To grow or permit to be grown on that field potatoes intended for replanting (classified seed or farm saved seed);

Transcription

1 June 2010 Control programme for fields officially designated as having potato cyst nematodes (PCN) present Guidance for growers and landowners The Food and Environment Research Agency (Fera) Introduction From 1 July 2010 a new PCN Directive, 2007/33/EC, takes effect. This document outlines the options available to growers in the event that a field is officially recorded as having PCN present and the field concerned is used to grow potatoes. In such cases a control programme to suppress the infestation must be followed in accordance with the Directive. The aim is to ensure that remaining clean land is protected and that population levels in the infested field decline over time. This document sets out the options for growers to achieve that aim. The intention is for growers to pursue an individually tailored control programme, most suited to their situation, based on the options in this document. While the document provides flexibility for growers, it is important to stress that any control programme must be consistent with the options presented and be aimed at the legally required objective of PCN suppression. There are also certain legal obligations and restrictions connected to infested fields, which are also described in this document. A checklist is provided for growers to discuss with their Plant Health and Seeds Inspector the implications arising from designation and the available options if they wish to grow potatoes.

2 Background The Plant Health and Seeds Inspectorate (PHSI) undertake official soil sampling of fields either as a requirement for the Seed Potato Classification Scheme, exports of potatoes or transplants, or the ware potato PCN survey (which is a new requirement under the Directive). The confirmation of the presence of viable PCN in these official samples has consequences for the production of seed potatoes (including farm saved seed), transplants and the production of ware crops. The official control programme is a consequence of the new Directive, which lays down statutory implications for farmers when their field has been officially designated as infested with PCN. A control programme to suppress PCN levels must be followed in the event that ware potatoes are to be grown in a field where the presence of PCN has been officially recorded. Information about PCN, including the new Directive, can be viewed on-line at: When a positive result is obtained from an official PCN test (i.e. a sample taken by the PHSI and tested by The Food and Environment Research Agency (Fera)), the field concerned will be recorded as infested. A statutory notice will be issued under the Plant Health (England) Order 2005, as amended, (or equivalent in Wales) on the occupier (landowner) or person in charge of the field (if a long term tenant). This notice will set out the restrictions and obligations which apply in relation to the field and which must be followed by the person on whom the notice is served. If PCN is found in a field which is rented out for potato growing, the landowner has a responsibility to inform future tenants about its status and any controls in place. Both the landowner and tenant could be subject to sanctions if potatoes are being grown and a control programme is not being followed. The control programme should be agreed with the person who has control over the field and what is done there. The landowner may agree to a tenant taking responsibility for following the most appropriate measures. Alternatively, the landowner may wish to specify the requirements that tenants must comply with. In the event that PCN is officially recorded in a field it will be an offence: To grow or permit to be grown on that field potatoes intended for replanting (classified seed or farm saved seed); To grow or permit to be grown on that field any plant listed in Annex I of the Directive (see Annex 1) intended for replanting, unless (for a plant in point 2 only) it is to be disinfested or marketed practically free of soil (following washing or brushing); To grow or permit to be grown on that field any potatoes not intended for replanting (i.e. ware or starch), except in accordance with the control programme described in this document. If the test was carried out for the ware survey, the notice will also set out the restrictions on any potatoes from that field which remain in store. They must not be planted and waste and soil from grading or processing must be disposed of carefully to prevent any spread of PCN. The control programme depends on adherence to some fundamental principles that are set out herein. While growers can decide which are the most appropriate options for their particular circumstances, the overall objective is to suppress PCN by preventing spread of the pest and pursuing a reduction in population levels over time. Failure to comply with the principles in this document will indicate that the objective is not being achieved, which could lead to enforcement action by the PHSI. Serious or repeated breaches of these requirements may lead to prosecution.

