PESTICIDE USAGE SURVEY REPORT 275
POTATO STORES IN THE UNITED KINGDOM 2016
A. Hinchcliffe, I. Barker, D. G. Garthwaite & G. Parrish
Pesticide Usage Survey Team
Fera
Sand Hutton
York UK
YO41 1LZ
A NATIONAL STATISTICS SURVEY
National Statistics are produced to high professional standards set out in the Code of Practice for Official Statistics. They are free from any political interference. The UK Statistics Authority has a statutory duty to assess National Statistics for compliance with this Code of Practice. Further information is available from the Office for National Statistics website (http://www.ons.gov.uk/ons/index.html). The statistics undergo regular quality assurance reviews to ensure that they meet customers’ needs.
The United Kingdom Statistics Authority has designated these statistics as National Statistics, in accordance with the Statistics and Registration Service Act 2007 and signifying compliance with the Code of Practice for Official Statistics. Designation can be broadly interpreted to mean that the statistics:
• meet identified user needs; • are well explained and readily accessible; • are produced according to sound methods; and • are managed impartially and objectively in the public interest.
Once statistics have been designated as National Statistics it is a statutory requirement that the Code of Practice shall continue to be observed. If you have any enquiries or feedback on the statistics included in this report they can be directed to the contact given below:
Pesticide Usage Survey Team – e-mail: [email protected] Telephone: 01904 462 302
Alternatively, please contact: Fera Science Ltd. at: [email protected]
DATA USES
The data are used for several purposes including:
• Quantifying pesticide usage and changes in the use of active substances over time;
• Policy, including assessing the economic and/or environmental implications of the introduction of new active substances and the withdrawal/non-authorisation of pesticide products (the data reported to organisations such as the OECD and EU enabling the UK to honour international agreements); evaluating changes in growing methods and Integrated Pest Management where this has an impact on pesticide usage;
• Informing the pesticide risk assessment (authorisation) process;
• Informing the targeting of monitoring programmes for residues in food and the environment;
• Contributing to assessing the impact of pesticide use, principally as part of the Pesticides Forum’s Annual Report;
• Responding to enquiries (for example, Parliamentary Questions, correspondence, queries under the Freedom of Information Act or Environmental Information Regulations, etc.);
• Providing information to assist research projects which can support all the above activities;
• Training/teaching programmes which are designed to improve practice in the use of pesticides by the farming/training industries;
• Informing the Wildlife Incident Investigation Scheme (WIIS) programme to help identify potential misuse of pesticides.
REVISIONS POLICY
This report presents a comprehensive summary of data for Potatoes harvested in 2016 and stored during 2016/2017. We will provide information on any revisions we make to the report or the datasets if any inaccuracies or errors occur. Details of any revisions, including the date upon which they were changed, will appear on the following website: https://secure.fera.defra.gov.uk/pusstats/surveys/index.cfm
2
CONTENTS PAGE
Executive Summary 4
Introduction 6
Trends 7
Ware Potatoes 9
Seed Potatoes 10
Appendix 1 – Ware Potato Tables 11
Appendix 2 – Seed Potato Tables 12
Appendix 3 – Comparison Table 13
Appendix 4 – Utilisation of Ware Potato Stores for Other Commodities 14
Appendix 5 – Definitions 15
Appendix 6 – Methodology 16
Acknowledgements 19
References 19
3 EXECUTIVE SUMMARY
This report presents information on all aspects of pesticide usage during storage of potatoes harvested in 2016 and stored during 2016/2017. Data were collected by a combination of visits and telephone surveys comprising of 69 merchants stores and 72 farm stores totalling 141 stores surveyed in the United Kingdom. A total of 9.6% of the ware potato crop tonnage stored and 26% of the seed potato tonnage stored were surveyed in this year’s survey round.
As for the 2014 report, the main body of the 2016 report differs from previous potato storage reports, in that the data collected on ware potatoes from both farm and merchant are now combined. This reflects the changes in potato storage practice over the last decade which has resulted in very little difference between the way in which farm and merchant stores are managed. In addition, data collection has changed from primarily a visit survey, to a combination of visit, postal and telephone surveys. Farm and merchant stores are still reported separately for the purposes of estimating the storage of other commodities and the use of chlorpropham where other commodities have been stored, as this would be expected to be more relevant to farm potato stores.
