The Scottish Government

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(Clavibacter michiganensis ssp sepedonicus)

Scottish Executive Environment & Rural Affairs ( SEERAD)
Plants, Horticulture and Potatoes ( PHP)
Scottish Agricultural Science Agency ( SASA)
Plant Health Division Defra - PHD
Plant Health Seed Inspectorates ( PHSI)

ISBN 0 7559 4674 X (Web only publication)

This document is also available in pdf format (260k)

1. INTRODUCTION AND SCOPE

1.1 This document acts as the Scottish Executive Environment and Rural Affairs Department ( SEERAD) Eradication and Containment Plan for potato ring rot. In conjunction with sections of the PHSI Handbook, it forms part of the Emergency Plan for the Plant Health Service in Scotland. This document will be reviewed and updated as necessary.

1.2 This document provides guidance on:

• The background to potato ring rot.
• Policy and statutory authority on its prevention, detection and control.
• Relevant factors to its prevention and containment.
• Eradication and containment procedures, including official ( i.e. carried out by or under the control of SEERAD) measures.

1.3 Responsibility for reviewing this Plan lies with Plants, Horticulture and Potatoes ( PHP) of SEERAD in conjunction with SEERAD inspectorate HQ and SASA, whose responsibilities are described in section 2.

2. RESPONSIBILITIES

2.1 Plants, Horticulture and Potatoes ( PHP), SEERAD

• Responsibility for plant health policy in Scotland.
• Administration of plant health legislation in Scotland.
• Liaison with interested organisations in Scotland on implementation of plant health policies in Scotland.

2.2 SEERAD Agricultural Staff ( SEERAD inspectors)

• Implementing plant health legislation requirements in Scotland.
• Technical advice in relation to plant health policy and outbreaks.

2.3 Scottish Agricultural Science Agency ( SASA)

• Provision of scientific advice to PHP on the formulation of plant health policy.
• Provision of scientific advice to SEERAD inspectors on implementation of plant health legislation.
• Diagnosis of suspected potato ring rot.
• Provision of scientific information and training, as requested.

2.4 Plant Health Division ( PHD), Defra

• Overall responsibility for UK plant health policy in international affairs. This includes representing the UK Plant Health Service, acting on behalf of and in consultation with the other parts of the service ( SEERAD, the Welsh Assembly Government Agriculture and Rural Affairs Department and the Department of Agriculture and Rural Development in Northern Ireland).
• Overall policy responsibility for implementation of plant health legislation in the UK and administration of plant health policy in England.
• Liaison with interested organisations either on behalf of the UK or in England as appropriate.
• Sending reports to the European Commission and other Member States.

3. BACKGROUND TO THE DISEASE

3.1 Background

Potato ring rot is a serious non-indigenous bacterial disease of potato, which is listed in Annex IAII of Directive 2000/29/ EC, as implemented by Schedule 1(A)2 of the Plant Health (Great Britain) Order 1993. This means that it is an harmful organism which is known to occur in parts of the Community, but whose introduction and spread is prohibited. It is caused by a bacterium referred to in the Directive and Order as Clavibacter michiganensis (Smith) Davis et al. subsp. sepedonicus (Spieckermann et Kotthoff) Davis et al ( Cms).

Potato ring rot has been reported in a number of EC Member States including Austria, Belgium, Denmark, Finland, France, Germany, Greece, Spain, Sweden and The Netherlands. There have also been outbreaks in a number of the countries who will be joining the Community in 2004, including Czech Republic, Cyprus, Estonia, Latvia, Lithuania and Poland.

The first outbreak of potato ring rot in the UK was in November 2003. Directive 93/85/ EC ('the Directive') outlines measures to control this disease throughout the Community. The Directive is implemented by the Plant Health (Great Britain) (Amendment) Order 1995, which amends the Plant Health (Great Britain) Order 1993.

3.2 Symptoms

3.2.1 Symptoms in the potato plant

The earliest symptom is wilting of the leaf margins, especially on the lower leaves and often on only one side of the plant. Wilting often occurs in discrete sectors bounded by leaf veins. High temperatures during the day may cause temporary wilting with recovery at night. The symptoms may easily be mistaken for rhizoctonia, blackleg or drought. The affected areas of leaves typically appear dull and greasy. Leaves curl and progressively lose their shine with the onset of yellowing, browning and eventual necrosis (see photographs in Disease Notice No.PB 1510) and QIC card 41 (both available from Defra Publications - phone 08459 556000 or see http://www.defra.gov.uk/planth/pestnote/rot.htm and http://www.defra.gov.uk/planth/pestpics/qic41.htm for details).

