Potato cyst nematode

• PCN is a microscopic worm that invades potato roots to feed, and at large infestation levels a noticeable yield reduction occurs, generally along with yellowing and wilting of foliage.
• PCN occurs as two species; Globodera rostochiensis and Globodera pallida, within which several pathotypes (races) have been identified throughout the world. In Northern Ireland G. rostochiensis (strain Ro 1) is the most common form.
• PCN can multiply very rapidly (up to 60 fold per year) and is very persistent in the soil (up to 20 years).
• Many older ware varieties still grown in Northern Ireland (Home Guard, British Queen, Pentland Dell, Kerr’s Pink, Dunbar Standard) are all very susceptible to PCN attack.
• Many newer potato varieties including some of those popular with organic producers are resistant to G. rostochiensis (Ro 1), and resistance to all forms of PCN is becoming more common in new varieties.
• At present PCN levels in ware ground are very low and a one year in five rotation, or longer, helps to maintain this.

• Have all possible potato fields tested for PCN to determine their PCN status - note that even in fields reported to be free there may still be low, undetectable levels of infestation or a very localised infestation. Details of this advisory sample testing procedure are available at DARD Agriculture Development Centres. The service is currently free.
• Have PCN species determination carried out during testing.
• Try to maintain a rotation of one year in at least five years.
• If at all possible do not grow on fields with PCN present.
• If PCN is present at low levels, as shown by testing, only grow an appropriate resistant variety.
• Only plant certified seed.
• Avoid transfer of PCN from infected land to non-infected land by ensuring boots, machinery and tractors are well cleaned between fields.
• Do not dump soil and potato waste on fields likely to have potatoes grown in them in the future.

• Organic standards lay down specific rotational requirements for potatoes, and a rotation of one year in four is probably the minimum acceptable to organic certification bodies.
• The DARD approach to control based on advisory field testing, and a rotation of one year in at least five, is very suitable for organic production.

• Fields tested for PCN for uncertified ware crops will not be scheduled if found to have PCN from an advisory test.
• The advisory testing for ware production and the statutory PCN testing for certified crop production are entirely separateWare crops may not be grown on land scheduled under seed potato legislation.
• Subsequent intended production of a certified crop (seed or ware) in such fields will still require a statutory PCN test as at present.