Soil Testing

Potato cyst nematode (PCN) is the name commonly given to two species of cyst nematode which are serious pests of potato crops world-wide, namely Globodera pallida and Globodera rostochiensis. They feed on the roots of the plant and can cause significant loss of yield, including crop failure.  The cysts can survive in the soil for many years (over 25 years under favourable conditions), multiplying rapidly when a new crop of host plants is planted.

Taking effective action against PCN is vital to maintain supplies of both healthy seed potatoes for the ware industry in Scotland, and uncontaminated land for potato production.

The main methods of control are to ensure seed potatoes are produced in land free of PCN and, where PCN are found, to place restrictions on the use of the land and the disposal of crops, waste and soil to prevent the pest spreading.

The new EU PCN Directive

PCN have been subject to controls under European legislation since 1969. A revised PCN control Directive, came into force on July 1, 2010. This aims to strengthen and harmonise controls against PCN, taking account of changes in the understanding of the biology of the pest, its distribution across the EU and practices within the potato industry.

The Directive is implemented in Scotland by the Plant Health (Scotland) Amendment Order 2010, which was laid before the Scottish Parliament on May 21, 2010. Under the Plant Health Fees (Scotland) Amendment Regulation 2010, fees are now in place for PCN testing.

Under Directive 2007/33/EC, seed potatoes must only be planted on land which has been found to be free from PCN infestation following an official soil test. Failure to pass this test results in the land concerned being ‘recorded' as infested with potato cyst nematode. No seed potatoes may be grown in this land, either for inspection within the SPCS or for farm saved seed.  Ware potatoes may be grown, but only if an Official Control Programme is in place. The land remains ‘recorded’ as infested until such time as a future official tests show that PCN are no longer present.

Growers wishing to produce seed potatoes, either for classification or for farm-saved seed which will be planted other than at the place of production, are requested to make an application for a soil test by 31 August of the preceding year.  The application form and guidance for making an application are set out on the PCN Soil Testing documents page

The new PCN Directive sets out a harmonised protocol for soil sampling for use by all EU Member States.  Fields are sampled at a standard rate of 1500ml/ha or, if certain conditions are met which reduce the risk of PCN infestation, at a lower rate of 400ml/ha.  These conditions relate to history of the land, either in relation to previous potato crops or PCN soil tests.  Sampling is carried out by staff from the Scottish Government Agriculture and Rural Delivery Division Area Offices.

If you have any technical enquiries about soil sampling for PCN, please contact Jon Pickup or email the Zoology Team. If you are enquiring about the results of any soil samples that you have applied for, please contact Seed Potato Classification Scheme.