3 Official Control Programme Immediate consequences There are certain legal restrictions and obligations relating to a field which is officially designated as being infested with PCN. These are described above, but are also set out in the Directive (Article 9). To grow ware potatoes, a control programme must be followed, which aims at least to suppress the level of PCN in the field. Suppression is not defined in the Directive, but the objective must be to prevent further PCN spread and to pursue a reduction in population levels over time. The control programme is necessary if ware potatoes are to be grown in a designated field. To return the field to use for seed potatoes it is recommended that potatoes are not grown at all. The field will then be eligible for a further official test after a minimum of 6 years since PCN was officially confirmed, or since the most recent potato crop was grown, whichever is later. Sampling to de-designate fields will be at the standard rate specified in the Directive 1500 ml/ha. Guidance for the development of the control programme The remainder of this document describes the components of good practice and control methods, both chemical and novel, to be considered in developing the control programme for an individual field. The programme should be discussed with the local PHSI and may be subject to official checks as necessary; a checklist is provided at Annex 2 to help growers/landowners discuss with their PHSI the consequences of the control programme and the options available to them. Various additional sources of advice are available to growers on PCN control. These include the booklet Potato Cyst Nematode: A Management Guide produced by MAFF in October 1999 but available on the Fera website at: as well as the Potato Council PCN Model calculator. The Council is currently investing in research to refine the use of this Model. Control measures These can be summarised as below, with further details provided in the following sections. In practice it is likely that a control programme will include a combination of these options. Remember that the aim is to suppress PCN levels in the infested field and the control programme should include appropriate elements to pursue that aim for the field in question: Choice of cultivar, based on the PCN species identified Rotation Chemical control Trap cropping Use of green manures and fumigants Effective waste disposal is an important element of any control programme. Ensuring good hygiene, using certified seed and testing land used to produce farm saved seed, will all help to minimise the risk of spreading PCN to uninfested land.

4 Pre-planting and post-harvest sampling can help to measure the success of the programme. Identification of the PCN species There are two species of PCN, namely Globodera pallida and G. rostochiensis. Globodera pallida (maturing cysts) Globodera rostochiensis (maturing cysts) Details of the species identified in the official test will be made available to help growers plan the most appropriate control programme. The identity of the PCN species infesting land is important because it will provide the basis for the selection of resistant varieties, if they are to be used. The biology of the species is also slightly different and needs to be borne in mind when devising the control programme. Populations of PCN also vary in the extent to which they can reduce yields (i.e. their pathogenicity) to potato and other hosts. Knowing the PCN species present may also help explain why some control measures may not seem to be working; G. pallida, for example, has an extended egg hatch compared to G. rostochiensis, so some pesticides which are short-lived may not exert good control. Any significant problems in control should be reported to Fera. Choice of cultivar Each population of PCN involves a variety of genotypes. This is true for any pest population, but with PCN their adaptation to environmental conditions can manifest itself in a significant change in the characteristics of the population that may affect its level of pathogenicity or even the dominant species, and hence this can have an effect on yield. Selection of the cultivar(s) to be grown in the short and long term is therefore a very important part of the control programme. Choice will depend on the PCN species(s) that has been recorded in the infested field(s). Even if resistant cultivars are available you should use these with care to avoid increasing the proportion, or species, of the PCN population that will not be affected by the varietal resistance. All cultivars resistant to G. rostochiensis that are currently used in England and Wales incorporate the H 1 (ex andigena) gene for resistance. Such cultivars work well against PCN populations lacking the gene that confers virulence against this gene, i.e. G. rostochiensis Ro1, but have no effect on other pathotype populations of this species, or G. pallida. Sustained use of such cultivars has selected for the latter species.

