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PCN model info button notes

30 January 2013

Multiple

Selecting this option allows total flexibility to look at various control options over a number of potato cropping seasons. The single option will simply show your options repeated over a number of seasons to better visualise the effects on population and yield.

Population at planting

An egg count should be entered from the laboratory report. Field sampling and laboratory analysis is under review by the newly-formed industry body, the Soil Pest Management Initiative. Once this has been finalised by the group, the new best practice document will be posted onto this site.

Length of rotation in years

The model assumes a decline rate or 20% every year. Changing the length of rotation will alter the starting point, or initial population for the following potato crop. If there is an issue with groundkeepers there will be an effect on the nematode population based on plant density but this is likely to be small.

Total yield

The figure should be the total biological yield planned not the graded or marketable yield.

Tolerance

The level of tolerance attributed to a potato cultivar indicates its capacity to deliver a commercially viable yield in spite of the damage and drain on nutrients brought about by a population of PCN. For example cv. Cara is considered to be highly tolerant of PCN and cv. Pentland Dell intolerant. Where there is a moderate to high level of tolerance but no resistance, the crop is able to successfully grow and develop but the nematodes will multiply, leaving a legacy of elevated levels of PCN.

Resistance

The level of resistance in a cultivar indicates its facility for reducing the potential for nematode multiplication. For example, full resistance to Globodera rostochiensis means there is no multiplication; whereas partial resistance to G. pallida means that there is some but limited multiplication. A notable caution with partial resistant cultivars is that they select for that part of PCN population that is able to overcome the associated resistant mechanism; therefore, the same potato cultivar should not be used in the same field in the following rotation.

Pi is the initial population of PCN. Pf is the final or post cropping population of PCN

Treatment

Granular nematicide application

  • Application and incorporation to 15cm by rotavation on flat ground is the most reliable method for PCN control
  • An acceptable alternative, is application and incorporation during bed tilling followed by stone and clod separation using a star based separator
  • Also acceptable, application during stone and clod separation using a webbed based separator will give good results provided that application occurs towards the front of the machine.
  • Never use variable rate.

 

% granular control

Data suggests 80% control using a granular nematicide. Control will vary on a field to field basis, due to quality and timing of incorporation and available soil moisture amongst other factors. To view the effects of varying levels of granular control, or to mimic your field conditions, alter the value.

% fumigant control

Data suggests 90% control using a fumigant nematicide. Control will vary on a field to field basis, due to quality of incorporation and sealing amongst other factors. To view the effects of varying levels of fumigant control, or to mimic your field conditions, alter the value.

% decline rate

This defaults at 20% decline a year, if your data suggests a different rate, adjust to your conditions.

Population Trend

The graph starts with the egg population at planting, or initial population (a). During the potato growing season, the PCN population will rise rapidly to the theoretical final population at harvest (b). This is followed by a steady decline (default is 20% a year) for the number of years selected in the rotation. If single crop is selected, the graph shows 5 similar potato crops using the input data to better visualise the outcome on population. Multiple crop will allow greater flexibility to alter inputs for each individual potato crop in the rotation.

If a nematicide is used, the population will drop according to the level of control (granular default is 80% control). This will then show the starting infestation population (c). The rapid in-season increase will then begin from that point, showing the effect of using a nematicide.

Disclaimer

While the Agriculture and Horticulture Development Board, operating through its AHDB Potatoes division, seeks to ensure that the information provided by this model is accurate at the time of its provision, subject to the accuracy of the information provided by the user, no warranty is given in respect thereof and, to the maximum extent permitted by law, the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted therefrom.