The estimated weight of ware potatoes stored from the 2016 harvest was approximately 3.45 million tonnes, of which this survey estimated that 69% received no post-harvest treatment (79% of the untreated crop was in refrigerated stores). The basic tonnage treated was 1.07 million tonnes, though some potatoes received multiple treatments. The total tonnage treated, which adds up the tonnages of multiple treatments, was 1.64 million tonnes.
The active substance chlorpropham, a potato sprout suppressant, accounted for 82% of the total tonnage treated, while 15% were treated with ethylene, 3% with spearmint oil, and less than 1% with either imazalil/thiabendazole or imazalil alone. A total of 9.2 tonnes of active substances were used to treat ware potatoes. Chlorpropham (95%), spearmint oil (4%), thiabendazole (<1%) and imazalil (<1%), accounted for the total weight of active substances used. Ethylene gas does not have a weight of active substance associated to it. Gro-Stop Electro was encountered for the first time in 2016, this formulation of chlorpropham contains eugenol (clove oil).
From this survey, it is estimated that 46% of the 550,582 tonnes of the stored seed potatoes were treated, either on entry to the store or during the storage period, with a single application of pesticides. The formulations recorded were imazalil/thiabendazole, imazalil and ethylene, accounting for 84%, 15% and 1% of the total tonnage treated respectively. In total, 6.14 tonnes of active substances were used, principally thiabendazole, accounting for 65% of the total weight, and imazalil 35%. A comparison is made between this survey and previous surveys conducted between 2006 and 2016. The tonnage of ware potatoes stored increased by 11% from that in 2014 despite a decrease of 2% in the area grown, reflecting the favourable 2016 growing season. The basic tonnage treated decreased by 34% and the total tonnage treated decreased by 63% from that recorded in 2014.
The 2016 season demonstrated a dramatic change. The weight of active substances used in 2016 was 9.2 tonnes, a decrease in usage of 75%. This marked reduction in usage could be explained by many cumulative factors. Growers and processors are increasingly concerned over acrylamide levels in the potato crop and the effects this has on potato quality, and so this is reflected by the proportion of untreated crop tonnage, increasing to 69% of the total ware tonnage stored in 2016.
In addition, the total tonnage of ware potatoes treated in store decreased by 63% since 2014. The significant reduction in the weight of active substances used since 2014 also reflects the current requirement for store managers to adhere to the ‘Step Down’ process to which introduced lower application rates for chlorpropham during the 2016/17 season. In addition, Stewardship best practice (endorsed by the CIPC Applicator Group and Red Tractor Farm Assurance) continues to allow just a single application to chlorpropham up to a maximum of 16 gr/tonne in refrigerated stores. Changes from July 2017 introduced the requirement for ‘active recirculation’ during and after chlorpropham application to stored 4 potatoes which may have influenced store management during the 2016/17 season as store managers were encouraged to “Be 2017 Ready” The usage of imazalil and imazalil/thiabendazole on ware crops also fell significantly between 2014 and 2016 contributing a reduction in weight of active substance applied of 1.78 tonnes alone.
The use of ethylene gas has no weight of active substances associated with it in 2016, whereas in 2014, some stores provided quantities of ethanol used in the Restrain Fuel generators that provided a treated weight for ethylene of 3.27 tonnes in the last report.
The total tonnage of stored seed potatoes in the United Kingdom had decreased by 10% between 2010 and 2012, while the basic tonnage treated decreased by 32%. In 2014, the total tonnage stored decreased by 8% since 2012, however the basic tonnage treated increased by 46%. Overall, the weight of active substances applied to seed potatoes doubled between 2012 and 2014 and the proportion of untreated crop decreased from 75% in 2012 to 60% in 2014. In 2016, the total weight of active substances applied to stored seed potatoes increased by 6% to 6.14 tonnes from 5.78 tonnes in 2014. This was despite an increase of 23% in the total tonnage of seed potatoes stored and partially helped by the untreated tonnage of seed potatoes stored which increased by 15% over the same period to represent 54% of the total seed potato crop stored in 2016.
After the introduction of the CIPC Stewardship Scheme in 2008, the 2016 report indicates a cessation in the usage of chlorpropham in ware potato stores where other commodities are stored. Between 2008 and 2016, the percentage of farm stores storing other commodities and using chlorpropham fell from 13% to none, whilst the percentage in merchant stores fell from 5% to none.
5 INTRODUCTION
The Expert Committee on Pesticides (ECP) advises government on all aspects of pesticide use. In order to discharge this function, the Committee must regularly monitor the usage of all pesticides. It needs accurate data on the usage of individual pesticides. Pesticide usage data is now also required under the EU Statistics Regulation (1185/2009/EC).
