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Establishing potato cyst nematode trap crops

This field lab explores the practice of establishing trap crops to control PCN - the UK's primary potato pest. 

Potato cyst nematode is one of the main threats to potato production and sustainability. Currently, the main control option is to use nematicides hazardous to operators and the environment, which only prevent one season's crop yield and do not prevent PCN increase.

An alternative cultural control method is the use of trap crops, which limit nematode multiplication and reduce existing soil PCN populations.


A group involving seed growers, consultancy and academic organisations, precision agriculture companies and SASA (Science and Advice for Scottish Agriculture) intend to engage with a facilitator and industry experts to draw up a planned strategy to tackle PCN.  This is likely to involve raising awareness among arable farmers, investigating mitigation measures, the role of precision farming solutions and potential new PCN tests.


This field lab is looking to develop good establishment practice for the trap crops S sisymbriifolium and S scabrum when drilled after cereal harvest. Key aspects are date of drilling, weed control and drilling depth.

Latest updates

After concluding the field lab trials, the group was awarded Innovate UK to continue testing factors that affect establishment success of the two trap crop species.

An update from Potato Review can be found here. Findings of their DeCyst™ project indicate that the following practices lead to better germination and establishment:

  • Shallow drilling of seed into moist soils
  • Common combi-drills or precision vegetable drills for sowing trap crop seed
  • "...promising results with interrow planting of DeCyst™ combined with clover and buckwheat in a standing crop of wheat, which flourished after combining, giving complete ground cover"
  • Cambridge roll post sowing to consolidate the seedbed for soil to seed contact and to reduce moisture loss 

Today (28th June), the three trials in Shropshire were drilled, trialling the same species as last year:
• S sisymbriifolium
• S. scabrum

Two nitrogen rates:
• 50kg/ha
• 100kg/ha

i.e a total of four treatment combinations. After completion of drilling, the afternoon rain should have aided germination.

At the Caynton and Ellerdine sites these four treatments were each replicated three times, in one randomised block.

At the Edgmond site they were each replicated six times in a stratified block design. This is where detailed results on PCN and crop growth will be obtained. Additional funding by AHDB is enabling rooting as well as ground cover to be measured.

Having the experiments on the three farms drilled on the same day by the same drill & operator and using the same organic fertiliser and same plot size will minimise variation.

At both Caynton and Ellerdine the trials are in the middle of commercial fields of the same trap crops, containing extra comparisons designed by the growers concerned. This will make grower meetings even more informative.

The group have been supported by AHDB to produce a film on trap cropping and how (in Shropshire), June harvesting of the cash crop allows the farmers to drill the trap crop without losing a cash crop.

The group successfully applied for top-up funding to continue the field lab for a second year. Three of the four growers from the first year of trials will continue, plus one new addition.

In the first year, the group focused on understanding best practice for trap crop establishment in terms of sowing date and depth; this year they will examine the impact on PCN levels and the effect of seed priming and additional nitrogen on establishment.

Trap crops: Same as last year, Solanum sisymbriifolium and Solanum scabrum at all farms.

Current recommendation for Solanum sisymbriifolium is for 50kg/ha N. Observations made in 2020, where digestate had been applied, suggested that more nutrient helped crop development, so the efficacy trial will also be used to test whether 100kg/ha N leads to better crop growth and greater PCN kill.

Seed priming:
The 2020 field lab and previous experienced indicated trap crop emergence is slow. Slow emergence increases weed competition. Seed priming increases speed and uniformity of germination and is used in some vegetables such as parsnips. An experiment, investigating seed priming, will be established at the farm of a group member from Lancashire, because speed of emergence is particularly important in northern parts of Britain.

PCN assessments: Only one of the three sites will include PCN assessments so that this can be done thoroughly. The one chosen has high PCN numbers. It has already been sampled down to 0.2ha blocks rather than the usual 1ha, showing the best location to be in plots NE or NW of the field. 5 replicates, stratified design.

Measurements include:

• Regular photograph records from hand-held drone
• Emergence counts on several dates to monitor first and final emergence speed and %
• Ground cover as measured by photography at approximately 50% leaf cover, 100% cover and pre-crop destruction, using an ‘easy leaf area’ smart phone app
• PCN counts pre-trap crop & after trap crop destruction

The growers found:

• 10th July is the latest viable trap crop sowing date in Shropshire, earlier in Lancashire
• Later sowing dates (July-August) resulted in little establishment
• S sisymbriifolium successfully established at one of the sites but didn't quite reach the biomass required for effective PCN control

With this understanding of the latest viable sowing date, the group would like to continue the trials into a second year to assess the impact of added nutrition and seed priming on crop growth. They will continue to assess PCN levels at the site with the highest reported PCN damage. They hope to use the learnings/data from this field lab to encourage the inclusion of trap crops in ELMS.

The full report can be accessed in the 'Documents' section of this page (top right corner, login is required but signing-up is free)

Final trial assessments were carried out in early October and two groups visited the Caynton and Tibberton sites for a final assessment of trap crop establishment.

