Garthdee Allotments

the e-home of the Garthdee Field Allotments Association

Tag: pests

A New Year Resolution

It’s time to declare war on New Zealand flatworms – total war. For me, they have replaced slugs as public enemy number one. Slugs only attack some of the crops we grow. NZ flatworms threaten to annihilate our earthworms.  They are also as ugly as sin and ooze evil from every pore.  There can only be one plotters’ response – EXTERMINATE!

Bruce on flatworm patrol

Why so now? I suggest two reasons. Firstly, a recent Conversation Newsletter Article (link coming up below) spelt out the importance of earthworms for healthy soil and plants, and the environment generally: and we all know the threat NZ flatworms pose to our earthworms.  In summary, the article says earthworms are:

  • brilliant organic matter recyclers and wormcasts contain key nutrients
  •  tireless engineers improving soil structure and condition
  • good indicators of soil health and toxicity levels
  • a food source for many species, so adding to biodiversity
  • expert restorers of damaged or neglected soils.

Earthworms are the good guys and our friend’s enemies are our enemies.

Secondly, research shows that some modern practices and tendencies in plot management seem to favour the NZ flatworm.  For example, I have started to use plastic membranes and carpet as weed inhibitors and winter soil protectors and these are known to encourage flatworms.

It seems unlikely that we will ever be able to completely defeat and remove our flatworms.  Recent Aberdeen University research reports (links below) show that flatworms are present on 70% of our plots and 90% of Slopefield’s plots are infested. However, there are lots of actions we can take to reduce flatworm numbers.  This may tip the balance back in favour of our earthworms.

Actions against NZ flatworms include:

  • removing clutter and flatworm refuges from our plots.  These are flat stones, plastic, wood, carpet and fabric
  • set up flatworm traps using the above and check them on a regular basis
  • kill trapped flatworms with lemon juice or drowning in salt water in secure containers
  • add organic matter to encourage earthworms
  • use grass paths to support earthworms
  • exercise strict bio-security to avoid spreading flatworms to new areas

When our plots were surveyed by researchers they found that flatworm refuges were found on many plots. Eighteen plots had a small number of refuges; 14 plots more than a small number; 14 had many refuges and only 1 was refuge-free.  The number of flatworms found increased with the number of refuges and carpet was found to be the worst source of flatworms, followed by plastic, fabric, stones and wood in that order.

So what is to be done?  In the first instance, I am going to stop using carpet to suppress weeds. I am going to do a big Spring tidy up, removing clutter. I am going to set my flatworm traps and check them regularly. I already keep a lemon squeezy on site.  I should also replace my central slab path (built up over many years as free slabs became available) with a grass one, but this is a big job and a sore one.

Know your enemy

So, I hope this can be a big focus for us over the year ahead.  If you want to read more about the NZ flatworm threat and responses these links will help:

Conversation Newsletter Article

GFAA Advice Notes

Report on GFAA Flatworm Study

Our New Zealand Flatworm Problem

We have just received the interim report from OPAL and the University of Aberdeen on our flatworm problem.  It does not make for great reading as it suggests that over 70% of our plots are infested with these pests.

Suggestions as to how to deal with flatworms, taken from this very helpful report, has been incorporated into a new page under the Advice and Support tab above.  You will also find a copy of the interim report.

New Zealand Flatworm Survey

The University of Aberdeen are conducting a survey of NZ Flatworms and are looking for a number of allotment holders to participate, both those with and without NZ Flatworms and would appreciate answers to the following questions

1. Do you have New Zealand Flatworm on your plot at present?
2. Have you had New Zealand Flatworm on you plot historically?
3. Would you be happy for someone from Aberdeen University to visit your plot and record presence and abundance of NZ Flatworm, soil pH, take a small soil sample and record earthworm numbers?
In addition they would ideally like to talk to you or alternatively get you to fill in a questionnaire to enable them to gauge the scale of the problem and find out more about your experience of NZ Flatworm. This would be done mid-March- April at a time convenient to you.

4. If you are not able to participate in the study they would really appreciate it if you could fill in this short survey Hard copies of the survey can be obtained by contacting Annie Robinson direct at

If you wish to participate please contact Annie as soon as possible. It would be helpful if you would be good enough to let me know if you decide to participate.


New Zealand Flat Worm Study

Thanks go to Bruce Taylor for alerting me to this study.

Aberdeen University has announced it has researchers taking part in a national survey of the New Zealand Flatworm‘s spread and its effects on our gardens, plots and fields.

2015-06-12 at 08.59

As we know the Flatworms kill our native earthworms, but the university site contains some truly gruesome details about how they go about their murdersome business and how difficult they are to eradicate once they get established. It appears that the flatworms can reduce to 10%  of their body weight for up to a year as they await another earthworm dinner.  Perhaps the weight-loss industry ought to be sponsoring this survey!

More details, including how you can participate, are available via these links:

Aberdeen University Research Press Release

National Flatworm Research Project

Unwelcome Visitors to Garthdee Field

Bare Faced Cheek!

I had noticed for a few weeks that something or somebody was chomping its way through the remains of my chard, but late this afternoon we arrived in time to catch the culprit in the act.


He/She stood her ground for a few moments before showing off her effortless hurdling skills over the fences between the plots: I finally caught this photo as she arrived at Michael’s plot up by the railway line.

Can anyone throw any light on the species and gender?

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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