INSECTICIDE DRIFT FROM SPRAYERS

AND THE EFFECT ON

BENEFICIAL ARTHROPODS IN WINTER WHEAT

by

CATHERINE MARGARET DC® SON B.TECH

Thesis submitted for the degree of Doctor of Philosophy of the University of London and the Diplana of Imperial College

Department of Pure and Applied Biology Imperial College of Science and Technology Silwood Park Ascot, Berkshire, SL5 7PY U.K. May, 1986

1 To my dear parents

2 ABSTRACT

More efficient methods of pesticide application are essential to reduce chemical costs and minimise harmful side-effects. Spray drift from a conventional hydraulic sprayer and Ulvamast "drift" sprayer was assessed and the effects on non-target arthropods were examined.

A wide range of droplet sizes, measured by laser analysis, was produced from the hollow cone nozzle (VMD 223;om; VMD:NMD ratio of 34), while the width of the droplet spectrum was reduced with the spinning discs (VMD 116-13Qum; VMD:NMD ratio of 1.6-3.9).

Droplets were collected on vertically positioned magnesium oxide-coated slides 0.75m above grass and up to 150m downwind from the hydraulic spray and ULV treatments. Estimated levels of chemical 75 -

150m downwind from the ULV spray were 2-10 times higher than for the hydraulic spray. Neutron activation analysis (NAA) was used to determine

the level of dysprosium in spray deposits on filter papers positioned

horizontally 0, 0.45 and 0.75m above the ground and on plants within and

10, 30 and 100m downwind from plots of winter wheat treated with hydraulic

and ULV sprays. Deposits on filter papers within the sprayed plots were

significantly higher than 10 - 100m downwind. No significant variation

occurred between deposits outside the treated plots.

The highest spray deposits were on the stems and lower leaves of the

plants. No deposits were detected on tillers downwind apart from on ears

3 10m outside the hydraulic spray.

The application of cypermethrin and permethrin to winter wheat resulted in changes in the abundance of non-target arthropods within the hydraulic spray and up to 10m downwind of the ULV treatments. Numbers of epigeal predators were decreased by both insecticides although recovery occurred less than one week later. A 10 - 12 m swath left unsprayed around the field edge is recommended to reduce the effect of spray drift.

Neither method of spray application achieved effective aphid control on ears and flag leaves.

4 CONTENTS

Page

TITLE PAGE 1

ABSTRACT 3

CONTENTS 5

LIST OF FIGURES 10 LIST OF TABLES 24 LIST OF PLATES 27 LIST OF APPENDICES 27

CHAPTER 1 GENERAL INTRODUCTION 29

PART ONE SPRAY DRIFT 32

CHAPTER 2 SPRAY DRIFT 33 2.1 Introduction 33

2.2 Physical factors affecting spray dispersal 34 2.2.1 Gravitational and aerodynamic forces 34 2.2.2 The effect of wind and turbulence 36 2.2.3 The effect of evaporation 41

2.3 Liquid properties influencing spray dispersal 43 2.3.1 Surface tension, liquid density and viscosity 43 2.3.2 Spray additives 44

2.4 The effect of the method of application on spray dispersal 44 2.4.1 Hydraulic sprayers 44 2.4.2 Controlled droplet application (CDA) 46

2.5 Factors affecting spray deposition 47

2.6 Meteorological conditions affecting spray dispersal 51 2.6.1 Wind velocity 51 2.6.2 Wind direction 52 2.6.3 Atmospheric stability and turbulence 52 2.6.4 Gustiness 54 2.6.5 Humidity and tenperature 55 2.6.6 Other meteorological factors 55 2.6.7 Conditions suitable for spraying 56

5 CHAPTER 3 DROPLET SPECTRA 57

3.1 Introduction 57

3.2 The laboratory measurement of the droplet size spectra from a hollow cone nozzle and stacked spinning discs 62 3.2.1 Materials and Methods 62 3.2.1.1 Experimental Technique 62 3.2.1.2 Experimental Procedure 65 3.2.2 Results 66 3.2.2.1 Droplet size spectra from hollow cone nozzle and stacked spinning discs 66 3.2.2.2 The effect of spray additives on the droplet spectrum of the Multi-Disc atcmiser 69 3.2.3 Discussion 70 3.2.3.1 Droplet size spectra from a hollow cone nozzle and Multi-Disc atomiser 70 3.2.3.2 The effect of spray additives on the droplet spectra from spinning discs 73

3.3 The measurement of the size ofdroplets moving downwind from plots sprayed conventionally and at ultra low volume 74 3.3.1 Materials and Methods 75 3.3.1.1 Field Trial 75 3.3.1.2 Droplet Sizing 78 3.3.2 Results 78 3.3.3 Discussion 82

CHAPTER 4 SPRAY DEPOSIT ASSESSMENTS 86

4.1 Introduction 86

4.2 Materials and Methods 90 4.2.1 Field Trial 90 4.2.2 Irradiation and counting 94 4.2.2.1 Filter papers 94 4.2.2.2 Plant material 96 4.2.2.3 Statistical analysis 98

4.3 Results 98 4.3.1 Filter papers 98 Inside treated plots 101 10 m downwind 102 30 m downwind 103 100 m downwind 104 Volume calculations 106 Calculated deposits of permethrin 106 4.3.2 Plant material 107 Glumes 108 Flag leaves 108

6 Stem and lower leaves 109 Calculated deposits of permethrin 109 Spray distribution 111

4.4 Discussion 113 4.4.1 Artificial targets (filter papers) 113 4.4.2 Natural targets (wheat) 115 4.4.3 Artificial vs natural targets 115

PART TWO SPRAYING IN RELATION TO THE CEREAL APHID PROBLEM 117

CHAPTER 5 CEREAL APHIDS AND THEIR NATURAL ENEMIES 118

5.1 Introduction 118

5.2 Cereal aphid species 118

5.3 Feeding-sites and damage 119 5.3.1 Direct damage 119 5.3.2 Virus transmission 121

5.4 Factors affecting aphidpopulations 122 5.4.1 Weather 122 5.4.2 Polyphagous predators 123 5.4.3 Aphidophagous predators 127 5.4.3.1 Coccinellidae 127 5.4.3.2 Syrphidae 128 5.4.3.3 Chrysopidae 129 5.4.3.4 Anthocoridae 129 5.4.4 Parasites 129 5.4.5 Pathogens 131

5.5 Causes of pest status 132 5.5.1 Fertilizers 132 5.5.2 Growth regulators 136 5.5.3 Herbicides 138 5.5.4 Fungicides 143 5.5.5 Insecticides 147 5.5.5.1 Organochlorine insecticides 147 5.5.5.2 Organophosphorous insecticides 148 5.5.5.3 Carbamate insecticides 153 5.5.5.4 Pyrethroid insecticides 153 5.5.6 Cultural practices 155

5.6 Control of cereal aphids 157

7 CHAPTER 6 THE EFFECT OF CYPERMETHRIN ON BENEFICIAL ARTHROPODS WITHIN AND DOWNWIND FROM THE HYDRAULIC AND ULV SPRAY TREATMENTS 164

6.1 Introductd on 164

6.2 Materials and Methods 166 6.2.1 Spray application 166 6.2.2 Insect sampling 167 6.2.3 Statistical analysis 170

6.3 Results 171 6.3.1 Pitfall trap catches 171 Carabidae 171 Pterostichus melanarius (111) 184 Staphylinidae 194 Coleopteran larvae 203 Araneae 212 6.3.2 Water trap catches 220 Total catches 220 Parasitic Hymenoptera 227 6.3.3 Malaise trap catches 233 Total catches 233 Parasitic Hymenoptera 236 6.3.4 Aphid observations 236

6.4 Discussion 240 6.4.1 Epigeal predators 240 6.4.2 Aerial arthropods 244 6.4.3 Aphids 246

CHAPTER 7 THE EFFECT OF PERMETHRINON CARABIDAE WITHIN AND DOWNWIND FROM HYDRAULIC AND ULV SPRAYS AND UNTREATED PLOTS 247

7.1 Introduction 247

7.2 Materials and Methods 248 7.2.1 Field trial 248 7.2.2 Statistical analysis 250

7.3 Results 250 7.3.1 Carabidae 253 Variation in carabid density with time 253 Variation in carabid density with distance 259 7.3.2 Pterostichus melanarius (111) 260 Variation in density with time 264 Variation in density with distance 273 7.3.3 Aphids 283 7.3.3.1 Heads 283 7.3.3.2 Flag-leaves 288

8 7.3.4 Permethrin deposits 291 - Carabi d numbers 291 Aphid numbers 295

7.4 Discussion 295

CHAPTER 8 GENERAL DISCUSSION 300

SUMMARY 308 ACKNOWLEDGEMENTS 312 REFERENCES 313 APPENDICES 340

9 LIST OF FIGURES

Paae

FIGURES 1 - 3 Wind velocity profiles and simplified eddy structures characteristic of the three basic stability states in air flow near the ground (from Elliott and Wilson, 1983) 38

FIGURE 4 Areas of dominance of sedimentation on turbulent transport (Lawson, 1979) 39

FIGURE 5 A schematic view of a tilting plume 39

FIGURE 6 Atmospheric turbulence caused by surface friction (from Elliott and Wilson, 1983) 53

FIGURE 7 Air turbulence caused by surface heating (from Elliott and Wilson, 1983) 53

FIGURE 8 Diagram of drift sampling layout 76

FIGURE 9 The mean VMD of droplets collected on vertical slides up to 150 m downwind from the hydraulic and ULV sprays 80

FIGURE 10 The mean NMD of droplets collected on vertical slides up to 150 m downwind fran hydraulic and ULV sprays 80

FIGURE 11 Diagram of drift sampling layout 92

FIGURE 12 Field trial layout indicating the over­ lapping swaths (Ulvamast) and the location of the sampling points 93

FIGURE 13 Mean hourly wind velocity and tanperature 95

FIGURE 14 Mean hourly relative humidity 95

FIGURES 15 - 17 The mean deposits of dysprosium (jug x 10 7 cm2) on filter papers downwind from the hydraulic and ULV sprays and untreated plots 100

FIGURE 15 0.75 m above the ground 100

FIGURE 16 0.45 m above the ground 100

10 FIGURE 17 Ground level 100

FIGURE 18 Calculated deposits of permethrin on plant material, based on actual deposits of dysprosium (Table 13) and assuming the same dosage rate for hydraulic and ULV sprays (75 g a.i./ha) 110

FIGURES 19-21 Distribution of dysprosium on the plants (as a percentage of the total amount of dysprosium detected) 112

FIGURE 19 Hydraulic spray 112 FIGURE 20 ULV spray 112 FIGURE 21 Untreated 112 FIGURE 22 The decline in the abundance of Tachyporus spp adults (Staphylinidae) in cereal fields 1970 - 1975 (from Potts, 1977) 135

FIGURE 23 The use of threshold levels (from Hancock, 1983) 159

FIGURE 24 Layout of field trial 169

FIGURE 25 Hydraulic spray: Captures of Carabidae (29 June - 27 July 1981) 173

FIGURE 26 Hydraulic spray: Captures of less common Carabidae (29 June - 27 July 1981) 174

FIGURE 27 ULV spray: Captures of Carabidae (29 June - 27 July 1981) 175

FIGURE 28 ULV spray: Captures of less common Carabidae (29 June - 27 July 1981) 176

FIGURE 29 Pre and post spray variation in overnight and daytime trap catches of Carabidae 178

FIGURE 30 Pre and post spray variation in the trap catches of Carabidae within and outside the hydraulic and ULV sprays 178

FIGURES 31-33 Pre and post spray trap catches of Carabidae within the hydraulic and ULV sprays 181

