Potato Review Group

Contents

Background: integrated control

Cultural control: rotations

Cultural control: amelioration of effects in the growing crop

Monitoring: soil sampling

Principles

Method

Biological control: trap cropping

Biological control: biofumigation

Standard biofumigation

Partial biofumigation

Biofumigation / trap crop options

Chemical control

General

Nematicides

Nematostats

Application of nematostats

Nematostat stewardship

Efficacy of control measures

Sustainable control of PCN

Further information:

Notes on PCN control

Soil sampling information

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Background: integrated control

  1. Control of potato cyst nematodes (PCN) requires integrated control within and between crops.
  2. This includes the following.
  3. Cultural control:
  4. Monitoring:
    • soil sampling
    • mapping hot spots in the growing crop
  5. Biological control:
    • trap crops
    • biofumigation
  6. Chemical control:

More …

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Cultural control: rotations

  1. Maintain rotations of at least 5 – 6 years. Longer rotations may be required to control G. pallida, as there is limited cultivar resistance to aid population control.
  2. Control volunteers between potato crops.
  3. During the winter before a potato crop is to planted, sample the field for PCN population and species. Remember to sample separately any areas where patches of infestation were recorded in previous crops.
  4. A count of 1 egg per g soil may represent a population of 2,000,000 to 10,000,000 eggs per ha and thus indicates a potential problem.
  5. Choose a cultivar with a suitable resistance to and tolerance of the nematode species, where possible. Resistant cultivars will help to maintain low PCN populations, tolerant cultivars will suffer lowest yield losses. If possible, avoid growing the same cultivar with partial resistance to G. pallida in the same field for successive crops, to reduce the likelihood of selection for virulent strains of G. pallida.
  6. If a field is free of PCN avoid introducing cysts, which may be carried in soil on seed tubers or farm machinery. (Seed crops should always be grown on land which is free from PCN – this is a statutory requirement for certified seed.)
  7. Modelled effects of different rates of decline of PCN populations can be found here.

More …

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Cultural control: amelioration of effects in the growing crop

  1. If any patches of PCN infestation are observed in a potato crop, map these areas accurately for separate sampling in future.
  2. PCN attack restricts root growth and thus the potential for nutrient uptake. Additional fertiliser may thus be required, including foliar applications. If such problems are anticipated, a portion of the fertiliser may be placed in the ridge. Phosphorus, which is important for root growth may be particularly suitable for this.
  3. If root growth is restricted, for example by poor soil structure, or if availability of water is limited, any damage to the crop caused by PCN infestation will be exacerbated.
  4. Some amelioration of the effects of PCN infestation has been shown for application of seaweed extract products; this may be due to beneficial effects of cytokinins on root growth. More …

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Monitoring: soil sampling for potato cyst nematode testing

Principles

  1. Testing will be particularly important if populations are low, as integrated control measures should already be practised if populations are high.
  2. Low populations may comprise small foci and are difficult to detect but have the highest multiplication rate. More …
  3. The more intensive the sampling, the greater the probability of detecting low populations. More …
  4. Different methods of sampling are required for detection of low population and for quantification of control of known populations.
  5. If two or more cultivars were grown in the field previously, sample these areas separately.
  6. If patches of infestation have occurred in a crop, map accurately and test these areas separately before the next potato crop. Samples from these areas may be taken for speciation after the potato crop but do not sample until late autumn, to allow cysts to mature.
  7. Have a speciation test performed periodically, unless the number of eggs in the sample is too low for this to be possible. Do not assume that the species will be the same as at a previous test.
  8. Keep samples moist, handle carefully and allow two weeks for analysis, particularly if speciation required.
  9. Failure to detect PCN in a sample is not evidence of the absence of PCN.
  10. Remember that analysis laboratories may sub-sample the soil samples sent to them.
  11. Since 2010 there have been additional requirements for sampling soil in fields where seed potatoes will be grown or where crops for re-planting (e.g. bulbs) are grown in the same rotation as potatoes. This involves more intensive sampling and a low proportion of ware fields will be subjected to this type of sampling each season. More …

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Method

There are two possible types of test: detection and quantification.

