Rodenticides on Arable Farms 2000-2010 - SASA

An OfficiAl StAtiStic PublicAtiOn fOr ScOtlAnd<strong>Rodenticides</strong> onArable Farms2000 - 2010Pesticide Usage in Scotland

Pesticide Usage in Scotland<strong>Rodenticides</strong> on Arable Farms2000 to 2010J. HughesScience and Advice for Scottish Agriculture (SASA)Roddinglaw Road, Edinburgh, Scotland, EH12 9FJpsu@sasa.gsi.gov.ukwww.sasa.gov.uk/pesticidesPublished by the Scottish Government, September 2012

CONTENTSPageSummary ........................................................................................................ 1Introduction ...................................................................................................... 2Definitions and notes ....................................................................................... 2Method ........................................................................................................ 3Results and discussion .................................................................................... 4Acknowledgements .......................................................................................... 7References....................................................................................................... 7Figure 1 Land-use regions of Scotland.......................................................... 8Figure 2 Estimated occurrence of anticoagulant rodenticides in Scotland2000-2010 ....................................................................................... 9Figure 3 Estimated quantity of anticoagulant rodenticide products applied inScotland 2000-2010 ........................................................................ 9Table 1 Number and regional distribution of holdings sampled .................. 10Table 2 Percentage of holdings using chemical control for vertebrate pests...................................................................................................... 11Table 3 Percentage of holdings on which pest control was conducted by thefarmer ............................................................................................ 11Table 4 Estimated occurrence of rodenticide formulations......................... 12Table 5 Estimated quantities of rodenticide products ................................. 13Table 6 Estimated quantities of rodenticide formulations ........................... 14Table 7 Chemical control of rabbits ............................................................ 15Table 8 Chemical control of moles ............................................................. 15Table 9 Raising and adjustment factors ..................................................... 16Appendix 1 UK approval status of compounds encountered.......................... 19

SummaryThroughout the surveyed period, rodenticides were used on more than threequarters of arable holdings. Farmers were responsible for rodenticide use on themajority of farms from 2000 to 2008. However, in 2010 baiting was conducted bypest control professionals on 55% of the farms sampled.Anticoagulant compounds were the most frequently encountered rodenticides,accounting for over 99% of all rodenticide use. The most commonly used activeingredients were the second generation compounds bromadiolone and difenacoum.These two rodenticides cumulatively accounted for more than 78% of all occurrencesof use and 80% of total quantity of rodenticide products applied during the surveyedperiod.Bromadiolone use in 2010 was double that encountered in 2000, in relation to bothoccurrences and quantity of product. Conversely, occurrence of difenacoum in 2010was almost a third less than in 2000 and the quantity used was almost two thirdsless. However, usage data showed considerable inter-survey variation over thedecade.Chemical control of rabbits was recorded on fewer than 10% of farms during thesesurveys. The most commonly used compound for rabbit control was aluminiumphosphide. Sodium cyanide use was recorded in the first half of the decade but wasnot encountered after its withdrawal in 2004.The percentage of holdings employing chemical control for moles in 2010 was justover one third of those doing so in 2000. A notable decline in chemical use occurredafter the withdrawal of strychnine in 2006. Thereafter aluminium phosphide was theonly active ingredient available for mole control.1