FIGURE 31 75 m* (* indicates within treated area) 181

11 FIGURE 32 10 m* 181

FIGURE 33 1 m* 181

FIGURES 34 - 42 Pre and post spray trap catches of Carabidae outside the hydraulic and ULV sprays 181

FIGURE 34 1 m to lee of hedge 181

FIGURE 35 1 in to windward of hedge 182

FIGURE 36 1 m dcwnwi nd 182

FIGURE 37 10 m downwind 182

FIGURE 38 30 m downwind 183

FIGURE 39 50 m downwind 183

FIGURE 40 75 m downwind 183

FIGURE 41 120 m downwind 183

FIGURE 42 200 m downwind 183

FIGURE 43 Pre and post spray variation in trap catches of P. melanarius within and out- side the hydraulic and ULV sprays 186

FIGURE 44 Pre and post spray variation in trap catches of male and female P. melanarius 186

FIGURE 45 Pre and post spray variation in trap catches of male and female P. melanarius 190 within and outside the hydraulic spray FIGURE 46 Pre and post spray variation in trap catches of male and female P. melanarius 190 within and outside the ULV spray FIGURES 47 - 52 Pre and post spray trap catches of male and fenale P. melanarius within the hydraulic and ULV sprays 191

FIGURE 47 Hydraulic spray 75 m* 191

FIGURE 48 ULV spray 75 m* 191

FIGURE 49 Hydraulic spray 10 m* 191

FIGURE 50 ULV spray 10 m* 191

12 51 Hydraulic spray 1 m* 192

52 ULV spray 1 m* 192

53 - 70 Pre and pest spray trap catches of male and female P. melanardus outside the hydraulic and ULV sprays 192

53 Hydraulic spray 1 m to lee of hedge 192

54 ULV spray 1 m to lee of hedge 192

55 Hydraulic spray 1 m to windward of hedge 195

56 ULV spray 1 m to windward of hedge 195

57 Hydraulic spray 1 m downwind 195

58 ULV spray 1 m downwind 195

59 Hydraulic spray 10 m downwind 196

60 ULV spray 10 m downwind 196

61 Hydraulic spray 30 m downwind 196

62 ULV spray 30 m downwind 196

63 Hydraulic spray 50 m downwind 197

64 ULV spray 50 m downwind 197

65 Hydraulic spray 75 m downwind 197

66 ULV spray 75 m downwind 197

67 Hydraulic spray 120 m downwind 198

68 ULV spray 120 m downwind 198

69 Hydraulic spray 200 m downwind 198

70 ULV spray 200 m downwind 198

71 Pre and post spray variation in overnight and daytime trap catches of Staphylinidae 200

72 Pre and post spray variation in the trap catches of Staphylinidae within and outside the hydraulic and ULV sprays 200

73 - 75 Pre and post spray trap catches of

13 Staphylinidae within and outside the hydraulic and ULV sprays 204

FIGURE 73 75 m* 204

FIGURE 74 10 m* 204

FIGURE 75 1 m* 204

FIGURES 76 - 84 Pre and post spray trap catches of Staphylinidae outside the hydraulic and ULV sprays 204

FIGURE 76 1 m to lee of hedge 204

FIGURE 77 1 m to windward of hedge 204

FIGURE 78 1 m downwind . 204

FIGURE 79 10 m downwind 205

FIGURE 80 30 m downwind 205

FIGURE 81 50 m downwind 205

FIGURE 82 75 m downwind 205

FIGURE 83 120 m downwind 205

FIGURE 84 200 m downwind 205

FIGURE 85 Pre and post spray variation in overnight and daytime trap catches of coleopteran larvae 207

FIGURE 86 Pre and post spray variation in trap catches of coleopteran larvae within and outside the hydraulic and ULV sprays 207

FIGURES 87 - 89 Pre and post spray trap catches of coleopteran larvae within the hydraulic and ULV sprays 210

FIGURE 87 75 m* 210

FIGURE 88 10 m* 210

FIGURE 89 1 m* 210

FIGURES 90 - 98 Pre and post spray trap catches of coleopteran larvae outside the hydraulic and ULV sprays 210

14 FIGURE 90 1 m to lee of hedge 210

FIGURE 91 1 m to windward of hedge 210

FIGURE 92 1 m downwind 210

FIGURE 93 10 m downwind 211

FIGURE 94 30 m downwind 211

FIGURE 95 50 m downwind 211

FIGURE 96 75 m downwind 211

FIGURE 97 120 m downwind 211

FIGURE 98 200 m downwind 211

FIGURE 99 Pre and post spray variation in overnight and daytime trap catches of Araneae 214

FIGURE 100 Pre and post spray variation in trap catches of Araneae within and outside the hydraulic and ULV sprays 214

FIGURES 101 - 103 Pre and post spray trap catches of Araneae within the hydraulic and ULV sprays 216

FIGURE 101 75 m* 216

FIGURE 102 10 m* 216

FIGURE 103 1 m* 216

FIGURES 104 - 112 Pre and post spray trap catches of Araneae outside the hydraulic and ULV sprays 216

FIGURE 104 1 m to lee of hedge 216

FIGURE 105 1 m windward of hedge 218

FIGURE 106 1 m downwind 218

FIGURE 107 10 m downwind 218

FIGURE 108 30 m downwind 218

FIGURE 109 50 in downwind 219

FIGURE 110 75 m downwind 219

15 FIGURE 111 120 m downwind 219

FIGURE 112 200 m downwind 219

FIGURE 113 Pre and post spray variation in overnight and daytime water trap catches 222

FIGURE 114 Pre and post spray variation in water trap catches within and outside the hydraulic and ULV sprays 222

FIGURES 115 and 116 Pre and post spray water trap catches of arthropods within the hydraulic and ULV sprays 225

FIGURE 115 75 m* 225

FIGURE 116 10 m* 225

FIGURES 117 - 122 Pre and post spray water trap catches of arthropods outside the hydraulic and ULV sprays 225

FIGURE 117 10 m downwind 225

FIGURE 118 30 m downwind 225

FIGURE 119 50 m downwind 226

FIGURE 120 75 id downwind 226

FIGURE 121 120 m downwind 226

FIGURE 122 200 m downwind 226

FIGURE 123 Pre and post spray variation in overnight and • daytime water trap catches of parasitic Hymenoptera 229

FIGURE 124 Pre and post spray variation in water trap catches of parasitic Hymenoptera within and outside the hydraulic and ULV sprays 229

FIGURES 125 and 126 Pre and post spray water trap catches of parasitic Hymenoptera within the hydraulic and ULV sprays 231

FIGURES 125 75 m* 231

FIGURE 126 10 m* 231

FIGURES 127 - 132 Pre and post spray water trap catches of

16 parasitic Hymenoptera outside the hydraulic and LJLV sprays 231

127 10 m downwind 231

128 30 m downwind 231

129 50 m downwind 232

130 75 m downwind 232

131 120 m downwind 232

132 200 m downwind 232

133 Pre and post spray Malaise trap catches of arthropods 5 m within the hydraulic and ULV sprays 234

134 Pre and post spray Malaise trap catches of arthropods 5 m downwind from the hydraulic and ULV sprays 234

135 Pre and post spray Malaise trap catches of arthropods 120 m downwind from the 234 hydraulic and ULV sprays

136 Pre and post spray Malaise trap catches of parasitic Hymenoptera 5 m within the hydraulic and ULV sprays 235

137 Pre and post spray Malaise trap catches of parasitic Hymenoptera 5 m downwind from the hydraulic and ULV sprays 235

138 Pre and post spray Malaise trap catches of parasitic Hymenoptera 120 m downwind from the hydraulic and ULV sprays 235

139 Pre and post spray variation in the number of aphids on tillers within the hydraulic and ULV sprays 237

140 Pre and post spray variation in the number of aphids on tillers 75 m, 10 m and 1 m within the sprayed plots 237

141 143 Pre and post spray variation in the number of cereal aphids on tillers within the hydraulic and ULV sprays 239

141 75 m* 239

17 FIGURE 142 10 m* 239

FIGURE 143 1 m* 239

FIGURE 144 Arrangement of pitfall traps 251

FIGURES 145 - 148 Pre spray distribution of Carabidae across the field 252

FIGURE 145 Within plot 252

FIGURE 146 10 m downwind 252

FIGURE 147 30 m downwind 252

FIGURE 148 100 m downwind 252

FIGURE 149 Pre and post spray trap catches of Carabidae within the hydraulic spray 254

FIGURE 150 Pre and post spray trap catches of Carabidae within the ULV spray 254

FIGURE 151 Pre and post spray trap catches of Carabidae within the untreated plots 254

FIGURE 152 Pre and post spray trap catches of Carabidae 10 m outside the hydraulic spray 256

FIGURE 153 Pre and post spray trap catches of Carabidae 10 m outside the ULV spray 256

FIGURE 154 Pre and post spray trap catches of Carabidae 10 m outside the untreated plots 256

FIGURE 155 Pre and post spray trap catches of Carabidae 30 m outside the hydraulic spray 257

FIGURE 156 Pre and post spray trap catches of Carabidae 30 m outside the ULV spray 257

FIGURE 157 Pre and post spray trap catches of Carabidae 30 m outside the untreated plots 257

FIGURE 158 Pre and post spray trap catches of Carabidae 100 m outside the hydraulic spray 258

18 FIGURE 159 Pre and post spray trap catches of Carabidae 100 m outside the ULV spray 258

FIGURE 160 Pre and post spray trap catches of Carabidae 100 m outside the untreated plots 258

FIGURES 161 - 168 Pre and post spray variation i in trap catches of Carabidae within and downwind from the hydraulic spray 261

FIGURE 161 5 days pre spray 261

FIGURE 162 3 days pre spray 261

FIGURE 163 1 day post spray 261

FIGURE 164 3 days post spray 261

FIGURE 165 5 days post spray 261

FIGURE 166 8 days post spray 261

FIGURE 167 10 days post spray 261

FIGURE 168 14 days post spray 261

FIGURES 169 - 176 Pre and post spray variation in trap catches of Carabidae within and downwind from the ULV spray 262

FIGURE 169 5 days pre spray 262

FIGURE 170 3 days pre spray 262

FIGURE 171 1 day post spray 262

FIGURE 172 3 days post spray 262

FIGURE 173 5 days post spray 262

FIGURE 174 8 days post spray 262

FIGURE 175 10 days post spray 262

FIGURE 176 14 days post spray 262

FIGURES 177 - 184 Pre and post spray variation in trap catches of Carabidae within and downwind from the untreated plots 263

19 FIGURE 177 5 days pre spray 263

FIGURE 178 3 days pre spray 263

FIGURE 179 1 day post spray 263

FIGURE 180 3 days post spray 263

FIGURE 181 5 days post spray 263

FIGURE 182 8 days post spray 263

FIGURE 183 10 days post spray 263

FIGURE 184 14 days post spray 263

FIGURES 185 - 188 Pre spray distribution of male and female Pterostichus melanarius across the field 265

FIGURE 185 Within plot 265

FIGURE 186 10 m downwind 265

FIGURE 187 30 m downwind 265

FIGURE 188 100 m downwind 265

FIGURE 189 Pre and post spray trap catches of male and female Pterostichus melanarius within the hydraulic spray 266

FIGURE 190 Pre and post spray trap catches of male and female Pterostichus melanarius within the ULV spray 266

FIGURE 191 Pre and post spray trap catches of male and female Pterostichus melanarius within the untreated plots 266

FIGURE 192 Pre and post spray trap catches of male and female Pterostichus melanarius 10 m out- side the hydraulic spray 268

FIGURE 193 Pre and post spray trap catches of male and female Pterostichus melanarius 10 m out- side the ULV spray 268