5 The use of resistant cultivars is particularly important where mixed populations of both PCN species have been found. A programme using cultivars of differing resistance levels needs to be employed to avoid a rapid shift in pathogenecity to the most common varieties. Further advice is given in the booklet Potato Cyst Nematode: A Management Guide referred to above. There is currently only one cultivar on the UK list classified as resistant to G. pallida (Vales Everest), but it is susceptible to G. rostochiensis, so repeated use is not advised. Information on resistance can be found on the British Potato Variety Database maintained by the Potato Council ( Varieties from the EU Common Catalogue may also be planted in England and Wales, but expert advice should be sought, as resistance testing is not currently standardised across Europe. If the failure of a resistant variety is suspected then Fera should be notified. This is usually an exceptional event but needs to be investigated as it might herald a change in the pathogenecity of the PCN population that could have consequences for the national crop. Some varieties are tolerant of PCN, which means they can withstand a certain level of PCN without significantly affecting yield. However, the regular use of such varieties is not advised as they may produce a false sense of security; PCN populations will continue to rise and hence affect later, intolerant varieties. The British Potato Variety Database is a helpful source of information. Rotation Extending the interval between potato crops is known to be an effective control measure. Without host plants, there will be a significant reduction in viable eggs in a PCN cyst in the first six years. Increasing the interval between potato crops will therefore help reduce PCN levels. The rate of decline is different for each of the PCN species, with G. pallida being particularly prolonged. Decline is also affected by the susceptibility/tolerance of the variety and by environmental factors, such as the soil type. Volunteer potatoes provide a source of PCN multiplication and should be controlled with herbicide treatments, and/or early roguing Chemical control Historically, thresholds for the application of chemical treatments have relied on the number of viable eggs per g to judge whether the use of a nematicide or nematistat is warranted. As the aim of this programme is suppression then a single viable cyst should be the trigger for the use of chemical control, in conjunction with the other components of this programme. The application of chemicals at planting to control PCN should be done with care. Many factors can influence their effectiveness, such as inefficient incorporation at planting, and the weather, so they should not be relied upon as a panacea. The use of fumigants will only be partially effective against PCN because of the protection afforded by the cyst wall.

6 Chemical controls are most efficient at low population levels, and so should be used as soon as PCN is detected. Global Positioning Systems (GPS) can be useful in identifying PCN hotspots to help target chemical applications, but be aware that PCN is likely to be present elsewhere in the field. Novel or innovative methods of control (i) Trap cropping If volunteer potato plants are difficult to control, they can be used to reduce PCN levels provided they are removed soon after emergence. Solanum sisymbriifolium is one of several plants that are being used commercially as a trap crop that stimulate hatch in the soil but do not allow PCN to complete its life-cycle, no matter how long the crop is left in the soil. Recent research in the field has suggested that this plant needs to accumulate a certain level of dry matter to achieve sufficient control, and that this may not be achieved in northern areas of the UK. Clearly, small trials should take place on farms before large-scale plantings are undertaken. (ii) Use of green manures and biofumigants Research into the effect of green manures and biofumigants on PCN is in its infancy, but these may contribute to an overall sustainable control programme. Disinfestation of tubers and roots and disposal of waste There are currently no scientifically validated methods for disinfesting seed potatoes, so the Directive requires that seed potatoes found to be infested with PCN must not be replanted under any circumstances. Removal of soil from tubers harvested from infested fields should be undertaken in such a way that there is minimal risk of spreading PCN.

7 Removal of soil by brushing and/or washing until practically free of soil is not wholly effective, but should minimise the risk of spread. The Directive requires that potatoes intended for industrial processing or grading must go to a site that has appropriate waste disposal facilities, such that there is no risk of infesting potato land. Such premises have to comply with the Waste Management Regulations, so in practice no additional requirements will be necessary. Excess soil should be left in the field where possible, or where a grower grades his own potatoes onfarm, the soil may be returned to the field of origin. Soil and potato waste may be returned to non-agricultural land (e.g. for construction purposes), or to sacrificial land that is unsuitable for growing potatoes for other reasons. Growers may wish to refer to the Fera Plant Health Code of Practice on Management of Agricultural and Horticultural Waste. This can be viewed on-line at In the case of plants for planting listed in point 2 of Annex I, they should not be planted on a designated field, unless they are to be subject to disinfestation or washing/brushing after harvesting. The Directive requires that any such plants derived from a designated field must be subject to one of these methods if they are destined for replanting. Unwashed stockfeed should only be used on farms that do not grow potatoes. Washed stockfeed carried a very low risk and can be used on any farm. If it is being spread on a field used to grow potatoes, or likely to be used as such, it is recommended to check that it is from a reliable source, including not being in contact with household or allotment waste. Good practice Certified seed Use certified seed because it will have been produced on land that has been tested and found free of PCN. Farm saved seed Farm-saved seed can increase the risk of spread of PCN. If part of a ware crop is retained for planting (i.e. as home-saved seed), then only tubers from a crop which has been grown on land tested and found free from PCN should be used, to protect fields that are not infested. Tubers taken from designated fields must not be planted anywhere. On-farm hygiene