As part of the on-going process for obtaining data, the Pesticide Usage Survey Teams of Fera Science Ltd., a joint venture between Capita PLC and the Department for Environment, Food & Rural Affairs (Defra), Science & Advice for Scottish Agriculture (SASA), a division of the Scottish Government’s Agriculture and Rural Economy Directorate and the Agri-Food & Biosciences Institute (AFBI), Department of Agriculture, Environment and Rural Affairs, Northern Ireland (DAERA), conducted surveys of pesticide usage in potato stores in 2016/17 by visiting holdings throughout the United Kingdom during the winter of 2016/17 and conducting a postal and telephone survey in the summer of 2017.
Since 2010, all surveys of pesticide usage in agriculture and horticulture have been fully co-ordinated by the survey teams of England & Wales, Scotland and Northern Ireland. The methodology used for sample selection and the collection of data from sample holdings is identical in each region. Reports are produced of pesticide usage throughout the United Kingdom. All teams have undertaken recent United Kingdom Statistics Authority (UKSA) audits and the data are accredited as National Statistics.
This is the third survey of usage on potato storage in the United Kingdom and the thirteenth survey of pesticide usage in potato stores carried out by the Great Britain Pesticide Usage Survey Teams. The previous report for the United Kingdom covered all pesticide usage on potatoes harvested and stored in 2014 (Garthwaite et. al., 2015).
Additional data on crop agronomy are collected for all surveys but may not be presented within the report. For additional data relating to the surveys please refer to the contacts below.
Information on all aspects of pesticide usage in the United Kingdom, or for Wales or the Defra regions of England, may be obtained from the Pesticide Usage Survey Team at Fera Science Ltd., Sand Hutton, York, UK YO41 1LZ. For further information please contact:
The survey team – e-mail: [email protected] Telephone: 01904 462 032 Or visit the website: https://secure.fera.defra.gov.uk/pusstats/surveys/index.cfm
Alternatively, please contact: Fera Science Ltd. at: [email protected]
Further data relating specifically to Scotland may be obtained from the Pesticide Usage Survey Team at Science and Advice for Scottish Agriculture, Edinburgh. Also available at: http://www.sasa.gov.uk/pesticides/pesticide-usage/pesticide-usage-survey-reports
Copies of reports on pesticide usage in Northern Ireland may be obtained from Her Majesty's Stationery Offices. Also available at: https://www.afbini.gov.uk/articles/pesticide-usage-monitoring-reports
Recently-published reports for the United Kingdom, Great Britain, England & Wales and Northern Ireland can also be viewed and downloaded on the Internet at: https://secure.fera.defra.gov.uk/pusstats/surveys/index.cfm
Alternatively, pesticide data for the UK can be extracted using the search tool – PUSSTATS: https://secure.fera.defra.gov.uk/pusstats/
6 TRENDS
WARE POTATOES
Figure 1 - Changes in pesticide usage on stored ware potatoes in the United Kingdom - 2006-2016 1,2
5,000,000
4,000,000
3,000,000 Tonnage stored Basic tonnage treated
tonnes Total tonnage treated 2,000,000 Tonnage untreated
1,000,000
0 2006 2008 2010 2012 2014 2016
Figure 2 - Changes in the weight of pesticide applied to stored ware potatoes in the United Kingdom - 2006-2016
60
50
40
30
20 Tonnes Tonnes of active substance
10
0 2006 2008 2010 2012 2014 2016
1The basic tonnage treated is the tonnage stored minus the untreated tonnage
2The total tonnage treated includes repeat applications
7 TRENDS
SEED POTATOES
Figure 3 - Changes in pesticide usage on stored seed potatoes in the United Kingdom - 2006-2016 1,2
600,000
500,000
400,000
Tonnage stored
300,000 Basic tonnage treated
tonnes Total tonnage treated Tonnage untreated 200,000
100,000
0 2006 2008 2010 2012 2014 2016
Figure 4 - Changes in the weight of pesticides applied to stored seed potatoes in the United Kingdom - 2006-2016
7
6
5
4
3
2 Tonnes Tonnes active of substance
1
0 2006 2008 2010 2012 2014 2016
1The basic tonnage treated is the tonnage stored minus the untreated tonnage
2The total tonnage treated includes repeat applications
8
WARE POTATOES
• An estimated 3,454,294 tonnes of ware potatoes were stored in the United Kingdom.