FIGURE 194 Pre and post spray trap catches of male and female Pterostichus melanarius 10 m outside the untreated plots 268

FIGURE 195 Pre and post spray trap catches of male and

20 female Pterostichus melanarius 30 m outside the hydraulic spray 270

FIGURE 196 Pre and post spray trap catches of male and female Pterostichus melanarius 30 m outside the ULV spray 270

FIGURE 197 Pre and post spray trap catches of male and female Pterostichus melanarius 30 m outside the untreated plots 270

FIGURE 198 Pre and post spray trap catches of male and female Pterostichus melanarius 100 m outside the hydraulic spray 272

FIGURE 199 Pre and post spray trap catches of male and female Pterostichus melanarius 100 m outside the ULV spray 272

FIGURE 200 Pre and post spray trap catches of male and female Pterostichus melanarius 100 m outside the untreated plots 272

FIGURES 201 - 208 Pre and post spray trap catches of male and female Pterostichus melanarius within and downwind from the hydraulic spray 274

FIGURE 201 5 days pre spray 274

FIGURE 202 3 days pre spray 274

FIGURE 203 1 day post spray 274

FIGURE 204 3 days post spray 274

FIGURE 205 5 days post spray 275

FIGURE 206 8 days post spray 275

FIGURE 207 10 days post spray 275

FIGURE 208 14 days post spray 275

FIGURES 209 - 216 Pre and post spray trap catches of male and female Pterostichus melanarius within and downwind from the ULV spray 278

FIGURE 209 5 days pre spray 278

FIGURE 210 3 days pre spray 278

FIGURE 211 1 day post spray 278

21 212 3 days post spray 278

213 5 days post spray 279

214 8 days post spray 279

215 10 days post spray 279

216 14 days post spray 279

217 - 224 Pre and post spray trap catches of male and female Pterostichus melanarius within and downwind from the untreated plots 281

217 5 days pre spray 281

218 3 days pre spray 281

219 1 day post spray 281

220 3 days post spray 281 221 5 days post spray 282

222 8 days post spray 282

223 10 days post spray 282

224 14 days post spray 282

225 - 228 Pre spray distribution of aphids on ears across the field 284

225 Within plot 284

226 10 m downwind 284

227 30 m downwind 284

228 100 m downwind 284

229 - 232 Pre spray distribution of aphids on flag-leaves across the field 285

229 Within plot 285

230 10 m downwind 285

231 30 m downwind 285

232 100 m downwind 285

22 233 Pre and post spray numbers of aphids on ears within and downwind from the hydraulic spray 287

234 Pre and post spray numbers of aphids on ears within and downwind from the ULV spray 287

235 Pre and post spray numbers of aphids on ears within and downwind from the untreated plots 287

236 Pre and post spray numbers of aphids on flag-leaves within and downwind from the hydraulic spray 290

237 Pre and post spray numbers of aphids on flag-leaves within and downwind from the ULV spray 290

238 Pre and post spray numbers of aphids on flag-leaves within and downwind from the untreated plots 290

239 The relationship between the deposits of permethrin and the number of carabids with­ in and downwind fromthe hydraulic spray 292

240 The relationship between the deposits of permethrin and the number of carabids within and downwind from the ULV spray 292

241 The relationship between the deposits of permethrin and the number of aphids per ear within and downwind from the hydraulic spray 293

242 The relationship between the deposits of permethrin and the number of aphids per flag-leaf within and downwind from the hydraulic spray 293

243 The relationship between the deposits of permethrin and the number of aphids per ear within and downwind from the ULV spray 294

244 The relationship between the deposits of permethrin and the number of aphids per flag-leaf within and downwind from the ULV spray 294

23 LIST OF TABLES

Page

TABLE 1 Terminal velocity (m/s) of spheres and fall time in still air (from Matthews, 1979a) 35 TABLE 2 Optimum droplet size ranges for selected targets (from Matthews, 1979a) 49

TABLE 3 Percentage of droplets collected on a 3.2 mm diameter target (from Johnstone, 1974) 49

TABLE 4 The VMD, NMD and ratio of a Micron Multi-Disc atomiser and a hollow cone nozzle 67

TABLE 5 The droplet spectra of a Micron Multi-Disc atomiser and a hollow cone nozzle 68

TABLE 6 Meteorological Data 77 p p TABLE 7 Theoretical calculated dosage/cm ( jug x 10“° a.i ./cm2 ) 81

TABLE 8 Theoretical amount of chemical drifting downwind expressed as the percentage of the total dosage 81

TABLE 9 The deposits of dysprosium on filter papers at 36 m inside the treated plots 99

TABLE 10 Volume of spray deposited on filter paper targets (ml x 10"6 /cm2 ) 105

TABLE 11 Drift deposits as a percentage of the total spray volume per c m 2 within the treated plots 105

TABLE 12 Calculated mean deposits of permethrin (jjg x 10-2 /cm 2 ) based on actual deposits of dysprosium (Figures 15 to 17; Table 9) and assuming the same mass application rate 107

TABLE 13 Deposits of dysprosium (mg/g plant material) within the treated plots 108

TABLE 14 Deposits of dysprosium and calculated deposits of permethrin (pg/cm2 flag leaf) 111

TABLE 15 Pesticide usage on cereals (British Agrochemicals Association, 1985) 133

TABLE 16 Types of pesticides used on cereals in 1974 and 1977, and estimated quantities of active

24 ingredient (Royal Commission on Environmental Pollution, 1979) 133

TABLE 17 Changes in the late June density of the adults and larvae of seme insect taxa in cereal crops in West Sussex 1970 - 1975 (mean number /m^ ) (from Potts, 1977) 134

TABLE 18 Species list (Carabidae) 172

TABLE 19 Pre and post spray variation in overall carabid density 177

TABLE 20 Variation in carabid density within and downwind from the treated plots 177

TABLE 21 The general trend in the pre and post spray abundance of Carabidae within and downwind from the sprayed plots 179

TABLE 22 Pre and post spray variation in the overall density of P. melanarius 184

TABLE 23 Variation in the overall density of P. melanarius within and downwind frem the hydraulic and ULV spray treatments 185

TABLE 24 Overall density of male and female P. melanarius for each spray treatment 185

TABLE 25 The general trend in the pre and post spray abund­ ance of P. melanarius within and downwind from the hydraulic and ULV spray treatments 187

TABLE 26 Variation in the overall densities of male and fonale P. melanarius within and outside the sprayed area 188

TABLE 27 The general trend in the pre and post spray abundance of male and female P. melanarius within and downwind from the sprayed plots 189

TABLE 28 Pre and post spray variation in staphylinid densi ty 194

TABLE 29 Variation in staphylinid density within and downwind from the treated plots 199

TABLE 30 The general trend in the pre and post spray abundance of Staphylinidae within and downwind from the sprayed plots 201

25 TABLE 31 Pre and post spray variation in the density of coleopteran larvae 203

TABLE 32 Variation in the density of coleopteran larvae within and downwind from the treated plots 206

TABLE 33 The general trend in the pre and post spray abundance of coleopteran larvae within and downwind frcm the treated plots 208

TABLE 34 Pre and post spray variation in the overall density of Araneae 212

TABLE 35 Variation in the overall density of Araneae within and downwind from the treated plots 213

TABLE 36 The general trend in the pre and post spray abundance of Araneae within and downwind from the sprayed plots 215

TABLE 37 Pre and post spray variation in overall water trap catches 221

TABLE 38 Variation in water trap catches within and downwind from the treated plots 221

TABLE 39 The general trend in the size of water trap catches before and after treatment and within and downwind from the hydraulic and ULV sprays 223

TABLE 40 Pre and post spray variation in the number of parasitic Hymenoptera within and downwind from the treated plots 227

TABLE 41 Variation in the number of parasitic Hymenoptera within and downwind from the treated plots 228

TABLE 42 The general trend in the abundance of parasitic Hymenoptera before and after treatment and within and downwind from the hydraulic and ULV sprays 228

TABLE 43 Pre and post spray variation in aphid numbers 236

TABLE 44 Variation in aphid numbers within the treated plots 238

TABLE 45 Pre and post spray variation in the numbers of aphids within the hydraulic and ULV sprays 238

26 LIST OF PLATES

PAGE

PLATE 1 Hawthorn hedgerows at the edge of the cereal crops 165

PLATE 2 Areas enclosed with polythene tubing 249

LIST OF APPENDICES

PAGE

APPENDIX 1 Diagram of the Ulvamast 340

APPENDIX 2 Malvern droplet sizing: Specimen print-out 342

APPENDIX 3 Map of field site and surrounding area 343

APPENDIX 4 The mean daily rainfall and maximum and minimum daily temperatures during May 1981 344

APPENDIX 5 The mean relative humidity and hours of sunshine during May 1981 345

APPENDIX 6 The mean daily rainfall and maximum and minimum daily temperatures during June 1981 346

APPENDIX 7 The mean relative humidity and hours of sunshine during June 1981 347

APPENDIX 8 The mean daily rainfall and maximum and minimum daily temperatures during July 1981 348

APPENDIX 9 The mean relative humidity and hours of sunshine during July 1981 349

APPENDIX 10 The mean daily rainfall and maximum and minimum daily temperatures during May 1982 350

APPENDIX 11 The mean daily relative humidity and hours of sunshine during May 1982 351

APPENDIX 12 The mean daily rainfall and maximum and minimum daily temperatures during June 1982 352

27 APPENDIX 13 The mean daily relative humidity and hours of sunshine during June 1982 353

APPENDIX 14 The mean daily rainfall and maximum and minimum daily temperatures during July 1982 354

APPENDIX 15 The mean daily relative humidity and hours of sunshine during July 1982 355

APPENDIX 16 The mean daily rainfall and maximum and minimum daily temperatures during the first half of August 1982 356

APPENDIX 17 The mean daily relative humidity and hours of sunshine during the first half of August 1982 357

APPENDIX 18 An analysis of variance using a Genstat programme 358

28 Chapter 1

GENERAL INTRODUCTION

The number of pesticide applications to cereal crops has increased so that during one growing season, an average field of wheat now receives two or more herbicides, two insecticides and up to four applications of fungicides, compared to a single application of herbicide to such a field in 1960 (Rands and Sotherton, 1985).

Most agricultural sprays are applied at about 200 1/ha using conventional hydraulic nozzles, although there is an increasing tendency to reduce the volume of spray applied. New techniques are also available to minimise the volume of liquid involved. The concept of "Controlled

Droplet Application" (CDA) emphasizes the importance of applying the correct size of droplet for a given target and ensuring uniformity of droplet size (Matthews, 1979a).

There has been considerable controversy about the use of CDA spraying of cereals and in particular whether "drift" spraying with one machine, the "Ulvamast", which releases small droplets (70 - lOOum in diameter) from an adjustable mast is acceptable. As droplet movement is entirely dependent on natural forces, the risk of drift into neighbouring areas and hazards to the environment were considered to be greater than if hydraulic nozzles directed the spray downwards. Furthermore, the increased concentration of spray in the "ultra-low-volume" (ULV) technique

29 was considered to increase the danger to non-target species (Royal

Canmission on Environmental Pollution, 1979). Several farmers adopted this method of pesticide application, particularly to apply fungicides, but there is no information on its efficacy nor on the implications of spray drift on the beneficial arthropod fauna in the field boundaries and adjacent crops.

