Unwelcome Visitors

The NZ flatworm

The NZ flatworm

Stuart recently circulated an email reminding us that New Zealand flatworms have been resident on our site for several years now.  If you are lucky enough not to have come across any on your plot, you want to look out for them – they are a murderous bunch and live almost exclusively on our native earthworms.

Some of our plotters report finding no earthworms in their soil for the last four years or more and NZ flatworms (Arthurdendyus triangulates) are the obvious suspects. They kill their smaller earthworm prey in the most unpleasant way – covering them in mucus to part-digest them, then sucking up their remains. They have a voracious appetite and will quickly decimate local earthworm communities if left uncontrolled.

Know your enemy

Know your enemy

They are not a problem limited to our area. Researchers from Scottish Natural Heritage indicate they are present across much of Scotland as this Advice Note and Distribution Map shows. Early reports from the 1960s, when they first appeared in the UK, warned of the possible elimination of our earthworm populations, but more recently commentators have suggested that with help our earthworms may be able to come to terms with the interlopers. Research is on-going at The James Hutton Institute and sightings should be reported to Dr Brian Boag via the above link.

Control Measures

Can we fight back? Unfortunately, it seems that once established the New Zealand flatworm cannot be eradicated: however, their local impact can be reduced to a degree. The following methods are suggested:

  1. Inspect any pots or containers of bought or swapped plants before planting to prevent new infestations.
  2. Look under flat stones or wood etc. as the flatworms retreat to these locations during the heat of the day.
  3. Lay such traps, or peg out sacking to find if they are present.
  4. Kill any flatworms found by grinding between stones, completely squashing, dropping them into very salty water or spraying them with lemon juice.
  5. Ground and Rove Beetles are reported to prey on the adults.
  6. Add farmyard manure to help introduce more earthworms.
Bruce on flatworm patrol

Bruce on flatworm patrol

Need more information?

Pat Wilson circulated a recent Factsheet – see Stuart’s email.

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  1. Pingback: New Zealand Flat Worm Study | garthdeeallotments.org

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