• 120,707 ha of ware potatoes were grown in the United Kingdom in 2016
• An estimated 1,071,307 tonnes were treated with an average of 1.86 treatments resulting in a total treated tonnage of 1,640,750 tonnes
• A further 2,382,987 tonnes (69%) remain untreated (79% of these in refrigerated stores)
Ware potatoes
Approximately 91% of ware potatoes were stored in boxes, the remainder in bulk stores.
Figure 5 - Storage methods used for ware potatoes in the United Kingdom - 2016
2%
23%
Unventilated ambient store Ventilated ambient store Refrigerated store
75%
Ware potatoes – Pesticide Usage
Active substance Total tonnes treated Active substance (tonnes)
Chlorpropham 1,327,406 8.74 Ethylene 239,896 0 Imazalil 3,844 0.04 Spearmint oil 52,836 0.37 Thiabendazole 2,248 0.05
Total 1,626,230 9.20
Chlorpropham was applied as a fumigant, in separate applications made by contractors during the storage period. Ethylene was applied as a gas throughout the storage period with its concentration monitored and maintained in store to prevent sprouting of tubers.
The use of ethylene and spearmint oil was confined to refrigerated box stores for sprout suppression. Similarly, the use of imazalil was mainly confined to refrigerated box stores (91% of tonnage treated). Imazalil/thiabendazole was primarily used in ventilated ambient stores (63% of tonnage treated) with the remainder being used in refrigerated box stores.
9
SEED POTATOES
• An estimated 550,582 tonnes of seed potatoes were stored in the United Kingdom.
• 16,733 ha of seed potatoes were grown in the UK in 2016.
• An estimated 250,770 tonnes were treated with a single pesticide application
• A further 299,812 tonnes (54%) remain untreated (78% of these in refrigerated stores)
Seed potatoes – Storage methods
All seed potatoes encountered in the survey were stored in boxes.
Figure 6 - Storage methods used for seed potatoes in the United Kingdom - 2016
<1%
35% Unventilated ambient store Ventilated ambient store Refrigerated store 64%
Seed potatoes – Pesticide Usage
Three pesticide formulations, ethylene, imazalil and imazalil/thiabendazole were the only pesticides encountered in seed potato stores accounting for 2%, 14% and 84% of the total treated tonnage respectively.
Active substance Total tonnes treated Active substance (tonnes)
Ethylene 3,120 0 Imazalil 247,650 2.73 Thiabendazole 142,678 3.41
Total 393,448 6.14
Imazalil and thiabendazole formulations were applied as sprays – normally on the elevator as the seed potatoes entered store. No specific diseases were cited for the use of fungicides.
Ethylene gas was encountered in seed potato stores for the first time in 2014 and is used to manipulate sprout development in refrigerated stores.
10 APPENDIX 1 – WARE POTATOES
Table 1. Number and distribution of stores sampled in the United Kingdom - 2016
Farm Stores Merchant Stores
Region
East Midlands 5 4 Eastern 9 7 North West 3 1 London & South East 1 0 Northern Ireland 32 0 Scotland 10 55 West Midlands 7 0 South West 2 0 Yorkshire & the Humber 3 2
Total 72 69
Table 2. Storage methods used for ware potatoes stored in the United Kingdom, 2016 (tonnes stored)
Unventilated Ventilated Refrigerated Total
Bulk storage 14,121 270,417 15,022 299,560
Boxed storage 55,602 535,721 2,563,411 3,154,734
Total - all storage methods 69,723 806,138 2,578,433 3,454,294
Table 3. Storage pesticide use on ware potatoes at stores in the United Kingdom, 2016 (tonnes treated)
Unventilated Ventilated Refrigerated Total Total - all
Bulk Box Bulk Box Bulk Box Bulk Box storage methods
Chemical
Chlorpropham 0 0 394,063 311,204 23,828 598,311 417,891 909,515 1,327,406 Ethylene 0 0 0 0 0 239,896 0 239,896 239,896 Imazalil 0 0 0 145 0 1,450 0 1,595 1,595 Imazalil/thiabendazole 0 0 0 1,435 0 813 0 2,248 2,248 Spearmint oil 0 0 0 0 0 52,836 0 52,836 52,836
Total 0 0 394,063 312,784 23,828 893,306 417,891 1,206,090 1,623,981