Records of cereal aphids attacking arable crops date back as far as the 18th century (Marsham, 1798), but they were not recognised as being of economic importance until the 1950's when they were identified as vectors of barley yellow dwarf virus (BYDV), a disease causing serious damage and yield loss in barley, wheat and oats (Oswald and Houston, 1951). The direct effects of cereal aphids on cereal yields were not realised until

1968, following severe outbreaks of the grain aphid, S i tobi on a vena e

(F.) in many countries and widespread insecticide application (Fletcher and Bardner, 1969; Kolbe, 1969). The subsequent increased frequency and intensity of cereal aphid attacks have been attributed to the expansion of cereal acreage and production, coupled with changes in cultural and harvesting practices such as increased pesticide usage, direct-drilling, straw burning and early sowing of winter cereals (Baranyovits, 1973;

Kolbe, 1973; Kolbe and Linke, 1974; Potts and Vickerman, 1975; Potts,

1977).

"Aphid-specific" predators and parasites and polyphagous predators may be important in controlling cereal aphid populations (e.g. Potts and

Vickerman, 1974; Edwards, Sunderland and George, 1979; Edwards and George,

30 1981; Chambers, Sunderland, Stacey and Wyatt, 1982) and the repercussions of increased pesticide usage on these beneficial arthropods must be evaluated.

This project examines the extent of downwind drift from a conventional hydraulic boom sprayer and the mast-type drift sprayer, the

"Ulvamast" (Part One), and assesses the effects of spray drift and the loss of insecticide to the soil within the treated areas on the natural enemies of cereal aphids (Part Two).

31 PART ONE

SPRAY DRIFT

32 Chapter 2

SPRAY DRIFT

2.1 Introduction

Spray drift occurs when small droplets or particles do not reach their target and are deviated from their original flight path by natural air movement (Gohlich, 1983). The proportion of spray reaching the target is often low and as much as a third of the spray applied to a crop may be lost to the soil (Matthews, 1979a), referred to by Himel (1974)' as

"endodrift" while losses outside the treated area were described as

"exodrift".

The damage to sensitive crops as a result of herbicide spray drift is well documented (Elliott and Wilson, 1983) and the discovery and widespread use of hormone herbicides have led to acute damage to susceptible crops sometimes several kilometres downwind (Akesson and

Yates, 1964).

Little information is available on the drift of insecticides, fungicides and growth regulators, although organochlorine residues have been detected in the milk from cows in pastures near sprayed fields

(Akesson and Yates, 1964) and bees have been destroyed by insecticide drift to orchards and clover (Hartley and Graham-Bryce, 1980). Mere

33 experimental data is required on the biological implications of spray drift, in particular non-target contamination and the effects on beneficial arthropods.

Spray dispersal is a complex process involving the interaction of many factors including the physical characteristics of the spray liquid, droplet evaporation, wind, turbulence and drop deposition (Wilson, 1977).

2.2 Physical factors affecting spray dispersal

2.2.1. Gravitational and aerodynamic forces

A droplet released in still air accelerates downwards under the force of gravity until the aerodynamic drag and gravitational forces balance when the droplet will fall at a constant terminal velocity (Vs)

(Yates and Akesson, 1973; EPPO, 1982).

The rate of fall of a droplet is primarily dependent upon the diameter and density of the droplet (Yeo, 1955; Johnstone, 1978), although the density and viscosity of the air are important (Matthews, 1979a). The terminal velocity (m/s) of a droplet can be predicted by Stokes Law:

34 Vs = a d 2/?d

1817

where d = droplet diameter (m)

/0 4 = droplet density (kg/m2)

g = gravitational acceleration

r) = viscosity of air (Ns/m2)

The terminal velocity of liquid droplets is canparable to that of spheres (Table 1) but larger droplets may be deformed due to aerodynamic forces increasing their effective mass and reducing their velocity below that calculated for a sphere (Elliott and Wilson, 1983).

Table 1 Terminal velocity (m/s) of sphere and fall time in still air (from Matthews, 1979a)

Droplet Specific gravity Fall time from diameter 3m (Sp. ar.= 1) (jum) 1.0 2.5

1 0.00003 0.000085 28.1 h 10 0.003 0.0076 16.9 min 20 0.012 0.031 4.2 min 50 0.075 0.192 40.5 s 100 0.279 0.549 10.9 s 200 0.721 1.40 4.2 s 500 2.139 3.81 1.65 s

Small droplets ( <30 jum diameter) have low terminal velocities and take several minutes to fall in still air (Table 1) so are exposed for longer to the influence of air movements (Maybank, Yoshida and Grover,

1974). For example, in a constant wind velocity of 1.3 m/s parallel to the ground, a 1 rim droplet released from a height of 3 m can theoretically

35 travel over 150 km downwind before settling out, while a 200 rim droplet

can settle in less than 6 m downwind, assuming that the droplet size

remains constant (Matthews, 1979a).

In practice, spray droplets are not released at rest but are

projected with an initial velocity characteristic of the ataniser. These

velocities are typically greater than the terminal velocities of the

droplets and aerodynamic forces slow the droplets down. Droplets

projected horizontally (e.g. from spinning-cups) into still air lose their

horizontal velocity after the "stopping distance" which is longer for

larger droplets. The stopping distance of most droplets from hydraulic

nozzles, which are vertically projected, is defined as the distance

through which the droplet must fall before it loses its excess velocity

(Johnstone, 1978; EPPO, 1982; Elliott and Wilson, 1983). For example,

droplets larger than 200 jum produced frcm hydraulic nozzles 0.5 m above a

crop are likely to be projected directly into the crop, while droplets

smaller than 50 jum acquire the local air velocity soon after leaving the

nozzle. Droplets of intermediate size travel part of the distance to the

target before being significantly affected by wind and turbulence. Thus,

the spray release height is an important consideration when predicting drift.

2.2.2 The effect of wind and turbulence

The local air velocity is affected by both wind and turbulence.

36 Frictional turbulence arises due to the roughness of the soil or vegetation creating resistance or drag on the airflow and this results in a wind profile in which the mean wind speed, U(z) , increases with height

(z) (Johnstone, Huntington and King, 1974). This increase is approximately logarithmic and is dependent on the crop form although its validity is limited to neutral stability conditions (Than, 1975). A spray- droplet released into such a wind profile will have a mean trajectory that makes an angle of Vs/u(z) with the horizontal (Elliott and Wilson, 1983).

Thus the local air velocity comprises a steady horizontal component determined by the wind, and a turbulent canponent determined by the air speeds within the frictionally driven eddies. The structure of eddies varies according to the stability states in the air flow close to the ground (Figures 1 to 3). The distribution of velocities found within the turbulent eddies is characterised by the eddy or friction velocity, u*

(Lawson and Uk, 1979).

For Vs > u* , the effect of turbulence will be negligible and

droplet movement will be dominated by sedimentation, but when Vs < u* droplet movement will be determined by u* independent of droplet size

(Lawson, 1979). In general, sedimentation dominates large droplet movement if Vs > 3u* , but turbulence daninates small droplet movement if

V s < 0.3 u* . As u* is proportional to the wind speed, the terms "large"

and "small" droplets are related to the existing wind speed (Figure 4).

37 Wind velocity profiles and simplified eddy structures characteristic of the three basic stability states in air flow near the ground ( from Elliott and Wilson , 1983 ) (where u(z) is the mean wind speed and z is height).

FIGURE 1 Neutral

FIGURE 2 Unstable FIGURE 3 Stable

38 FIGURE 4 Areas of dominance of sedimentation on turbulent transport (from Lawson ,1979).

Sedimentation » Turbulence - 'big' drops - VS>3U* Turbulence » Sedimentation - 'small'drops - Vs< U*/^

FIGURE 5 A schematic view of a tilting plume. (see key on page 40)

39 Large droplets sediment at an angle to the horizontal defined by

Vs/U(z) . If the mean wind speed between the ground and the height at which the droplet is released h, is u h , then the droplet reaches the ground at a distance, x downwind where

x = huh

Vs

and the droplets follow the trajectory A-C (Figure 5)

Turbulence causes a spreading of the droplet cloud about the line

AC and the distribution of droplets about the cone centre line (AC) is often assumed to be Gaussian (Bache, unpublished; Lawson, 1983). This approach to the theoretical modelling of spray dispersal is based on the assumption of the 100 per cent removal of the plume as it reaches the underlying surface (Bache and Sayer, 1975; Dumbauld, Rafferty and Cramer,

1976; Lawson and Uk, 1979; Lawson 1983). The distribution of small droplets across the cone is therefore approximately synmetrical, but the intersection of the plume with the ground leads to an assymmetrical distribution of spray deposit on the ground and the presence of a long downwind "tail" (Elliott and Wilson, 1983). The peak deposit occurs at a

V max downwind given approximately by

V max = hu

u*

40 The peak ground deposit varies according to the conditions although in the unstable conditions in the United Kingdom the deposit peak is found at about 10 x h (Elliott and Wilson, 1983). In more stable conditions the angle of spread of the cone of droplets is reduced and where the plume does reach the underlying surface, the amount of deposit will be higher than in neutral conditions.

Spray dispersal models are continually being improved and modified to incorporate more variables. For example, the "random-walk" model

(Thompson and Ley, 1982) includes the consequences of droplet evaporation and partial droplet reflection at the surface. Other authors have derived detailed regression analyses between measured drift deposits in the field and factors such as droplet size, wind speed (vertical and horizontal), atmospheric stability and temperature (e.g. Threadgill and Smith, 1975), but such analyses are restricted to the particular experimental conditions and cannot be used to predict drift deposits under other conditions.

2.2.3. The effect of evaporation

The evaporation of airborne spray droplets increases their drift potential by reducing their diameter (Sharp,1984). Water is ccmmonly used as a carrier and diluent for conventional sprays, but evaporation is a problem and can induce rapid changes in the droplet spectra soon after leaving the atomiser (Akesson and Yates, 1964; Maybank and Yoshida, 1971;

Johnstone, 1974).

41 Larger droplets ( > 150pm) evaporate less rapidly and for a droplet of 500 jum, water loss and subsequent reduction in size before deposition on the target will be negligible (Grover, Maybank and Yoshida, 1972).

As a droplet becomes smaller, the surface : volume ratio increases and the rate of evaporation is rapid (Johnstone, 1974). The dispersal of

small droplets (< 50jum) is influenced by turbulence which extends the time that the droplets remain airborne (Hartley and Graham-Bryce, 1980), so some small droplets will evaporate fully to residual cores, typically less than 20 pm, with a low efficiency of deposition to the underlying

surface (Elliott and Wilson, 1983).

The effect of evaporation on the diameter of droplets in the

intermediate size range may change dispersal from sedimentation to

turbulence and the proportion of droplets likely to drift increases

(Elliott and Wilson, 1983).

Methods of reducing evaporation are described later in Section 2.3.2

(page 44 ).

42 2.3 Liquid properties influencing spray dispersal

2.3.1. Surface tension, liquid density and viscosity

The droplet spectrum produced from an ataniser is affected by the density, surface tension and viscosity of the spray liquid to a variable extent depending on the method of droplet formation, e.g. sheet break-up from flat fan or cone nozzles, spinning discs (Maybank and Yoshida, 1969,

1971; Grover, Maybank, Yoshida and Plimmer, 1973; Yates and Akesson,

1973; Nordby and Skuterud, 1975; Bouse, 1976).

The relationship between the droplet size and the physical properties of the liquid is canplex. In general, a reduction in the surface tension of a spray fluid promotes the production of smaller droplets unless the mechanism of droplet formation is through ligament break-up (Akesson and Yates, 1964; Stephens, 1984).

A reduction in the liquid density influences the flow rate and produces a spray with larger droplets (Elliott and Wilson, 1983). The effect of viscosity on droplet size is more involved and conflicting reports appear in the literature. An increase in viscosity prevents the secondary break-up of droplets and tends to increase the VMD of the spray, although an increase in viscosity with low surface tension may result in a high number of small droplets (Yates and Akesson, 1973; Cowan, 1983).