Detection

  1. This is the method to use when populations are low. This method will also provide an indication of the risk on new or rented land.
  2. The sample should comprise 1 kg soil per ha.
  3. Use a 10 – 15 mm diameter corer, to a depth of 10 – 25 cm.
  4. Take 49 cores per 1 ha block in a grid pattern.
  5. The whole sample should be analysed by the laboratory for detection of PCN (presence of cysts).
  6. If cysts are found, a further test should be performed to count eggs / g soil.
  7. This should be performed on a sub-sample sample of no less than 400 g soil – the larger the better. More …
  8. Before sending samples, it is important to check the size of sample which the laboratory will use. (For example, FERA will use the whole 1 kg sample for detection and a 400 g sub-sample for quantification but some laboratories use sub-samples of only 100 – 200 g.)

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Quantification

  1. This is the method to use to assess efficacy of control of known populations of PCN.
  2. The sample should comprise 400 g soil per 1 ha block.
  3. Use a 10 – 15 mm diameter corer, to a depth of 10 – 25 cm. If samples are taken in a “W” pattern this should be across the direction of cultivation.
  4. Take 49 cores per 1 ha block in a grid pattern.
  5. Send the whole sample to the laboratory for analysis of eggs / g soil.
  6. This should be performed on a sub-sample sample of no less than 400 g soil – the larger the better. More …
  7. Before sending samples, it is important to check the size of sample which the laboratory will use. (For example, FERA will use the whole 1 kg sample for detection and a 400 g sub-sample for quantification but some laboratories use sub-samples of only 100 – 200 g.)

See also: AHDB PCN soil sampling guide.  This is an external website which opens in a new window and provides a link to the current industry standard guide on soil sampling for PCN.

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Biological control: trap cropping

  1. A trap crop should stimulate egg hatch but prevent completion of the life cycle of both species of PCN, thus reducing the population.
  2. A cultivar which is fully resistant to the PCN species present is thus a trap crop.
  3. A very short duration crop (e.g. an early or salad crop) could be a trap crop but the roots would have to be killed before cysts form. More …
  4. As the PCN life cycle can be completed quickly a short duration crop is not a reliable trap crop:
    • the life cycle of G. rostochiensis may be completed in 38 – 48 days (or less than 500 degree days C > 6.2 oC)
    • the life cycle of G. pallida may be completed in 610 degree days C > 3.9 oC.
    • More …
  5. A more reliable method of trap cropping is growth of non-potato species of Solanum.
  6. Solanum sisymbriifolium has been shown to be a potentially effective trap crop as egg hatch of both PCN species is stimulated but cysts do not form. More …
  7. Solanum scabrum has also been shown to be an effective trap crop. More …
  8. Good growth of a trap crop is required to produce a large enough root system to stimulate sufficient egg hatch, so a field may need to be dedicated to this plant for a season.
  9. S. sisymbriifolium and S. scabrum are potential hosts of late blight and PVY and S. sisymbriifolium is a potential problem weed, so care is required in management.
  10. Limited use of Solanum spp. as trap crops could form part of an integrated control programme for control of PCN populations.

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Biological control: biofumigation

Standard biofumigation

  1. Biofumigation has nematicidal effects.
  2. Biofumigation crops are usually Brassica species, particularly B. juncea, which contain high concentrations of particular glucosinolates.
  3. When the crop is flailed and incorporated, glucosinolates are broken down to isothiocyanates which have a fumigant effect in soil but the operations must be performed rapidly in warm, moist soil.
  4. There is some evidence of suppression of potato cyst nematodes, free living nematodes and some weeds.
  5. Biofumigation may also reduce some soil borne diseases. More …
  6. The biofumigation crop requires careful management to achieve maximum yield of glucosinolates, which occurs at flowering, but avoid the risk of volunteers.
  7. Occasional use of biofumigation might help to reduce high potato cyst nematode populations, as part of an integrated control programme.
  8. B. juncea is a host of beet cyst nematode (BCN), so use within the rotation must be considered. More …