Not treated 14,121 55,602 24,191 418,306 2,072 1,868,695 40,384 2,342,603 2,382,987
Table 4. Usage of individual active substances on stored ware potatoes in the United Kingdom, 2016 Tonnes treated Tonnes (a.s) % tonnes % as
Chemical
Chlorpropham 1,327,406 8.74 82 95 Ethylene 239,896 0 15 0 Imazalil 3,844 0.04 <1 <1 Spearmint oil 52,836 0.37 3 4 Thiabendazole 2,248 0.05 <1 <1
Total 1,626,230 9.20
11 APPENDIX 2 – SEED POTATOES
Table 5. Storage pesticide use on seed potatoes in the United Kingdom, 2016 (tonnes treated) Unventilated Ambient Ventilated Ambient Refrigerated Total Total - all
Bulk Box Bulk Box Bulk Box Bulk Box storage methods Pesticide Ethylene 0 0 0 0 0 3,120 0 3,120 3,120 Imazalil 0 0 0 87,968 0 17,004 0 104,972 104,972 Imazalil/thiabendazole 0 5,850 0 43,311 0 93,516 0 142,677 142,67 7
Total tonnage treated 0 0 0 131,279 0 113,640 0 250,769 250,769
Not treated 0 6,131 0 60,235 0 233,446 0 299,812 299,812
Total tonnage stored 0 11,981 0 191,514 0 347,086 0 550,581 550,581
Table 6. Usage of individual active substances on stored seed potatoes in the United Kingdom, 2016 Total tonnes treated Tonnes (a.s) % tonnes % as
Chemical
Ethylene 3,120 . <1 . Imazalil 247,650 2.73 63 44 Thiabendazole 142,678 3.41 36 56
Total 393,448 6.14
12 APPENDIX 3 - COMPARISON
Table 7. Comparison of production, storage and treatment of potatoes in the United Kingdom - 2006 - 2016
2006 2008 2010 2012 2014 2016
Area grown (ha) Ware 128,212 131,475 120,873 131,825 123,317 120,707 Seed 14,788 15,380 17,440 16946 17,214 16,733
Tonnes stored Ware 3,841,724 4,106,855 3,896,359 2,952,083 3,098,269 3,454,294 Seed 417,371 457,996 509,803 457,519 422,591 550,582
Basic tonnes treated 1 Ware 1,791,136 1,906,591 2,034,962 1,681,507 1,435,552 1,071,307 Seed 152,025 144,984 171,007 115,969 168,884 250,770
Total tonnage treated 2 Ware 3,183,264 4,045,106 3,807,290 2,907,145 2,677,280 1,640,750 Seed 154,829 160,254 171,007 120,593 168,884 244,919
Tonnes untreated 3 Ware 2,050,588 2,200,264 1,861,397 1,270,576 1,662,717 2,382,987 Seed 265,346 313,012 338,796 341,550 253,707 299,812
Weight applied (tonnes) Ware 55 42 37 31 36 9 Seed 2 2 5 3 6 6
1 Basic tonnes treated = tonnes stored – tonnes untreated 2 Total tonnage treated = basic tonnes treated x number of treatments 3 Tonnes untreated = potatoes stored which receive no pesticide treatments during storage
13 APPENDIX 4 – UTILISATION OF WARE POTATO STORES FOR OTHER COMMODITIES
There have been instances in the detection of chlorpropham residues in commodities other than potatoes, for example cereals. Residues of chlorpropham can persist within the fabric of the store, wood and even concrete, for a number of years. These residues can potentially be transferred to other commodities (which don’t have an approval for chlorpropham) placed in the stores after the potatoes have been removed. To oversee the use of chlorpropham, a Potato Industry CIPC Stewardship Group was set up in 2008. As part of its work, the group is aiming to assess the extent of usage of potato stores for other commodities and asked the pesticide usage team for its involvement in monitoring the extent of this usage. The following table contain the results from these additional questions. There was some storage of other commodities in seed potato stores but there was obviously no usage of chlorpropham at these stores and this information is not presented in the report. A decrease in the storage of other commodities in potato stores was evident during the 2016 season (Table 8). Table 8 shows a decrease in the storage of other commodities in potato stores during the 2016 season. Significantly, in 2016, there has been a cessation in the usage of chlorpropham in potato stores where other commodities are stored for the first time since the introduction of the CIPC Stewardship Scheme in 2008.