IntroductionThis report summarises the results of six biennial surveys of rodenticide use onarable holdings in Scotland between 2000 and 2010. It also includes information onthe use of chemicals to control moles and rabbits.The rodenticide surveys were performed alongside pesticide usage surveys onarable crops conducted by the Pesticide Survey Unit at Science and Advice forScottish Agriculture (SASA), a division of the Scottish Government’s Agriculture,Food and Rural Communities Directorate.Rodenticide use data were collected from a sample of arable holdings. Sample sizevaried among surveys, accounting for approximately 2% of the total arable holdingsin Scotland (Table 1). Estimates of national rodenticide use have been calculatedbased on the sampled data.The 2000 and 2002 survey data have been published previously 1,2 but aresummarised in this report to provide an overview of rodenticide use over the lastdecade. There are some differences in the estimated quantity of rodenticidesreported previously and in this summary report (please refer to the method sectionfor explanation). The data from the surveys conducted from 2004 to 2010 arepublished for the first time in this report.Definitions and NotesThe term ‘rodenticide’ is used to describe a substance used to kill or control rodents.Surveys only concerned chemical control of vertebrate pests and information onother control methods, such as trapping or shooting, were not collected.The term ‘formulation(s)’ is used to describe the active ingredient or mixture of activeingredients formulated together. The term ‘product’ is used to describe the marketedrodenticide product containing active ingredients, bait and other co-formulants.The term ‘occurrence’ is used to describe the number of holdings on which aformulation has been used. If a holding has used a product with the sameformulation more than once or more than one product with the same formulation it isrecorded as a single occurrence.Throughout the tables, data based on fewer than 10 sampled occurrences aremarked with an asterisk and should be treated with caution as these estimates mayhave an unacceptably high associated error.The term ‘holding’ is the basic unit used in the agricultural census and, in this report,is synonymous with the term ‘farm’.Due to rounding, there may be slight differences in totals both within and betweentables.2

MethodIn each survey rodenticide use data were collected from a random sample ofholdings growing arable crops (Table 1). The holdings were grouped by land-useregion 3 (Figure 1) and stratified by five size groups based on the total area of arablecrops grown. Sampling within size groups was based on area rather than numbers ofholdings, so that smaller size groups did not dominate the sample. This stratificationwas designed to take into account differences in rodenticide use pattern in relation togeography and holding size when making estimates of national use.Data were collected by interview with farmers. When rodenticides were applied by apest control contractor the data were obtained from the on farm rodent control recordbook or from the contractor.Previously, in the 2000 and 2002 reports, when rodenticide data could not beobtained from pest control contractors their occurrence was recorded as unspecifiedbut quantity of use was estimated and assigned to different active ingredients basedon known contractor use patterns in the national sample. In this report suchestimation was not conducted and if rodenticides were used but the product or activeingredient data were not obtainable this was recorded as unspecified use for bothoccurrence and quantity. This change in methodology was undertaken due tomarked differences in the type and quantity of bait used by different contractorswhich introduced additional uncertainty into the national estimate. However, as mostunspecified use relates to pest control contractor applications it should be noted thatthis missing data will influence the overall estimated use pattern.The sample data were used to estimate national rodenticide use by multiplying themby a raising factor dependent on the number of farms within each region and sizegroup to match the data recorded in the relevant June Agricultural Census for arablecrops in each survey year 4-9 . Due to small sample sizes the data from some regionswere merged and a secondary adjustment factor was applied to the raising factors toaccount for region and size groups for which no holdings were sampled. Details ofregions, size groups, raising and adjustment factors are presented in Table 9.3