More …

Partial biofumigation

  1. Roots of Brassica spp release glucosinolates into soil during growth.
  2. This can give a small reduction (e.g. 10 %) in PCN population, without flailing and incorporation of the canopy.
  3. This effect may be achieved with a cover crop such as oilseed radish.

More …

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Biofumigation / trap crop options

  1. Higher PCN population:
    • consider Indian mustard (B. juncea) over summer, incorporate in autumn
    • Solanum sp. trap crop
  2. Higher PCN and sugar beet in the rotation:
    • utilise a BCN resistant oilseed radish crop and incorporate
  3. Lower PCN and no incorporation:
    • Utilise oilseed radish
  4. Rhizoctonia, canker and powdery scab:
    • growth of Indian mustard and incorporate
  5. Free living nematodes (FLN):
    • fallow or brassica crop with resistance to targeted FLN

More …

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Chemical control of potato cyst nematodes

General

  1. It may be necessary to apply nematostats to control multiplication from low populations of PCN if susceptible cultivars are grown, even if yield losses in the current crop would be minimal.
  2. No chemical will provide complete control of PCN.

Nematicides

  1. A nematicide kills nematodes directly and may also kill eggs or juveniles within cysts.
  2. There are currently no nematicides approved for use in the UK
  3. Bayer suggests that “Velum Prime” has nematicidal effects: there may be nematicidal effects on juveniles if there is a high concentration of the product for a sustained time but there is no evidence of effects on eggs in cysts. More …

Nematostats

  1. A nematostat does not kill nematodes directly but causes paralysis of juveniles in soil while moving from cysts to roots; death may be an indirect effect of starvation.
  2. Fosthiazate (“Nemathorin”, Syngenta): an organophosphate, granular nematostat with similar properties, mode of action and efficacy to and oxamyl.
  3. Fluopyram (“Velum Prime”, Bayer): an SDHI chemical applied as an in-furrow spray. Applied alone, this product is less effective than fosthiazate unless there is a low PCN risk. Bayer recommends application with a half-rate application of fosthiazate but this use should be checked with Syngenta. More …
  4. Garlic extract (“NEMguard PCN”, Certis): a granular nematostat. Percolation of water down the soil horizon is required to disperse the active ingredients; the manufacturer does not recommend application to soils with a high silt content.
  5. Check manufacturers’ information for details of product usage.

Application of nematostats

  1. Granular nematostats should be incorporated into the ridge as close as possible to the time of planting, as degradation can begin after application and a high concentration is required when root growth begins and root exudates stimulate egg hatch.
  2. Incorporation of granular nematostats should be to a depth of 20 cm, to provide a high enough concentration in the area where initial root development occurs. More …
  3. Distribution of granules should be checked, particularly when setting up new machinery or training new members of staff.  This can be done with the “rice test” (spread rice grains on the soil surface before nematostat incorporation then check the placement of the rice in the ridge. More … )
  4. “Velum Prime” (fluopyram) is applied as an in-furrow spray at the time of planting. More …
  5. Check manufacturers’ information for details of product usage.

Nematostat stewardship

  1. Stewardship schemes have been promoted for use of nematostats.
  2. These include training of operators, provision of safer packaging, safer transfer systems and best use practice.
  3. It is important that users practice nematicide stewardship, to reduce the likelihood the products being banned.
  4. Check manufacturers’ information for details of stewardship schemes.

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Efficacy of control measures

Typical percentage reductions in PCN populations.