When infected stems are cut close to ground level, discoloration of the vascular tissue is not obvious but it may ooze a creamy bacterial slime. Whole stems can wilt and die, but it is unusual for all the stems on a plant to be killed.

3.2.2 Symptoms in the potato tuber

For routine screening of stocks, potato tubers should be cut transversely close to the heel (stolon) end. However, if suspicious symptoms are found in a stock, some tubers should be cut longitudinally through the heel end to check for symptoms. In the early stages the tissue around the vascular bundles appears semi-translucent, glassy and water-soaked. As the infection progresses the vascular ring becomes discoloured and the tissue around it degrades and develops colourless rot with a paste-like consistency. If the cut tuber is squeezed a pale creamy, cheese-like ooze emerges. Later, the vascular discoloration becomes a more distinct brown and the necrosis can extend into the surrounding tissue.

In advanced stages, the outer cortex separates from the inner cortex and the bacterium can ooze from the heel end and eyes. This may result in reddish-brown, slightly sunken and star-shaped lesions on the skin from which bacteria may ooze, causing soil particles to adhere. External symptoms are not common but advanced vascular infections can cause slightly sunken lesions to form below the skin. Secondary bacterial infections would normally result in the total breakdown of the tuber. In some interceptions, rapid rotting of the central part of the tuber has been seen to accompany rotting of the vascular ring (again, see Disease Notice No.PB 1510).

3.3 Other hosts

There was some evidence from the USA in the 1980s that sugar beet can act as a symptomless carrier of the pathogen, but this has not been confirmed by recent research. The risk is probably minimal for modern varieties and so no special measures are required for this crop. CSL is studying which field weeds may contribute to survival and spread. It is clear from inoculation experiments involving wounding that some weeds, such as couch, may have the potential to act as hosts or symptomless carriers but it is not known if weeds can act as hosts or can harbour the pathogen in natural outbreak situations.

Weeds are not as important as they are for brown rot and, on the basis of current knowledge, are not subject to specific controls under the Directive . No specific measures would therefore be required in the event of an outbreak.

4. POLICY AND STATUTORY AUTHORITY

4.1 Summary

Policy and statutory authority are as outlined in the Directive. Additional measures to those in the Directive will be considered in response to an identified risk. The notification arrangements in The Potatoes Originating in Germany (Notification) (Scotland) Order 2001 are an example of such measures. The Directive lays down measures to be taken by member states against potato ring rot, with respect to potato plants and tubers in order to:

• Locate it and determine its distribution.
• Prevent its occurrence and spread.
• If found, to prevent its spread and to control it with the aim of eradication.

The principal control measures are as follows:

SEERAD inspectors will carry out annual surveys for the presence of Cms ('the organism') on tubers and, where appropriate, plants of potato and investigate the source and extent of any infection, including:

• Holding action in cases of suspect occurrences, including prohibiting the movement of consignments from which samples have been taken and results awaited.

• Action to trace the origin of any suspect consignments.

• Determine the extent of risk or contamination as a consequence of pre or post harvest contact or through any production link with the suspect consignment.

• Where the organism is confirmed in potatoes on production premises, those premises, affected crops and fields, and associated machinery and equipment will be designated as contaminated.

• Potato material and associated machinery and equipment etc. known or likely to be contaminated will be subject to officially controlled disposal or cleansing and disinfection.

• On production premises designated as contaminated, specific controls will be introduced.

• Zones will be demarcated around designated premises, based upon identification of the contaminated items and/or area of land and an investigation into the probable extent of the contamination and possible risk of its spread, within which specific measures must be taken immediately and for at least 3 years after designation.

• Seed potatoes must comply with the Plant Health Directive (2000/29/ EC) and derive in direct line from material obtained under an officially approved programme which has been officially tested and found free from the organism.

Measures on the movement of host plants are also included in the Plant Health Directive .

5. FACTORS FOR CONSIDERATION IN PREVENTING AN OUTBREAK OR PREVENTING THE SPREAD OF RING ROT

• This is RING rot, not brown rot. Avoid the temptation to regard the two as similar beyond the fact that they are both bacterial diseases.