43 2.3.2 Spray additives

A wide range of surfactants, oils, polymers, and other macromolecules have been recommended as additives to modify the dispersal of pesticide sprays. Many are claimed to minimise drift hazards, usually by increasing the viscosity of the spray liquid (e.g. Grover et al.,

1973; Maybank, Yoshida and Shewchuk, 1976; Yates, Akesson and Bayer,

1978).

Methods of reducing the evaporation of water droplets have included the incorporation of amine stearates in the spray fluid which caused changes in the surface tension of the liquid (Akesson and Yates,

1964). Vegetable and mineral oils are also used to reduce losses through evaporation (Bode and Butler, 1983; Stephens, 1984).

2.4 The effect of the method of application on spray dispersal

2.4.1 Hydraulic sprayers.

Most agricultural sprayers use hydraulic nozzles (producing either a fan or hollow cone spray pattern) to meter and break up the liquid into droplets. Liquid is forced through the orifice as a sheet which becomes unstable and breaks up into droplets which may vary in size from 1 - lOOOjum (Graham-Bryce and Matthews, 1981). Fraser (1958) classified the mode of disintegration of the liquid sheet as perforated, rim or wavy-sheet.

44 The type, size and orientation of the spray nozzle are all important factors in minimising losses through "run-off" or drift and should be selected to suit the target (Yates and Akesson, 1973). Sprayer maintenance is vital as worn or damaged nozzle parts can substantially distort the spray distribution and alter the droplet size characteristics

(Grover et al., 1973).

The height of the nozzles above the target crop can contribute to the extent of downwind drift (e.g. Butler and Bode, 1976; Byass and Lake,

1977; Maybank, Yoshida and Grover, 1978; Smith, Harris and Butler, 1981), and to minimise the effects of evaporation and wind, the height is recanmended as ^0.4 m above the crop (Nordby and Skuterud, 1975; Gohlich,

1983).

Boon bounce due to the movement of the sprayer over uneven ground and tractor speed variations result in variable spray deposition and increased drift hazards (Nation, 1980, 1982; Lawson, 1983).

Many assessments of ground and airborne drift deposits have been made under different conditions, nozzle types and methods of deposit measurement, and a particularly comprehensive set of trials' results was published by Maybank and his co-workers (Maybank et al, 1978).

General conclusions about the magnitude of drift deposits frcm single swath, tractor-mounted nozzles operating under typical herbicide

45 application conditions, e.g. boon height 0.5 - 1.0 m; wind speed 1 - 4 m/s; nozzles 8002 operating at 300 kPa; temperature 20°C; humidity 70 per cent have been summarised by Elliott and Wilson (1983):

(a) total drift is, on average, approximately 5 per cent of

the applied active ingredient (a.i.) of which 50 per cent is

deposited within 10 m downwind.

(b) ground deposit densities decrease in the first 20 m downwind,

. O reaching about 10 x applied dosage at 10 m.

(c) the ground deposit density begins to fall off more rapidly 10

- 100 m downwind, reaching about 10 "4 x applied dosage at

100 m.

(d) ground deposits further than 300 m downwind are typically 10‘5

x applied dosage.

2.4.2 Controlled droplet application (CPA).

The system of CDA aims to accurately deliver the pesticide to the target by applying a narrow spectrum of droplets of the most appropriate size and number for the biological target (Himel and Uk, 1975) in a minimal volume of liquid. Potentially, more efficient application offers the opportunity to reduce the total quantity of active ingredient used with environmental gains and reduced chemical costs for the farmer (Poyal

Ccmmission on Environmental Pollution, 1979).

Droplets are produced by either centrifugal or electrostatic forces.

Centrifugal energy nozzles have been developed by which the spray liquid

46 is fed near the centre of a rapidly spinning surface (disc, cup or cage) and centrifugal force spreads the fluid to the periphery at or near which the droplets are formed (Walton and Prewett, 1949; Maybank and Yoshida,

1971; Yates and Akesson, 1973; Matthews, 1979a). The size of the droplets thrown off the edge of the disc is inversely proportional to the angular velocity, but is also affected by the flow rate (Matthews, 1981). Three essentially different types of liquid disintegration according to the flow­ rate have been identified and are described by Frost (1978).

To allow higher flow rates to be applied with vehicles or aircraft, a series of stacked discs is sometimes mounted to revolve around a stationary horizontal shaft through which each disc is fed individually

(Bals, 1977; Matthews, 1981). The system is used in the "Ulvamast" (Mk2) sprayer which has a spray-head comprising fifteen serrated plastic discs

(Appendix 1).

2.5 Factors affecting spray deposition

Deposition on or collection by the crop canopy, soil surface, cr other target (e.g. insect) may occur by gravitational sedimentation cr inertial impaction (including interception), or by a combination of both processes.

Large droplets 0 3 0 0 /Jm) tend to deposit primarily by sedimentation due to gravity (Graham-Bryce and Matthews, 1981). Inertial impaction becomes increasingly evident as the droplet size falls below approximately

47 150 ;um and is the dominant deposition mechanism for droplets 1 - 50 jum in diameter although sedimentation may occur under unusually still or sheltered conditions (Johnstone, Rendell and Sutherland, 1977a; Little,

1979).

A droplet will tend to follow the airstream flowing around an obstacle unless its momentum is sufficient to penetrate the boundary layer around the obstacle and impact (Ripper, 1955; Johnstone, 1974; Ekblad,

1978).

The impaction or collection efficiency of a target in an airstream laden with small droplets varies in a ccmplex way with the airstream velocity, droplet size and velocity and the relative size of the target

(Johnstone, 1978). In general, the collection efficiency increases with droplet size and its velocity relative to the obstacle, and decreases as the obstacle increases in size (Matthews, 1979a). Consequently, the optimum droplet size range varies according to the target (Table 2).

The collection efficiencies of a few simply-shaped obstacles are reasonably well-known (e.g. May and Clifford, 1967). For example, in an 8

Km/h airstream, the percentage number of droplets collected by a 3.2 mm diameter vertical cylinder varies with their diameter (Table 3). However, it is difficult to relate this to the ccmplex structure of a plant and its ability to filter droplets from the airstream varies considerably. For example, conifer needles are more efficient than broad-leaved foliage in removing droplets <100 jum in diameter (Himel, 1969), while very small

48 Table 2 : Optimum droplet size ranges for selected targets (from Matthews, 1979a)

Target Droplet size range (jam)

Flying insects 10 - 50 Insects on foliage 30 - 50 Foliage 40 - 100 Soil (avoidance of drift) 250 - 500

Table3: Percentaae of droplets collected on a 3.2nm diameter target (from Johnstone, 1974)

Droplet diameter Percentage number (Jum) collected

10 15 20 52 40 78 100 92

droplets (< 20 jum) readily move in the airstream around obstacles and only

tend to be filtered out by thin stems, plant hairs and other fine

processes (Elliott and Wilson, 1983). Below 1 jum, eddy diffusion assumes greater importance and particles are transported by Brownian motion across

the boundary layer to the leaf surface (Little, 1979).

Lawson and Uk (1979) compared the collection efficiencies of a mature stand of wheat and a ploughed fallow field and found that the crop was 70 and 20 per cent more efficient at removing 50 jam and 150 jum droplets respectively. However, deposition of 50 jam droplets in mature wheat may be variable and has been attributed to the effects of mutual sheltering and leaf orientation and flutter (Callander, personal

49 communi cation).

Higher wind velocities tend to increase impaction (Graham-Bryce and

Matthews, 1981) and the proportion of spray caught in the upper canopy is increased while ground and low canopy deposits are reduced (Bryant, Parkin and Wyatt, 1984). Reduced windspeeds within the crop canopy favour deposition of larger droplets by sedimentation but reduce the impaction efficiency of smaller droplets (Little, 1979).

Air turbulence causes droplets to be deposited on the windward surfaces of plants and coverage of the underside of leaves will be poor unless air turbulence causes the foliage to flutter (Morton, 1977;

Matthews, 1981). Very small droplets (<20 jam) are prone to drift in turbulent daytime conditions as, although turbulence may bring them down to the underlying surface, their probability of deposition is lew

(Elliott and Wilson, 1983).

The velocity of large droplets produced from conventional hydraulic nozzles can be quite high and the droplets may bounce and/or shatter on impaction with the upper cancpy leaves although this results in improved penetration (Bryant et al, 1984; Taylor, 1985; Young, 1985). Large droplets are not well retained on steeply sloping, waxy plant surfaces

(Taylor, 1985). Droplets produced from horizontal spinning discs (e.g.

"Micromax" spinning cup) only have vertical velocity due to gravity and the low momentum and narrower droplet spectrum result in ineffective partitioning throughout the canopy (Cooke et al 1985; Western et al,

50 1985; Young, 1985). Vertical spinning discs (e.g. Technoma "Girojet") have a slight downward velocity and penetration of droplets may be improved (Young, 1985).

2.6 Meteorological conditions affecting spray dispersal

The uniformity of the spray deposit and risk from drift are primarily dependent on the wind velocity and direction and the air turbulence.

2.6.1 Wind velocity

Wind velocity is the main influence on the number and size spectra of droplets which become "airborne" to form drift (see Sections 2.1 and

2.5).

Characteristics of the wind depend on the horizontal pressure gradients of the lower atmosphere, the roughness of the underlying surface and the atmospheric stability. Strong winds are associated with strong pressure gradients and smooth terrain and are usually more predictable in direction than light winds which occcur with weak pressure gradients. In general, the stronger the wind, the further the spray droplets travel before deposition (Elliott and Wilson, 1983). Cooling of the land in the evening results in the increased stability of the atmosphere and consequently a decrease in wind velocity. A corresponding increase in wind velocity usually occurs soon after dawn (Johnstone et a l ,

51 1977a).

The height of the spray boon affects the extent of the influence of the wind at the nozzle (page 45 ). As the boom is raised, the number of droplets which are entrained by the wind increases. Stronger winds tend to break up the spray pattern close to the nozzles and increase the proportion of airborne droplets (Elliott and Wilson, 1983).

2.6.2 Wind direction

In very stable conditions, wind direction may fluctuate dramatically over only a few minutes (Morton, 1977). Drift into lateral as well as downwind areas in prevailing winds of 1.5 - 2.5 m/s has been detected up to

1 km outside the target area (Lloyd, Bell and Howgego, 1981). Topography of the field and obstacles such as trees and hedges may cause changes in wind direction and generate additional turbulence (Little, 1979; Matthews,

1979a).

2.6.3 Atmospheric stability and turbulence

Turbulence arising as frictional convection due to the roughness of the ground or crop creating drag on the airflow (Figure 6) was discussed in Section 2.2.2 (page 36). The other type of turbulence is caused by pockets of heated air rising as they are less dense than the surrounding air (Figure 7).

52 FIGURE 6 Atmospheric turbulence caused by surface friction {from Elliott and Wilson, 1983). airflow ------► Q c C c O O

FIGURE 7 Air turbulence caused by surface heating (from Elliott and Wilson , 1983) . During unstable or "lapse" conditions, air warmed by contact with the land heated by sunshine, rises in "bubbles" or "thermals" which enhance atmospheric turbulence. These conditions prevail on sunny days with light winds and are characterised by an average air temperature which decreases with increasing height. At night, particularly if the sky is clear, the ground rapidly loses heat due to radiation and the air in contact with it also cools, becoming dense with no tendency to rise. In these stable or "inversion" conditions, the air temperature increases with increasing height (Johnstone, 1974,1978; Matthews, 1979a; Elliott and

Wilson, 1983).