  • Nematostat = 20 – 40 % reduction in rate of multiplication.
  • Annual decline in absence of host crops = 15 – 33 %, typically 20 %.
  • Solanum  sp. trap crop = 75 – 80 % reduction in experiments.
  • Biofumigation crop with autumn incorporation = 40 – 70% reduction in experiments.
  • Biofumigation crop with spring incorporation = 10 – 30% reduction in experiments.
  • Partial biofumigation (no incorporation) = 10 % reduction.

More …

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Sustainable control of PCN

  1. Follow an IPM programme, as illustrated in the example below.
  2. If soil sampling shows a low PCN population (e.g. one patch of no more than 2 eggs / g soil) the following points should be considered before application of nematostat.
    • Will a resistant cultivar be grown?
    • Is this a hot spot which has been identified previously?
    • Was the intensity of soil sampling sufficient to reliably detect low populations or other hot spots?
    • Does previous cropping justify treating only part of the field? E.g. a history of a hot spot here, only; or cultivars with different resistance grown in different parts of the field?
  3. If soil sampling shows no PCN, the following points should still be considered.
    • Is there a history of PCN in the field?
    • If there was a previous hot spot has this been sampled separately?
    • If there is no history of PCN in the field has the gate area been sampled (PCN may be introduced via soil on machinery and may be detected first in the area around the gate)?
    • Is further sampling required to confirm that populations of PCN are too low to be detected?

IPM diagram for PCN

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Further information

See the manufacturers’ websites for details of agrochemical use.

 

Notes on PCN control

Nematodes 2021 (Management of low populations of PCN; effects of specialised cover and brassica crops for biofumigation / trap cropping)

Cover crops in the potato rotation 2020 (Includes influence on nematode populations)

PCN biology and control 2019 (Cultivars with resistance to G. pallida; cultivars with tolerance of PCN; control with fosthiazate, oxamyl and fluopyram)

Potato cyst nematodes 2018 (New cultivars with resistance to G. pallida; detection of hot spots and low populations; use of fluopyram)

Potato cyst nematodes 2017 (Species distribution in the UK; population dynamics; introduction to fluopyram)

Potato cyst nematode revision 2015 (Biology, life cycle and integrated control)

Control of soil pests 2015 (Includes “rice test” to check “Nemathorin” distribution)

Updates on potato pests 2014 (Includes instructions for “rice test” to check “Nemathorin” distribution)

Potato cyst nematodes 2013 (Contribution of non-chemical control methods to integrated control; investigation of biological control)

Nematode control updates 2012 (Updates on: nematostat usage, including checking incorporation; and biofumigation)

Pest control 2010 (Includes: PCN sampling standards for for a 2007 EU Directive; intensity of sampling in Dutch and UK systems)

PCN and biofumigation 2009 (Control of PCN with biofumigation, including management of biofumigation crops)

Soil pest control updates 2008 (Includes: pot experiments on control of PCN with garlic extract; cultivar tolerance)

Pesticides update 2007 (Includes: summary of available nematostats; cultivar tolerance; application of oxamyl via drip irrigation – never developed further)

Solanum sisymbriifolium for PCN control 2006 (Trap cropping, including management of the trap crop and potential risks)

Nematicide stewardship 2005 (Industry standards for appropriate use)

Potato cyst nematodes 2002 (Principles of trap cropping)

Pest control 2001 (Includes PCN species frequencies in the UK)

PCN control 2000 (Use of fosthiazate; amelioration of PCN effects with seaweed extract; problems with contour mapping of populations from GPS samples)

Nematicide application 2000 (The importance of correct incorporation)

PCN control 1999 (Introduction to fosthiazate)

PCN control 1997 (Reducing nematostat rate reduces the potential duration of control; some products now outdated)

PCN sampling 1996 (Sampling efficiency increases with intensity)

Notes for 1993 (Chapter 11: PCN – principles of chemical control)

 

Soil sampling information

AHDB PCN soil sampling guide.  This is an external website which opens in a new window and provides a link to the current industry standard guide on soil sampling for PCN.

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