• Ring rot is unlikely to spread from plant to plant in the field but infection may spread from tuber to tuber by physical contact and through contact with contaminated containers, equipment and premises during handling, grading, processing etc. The bacterium will survive in a desiccated state on equipment and in dust in stores for several years. However, once wetted or at high relative humidity the bacterium does not survive for as long in the absence of potato host material. In wet soil, the bacterium has been shown to survive for several months. In drier soil, survival can be for more than a year.

• All those involved in growing, packing or processing potatoes must be made aware that the use of the same equipment and machinery to grade/process ware and seed potatoes poses a very high risk of cross-infection, particularly from different growers.

• Tuber cutting is an ideal means of spreading ring rot within and between potato stocks.

• Spread of ring rot is most common via clonal multiplication links. Seed traceability, in the event of an outbreak, should always be up (parent stock), sideways (sister stocks) and down (daughter stocks).

• Cross infection from stock to stock can occur, most commonly, via superficial damage to tubers through direct physical contact with infected tubers or through contact with contaminated machinery or wash water.

• Ring rot infection can pass through one or more field generations without causing symptoms in stems and tubers. The spread of the disease in latently infected tubers is therefore very important in the case of this pathogen.

• Not all tubers or aerial stems on an infected plant necessarily become infected.

• Finding symptoms in tubers is more likely than in aerial parts of the plant. Varietal differences in reaction, as well as the lateness of expression of symptoms in the season make growing crop inspections specifically to detect the disease inappropriate.

• Spread of the disease from plant to plant in the field is likely to be low although there is experimental evidence that some insects (Colorado beetle, leafhoppers and aphids) can transmit the disease. The movement of machinery through a crop with infection in the haulm could also potentially spread infection (via ooze or infected sap). Field outbreaks are likely to be restricted to individual seed stocks, unless others are clonally-related or have been put over the same grading or other machinery after an infected stock.

• Ring rot, in contrast to brown rot, is not known to be spread long distances by water. The pathogen can survive in de-ionised water for more than a month but there is no known aquatic weed host to build up inoculum levels. There is however clear evidence that contaminated wash water from infected tuber lots can transmit the pathogen to subsequent lots washed in the same water.

• Ring rot will survive longer on dry surfaces than on wet ones and longer at low relative humidity than at high relative humidity.

• Disinfection of machinery under Notice need not take place in the field - local movement of machinery may be permitted provided it is not taken across potato land.

• The bacterium can survive for at least a month on machinery and considerably longer if the machinery dries rapidly and is kept under dry conditions after contamination.

• Disinfection, wherever used for machinery and equipment, should be preceded by the thorough washing off of all soil and debris first. This is because organic material and soil can significantly reduce the effectiveness of disinfectants. Steam cleaning is particularly effective but will not be appropriate for all situations.

• There are numerous disinfectants suitable for use in the varying circumstances under which ring rot could be found and hot water (70 ^oC+) can also be an effective treatment for certain items. SEERAD inspectors will provide further disinfection advice to growers on a case by case basis.

• Hygiene measures in respect of boots, leggings, knives etc. is of paramount importance in dealing with an outbreak of ring rot.

• Where referred to, samples collected for testing will normally consist of 210 whole tubers, of whatever size. Official sampling will be undertaken by SEERAD inspectors, although in some cases it may be agreed that non-official samples will also be submitted for testing, to provide additional coverage.

• Testing will be of 200 tubers, as required by the Directive, and the remaining 10 will be 'spares' in case of loss etc. in transit. This gives an 87% chance of detecting a 1% level of infection, assuming that the sample is representative of the total lot. Much larger samples however need to be tested to detect low levels of infection in stocks and to give a high level of assurance that ring rot is not present in a stock. Recent work in Belgium has shown that up to 20 samples of 200 tubers had to be taken and tested to detect a very low level of infection in a large stock. In an outbreak situation there may be occasions when it will be necessary to undertake more intensive sampling and testing of individual stocks. For example to screen potentially infected seed stocks or to investigate the primary source of an outbreak. Such decisions will be decided on a case by case basis by PHP, SEERAD inspectorate HQ and SASA.

6. PUBLICITY

Posters and a Plant Health Information Sheet ( PB 1510) and a Quarantine Information Card ( QIC 41) (see section 3.2.1) on potato ring rot are available and should be widely distributed to persons/firms involved in potato production, processing or agronomy. Additional information is available on the plant health section of the Defra website ( http://www.defra.gov.uk/planth/ph.htm)

PHP maintains contact with interested organisations and growers to advise them directly on the risks associated with potato ring rot and the implementation of the Directive.