Periods of light winds, associated with stable or "inversion" conditions, will favour deposition onto horizontal collecting surfaces e.g. upper surfaces of cotton leaves, but stronger winds enhance collection by vertical surfaces, in particular the sides of stems and narrow, upright leaves e.g. cereals, which face towards the drifting spray

(Johnstone, 1978; EPPO, 1982).

2.6.4. Gustiness

The major factors determining gustiness when considering spraying over relatively uniform surfaces of moderate roughness, are the mean wind velocity, atmospheric stability and (close to the sprayer) vortices

shedding from the sprayer (Elliott and Wilson, 1983).

54 2.6.5 Humidity and temperature

Humidity determines the extent of the evaporation of water from spray droplets and its importance depends on the droplet spectrum and the chemical (Maybank and Yoshida, 1971; Johnstone, 1974). Higher temperatures will increase the rate of evaporation of water from spray droplets and are usually associated with reduced humidities (Yates and

Akesson, 1973). Evaporation is discussed in Section 2.2.3.

2.6.6 Other meteorological factors

Removal of minute aerosol particles suspended in the atmosphere may be facilitated by rain drops and radiation from the sun may degrade airborne droplets (Yates and Akesson, 1973).

55 2.6.7 Conditions suitable for spraying

Basic criteria to be considered before spray application have been reviewed by several authors (e.g. Adams, 1978, 1980, 1981; Spackman and

Barrie, 1982; Spackman, 1983) and summarised by Elliott and Wilson (1983) who recanmended the following conditions are avoided:-

, j (a) strong winds ...... spray droplets will be carried long

distances and spray coverage of the

crop will be variable.

(b) almost calm conditions

on sunny days...... the wind direction is erratic and

convection currents can transport spray

over considerable distances.

(c) calm conditions at dusk,

night and dawn, along

with a clear sky...... stable conditions in which very small

droplets may be carried some distance

before deposition occurred.

British weather is highly variable but given the above circumstances, the

conditions most suitable for spraying are a wind speed of 7 - 18 km/h at

a height of 10m ; no precipitation at the time of spraying or in the

preceding hour and an air temperature greater than 7° C and less

than 30° C ( Elliott and Wilson , 1983 ).

56 Chapter 3

DROPLET SPECTRA

3.1 Introducti on

Losses of spray droplets through drift and the extent of the ecosystem contamination are affected by the range of droplet sizes produced from agricultural sprayers (Rathburn, 1970; McDaniel' and Himel,

1977; Yates, Cowden and Akesson, 1982). Since spray efficiency can be improved by applying an appropriate range of droplet sizes for a specific pest problem (Matthews, 1979a; EPPO, 1982), accurate knowledge of droplet spectra from different nozzles is needed.

The literature on droplet collection and measurement has been reviewed by Matthews (1975). Techniques used for aerosol particle size determination and for ULV and "low volume" (LV) sprays have been described

(Rathburn, 1970; WHO, 1971; Pengilly, 1977; Carroll and Bourg, 1979).

Artificial surfaces, regardless of their size, shape, location and orientation, can only give an estimate of the size and number of spray droplets collected by biological targets, particularly as the movement of plant parts in the wind (for example, bending and leaf flutter) cannot be imitated (Uk, 1977). However, the method of droplet sampling must try to assure equal collection efficiency for all droplets, independent of their size (EPPO, 1982). Factors affecting the collection efficiencies of

57 objects were discussed in Chapter 2 (page 48 ) and reviewed by May and

Clifford (1967).

Droplets are often collected on glass slides coated with various materials (e.g. magnesium oxide), thin paper strips, narrow rods or wires. A coated glass slide waved through a spray cloud is a poor method of sampling droplets less than 40 pm in diameter (Mount and Pierce, 1972;

Matthews, 1975). Similarly, rotating slides (Thornhill, 1979) were unsuitable for collecting droplets less than 30 pm in diameter ('Andrews,

Flower, Johnstone and Turner, 1983). The sampling of airborne aerosol droplets is either with a cascade impactor which has a greater efficiency for collecting droplets 1.5-50 pm in diameter (May, 1945; Rathburn,

1970), or by rotating small diameter rods coated with magnesium oxide which collect droplets in the range 10 - 100 pm or 1 - 10 pm depending on the diameter and shape of the rods (Lee, 1974; Matthews, 1975). A

"harp", comprising fine wires stretched across a frame, has been developed for the collection of droplets (0 - 60 pm) (McDaniel and Himel, 1977;

Nguyen and Symmons, 1984).

Alternatively, sufficient time is allowed for the droplets to sediment on to collecting surfaces in an environment free of air currents, provided by a "settling-chamber". (Mount and Pierce, 1972; Matthews,

1979a; EPPO, 1982). However, droplets less than 5 pm do not readily settle and tend to remain airborne (Rathburn, 1970).

Droplets can be collected on a variety of surfaces on which a mark,

58 stain or crater is left by their impact. A standard surface is magnesium oxide and the true droplet diameter is equal to 0.86 times the crater diameter produced by the impinging droplets for droplets in the size range

20 - 200 p m (May, 1950).

Other collecting surfaces on slides include a silicone coating which forms an oleophobic layer that prevents the irregular spreading of droplets (Rathburn, 1970; Mount and Pierce, 1972; Matthews, 1975).

Teflon plastic films are more permanent than the two former surfaces

(Anderson and Schulte, 1971) and Carroll and Bourg (1979) considered mechanical slide rotators with teflon-coated slides to be one of the most efficient methods of sampling ULV droplets.

Kaolin has also been used as an alternative to magnesium oxide and has been recommended as a suitable collection surface for droplets between

20 and 3000 ;jm in diameter, although their velocity needs to be low to avoid shattering on impact (Middleton, 1967; Matthews, 1975). A matrix such as petroleum jelly and light oil may also be suitable as the droplets maintain their natural spherical shape and no spread factor is required

(Daum, Burt and Smith, 1968; Rathburn, 1970; WHO; 1971). Immediately after spraying, the droplets are covered with a thin layer of oil to prevent evaporation (Komson, 1977). This method is particularly useful

for the collection of large droplets that may otherwise shatter on

impaction.

Suitable alternative surfaces include kromekote paper (Higgins,

59 1967), fixed glazed photographic paper (King and Johnstone, 1973; Turner and Huntington, 1970), filter papers (Jarman, 1956) and. PTFE tape

(Johnstone, Huntington and Coutts, 1974). A dye is added to the spray liquid and the stains on the paper surface measured. The minimum droplet size for which this method can be used is 10 - 20 ;om, however, the definition of the spot attained on the card is dependent on the type of paper and dye used and pesticide formulation (Jarman, 1956;, Rathburn,

1970). For example, the stains on filter papers may be irregular in shape and the dye may run along the fibres of the paper (Dorman, 1952;

Matthews, 1975). Krcmekote paper has also been found to give poor definition of droplets (King and Johnstone, 1973).

Dyed cards may be used to avoid contamination of non-target areas with dyed spray. Spray droplets on impact displace dye as the solvent spreads leaving a clear spot but high spray densities may result in the coalescence of individual spots and inaccurate deposit assessment (King and Johnstone, 1973).

The droplets, collected on a suitable surface, can be measured under a microscope with a graticule (for example, a Porton G12 graticule), or with a semi-automatic (Fleming Particle Size Analyser) or automatic

(Quantimet Image Analyser) size analyser. The graticule is calibrated and the diameters of the craters or stains measured by comparison with the graticule markings. The "true" diameter of the droplet is obtained by applying the appropriate correction factor to account for the spread on the collecting surface (EPPO, 1982).

60 Droplets larger than 10-20 pm in diameter can be sampled on plants

and insects by the fluorescent particle method which is based on the uniform suspension of a known number of solid, insoluble micron-sized

particles of zinc-cadmium sulphide in a known volume of non-volatile

liquid (Himel, 1973). The droplets deposited can be traced as clusters of

particles which fluoresce under ultra violet irradiation. The;number of

particles in each cluster can be counted under a microscope and statisical estimation of the original droplet size made (Himel, 1973; Uk, 1977).

The size of oil-based aerosol droplets on insect targets

(mosquitoes) have been determined directly using a scanning electron microscope (lofgren, Anthony and Mount, 1973).

Most of the procedures described have relied upon the collection of droplets on various media and often these techniques are laborious and errors may arise due to drift, evaporation, poor collection efficiencies,

large numbers of small droplets, and the need to determine spread factors

(Yates et al., 1982). However, more recently a number of optical

techniques have been introduced offering advancements in the measurement

and processing of droplet size data. Photography (Pengilly, 1977),

holography (Dunn and Walls, 1978) and other laser techniques (Swithenbank

et al., 1975; Parkin, Wyatt and Wanner, 1980) have all been applied to measure agrochemical sprays.

61 3.2 The laboratory measurement of the droplet size spectra from

a hollow cone nozzle and stacked spinning discs

Laser analysis was used to evaluate the droplet spectra produced by a Chafer green (hollow cone) nozzle (J. W. Chafer Ltd., Chafer House, 19

Thorne Road, Doncaster, South Yorkshire, DNl 2HQ) and a Micron Multi-Disc

Atomiser (CDA Ltd., Lockinge, Wantage, Qxon 0X12 8QJ) and estimate the proportion of droplets liable to drift or "run-off". The effect of emulsifying agents on the droplet spectra was also assessed.

3.2.1 Materials and methods

3.2.1.1 Experimental Technique

The droplet spectra were measured using a Malvern Instruments'

Droplet and Particle Analyser Type ST1800 (Malvern Instruments, Spring

Lane, Malvern, Worcestershire). Spray droplets were sized by analysing the light scattered by the particles passing through a laser beam

(Swithenbank et al., 1975). The diffracted light is collected by a lens and focused on a detector placed in the focal plane of the lens. The focal length of the lens governs the droplet size range detected and during these experiments, a lens of focal length 800 mm was used to measure droplets in the range 15 - 1500 ;um diameter (Arnold, 1983).

The energy distribution of the diffracted light is compared with the

Rosin-Rammler distribution model (Swithenbank e t a l ., 1977). The

62 computer programme used fits the observed data to the mathematical distribution which takes the form (Arnold, 1983):

[ - ( x/x )N ]

R = e

where R = the volume fraction of particles or droplets larger than x.

x = a droplet or particle size parameter, usually referred to as

the Rosin - Rammler mean diameter.

N = a measure of the dispersion of droplet sizes.

The computer obtains the best fit of the actual energy distribution to the calculated energy distribution by modifying the parameters x and N.

Using the terms PE and W, which are equivalent to x and N respectively, and with the lowest error value, E, the computer prints the results in the form of a table ( Appendix 2 ).

D represents the size range in ;um and the value P i s the percentage by volume in the specified size range. The residual fraction (as a percentage by volume remaining below the lower figure in the size range D) is shown in the table as R. The value for N is found by calculating the number of droplets in each group from P and converting it to a percentage of the total number of droplets (Heijne, 1981).

63 A computer programme developed by Heijne (1979) was used to convert the values for PE and W to VMD, NMD and the VMD:NMD ratio which are parameters more commonly used to describe the droplet spectra of agricultural spray nozzles.

The volume median diameter (VMD) is defined as the droplet diameter which divides the spray into two equal parts by volume, so that one half of the volume contains droplets smaller than the droplet whose diameter is the VMD, and the other half of the volume contains larger droplets.

The number median diameter (NMD) divides droplets into two equal parts by number without reference to the volume, thus emphasizing the small droplets (Matthews, 1979a). The value of this parameter depends upon the technique used to measure the spray droplets. For example, in the case of sprays from hydraulic nozzles, the NMD is low and it is sometimes more useful to calculate the percentage of spray by volume below a particular droplet diameter e.g. 100 jum (Arnold, 1983).

