flatworm measuring between 3-8 cm, although this again depends on its degree of extension. Its colour varies from cream or white to peach or mid-brown, often with a distinct red tinge near the head.

Flatworm egg capsules

Flatworm egg capsules appear in the summer and resemble shiny smooth blackcurrants. They are between 4-11 mm long and 3-8 mm wide. Juvenile flatworms emerge after about a month and are creamy white/pink in colour.

Other creatures such as leeches or slow-worms have in the past been mistaken for flatworms, but careful examination should help avoid mistakes. There are also several native flatworms which are mostly small and inconspicuous (about 2cm). These pose no threat to the earthworm population and should be left alone

Leech: tough body wall with fine cross lines and a sucker at each end.

 leech.jpg (7726 bytes)

Earthworm: thin, rounded, obviously segmented body

eathworm.jpg (6137 bytes) 

Recommended measures

The following measures are recommended to reduce the risk of the flatworm being introduced into or spread from your premises :-

  • Inspect incoming consignments of plants
    Inspect pots or trays carefully particularly if they come from an area where findings of the flatworm have been reported.
  • Maintain good hygiene
    Always use fresh, sterile compost or other sterile growing medium when potting up plants, not material taken from places where flatworms might be hiding. For example, a container of compost or growing medium which has been opened and left lying on the ground may prove an attractive hiding place for flatworms.
    Clear up spilt compost or other growing medium, disposing of or thoroughly cleaning used pots and other containers.
  • Check regularly under matting or pots standing directly on the ground for flatworms or their egg capsules
    Flatworms are found on the soil surface. They will seek damp places, such as under loose turves, plastic or other sheeting, rocks, flat stones, plant containers etc. for shelter during the day. Egg capsules can also be found in such areas.
    Where containers stand on black polythene or capillary matting, frequently check, where possible, the underside of the polythene or matting for the flatworm.
    Whenever pots are standing directly on the ground, check whether flatworms have hidden under the pot and are either still on the ground surface or have adhered to the underside of the pot.
  • Lift plants from their pots frequently to check for the presence of flatworms or their egg capsules
    Flatworms and their egg capsules can also be found inside plant containers between the root ball and the edge of the container.
  • Set traps
    One of the locations where flatworms are most frequently found is in private gardens. Where nursery or other premises are adjacent to private gardens, set 'traps' close to the boundary, consisting of a weighted down sheet of black plastic or plank of wood. check the underside of these traps frequently for the presence of flatworms or their egg capsules.
  • Inspect all outgoing consignments of plants carefully whether for export or not
    Check planting material leaving the nursery or other premises carefully for the presence of flatworms whether or not it is for export.

Action on discovering a suspected flatworm                                      

If you suspect that you have found a New Zealand or Australian flatworm, or their egg capsule, do not touch it as the mucus covering the flatworm can cause skin irritation. Please contact the relevant organisation below with details of the time, place and nature of the discovery.

The species will be identified and confirmed cases notified to the appropriate Agriculture Department. This may lead to further investigations by the Departments or their agents

Where to send flatworms for identification

In England and Wales

Please send your find, live, in a crush proof container with some moist paper or damp moss to:

Mike Lole
ADAS Wolverhampton
Wergs Road
Tel: 01902 693266
Fax: 01902 693166

In Scotland

Agricultural and Horticultural Businesses only

Please send details of your find (not the suspected flatworms themselves) to:
Dr J Pickup
East Craigs
EH12 8NJ
Tel: 0131 244 8859
Fax: 0131 244 8940

For findings on private premises

Please send details of your find or, if you wish to have your find identified, please send it live in a crush proof container with some moist paper or damp moss, to:
Dr B Boag
Tel: 01382 562731
Fax: 01382 562426


There are no proven chemical methods of control, but the Agricultural Departments are funding research into these and other means of control. In the meantime, consult your local DEFRA Plant Health and Seeds Inspector in England or Wales, Horticultural Officer in Scotland or equivalent inspector in Northern Ireland for further advice.

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