7. ACTION ON SUSPICION OF RING ROT

Positive confirmation of ring rot will take between a few days and several weeks and must follow a specified test methodology laid down in Annex 1 of the Directive .

Where ring rot is suspected, the following actions must be taken:

7.1 Potato tubers with typical symptoms of ring rot in tubers or wilting in potato plants.

Suspicion of ring rot may be based on visual symptoms but positive confirmation must be made by laboratory testing undertaken at SASA. A presumptive diagnosis should normally be able to be given within 3 working days based on results of gram staining, immunofluorescence ( IF) and polymerase chain reaction ( PCR) tests. Final confirmation of the disease however, requires a positive eggplant test which can take several weeks. This final confirmation is a requirement of the Directive and involves isolating the bacterium on agar, inoculating eggplants with the pure culture, producing typical disease symptoms in the plants and than re-isolating the bacterium from the infected tissues.

Samples exhibiting suspicious symptoms must be notified to SASA in advance of sending material. They should be sent by 1st class letter post or courier, marked 'URGENT', to

Strong, secure paper packaging should be used.

Pending positive confirmation of ring rot by SASA, SEERAD inspectors will,

• Serve a Notice under Article 22(2) of the Plant Health Order to prohibit movement of potato plants and tubers on and off the farm or unit at the time. Potato plants or tubers may be moved under Notice, in exceptional circumstances to be agreed on an ad hoc basis with PHP, in consultation with, SEERAD inspectorate HQ and SASA, and provided there is no identifiable risk of potato ring rot spreading,.

• Obtain full details of the origin of the plants and tubers to trace the source of suspected ring rot, e.g. supplier details, certificate number of seed planted, intermediary wholesalers.

• Take appropriate additional precautionary measures to prevent any spread of the suspected potato ring rot. These measures may apply within and off the premises associated with the suspected occurrence and could include, for example, restrictions on the use of potentially contaminated machinery, or the prohibition of the movement of sister stocks suspected of being contaminated. The measures should be appropriate to the level of estimated risk from the type of premises and the circumstances involved. For example, bagged ware potatoes in store may present less of an immediate risk than seed tubers.

7.2 Latent infection in potato tubers

Suspicion of ring rot must be based on a positive result from screening tests such as an IF test , PCR test or selective plating carried out at SASA.

Action as 7.1 above.

8. ACTION ON CONFIRMATION OF POTATO RING ROT IN POTATO.

8.1 Initial Action

As soon as potato ring rot is confirmed in accordance with section 7.1, a Statutory Notice must be served by SEERAD inspectors under Article 22(2) of the Plant Health Order. This will demarcate the premises to be "a zone contaminated with Clavibacter michiganensis subsp . sepedonicus (Potato Ring Rot)" and designate relevant items as 'contaminated' and 'probably contaminated'. The Notice must also prohibit the planting of potato tubers designated as 'contaminated' or 'probably contaminated' and require the approved disposal of contaminated and probably contaminated material.

Where ring rot is confirmed in potatoes, the tubers or plants, consignment and/or lot, and the machinery, vehicle, vessel, store or units, and other objects including packaging from which the sample was taken, and where appropriate, the field(s) from which the potatoes were harvested, must all be designated as contaminated. Other potato crops and consignments on the farm that are not so designated must be included in the assessment referred to at section 8.2.

Section 8.2 outlines the areas to be considered in assessing the risk of spread of ring rot to other plants and premises. The scale of any testing programme carried out in support of this assessment will be determined by PHP on the advice of SEERAD inspectorate HQ and SASA taking account of the particular circumstances of the outbreak. Those consignments, crops and associated fields included in this assessment, but in which the organism has not been confirmed, along with associated packing, stores, premises, equipment, machinery and vehicles, must be designated as probably contaminated .

PHP will notify PHD who will notify other Member States and the Commission of details of any contamination and, if appropriate, demarcation.

8.1.1 Disposal of contaminated tubers and plants

Suitable methods of disposal of any contaminated tubers or plants are:

• Incineration.

• Use of potato tubers as animal feed following boiling for at least 30 minutes - it is essential that the material is well cooked.