Table 8. Ware potato stores holding other commodities and using chlorpropham in the United Kingdom, 2008 – 2016 (% of total stores)
2008 2010 2012 2014 2016 Storage of other commodities Farm 38% 9% 6% 16% 6%
Merchant 13% 4% 3% 17% 11%
Storage of other commodities & using chlorpropham Farm 13% 4% 3% 2% 0%
Merchant 5% 2% 0% 1% 0%
NUMBERS OF WARE POTATO STORES WITH OTHER COMMODITIES
In 2016, 9% of the total farm and merchant premises were storing commodities other than potatoes within the same store (but not necessarily at the same time). For the first time since the introduction of the CIPC Stewardship Scheme in 2008, no stores were encountered (farm or merchant) that were storing other commodities and using chlorpropham (Table 9).
Table 9. Storage of other commodities within potato stores on sampled holdings – number of stores in the United Kingdom, 2016
Storing other commodities in 2016 & Storing other commodities in 2016 Total number of stores using chlorpropham
Farm stores 4 0 72 Merchant stores 8 0 69
Total 12 0 141
14 APPENDIX 5 - DEFINITIONS
a) 'Applications' is used throughout this report to refer to the number of pesticide treatments applied to a store (whole or part). b) 'Basic tonnes treated' is the gross weight of potatoes treated with pesticides excluding repeat applications, i.e. the total tonnes stored minus the untreated tonnage (“Tonnes untreated”). c) 'Total tonnage treated' is the gross weight of potatoes treated with pesticides including repeat applications, i.e. basic tonnes treated x number of applications. d) ‘Bulk stores’ include loose potatoes in a variety of stores, as opposed to those stored in boxes. Potatoes stored in bags are excluded from this survey. e) ‘Unventilated ambient stores’ include structures that are naturally ventilated and rely on convective ventilation. f) ‘Ventilated ambient stores’ include structures using forced air ventilation. They do not use refrigeration methods. g) ‘Refrigerated stores’ include structures using refrigeration; they may also have forced air ventilation. h) ‘Merchant’ includes AHDB (Agricultural & Horticultural Development Board) Potatoes registered purchasers, who have traded 100 tonnes of potatoes or more in the most recent full crop year and qualify for payment of AHDB Potatoes levy, and also farm owned stores storing potatoes from their own and other growers’ holdings. They will have stored potatoes for a period of more than 2 months. i) A ‘Farm Store’ holds only potatoes from the single holding where the store is located, for a period of more than 2 months. j) In this report the term ‘formulation(s)’ is used to describe the pesticide active substance or mixture of active substances in a product(s). k) ‘Seed potatoes’ are those stored and used for planting the next season’s crop. Prior to planting, seed potatoes are placed in a ‘chitting house’ where the tuber can produce shoots & rootlets prior to planting. l) ‘Ware potatoes’ are those used for human consumption, including those processed by a manufacturer. m) ‘Arable crops’ include cereals, combinable peas & beans, oilseed rape, linseed, potatoes and sugar beet. n) There is no standard recommended rate per tonne of potatoes for the use of ethylene. The application equipment is pre-set to maintain the required level of ethylene concentration in each store. Consequently, the quantity of ethylene used will vary according to the store capacity, crop volume, the quality of store construction and the duration of storage. In most cases the actual amount of ethylene used was not available. Therefore, the quantity of ethylene relates to information collected from stores where the data were available. o) Storage is defined as potatoes being in store for two months or longer
15 APPENDIX 6 - METHODOLOGY
METHODS
The samples of holdings to be surveyed were selected using data from the Agricultural Census Returns, June 2015 for England & Wales (Anon., 2016 a, b), for Scotland (Anon., 2016c) and Northern Ireland (Anon, 2016d).
The samples for the arable survey (Garthwaite et. al., 2017) were drawn from the census returns so as to represent the area of all arable crops grown throughout England, Scotland, Wales and Northern Ireland. For England the sample was selected within each of the eight Government Office Regions (GOR’s), the Welsh Assembly Government provided a further sample, which represented the area grown in Wales, and for Scotland the country was divided into 11 land-use regions (Wood, 1931).
The samples for the arable survey were stratified according to the total area of all arable crops grown in each region and by farm size group based on the total area of arable crops on each farm. The area of arable crops sampled in each size group and each region was proportional to the total area of arable crops grown on holdings of each size group in each region. All three survey teams followed the same methodology for data collection and used the same forms and instructions for their completion. The size groups, based on the total arable area are as follows: <50ha (A); >50-<=100 ha (B); >100-<=150 ha (C); >150-<=250 ha (D); >250-<=500 ha (E) and >500 ha (F).