Whilst trap crop growth was good at Caynton, the Tibberton site had significant weed cover and very little trap crop establishment, making a ground cover assessment difficult and ambiguous. The earliest planting date in late June had good growth, whereas later planting resulted in poor establishment and ground cover. It was suggested that the late June date was probably the latest safe sowing date to achieve sufficient ground cover and thus PCN control in North Shropshire. Later sowing would require much higher seeding rates.

Four plants from each of the most advanced plots for S. sisymbriifolium and S. scabrum were excavated and root systems compared. These will be weighed to determine root weight/mass.

Two S. sisymbriifolium plants were taken from the most advanced plots so that they could be weighed, oven dried and reweighed for dry matter production. Neither reached 700g dry matter/m2 once dried. This supports the conclusion that sowing before the end of June is crucial, though this may depend on locality - sowing until mid July in south Shropshire may be possible.

The Caynton site will be sampled for PCN and analysed at HAU.

The final report on the results can be found under the ‘reports’ section of the field lab page.

A month after the first sowing, both trap crops had a second sowing at the end of July or early August at all sites. Both trap crops have emerged at Caynton and Lilyhurst, particularly Solanum Sisymbriifolium sown at 1.5cm, based on assessments of the number of plants emerging in a 2m row after the 1st sowing. At the Ormskirk and Tibberton farms, emergence is very limited.

More info on the progress and farms can be found in the Documents section in the top right corner of this page.

Drilling took place at two sites in late June - a little before the planned date as soil conditions were good for drilling.

Trial site 1: ME Furniss near Newport Shropshire, planted on 25th June 2020 (hot dry day, 27c, soil temp. 25c).

The field was wholecrop wheat, harvested one week before. Lemken solitaire with power harrow. Plot sizes 4m drill width and 15m long with 8m guards (mainly for turning equipment. Plots drilled as a replicated and randomised experiment/trial. Two species: Solanum sisymbriifolium and Solanum scabrum drilled at both 1.5cm and 3cm depths (approximately). Sandy loam soil. 50kgN/ha applied to field as slurry in week prior to planting.

Trial site 2: N Belcher, Shropshire, planted on 29th June 2020 (cool day, 14c, soil temp. 13c).

Planted in unplanted area within a potato field. Same equipment, set up, trial design (replicated and randomised), trap crop seeds and drill depths as trial site 1. Sandy loam soil.

More information and photos from the trial can be found in the 'Results' section on the field lab page. A video of the trap crop drilling and set-up can be found here: https://www.youtube.com/watch?v=3MR5cyp2c4I



The Shropshire Potato Growers Discussion Group consists of farmers who have been visiting field experiments of Harper Adams University over several years. They have made their own trials and changes to practice and have shared the results with each other. In particular they have improved their soils and partially controlled pathogenic nematodes by use of cover crops and biofumigants. This experience has made them both interested in and capable of establishing trap crops.

Four group members are hosting trials in 2020. They are all experienced at establishing over-wintered biofumigant crops and all have fields available for drilling at one of the required times. Other important factors are availability of irrigation to aid establishment if necessary and access to suitable drills.

An important objective of the work is to hold regular meetings to discuss the development of the experiments, results, relevant observations and the future directions of the research. These meetings will be attended by the hosts of the trial sites, other members of the Shropshire Potato Growers Discussion Group, the seed supplier (Produce Solutions), Andrew Wade (OptiGrow), Ivan Grove (Independent) and Matthew Back (HAU).

This field lab is looking to develop good establishment practice for the trap crops S sisymbriifolium and S scabrum when drilled after cereal harvest. Key aspects are date of drilling, weed control and drilling depth.

A randomised plot design will allow analysis by Harper Adams University. Treatments:

• Two species: Solanum sisymbriifolium and Solanum Scabrum
• Two planting dates: early July and early August
• Two planting depths: 1cm and 3cm


• Photographic records (hand held and drone cameras) - to track progress and as a discussion point at meetings
• Emergence counts to monitor first and final emergence speed and percentage
• Ground cover, measured by photography at approx. 50% leaf cover, 100% cover and pre- crop destruction; using the ‘easy leaf area’ phone app
• PCN counts pre trap crop (Pi) and after trap crop destruction (Pf)

Group established


Interviews with growers


Innovative Farmers funding confirmed


Sampling initial PCN levels


First drilling date


Second drilling date


Field visits post-establishment


Field visit


Results Meeting


AHDB webinar on trap crops for PCN reduction


Year 2 planning meetings


Trap crop seed supplied


Plots marked out & baseline PCN sampling


2nd year trap crop drilling


Group farm visit


Open fam walk


Open results meeting/webinar


Group Coordinator

A silhouette of an unidentifiable person.
Andrew Wade


Andrew is Director and senior advisor at Optigro, an agricultural consultancy firm. He set up Optigro after 38 years with Agrovista as an agronomist and team manager.