New Zealand Flatworms

A study in 2016-17 by members OPAL and the University of Aberdeen found that over 70% of our plots at Garthdee Field were infested with New Zealand Flatworms.  It is more than likely that your plot has flatworms, even if you have not seen any.

It’s very important that we all take action to contain and eliminate NZ Flatworms.  They are known to eat and destroy our native earthworms that we rely on to keep our soil in good condition.  The researchers made the following recommendations:

  • Awareness raising is extremely important. New plot holders should be provided with information on New Zealand Flatworms in their joining packs, including what they look like, so they can keep an eye out for them, something that is already happening at Garthdee. This will help control efforts and minimise numbers at the allotment, but most importantly reduce the risk of transfer of the New Zealand Flatworm (eggs or juveniles) from allotments to home gardens or elsewhere via plant material or soil.
  • Removal of clutter from plots can help minimise areas of shelters for the New Zealand Flatworms to hide under.  Examples of clutter include areas of carpet, flat stones, wood, weed control fabric and anything else flatworms can hide under during the day.
  • Temporary traps using weighted plastic can, however, be useful if one wishes to carry out control. In that case, systematic checking of the traps and control needs to be carried out regularly (otherwise the traps would help the flatworms rather than hinder) and over an extended period.
  • Any conditions which make the soil more suitable for earthworms will help tip the balance in their favour, e.g. incorporating organic matter into soil will benefit earthworm populations.
  • Kill any Flatworms found by squirting them with lemon juice or dropping them in heavily salted water.  Do NOT squash them underfoot as this may transfer eggs or young on your boots.
  • Further information about New Zealand Flatworm and advice for gardeners on minimising the impact of New Zealand Flatworms can be found on the OPAL website: www.opalexplorenature.org/nzflatworm. This website can also be used to leave observations such as observed changes in abundance of flatworms or earthworms in one’s plot, or changes related to action taken.  A copy of the full OPAL and University of Aberdeen’s Report is available for download as a PDF.  Report on New Zealand Flatworm study conducted at Garthdee Allotment.