• Deep burial of tubers or plants covered by backfill immediately at a landfill site licensed by the Scottish Environmental Protection Agency ( SEPA) with the prior, written, authority of an inspector. It may be possible for deep burial (minimum 2 metres) on farm providing SEPA (who must be consulted first) is satisfied that there will be no risk of contaminating ground water. Where material is transported off farm it must be in a covered and contained vehicle. The vehicle must be cleaned and disinfected after use.

• Direct and immediate delivery of potato tubers for industrial processing to a site which operates officially approved waste disposal facilities and which has a system of disinfection of storage areas and departing vehicles.

8.1.2 Disposal of contaminated solid waste (bags, soil, packaging etc)

• Solid waste may be deep buried and covered by backfill immediately at a landfill site licensed by SEPA. It must be transported in a covered and contained vehicle.

• Solid waste may also be incinerated.

8.1.3 Disposal of contaminated liquid waste

• Liquid effluent must be filtered, settled or otherwise subjected to approved treatment to remove all solids. Alternatively it can be stored in a lagoon or other holding facility for 60 days.

• All removed plant material such as stem foliage, soil and tuber debris must be destroyed as above.

• The disposal of or possible future use of any remaining liquid effluent after storage or treatment will be decided on a case by case basis by PHP on the advice of SEERAD inspectorate HQ and SASA.

• Other disposal methods may be used following approval by PHP on the advice of SEERAD inspectorate HQ and SASA.

8.1.4 Disposal of probably contaminated tubers and plants

The same disposal options are available as those for tubers and plants which have been designated as contaminated .

In addition , potatoes may be:

• Packed on the farm as ware potatoes for direct sale, without repacking, on local retail markets, with all waste being disposed of in a manner to be agreed with the local SEERAD inspector.

• Packed as ware potatoes for retail sale, without re-packing, at sites where the waste disposal arrangements and disinfection facilities have been officially approved by the local SEERAD inspector.

8.1.5 Disinfection or disposal of machinery, stores and equipment designated as contaminated or probably contaminated

The Notice must also require contaminated and probably contaminated premises, stores, equipment, wooden boxes, vehicles and machinery to be destroyed or treated to eliminate the risk of spread of the organism.

The options include:

• Thorough cleaning and disinfection using an approved product appropriate for the particular circumstances. SEERAD inspectors will provide disinfection advice on a case by case basis.
• Incineration.
• Disposal at a landfill site licensed by SEPA.

8.2 Investigation to determine extent and source of potato ring rot contamination

An investigation must be carried out to determine the extent and possible source of the outbreak. In addition, an assessment of the risk of spread to other plants or premises must be carried out.

This will include:

• All potato material at the contaminated premises or grown nearby.

• Premises which are linked to the outbreak, including by shared equipment or contractors.

• Potato material from the premises above, or present on such premises at the same time as designated potato material.

• Central stores handling potatoes from the above premises.

• Any machinery, vessel, store, packaging etc. linked to the outbreak, including bulk containers that may have been used for transportation.

• Any potatoes which are clonally related to an infected stock or a stock grown on contaminated premises.

8.3 Additional measures for seed potatoes

Where ring rot is confirmed in seed potatoes, all clonally related potato stocks must be held under a Notice issued under Article 22(2) of the Plant Health Order and be tested for latent potato ring rot infection.

8.4 Zones around outbreak sites

Following confirmation of ring rot in accordance with section 7.1 the affected premises will have been designated as "a zone contaminated with Clavibacter michiganensis subsp. sepedonicus (Potato Ring Rot)" (see 8.1). Subsequent to the results of the investigations in 8.2 above it may be necessary to designate a greater area around the outbreak as "a zone contaminated with Clavibacter michiganensis subsp. sepedonicus (Potato Ring Rot)". This decision will be taken by PHP, on the advice of SEERAD inspectorate HQ and SASA, when all of the relevant information regarding the outbreak has been provided.

8.5 Cropping restrictions on the outbreak farm

The Directive provides for cropping and related restrictions to be imposed. Growers should be given details of all the options open to them. A decision may then be made upon the course of action that they wish to follow. The following specific controls will be introduced by a Notice issued under Article 22(2) of the Plant Health Order. The grower must then inform the local SEERAD inspector of the preferred choice, which should be referred to SEERAD inspectorate HQ. A revised Notice under Article 24(4) of the Order incorporating the decision will then be issued, after due consideration of the relevant information.