Results and DiscussionOverall changes in rodenticide use pattern between 2000 and 2010 are discussed inthis section. However, the data showed considerable inter-survey variation anddiscussion of temporal changes in use does not indicate statistical significance.Extent of rodenticide use and primary user (Tables 2 and 3)The percentage of farms using rodenticides was consistently high throughout thesurveyed period, ranging from 76 to 86% (Table 2). Temporal differences in use mayhave been influenced by a number of factors such as rodent population or whetherfarms sampled in that year had livestock or grain stores or were members of aquality assurance scheme in which rodenticide use was mandatory.Farmers were responsible for rodenticide use on the majority of farms, 58 to 73% ofthe sample, from 2000 to 2008 (Table 3). In 2010 baiting was conducted by pestcontrol professionals on 55% of holdings.Rodenticide compounds encountered (Appendix 1)Eight anticoagulant rodenticide compounds were encountered during the surveys;brodifacoum, bromadiolone, chlorophacinone, coumatetralyl, difenacoum,diphacinone, flocoumafen and warfarin. Anticoagulant rodenticides (ARs) prevent thesynthesis of blood clotting factors and result in death from haemorrhage. Thesecompounds are split into two groups. The first generation anticoagulants (FGARs)include the coumarin compounds; coumatetralyl and warfarin and the 1,3-indandiones; chlorophacinone and diphacinone. These were succeeded, followingresistance development, by the more acutely toxic and persistent second generationanticoagulant rodenticides (SGARs); brodifacoum, bromadiolone, difenacoum andflocoumafen.Non-anticoagulant rodenticides, alphachloralose, aluminium phosphide, powderedcorn cob and zinc phosphide, were also recorded. Alphachloralose is animmobilising agent which depresses the central nervous system. Aluminiumphosphide containing products are laid in burrows where they react with moisture inthe soil and air releasing toxic phosphine gas. Zinc phosphide is used in baits andreacts with acid in the digestive system on ingestion to produce phosphine.Powdered corn cob is also ingested, causing dehydration leading to reduced bloodvolume and blood pressure, tissue ischemia and circulatory shock culminating indeath. In addition, difenacoum products formulated with calciferol and cholecalciferol(vitamins D 2 and D 3 ) were also encountered. These compounds causehypercalcemia leading to heart problems and kidney failure. They are alsosynergistic with anticoagulant rodenticides, displaying enhanced hypercalcemic andhemorrhagic effects when used in combination.A summary of the UK approval status of the compounds encountered during thesesurveys is provided in Appendix 1.4

Occurrence of rodenticide use (Table 4 and Figure 2)Throughout the reported period, anticoagulant compounds were the most frequentlyencountered rodenticides, accounting for over 99% of all specified occurrences ofuse. First generation anticoagulants accounted for 20% of total rodenticideoccurrences in 2000 and 3% in 2010. Whereas, second generation compoundsaccounted for 80 and 97% of all rodenticides in 2000 and 2010 respectively.The most commonly used compounds were bromadiolone and difenacoum. Theseactive ingredients are the only SGARs with approval for outdoor use in the UK, andcumulatively accounted for between 78 and 96% of all occurrences of rodenticidesduring the surveys. The relative proportion of use of these compounds changed overthe surveyed period. The percentage of holdings using bromadiolone increased from27 to 59% over the decade and occurrence of use increased from 32 to 58% of allrodenticide occurrences. Difenacoum (including use as a single active ingredient andin formulation) was used on 38% of holdings in 2000 and 30% in 2010, accountingfor 46 and 30% of all rodenticide occurrences in those years respectively. It shouldbe noted however that these were not linear trends and there was inter-surveyvariation in use over the decade.Brodifacoum, which is approved only for indoor use, was used on 2 to 4 % ofholdings between 2000 and 2008 and on 9% of holdings in 2010. Flocoumafen,which is also approved for indoor use, was only encountered in 2002 and 2004 onless than 1% of holdings.Quantity of rodenticide product use (Table 5 and Figure 3)As with the occurrence data, 99% of rodenticidal products used by weight wereanticoagulants (Table 5 and Figure 3). There was considerable variation in thequantity of rodenticides used over the decade. As discussed previously, variationover time may be a function of a number of factors such as pest pressure and thetype of farms sampled in each year.SGAR containing products accounted for 88% of total rodenticides applied in 2000and 99% in 2010, whilst FGAR products were 12 and 1% of the total quantity appliedin 2000 and 2010 respectively. However, whilst the quantity of FGAR productsdeclined over the surveyed period, from almost 18 tonnes in 2000 to less than half atonne in 2010, the quantity of SGAR products were very similar at the start and endof the decade at around 126 tonnes.Bromadiolone and difenacoum accounted for 80 to 97% of all products applied overthe decade. The quantity of bromadiolone used in 2010 was more than twice thatrecorded in 2000 whilst difenacoum applications were almost two thirds less. Thequantity of brodifacoum used was almost three times greater in 2010 than in 2000.In addition to the discussed rodenticide product use (Table5), the estimated quantityof active ingredients applied is presented in Table 6.5