8 PCN is most likely to be spread in soil and once it has reached detectable levels on a farm it is likely to have spread on machinery to other fields on the farm. Cleaning footwear and machinery therefore helps reduce the spread of PCN. Transplanting plants from PCN-infested soil also poses a risk to clean land and should be avoided. Thus hygiene measures should apply to whole fields, not just parts of fields. Measuring success The success of the control programme could perhaps be measured by an improvement in crop health or an increase in yield, although yield can vary anyway between seasons. For a more accurate assessment of PCN populations, periodic soil sampling and testing could be undertaken. There is no prescribed rate of sampling, but 400 ml/ha would be consistent with the sampling rate for ware potato fields used in official surveys. Monitoring the number of viable cysts per g of soil over time would provide the minimum assessment of the rate of decline of PCN. For a more detailed assessment, egg counts could be done before and/or after planting in one season to provide a Pi value (initial population level) and/or a Pf value (final population level). Sampling can also be done during periods of non-cropping in the rotation to monitor the decline of population levels if required. Lifting of restrictions The rate of decline of PCN will vary according to individual programme employed. The earliest date for re-testing is after a minimum of 6 years since PCN was confirmed or since the growing of the most recent potato crop. The exact period will depend on the level of infestation detected and the control measures applied in the meantime. Restrictions and the requirement for a control programme will be revoked once a field has been officially confirmed as free of PCN, but it is hoped that the philosophy that has been embedded in the programme will continue to exert an influence in the crop management plan, maintaining a low level of PCN and hence reduce the risk to the national crop. Such results will provide a level of assurance about control methods in England and Wales in accordance with the new Directive.

9 Annex 1 PLANTS SUBJECT TO THE PCN DIRECTIVE 1. Host plants with roots: Capsicum spp., Lycopersicon lycopersicum, Solanum melongena 2a. Other plants with roots: Allium porrum, Beta vulgaris, Brassica spp., Fragaria spp., Asparagus officinalis 2b. Bulbs, tubers and rhizomes, not subjected to officially approved measures (on washing/brushing or disinfestation after harvesting), grown in soil and intended for planting, other than those for which there shall be evidence by their packaging or by other means that they are intended for sale to final consumers not involved in professional plant or cut flower production, of: Allium ascalonicum Allium cepa Dahlia spp. Gladiolus Hyacinthus Iris Lilium Narcissus Tulipa

10 Annex 2 CHECKLIST FOR DISCUSSION WITH THE PHSI ABOUT THE CONTROL PROGRAMME NB: A control programme is required if you intend to grow ware potatoes on a field officially recorded as infested. No seed potatoes may be grown in such a field. 1. Name and address of applicant 2. Identification of the sampled unit to which the control programme will apply include relevant farm codes and further description as necessary. 3. Reference number and date of the Statutory Notice recording the field as infested. 4. Species of PCN present. 5. Year in which you intend to plant the first crop of ware potatoes, if known. 6. Variety/varieties to be grown. Source (certified, farm-saved seed or other). 7. Rotation for future potato crops, including control of rogue potatoes and other crops to be grown. 8. Sampling strategy for PCN. 9. Chemical or other control methods to be used before or during first crop please give full details of product, timing, method of application etc. 10. Novel or innovative methods of control to be used. 11. Methods of disposal of waste 12. Source of seed potatoes 13. Hygiene strategy