In England and Wales, most of the data on arable pesticide usage was collected by a sub-contractor, using the sampling frame and stratification methodology indicated above. Whilst the sub-contractor collected detailed field pesticide usage they did not collect supplementary data on potato storage.
To increase the data relating to potato storage in England and Wales a separate sample was taken using the same stratification indicated above (region and arable farm size group), but only from holdings who indicated on their 2015 June Survey returns that they were growing potatoes. A total of 329 holdings were selected and an introductory letter was sent to each, explaining the purpose of the survey and enclosing a postal reply form requesting the total area of arable cropping, the area of potatoes grown, and the tonnage of potatoes stored from the 2016 harvest.
Of the 66 replies received in England & Wales, 19 holdings were not growing potatoes, 11 grew potatoes but did not store in 2016 and 36 holdings grew and stored potatoes in 2016. Of these, 30 holdings growing and storing potatoes in 2016 were contacted by telephone to confirm the store type and storage treatment details and provided data.
The Pesticide Survey Unit at SASA (Science and Advice for Scottish Agriculture) provided information on 10 farms and 55 merchant potato stores in Scotland.
The Pesticide Usage Survey Team at AFBI-NI (Agri-Food & Biosciences Institute - Northern Ireland) provided data on a further 32 farm potato stores in Northern Ireland.
Data were raised to estimate national pesticide usage (Thomas, 1999). The raising factor used for ware potatoes was based on UK potato stock movement information provided by AHDB Potatoes. A separate raising factor was used for seed potatoes, which were based on SASA and AHDB Potatoes estimates for the average yield of marketable seed potatoes in the United Kingdom in 2016 and the seed potato areas recorded by FERA for England & Wales (Anon., 2017e), for Scotland (Anon., 2017c) and Northern Ireland (Anon, 2017d).
Whilst there were no positive returns from farm or merchant potato stores in Wales, this does not indicate that there are no potato stores in this country. As such, the tonnage of potatoes stored in Wales has been accounted for in the raising factors to make estimates of usage in the United Kingdom.
16 Both raising factors, for ware and seed potatoes, were calculated by dividing the United Kingdom estimated tonnage stored by the sampled stored tonnage. For ware potatoes the raising factor was 10.36 and for seed potatoes 3.9. The raising factors used have assumed that usage at the sampled stores is representative of potato stores in the United Kingdom.
The Questionnaire
The questionnaire consisted of two forms, which were completed by an experienced surveyor during an interview with the farmer, or for commercial stores, by a store representative following receipt of a comprehensive set of instructions.
Form 1 summarised the area of potatoes grown on each holding during the 2016 growing season.
Form 2 detailed all aspects of pesticide usage in each store. A separate form was completed for each method of storage and treatment programme. Seed and ware potatoes were recorded separately.
A further questionnaire was sent to 72 merchants’ stores in England & Wales, of which storage data was received from 14. 6 stores were no longer storing and no responses were made from the remaining 52. The format of the questionnaire and instructions for its completion followed the same methodology as the farm visits.
Where necessary, further checks have been made to ensure that farm stores were only storing potatoes harvested from their own holding; this has been done following consultation with individual growers and checking that the average yields on the holding were within the range provided by AHDB Potatoes. In some cases purpose built stores may have been built in co-operation with individual merchants in order to store potatoes that they would ultimately purchase. These have remained as farm stores if the potatoes were only from their own holding.
Rounding Due to rounding of figures, the sum of constituent items in the tables may not agree exactly with the totals shown.
17 Error checking
Extensive checks are made on the data before, at the time of and following data entry. Data checking routines are used to verify the authenticity of the data collected including: the approval status of all crop/pesticide combinations; high and low rates of application; the methods of application used to apply pesticides; crop growth stages at the time of application and the timing of pesticide applications.
Further checks are made on the integrity of the relational database used to store the raw data collected ensuring that links to product databases are in place prior to the production of the report. The product databases used for the pesticide usage surveys are maintained alongside the commercial product database, LIAISON , which is used extensively by agronomists and the major farm management software companies.
Where inconsistencies are found, for example where there are high rates of application or non-approved product usage, these are checked first against the farm records and secondly with the grower and amended if necessary.
Reports are written and checked within the team after which they are sent to reviewers within the Working Party on Pesticide Usage Surveys for their comments and checking.
The final report is pre-announced and published via the ONS Publication Hub and the Fera website in line with the Code of Practice for Official Statistics.