The ratio between these parameters (VMD:NMD) indicates the range of droplet sizes; the more uniform the size of droplet, the nearer the ratio is to unity (Johnstone, 1978).

64 3.2.1.2 Experimental procedure

Droplet measurements from the Chafer green hollow cone nozzle were

made with the nozzle at 5 cm from the centre of the laser beam. The

nozzle was operated at a pressure of 262 kPa ( a typical pressure used in

the field), which gave a flow rate of 0.77 ml/min. with water.

A background measurement was made without spray and then a signal

measurement with the spray passing through the beam. Ten separate

replicate readings were made of both the signal and the background. The mean VMD, NMD and VMDrNMD ratios obtained are shewn in Table 4.

As the Micron Multi-Disc Atomiser produces droplets around the

circumference of its spinning-discs, a shroud was necessary to allow a narrow stream of droplets to cross the laser beam and avoid lens contamination. The rotational speed of the discs was governed by the voltage and was recorded at 13V and 14V for each formulation used with a digital light tachometer. The flow rate was maintained at 0.48ml/min (as used in the field trials) by adjusting the pressure when necessary. A range of colour-coded restrictors was used according to the viscosity of the different test formulations, which were water; 20 per cent 'Ulvapron'

(B.P. Trading Limited, Brittanic House, Moor Lane, London), a light mineral oil with an emulsifier; and 10, 25, 50 and 100 per cent

Codacide oil (Microcide Limited, Stanton, Suffolk), a vegetable oil (rape seed oil) and emulsifier (Table 4).

65 3.2.2 Results

3.2.2.1 Droplet size spectra from hollow cone nozzle and stacked

spinning discs.

The VMD value for the cone nozzle was 223 +2.4 pm compared with

VMD's of 130 +1.3 pm and 116 +0.7 pm for the spinning discs operating

at 5750 and 6215 rpm respectively (Table 4). The volume of small droplets

(<103 pm) was 32 and 41 per cent at disc speeds of 5750 and 6215 rpm

respectively and 13 per cent for the cone nozzle (Table 5), while a small

volume of spray from both contained droplets less than 24 p m diameter.

The percentage volume was 0.8 - 1.3 for the spinning discs and 0.4 for the

hollow cone nozzle.

The cone nozzle produced a greater volume of large droplets, with

27.5 per cent of the spray volume comprising droplets larger than 300 pm

and approximately 7 per cent larger than 426 pm (Table 5). The volume of

large droplets (>300 pm) in the spray cloud from the spinning discs varied

from 0.6 to 0.3 per cent depending on the rotational speed of the discs.

In general the number of small droplets (<103 pm) increased with an increase in disc speed.

The VMD:NMD ratio was very high for both types, in particular for the hollow cone nozzle, and this was indicative of the wide spread of droplet sizes in the sprays.

66 Table 4 The VM), NMD and ratio of a Micron Multi-Disc ataniser and a hollow cone nozzle.

The values shown are the mean of 9 replicates with standard errors.

Nozzle Formulation Pressure Flow Rate Voltaae Restri ctor Disc Speed VMD NMD VMD/NMD (kPa) (1/min) (v)- (rpm) Cum) Cum) ratio

Micron Water 124.0 0.48 13.0 Yellow-yellow 5750 130 +1.3 8 +0.4 15.6 +0.9 Multi- 124.0 0.48 14.0 Yellow-yellow 6215 116 +0.7 5 +0.3 21.7 +1.4 Disc Atomi ser 20% Ulvapron 124.0 0.48 13.0 Yellow-yellow 5780 124 +0.7 47 +6.7 3.1 +0.4 124.0 0.48 14.0 Yellow-yellow 6250 111 +0.7 28 +0.8 3.9 +0.1

10% Codacide 137.8 0.48 13.0 Yellow-yellow 5780 128 +0.4 48 +1.3 2.6 +0.1 oil 137.8 0.48 14.0 Yellow-yellow 6250 108 +0.6 40 +2.0 2.6 +0.1

25% Codacide 137.8 0.48 13.0 Yellow-yellow 5700 131 +0.6 47 +2.3 2.8 +0.1 oil 137.8 0.48 14.0 Yellow-yellow 6200 116 +0.3 42 +1.2 2.7 ±o.i

50% Codacide 165.4 0.48 13.0 Yellow-yellow 5520 146 +0.9 64 +3.3 2.3 +0.1 oi 1 165.4 0.48 14.0 Yellow-yellow 6120 132 +0.7 66+1.6 2.0 +0.1

100% Codacide 248.0 0.48 13.0 Blue-yellow 5165 89 +0.4 45 +3.3 2.1 +0.2 oil 248.0 0.48 14.0 Blue-yellow 5574 84 +0.4 52+1.2 1.6 +0.03

Hollow Water 261.8 0.77 223 +2.4 6.8+0.1 34.0 ±1-0 cone Table 5 The droplet spectra of a Micron Multi-Disc atomiser

and a hollow cone nozzle.

Percentage by volume of droplets in certain sizes

Formulation Atomiser >426jum 300-426jum 171-300jum 103-17bum <103jum

Water Cone 6.9 20.6 39.3 20.2 12.8

Spi nni ng-■disc 5750 rpn 0 0.6 25.1 41.2 32.7 6215 rpm 0 0.3 17.9 40.1 41.1

Water/Oil emulsions:- 20% Ulvapron 5780 rpn 0 0 11.9 57.0 30.9 6250 rpm 0 0 6.9 50.4 42.5 10% Codacide 5780 rpn 0 0 14.6 56.8 38.6 6250 rpm 0 0 3.2 51.4 45.3 25% Codacide 5700 rpn 0 0 17.5 55.6 26.8 6200 rpm 0 0 7.1 55.3 37.5 50% Codacide 5520 rpn 0 0 28.9 53.1 17.9 6120 rpm 0 0 15.3 60.9 23.8

Oil spray 100% Codacide 5165 rpn o' 0 0.07 28.9 71.0 5574 rpm 0 0 0 19.2 80.8

All values represent the mean of 3 tests (each with three replicates). Details of experimental conditions are shown in Table 4.

68 3.2.2.2. The effect of spray additives on the droplet spectrum of the

Multi-Disc atomiser.

The addition of 20 per cent Ulvapron reduced the large droplet part of the spectra from the spinning discs (Table 5). The percentage of droplets greater than 171 jum decreased by more than 50 per cent at both disc speeds and the volume of spray containing droplets in the size range

103-171jum increased to 57 and 50.4 per cent at the disc speeds evaluated,

so that the VMD's were correspondingly lower (Table 4). This formulation

reduced the VMD:NMD ratio to approximately 3 and 4 at disc speeds of 5780

and 6250 rpm respectively.

The formulations containing 10-50 per cent Codacide oil had a similar effect on the droplet spectra (Table 5). The percentage of spray by volume in the range 103-171jum increased and the percentage of small droplets below 103jum declined as the proportion of oil in the emulsion increased. An associated increase in the VMD of the spectra was apparent

(Table 4). The percentage of very small droplets (<24 Aim) also diminished in the 10, 25 and 50 per cent formulations by 75-88 per cent depending on the volume of Codacide oil and disc speed. However, when 100 per cent

Codacide oil was sprayed through the spinning discs, the VMD was reduced, for example, to 89 +0.4jum at a disc speed of 5165 rpm (Table 4). The percentage of droplets below 103 Aim increased to 71-80 per cent, although the proportion below 24 per cent was still lower than for water only and the droplets were predominantly in the range 63 - 103jum.

69 The size of droplets became more uniform as the proportion of

Codacide oil increased so the VMD:NMD ratio approached 1.0. This was

illustrated by the narrow spread of the droplet distribution (Table 5).

3.2.3 Discussion.

3.2.3.1 Droplet size spectra from a hollow cone nozzle and Multi-Pi sc

atomi ser

The droplet spectrum of pesticide sprays is one of the most

important factors contributing to the movement and subsequent deposition of spray droplets (Maybank and Yoshida, 1971; Matthews, 1975; Combellack and Matthews, 1981; Thompson and Ley, 1982). Although there is considerable literature on the droplet spectra from cone and fan nozzles

(e.g. Maybank et al., 1974; Combellack and Matthews, 1981; Arnold, 1983;

Elliott and Wilson, 1983), comparisons of these data are limited due to variations in test conditions (e.g atomiser, pressure, method of sampling droplets, formulation). However, the VMD of aqueous sprays from a hollow cone nozzle was approximately 223 jum and 230 jum from samples measured by laser analysis (Table 4) and by collection on magnesium oxide coated slides (Lloyd and Bell, 1982) respectively.

The droplet size distribution of sprays from rotary atomisers

(spinning discs or cups) has been studied (e.g. Bals, 1978; Heijne, 1979,

1981; Maybank et al., 1980). Less information is available on droplet

70 spectra from stacked spinning-discs, although the VMD was originally

quoted as 60 jum at a disc speed of 9000 rpm (Haigh, 1978). At rotational

speeds of 7000-7500 rpm, sprays collected on magnesium oxide coated slides

and cellulose acetate films gave VMD's of 80-90jum (Lloyd and Bell, 1982),

compared with values of 116-130jum at disc speeds of 5750-6215 rpm (Table

4). Any discrepancy between these values is related to differences in disc speed and droplet sampling techniques. Droplet collection by sedimentation onto coated slides will favour the larger droplets which settle out more rapidly than droplets (<100 jum) with low terminal velocities (Chapter 2 Section 2.5).

The size of droplets from the stacked spinning discs is related to the rotational speed of the discs (Rutherford and Orson, 1982) and a decrease in the operational voltage which reduces the rotational speed increased the VMD and reduced the proportion of small droplets (Tables 4 and 5). Several authors have demonstrated this for other rotary atomisers

(e.g. Johnstone, Rendell and Sutherland, 1977b; Kcmson, 1977; Heijne,

1979; Matthews, 1979b; Graham-Bryce and Matthews, 1981). Under some circumstances air movement across the edge of the discs may affect droplet formation from adjacent discs, particularly when such atomisers are fitted to aircraft.

Small droplets (<100jum in diameter) may be transported outside the target area by wind and turbulence (Johnstone, 1978). The percentage of total spray volume present in droplets less than 100 jum, and therefore liable to drift, has been quoted as 0.5 - 10 per cent for hydraulic

71 nozzles (e.g. Maybank et al., 1974; Grover, Maybank and Yoshida, 1978;

Maybank et al., 1980; Lloyd and Bell, 1982; Elliott and Wilson, 1983), compared with a value of 60 per cent calculated for the Ulvamast (Lloyd and Bell, 1982). The drift potentials of spray from the Multi-Disc ataniser and hollow cone nozzle, based on the proportion of small droplets

(<100jum diameter) in each spray, were equivalent to 30 - 40 per cent and

13 per cent by volume of the sprays respectively (Table 5). Assuming application and dosage rates described on page90, the volume outputs were in the ratio of 1 : 86 (Ulvamast : hydraulic) while the corresponding concentration of pesticide in the sprays were in the ratio of 80 : 1.

Relating these factors, the spray drift potential ratio, expressed in chemical terms becomes 2.5 : 1. A reduction to 20 per cent in the total quantity of active ingredient is recommended by the Ulvamast manufacturers and the drift potential ratio can be modified to 1 : 2 (Ulvamast : hydraulic).

Droplets > 350 jum in diameter can comprise 25 per cent of the total spray volume and are poorly retained on the target plants (Elliott and

Wilson, 1983; Western et al.,1985). Approximately 30 per cent of the hydraulic spray by volume was > 300 jum in diameter and the potential wastage through 'run-off' was high, whereas the spinning-discs dramatically reduced the large droplet component of the spray (Table 5).