8.5.1 Cropping restrictions on contaminated fields or units of protected cropping

EITHER:

In the contaminated field or unit of protected cropping, for the next 3 years from the start of the next growing season (or longer if Notice requirements are not complied with) -

• Growers must eliminate volunteer potatoes.

• Potatoes must not be planted.

• The field or unit must be free from volunteer potatoes for at least 2 consecutive years prior to planting the first potato crop. For example, if the field is not free from potato volunteers in year 2 then the earliest that potatoes may be planted is year 5, provided that no volunteers are found in years 3 and 4. This will be verified by SEERAD inspectors.

In the first potato cropping season thereafter -

• Officially classified seed potatoes must be planted and for ware production only.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

During the next potato cropping season,

• Officially classified seed potatoes must be planted for either seed or ware production.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

OR ALTERNATIVELY

For the next 4 years from the start of the next growing season (or longer if Notice requirements are not complied with) in the contaminated field -

• Growers must be restricted to bare fallow or permanent pasture (which must be kept close cut or intensively grazed).

• Growers must eliminate any volunteer potatoes.

In the first potato cropping season thereafter,

• Officially classified seed potatoes must be planted for either seed or ware production.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

8.5.2 Cropping restrictions in other fields on contaminated holdings

For the first year following confirmation of potato ring rot. In the other fields -

EITHER

• Growers can opt not to plant potatoes, but must take measures to eliminate volunteer potatoes .

OR ALTERNATIVELY

• Growers must plant officially classified seed potatoes but only for ware production, provided that they have eliminated the risks of volunteer potatoes. This must be established by SEERAD inspectors prior to planting.

• Growing crops will be inspected by SEERAD inspectors and any volunteer potato plants must be tested for the organism.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

In the second year following confirmation of potato ring rot (providing Notice requirements have been met). In the other fields on contaminated holdings:

• Growers may plant only officially classified seed potatoes for seed or ware production.

• Growers must take measures to eliminate volunteer potatoes.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

In the third year following confirmation of potato ring rot (providing Notice requirements have been met). In the other fields on contaminated holdings:

• Growers may plant only officially classified seed potatoes for seed or ware production.

• Growers must take measures to eliminate volunteer potatoes.

• An official survey, including laboratory testing of the harvested tubers, must be carried out.

In those production systems where complete replacement of the growing medium is possible:

• No tubers, plants or true seed shall be planted unless the production unit has been subjected to officially supervised measures to eliminate the organism and remove any potato or other solanaceous material. This must include, at least, a complete change in growing medium and cleansing and disinfection of the production unit, and all equipment. The production system must subsequently be granted approval for potato production by PHP.

• Potato production shall be from officially classified seed potatoes, or from mini-tubers or micro-plants from tested sources.

8.5.3 General controls applicable to the premises designated as contaminated

Following the designation of premises as contaminated and in each of the subsequent growing years, up to and including the first permissible potato cropping season on the fields designated as contaminated:

• Growers must clean and disinfect all machinery, equipment and storage facilities used for potato production on the premises. This must be notified to and verified by SEERAD inspectors.

8.5.4 Additional controls affecting demarcated zones

Under the terms of the Directive, Member States are required to enforce a number of control measures under Notice, to be issued under Article 22(3) of the Plant Health Order, which will affect all land and premises within the demarcated zone around an outbreak. The extent of the demarcated zone must be agreed by PHP. The following must come into effect immediately and remain in force for at least 3 years following confirmation of the outbreak:

• Any premises growing, storing or handling potatoes (including those of contractors) will be supervised and controlled under the terms of the Notice.

• All machinery, equipment and stores associated with potato production must be cleaned and, where appropriate, disinfected.

• Growers must plant only officially classified seed potatoes for all potato production. Seed potatoes produced on land which is linked to the outbreak (see 8.2) must be sampled by SEERAD inspectors after harvest and sent to SASA for latent testing.

• Harvested seed potatoes must be handled separately from ware potatoes.

• An official survey, including testing, will be carried out. The full details of this will be decided by PHP on the advice of SEERAD inspectorate HQ and SASA on a case by case basis but is likely to involve at least the sampling and testing of potatoes.

The Directive also makes provision to establish a programme, where appropriate, to replace seed potato stocks within the zone over a period of time. PHP will decide whether it is necessary to establish such a programme.