Chemical control of rabbits (Tables 2, 3 and 7)Chemical control of rabbits was encountered on fewer than 10% of farms and wasconducted by farmers on 89 to 100% of holdings. Sodium cyanide use was recordedin the first half of the decade but was not encountered after its approval was revokedin 2004. The most commonly used compound overall was aluminium phosphide.Chemical control of moles (Tables 2, 3 and 8)The percentage of holdings employing chemical control for moles in 2010 (5%) wasjust over one third of those doing so in 2000 (14%). The decline was most notableafter the withdrawal of strychnine in 2006 which until then had been the mostcommonly used chemical control agent. Thereafter aluminium phosphide was theonly compound available for use. The proportion of control conducted by farmerswas influenced by the change in active ingredient used; in the earlier part of thedecade when strychnine use was prevalent the majority of mole control was appliedby pest control contractors (ca 75%) as approval was restricted to those holding alicence. Once strychnine was removed from the market most mole control wasconducted by farmers.6

AcknowledgementsThe author would like to thank the farmers and pest control contractors who providedthe information used in this report. Thanks are also given to SASA staff whocollected the data; Chris Bierley, John Kerr, Gillian Reay, Louis Thomas, AndrewWalker and Jeremy Snowden, to Jennifer Watson and Michael Taylor from SASA foreditorial assistance and to Lee Walker (CEH), Alan Buckle (University of Reading)and Gill Hartley (SASA) for helpful comments on the manuscript. In addition theauthor is grateful for support from Adrian Roberts of Biomathematics & StatisticsScotland.References1. Thomas, L A. <strong>Rodenticides</strong> on Arable Farms 2000. SEERAD, Edinburgh 20022. Thomas, L A. <strong>Rodenticides</strong> on Arable Farms 2002. SEERAD, Edinburgh 20053. Wood, H J. An Agricultural Atlas of Scotland; George Hill and Sons, London1931.4. Agricultural Statistics, Scotland 2000, HMSO, Edinburgh 20005. Agricultural Statistics, Scotland 2002, HMSO, Edinburgh 20026. Agricultural Statistics, Scotland 2004, HMSO, Edinburgh 20047. Agricultural Statistics, Scotland 2006, HMSO, Edinburgh 20068. Agricultural Statistics, Scotland 2008, HMSO, Edinburgh 20089. Agricultural Statistics, Scotland 2010, HMSO, Edinburgh 20107

Figure 1Land-use regions of Scotland8

Estimated Quantity of <strong>Rodenticides</strong> Applied (tonnes)Estimated Number of OccurrencesFigure 2 Estimated occurrence of anticoagulant rodenticides inScotland 2000-20101200010000Total First Generation AnticoagulantsTotal Second Generation AnticoagulantsBromadioloneDifenacoumBrodifacoum800060004000200002000 2002 2004 2006 2008 2010Survey YearFigure 3 Estimated quantity of anticoagulant rodenticideproducts applied in Scotland 2000-2010160140120Total First Generation AnticoagulantsTotal Second Generation AnticoagulantsBromadioloneDifenacoumBrodifacoum1008060402002000 2002 2004 2006 2008 2010Survey Year9

Table 1Number and regional distribution of holdings sampledRegion 2000 2002 2004 2006 2008 2010Highlands & Islands 6 8 7 5 8 8Caithness & Orkney 6 11 6 1 6 5Moray Firth 24 30 28 30 35 27Aberdeen 59 46 51 24 38 35Angus 38 41 57 58 55 37East Fife 21 21 22 5 19 20Lothian 25 19 23 23 30 11Central Lowlands 23 36 32 22 30 18Tweed Valley 33 33 27 31 30 8Southern Uplands 5 7 5 4 5 3Solway 11 12 12 12 9 7Total holdings sampled 251 264 270 215 265 179Number of arable holdings in Scotland 11917 12339 11927 10957 10921 10302Percentage of holdings sampled 2.1 2.1 2.3 2.0 2.4 1.710