Data limitations and use of data
Our experience has shown that the proposed face to face interview and ‘main contact plus reserves approach’ delivers the highest quality data and minimises non-response bias; no other approach is likely to yield fit for purpose data to meet the quality requirements of the UKSA Code of Practice for Official Statistics. Drawing a fresh stratified random sample each year is clearly an appropriate survey methodology.
Whilst there are detailed data available on the cropped areas of ware and seed potatoes in the United Kingdom there are no such figures for stored potatoes. The only data available on stored ware and seed potatoes are estimates produced by AHDB potatoes. In the absence of any other data it has been these figures that have been used to create raising factors and to make national estimates.
In contrast to surveys conducted up to, and including 2010, which were conducted mainly by visit, the 2016 survey for England & Wales was predominantly a postal survey. There are inherent problems with postal surveys, the main one of which is an unknown response rate, which can be quite low. For the farm stores in England & Wales a total of 321 letters were sent, assuming a 20% response rate to achieve a total of 60 stores, which would then be in-line with the numbers recorded for 2010. However, whilst a 26% response rate was achieved overall, only 9% of the total responses were from farms growing and storing potatoes. For future surveys increasing the number of postal send-outs or making phone calls to non-respondents will be considered.
As part of this survey Fera has implemented the UKSA Code of Practice for Official Statistics, published in 2009. Whilst all eight principles apply, we acknowledge, the following: • Integrity – in particular, that statistical reports must be issued separately from other statements or comments about the figures, that the public interest prevails. • Confidentiality – the identity of individuals or their information is not revealed, information is kept secure and respondents are informed how their confidentiality will be protected . • Proportionate burden - seeking participation through informed consent. • Accessibility – to all users, providing information on the quality and reliability of the statistics, adopting formats that enhance clarity and consistency, disseminate in formats that encourage analysis and re-use.
In accordance with the UKSA Code of Practice for Official Statistics, we work with Defra and HSE statisticians to build on our existing extensive and effective relationships with users of the surveys to further enhance user engagement. There are a broad spectrum of users and stakeholders across policy, research, agricultural supply industry (including consultancies), farming and horticultural businesses, NGOs and members of the public. Over the years we have an excellent record of listening to our users and incorporating their feedback into the way we collect and report our statistics.
18 ACKNOWLEDGEMENTS
Thanks are due to all the growers who willingly participated in this survey, providing invaluable information upon which this report is based. Many thanks are also due to Jackie Hughes, Stephen Jess, Trudyann Kelly, Michael Lavery, David Matthews, Carol Monie, Gillian Reay, Johan Wardlaw, David Williams and Alan Withers for their role in the collection and provision of data; Yvonne Powell-Wainwright and Josephine Roberts for their role in maintaining the pesticides database; and Jennie Blackburn, Sarah Thompson and John Bleasdale for their help with the cropping areas of potato crops in England & Wales respectively. Thanks also go to the members of the ECP Working Party on Pesticide Usage Surveys, Sarah Cook, Peter Gladders and Sacha White, for their invaluable comments.
Thanks also to AHDB Potatoes for their help in estimating the tonnage of potatoes stored.
REFERENCES
Anon . (2016a) Agricultural Statistics in England 2015. London: HMSO
Anon . (2016b) Agricultural Statistics in Wales 2015. London: HMSO
Anon . (2016c) Agricultural Statistics, Scotland 2015. Edinburgh: HMSO
Anon . (2016d) Agricultural Statistics, Northern Ireland 2015. Belfast: HMSO
Anon . (2017a) Agricultural Statistics in England 2016. London: HMSO
Anon . (2017b) Agricultural Statistics in Wales 2016. London: HMSO
Anon . (2017c) Agricultural Statistics, Scotland 2016. Edinburgh: HMSO
Anon . (2017d) Agricultural Statistics, Northern Ireland 2016. Belfast: HMSO
Anon . (2017e) Seed Potato Production in England & Wales, FERA website
Garthwaite, D., Barker, I., Parrish G . (2015) Pesticide Usage Survey Report 266 - Potato Stores in the United Kingdom 2014. London: Defra
Garthwaite, D., Barker, I., Ridley, L., Mace, A., Parrish, G., MacArthur, R., & Lu, Y. (2017) Pesticide Usage Survey Report 271 – Arable Crops in the United Kingdom 2016. London: Defra
Thomas, M. R ., (1999), Guidelines for the Collection of Pesticide Usage Statistics within Agriculture and Horticulture, OECD, Eurostat, http://www.oecd.org/chemicalsafety/pesticides-biocides/2078031.pdf (last accessed 02.08.2015)
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