Table 2Percentage of holdings using chemical control for vertebrate pestsPest 2000 2002 2004 2006 2008 2010Rodents 76 78 86 82 77 85Rabbits 9 9 9 2 5 6Moles 14 22 14 16 5 5Table 3 Percentage of holdings on which pest control was conducted by the farmerRefers to holdings on which chemical control was recorded, the remainder was conducted by pest control contractor.Pest 2000 2002 2004 2006 2008 2010Rodents 65 73 60 67 58 45Rabbits 93 96 100 100 96 89Moles 24 27 24 61 88 6211

Table 4 Estimated occurrence of rodenticide formulationsEstimated national number of occurrences and percentage of farms using each formulation of active ingredientsFormulation 2000 2002 2004 2006 2008 2010No. % No. % No. % No. % No. % No. %Alphachloralose* 7

Table 5 Estimated quantities of rodenticide productsEstimated national quantity of rodenticide products (including active ingredients, bait and other co-formulants) applied (kg)Active Ingredients in2000 2002 2004 2006 2008 2010ProductAlphachloralose* 25Aluminium phosphide*

Table 6 Estimated quantities of rodenticide formulationsEstimated national quantity of active ingredients in each formulation applied (kg)Formulation 2000 2002 2004 2006 2008 2010Alphachloralose* 0.985Aluminium phosphide* 0.205 25.200 10.572 1.653Brodifacoum 0.038 0.043 0.498 0.043 0.104 0.225Bromadiolone 2.210 2.668 4.820 2.250 4.120 4.624Calciferol/difenacoum* 0.354 0.650Cholecalciferol/difenacoum* 0.445 0.042 aChlorophacinone 0.310 0.413 0.329 0.153 0.226 0.106Coumatetralyl 10.339 4.466 2.941 4.601 0.679Difenacoum 4.058 1.885 2.400 1.602 2.253 1.502Diphacinone* 0.037 0.026 0.004 bFlocoumafen*

Table 7 Chemical control of rabbitsEstimated national number of occurrences, percentage of holdings using each formulation and quantity appliedFormulation 2000 2002 2004 2006 2008 2010Number of Occurrences (% of holdings)Aluminium phosphide 461 (4%) 931 (8%) 1130 (9%) 248 (2%) 547 (5%) 640 (6%)Sodium cyanide 604 (5%) 342 (3%)Unspecified rabbit control 44 (

Table 9 Raising and adjustment factorsThe sampled data within a region and size group are multiplied by the appropriate raising and adjustment factors to create an estimate of totaluse (refer to methods). For example, a total recorded rodenticide use of 1 kg on 20-49.9 ha farms in Angus in 2000 would be multiplied by192.5 (raising factor) and 1.3165 (adjustment factor 1) to give an estimated use in that region and size group of 253 kg.2000Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney and Highlands & Islands 201.22 74.00 46.00 NA NA 1.0045Moray Firth 578.00 147.50 28.14 13.83 7.13 1.0000Aberdeen 208.17 61.31 26.72 13.27 10.73 1.0000Angus NA 192.50 33.50 18.78 10.20 1.3165East Fife 108.00 64.50 25.86 14.17 12.60 1.0000Lothian 123.00 46.00 64.00 14.17 6.71 1.0000Central Lowlands 151.67 74.67 50.40 25.00 14.67 1.0000Tweed Valley 144.00 64.50 23.33 14.44 8.13 1.0000Solway and Southern Uplands 202.00 49.80 19.50 14.00 4.33 1.00002002Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney and Highlands & Islands 161.00 71.00 25.00 NA NA 1.0038Moray Firth 116.80 33.56 36.40 20.25 8.43 1.0000Aberdeen 619.5 76.70 34.71 16.75 10.00 1.0000Angus 192.00 42.56 35.36 18.67 14.70 1.0000East Fife 111.00 32.25 34.00 20.00 9.29 1.0000Lothian 127.00 40.50 40.33 15.33 12.71 1.0000Central Lowlands 107.25 42.70 26.67 15.2 11.00 1.0000Tweed Valley 31.50 32.75 24.33 15.00 11.00 1.0000Solway and Southern Uplands 79.57 39.71 26.00 NA 7.50 1.0162NANot applicable, no holdings sampled in this region/size group16

TABLE 9Raising and adjustment factors (continued)2004Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney and Highlands & Islands 329.57 37.25 25.00 NA NA 1.0040Moray Firth 543.00 75.50 26.00 13.33 6.40 1.0000Aberdeen 571.00 75.80 29.00 16.78 8.64 1.0000Angus 177.00 49.57 29.31 14.50 6.96 1.0000East Fife NA 41.33 23.00 16.00 9.57 1.2407Lothian NA 79.00 29.75 13.00 8.36 1.3018Central Lowlands 202.75 63.00 20.91 20.75 7.17 1.0000Tweed Valley NA 131.00 25.40 17.14 9.14 1.2411Solway and Southern Uplands 181. 67 43.83 16.60 15.00 7.00 1.00002006Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney and Highlands & Islands 518.75 77.00 NA NA NA 1.0242Moray Firth 168.67 38.86 24.00 15.40 6.63 1.0000Aberdeen 1068.00 143.00 50.88 29.80 20.20 1.0000Angus 319.00 71.40 19.21 13.80 6.30 1.0000Lothian and East Fife NA 199.00 38.14 26.00 10.50 1.2861Central Lowlands 238.67 82.00 26.25 29.00 10.00 1.0000Tweed Valley 128.00 56.50 31.25 14.71 6.65 1.0000Solway and Southern Uplands 258.50 34.83 19.00 6.50 7.00 1.0000NANot applicable, no holdings sampled in this region/size group17

TABLE 9Raising and adjustment factors (continued)2008Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney 223.33 54.50 31.00 NA NA 1.0099Highlands & Islands 210.67 67.00 22.00 NA NA 1.0044Moray Firth 237.00 37.29 20.67 10.57 7.80 1.0000Aberdeen 326.67 77.56 51.22 28.83 12.18 1.0000Angus NA 56.50 20.50 16.18 8.05 1.2955East Fife NA 52.50 36.00 14.60 9.88 1.2344Lothian NA 39.50 16.67 11.29 7.00 1.3223Central Lowlands 231.67 57.29 27.38 12.00 8.43 1.0000Tweed Valley 131.00 54.50 28.25 11.67 9.79 1.0000Solway 388.00 49.75 30.50 8.00 11.00 1.0000Southern Uplands 132.00 40.00 28.00 9.00 9.00 1.00002010Region/Size Group (ha) 0-19.9 20-49.9 50-99.9 100-149.9 150+ Adjustment factorCaithness & Orkney and Highlands & Islands 235.00 50.33 22.50 14.00 NA 1.0005Moray Firth 463.00 60.25 27.50 15.80 6.45 1.0000Aberdeen 485.00 161.00 40.18 12.67 21.00 1.0000Angus NA 80.50 40.50 15.64 11.64 1.3252East Fife and Lothian NA NA 39.33 19.00 10.65 1.6995Central Lowlands NA 50.86 52.50 32.00 11.60 2.0625Solway, Southern Uplands and Tweed Valley NA 86.75 63.0 21.80 27.00 1.7435NANot applicable, no holdings sampled in this region/size group18

Appendix 1 UK approval status of compounds encounteredActive Ingredient UK Approval Status during Survey PeriodFirst generation anticoagulantsChlorophacinone ApprovedCoumatetralylApprovedDiphacinone Withdrawn 2006WarfarinApprovedSecond generation anticoagulantsBrodifacoumApproved, indoor use onlyBromadioloneApprovedDifenacoumApprovedFlocoumafenApproved, indoor use onlyNon-anticoagulantsAlphachloralose ApprovedAluminium phosphide ApprovedCalciferol Withdrawn 2006Cholecalciferol Withdrawn 2006Powdered corn cob ApprovedSodium cyanide Withdrawn 2004Strychnine Withdrawn 2006Zinc phosphide Withdrawn 200619

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