The very wide range of droplets from the hollow cone nozzle (VMD : NMD ratio of 34) is indicative of poor spray efficiency and losses through

"run-off” and drift and, although the width of the droplet spectrum is reduced with the spinning-discs (VMD : NMD ratio of 15 - 20), a narrower

72 spectrum of droplet sizes is achieved by adding emulsifying agents (see below).

3.2.3.2 The effect of spray additives on the droplet spectra from

spinning discs

Spray additives such as Ulvapron and Codacide oil are claimed to reduce evaporation, eliminate very small droplets and minimise the drift hazard. In general, the proportion of droplets >171 jum declined and the width of the droplet spectrum was considerably reduced by the additives

(Table 4). The VMD was not significantly affected apart from when the sprays contained 100 per cent Codacide oil, and both surface tension and viscosity were significantly different from the emulsions of oil in water, and the droplet diameter is related in the following equation derived by

Walton and Prewett (1949):-

d

where -d = droplet diameter (jum)Cum) w = angular velocity (rad/s) D = diameter of disc (n (nm) m ) V = surface tension of liquid (mN/m)(m jq = density of liquid (g / cm3 ) k = constant

73 3.3 The measurement of the size of droplets moving downwind from

plots sprayed conventionally and at ultra lew volume

Most assessments of spray drift have been made during aerial applications (e.g. Akesson and Yates, 1964; Maybank et al., 1978;

Lawson and Uk, 1979). Similar studies with hydraulic ground sprayers have been reported (e.g. Grover et al., 1978), but comparatively little work has been done to determine the extent of pesticide drift under various conditions in the UK. (Byass and Lake, 1977). Recently the drift potential of the Ulvamast and conventional hydraulic sprayers has been evaluated (Lake, Frost and Lockwood, 1978; Lloyd and Bell, 1982).

The use of "twin-tracers" to permit the comparative assessment of droplets sampled from simultaneous spray application was described by

Johnstone (1977a) and Lloyd and Bell (1982).

Under field conditions and using different coloured dyes as tracers, droplets produced from a conventional hydraulic boom sprayer and an

Ulvamast Mk.2 were collected on vertical glass slides coated with magnesium oxide up to 200 m downwind. The size of the droplets moving outside the treated area was determined in the laboratory.

74 3.3.1 Materials and Methods

3.3.1.1 Field trial

The trial was carried out in a field of grass 0.3 m high. A conventional tractor-mounted hydraulic boom sprayer (Chafer T2000) and an

Ulvamast Mk 2 were driven simultaneously, a short distance apart, up and down a single spray track 120 m long. The spray strip was positioned at right angles to the wind direction so that the drift from each sprayer passed over the same droplet sampling layout (Figure 8).

The 12 m hydraulic boon, positioned 0.5 m above the crop, was fitted with Chafer green hollow cone nozzles (VMD 223 jum), 0.35 m apart. The liquid pressure was 262 kPa, delivering 0.77 1/min and applying 215 1/ha at 7 km/h.

Liquid from a 270 1 tank on the Ulvamast Mk 2 was pumped to the spinning-discs operated at 12 v (7000 - 7500 rpm) (VMD 116 jum at 6215 rpm.) and fed with 0.48 1/min to give an application rate of 2.5 1/ha at 10 km/h. The mast was adjusted to approximately 1.2 m above the crop to give a suitable swath in the prevailing winds of 15 - 22 km/h.

Ten bouts, each 12m wide, were made with the sprayers.

75 FIGURE 8 Diagram of drift sampling layout.

single spray track ▲ vertically positioned, magnesium oxide coated slides

—>wind direction

O) A A A A AA A * A 10m A A A A A A A * A

A A A AAA A A

5 10 20 50 75 100 150 200

Distance from edge of sprayed area (m ) An aqueous solution of Lissamine Green (0.4 per cent) was sprayed through the Chafer T2000 and an aqueous solution of Orange G (1 per cent) was sprayed simultaneously through the Ulvamast Mk2.

The droplets were collected on magnesium oxide coated slides prepared by burning two 10 cm strips of magnesium ribbon below a glass slide to give a uniform deposit of magnesium oxide in the central area of the slide (May, 1950). The slides were attached in a vertical position, facing into the wind, on canes at 0.75m above the crop. Three canes, 10m apart, were erected at 5, 10, 20, 50, 75, 100, 150 and 200m downwind from the edge of the strip to be sprayed. The slides were exposed to the drifting spray throughout the period of spraying.

Measurements of wind velocity and temperature at 1, 2, and 4m above the ground were recorded and are shown in Table 6 (Lloyd, personal communication).

Table 6 Meteorological data

Height above ground (m) Temperature (°C) Wind velocity (km/h)

1 16.9 15.5 2 20.2 4 16.2 22.4

77 3.3.1.2 Droplet Sizing

The size of droplets collected on the slides at each sampling

station was determined using a Fleming Particle Size Micrometer and

Analyser Type 526 (Fleming Instruments Ltd., Caxton Way, Stevenage,

Hertfordshire). Calibration was carried out according to the manufacturers’ instructions to give a full-scale deflection on the meter

scale at 250 jum. The upper limit of the highest channel (J) was set at

this value on the meter and the other channel limits (A - I) were set in a

>J2 progression from the upper limit. All of the channel counters were

zeroed and slides were scanned. Each stain (either green or orange) w7as

counted into its correct size channel if the two images alternately

separated and superimposed.

The VMD, NMD and VMD : NMD ratio of the droplets collected on the

slides were determined using a computer programme (Arnold, 1983).

"Genstat" (Alvey, Galwey and Lane, 1982; Rothamsted Experimental Station,

1977 ) , was used to perform an analysis of variance (ANOVA) on the

data and to extract the mean values for graphical representation.

3.3.2 Results

The mean VMDs of droplets from the conventional hydraulic sprayer 5m

and 10m downwind were 119.0 +_ 3.0 jum and 108.0 + 3.5 jum respectively

(Figure 9). The decrease in size was statistically significant at

P<0.05. Further significant reductions in VMD occurred 20m (PC0.001) and

78 50m (PC0.001) downwind, but no subsequent variation was apparent up to

150m where the mean VMD declined to 42.0 +6.5 jum (Figure 9). This value was significantly lower than the VMD of droplets collected at 100m (P<0.05).

The VMD of droplets from the Ulvamast sampled 5 - 20m outside the treated area were not significantly different but a 44 per cent increase was recorded at 50m (P<0001) (Figure 9). The VMD then decreased 75m downwind (P<0.001) with no major change 100 and 150m downwind. No droplets were collected 200m downwind.

The difference in VMD between the two sprayers decreased from 2.5

-fold to 1.5 -fold (hydraulic > Ulvamast) with increase in distance downwind.

Less variation occurred in the NMD of droplets from both sprayers,

although the NMD of the hydraulic spray decreased significantly 20m

(P<0.001) and 150m (PC0.001) downwind (Figure 10) and the NMD 50m from the

Ulvamast spray was significantly higher than the values at preceding

sampling-points (P<0.001, PC0.05 and PC0.001 for the comparisons with 5m,

10m and 20m samples respectively) (Figure 10). The mean NMD subsequently

declined at 75m (P<0.005) and 150m (P<0.001).

The NMD of droplets produced conventionally was significantly higher

than the ULV spray 5m (P<0.001) and 10m (PC0.001) but the NMD was higher

in samples collected 50m downwind (P<0.05).

79 IUE9 h vlm mda daee,VDo rpes collected droplets of VMD diameter, median volume The 9 FIGURE Mean NMD (um) 3 Mean VMD (um) UE 10 GURE h nme ein imtr M fdolt collected dropletsof NMD diameter, median number The onid rm h hdalc «ad ULV(°)sprays. («)and hydraulic the from downwind onid rm h hydraulic the from downwind 80 (•)and ULV (°) sprays.

Assuming a pesticide dosage of 75g a.i./ha, the theoretical amount of chemical at each sampling point was estimated from the droplet density/cm2 (area of magnesium oxide was approximately 4 cm 2 ), application rate and VMD (Table 7). The number of droplets exceeded 200/ slide up to 50m from the hydraulic spray and was not recorded so no chemical dose was calculated.

p -3 2 Table 7 Theoretical calculated dosage/cm (jug x 10 a.i./cm ).

Method of Application Di stance downwind (metres)

5 10 20 50 75 100 150

Hydraulic 0.06 0.02 0.004

Ulvamast 1.14 2.44 1.96 2.66 0.26 0.05 0.03

Table 8 Calculated amount of chemical drifting downwind expressed as the percentage of the total dosage applied.

Method of application Di stance downwind (metres)

5 10 20 50 75 100 150

Hydraulic 0.08 0.03 0.005

Ulvamast 1.52 3.25 2.61 3.55 0.35 0.07 0.04

81 Approximately twice as much chemical was collected from the ULV

spray at 10m compared with 5 m, although little significant variation in

the theoretical deposits occurred 10 - 50 m downwind (Tables 7 and 8). At

75 m downwind, the theoretical amount of chemical sampled from the ULV

spray was significantly less. At 75 - 150 m downwind, estimated levels of

chemical from the ULV spray were 2-10 times the corresponding values for

the hydraulic spray.

3.3.3 Discussion

Both sprayers produce droplets which will be liable to drift,

although the drift potential of the Ulvamast was 2.5 times that of the

hydraulic sprayer (page72).

The collection efficiency of an artificial sampling surface is

dependent upon its size, shape, surface micro-topography and position.

The density, diameter and velocity of the droplets and the velocity and

direction of the air flow are also important factors. (Johnstone et

al., 1977b; Uk, 1977; Ekblad, 1978). Droplets are more likely to be

deflected around an obstacle when they are small or the obstacle is large

or the air speed low (Johnstone, 1974). The magnesium oxide technique is

known to be suitable for sampling droplets in the size range 10 - 200 jjm

(EPPO, 1982), although droplets less than 30 jum in diameter have

insufficient velocity to impact and droplets below approximately 100 ;jm may bounce unless they impinge at velocities greater than their

82

' ' . ‘f t terminal velocity (Matthews, 1975). Difficulty in achieving a stable

layer of magnesium oxide.of sufficient thickness to accommodate large

droplets prevents the efficient collection of droplets > 200 jum in

diameter (May, 1950).

Larger drops (> 100 jum VMD) were collected on slides 5 - 10 m from

the hydraulic spray as they had sufficient momentum to impact. Droplets>l00xim but<250 jum in diameter can be carried away from the hydraulic nozzles but

their settling velocity is such that very few become airborne for any

great distance and they are unlikely to be collected, irrespective of the

target (Byass and Lake, 1977; Basford, 1978).

Small droplets (^100 urn in diameter) are particularly prone to drift

as they possess low sedimentation velocities and take a long time to reach

the ground (Hartley and Graham-Bryce, 1980). Thus they can be carried out

of the target area by even very light horizontal winds and their

deposition is dominated by inertial (wind-induced) impaction, especially

for droplets 4 5 0 jum in diameter (Uk, 1977; Lawson, 1979; EPPO, 1982;

Nguyen and Synmons, 1984). • For example, droplets 40 - 80 jum in diameter

and produced from the hydraulic spray were collected 20 - 150 m downwind

when given sufficient momentum by the airstream velocity to impact.

Droplets produced from the Ulvamast possess little vertical velocity

(Young, 1985) and so wind and gravity are used to transport the spray

droplets to the target. The impaction of droplets 40 -50 jum VMD 5 - 20 m

downwind was probably facilitated by the wind having sufficient strength

83 to impart enough momentum to the droplets so that they were able to leave the airstream flowing around the targets and impact (Little, 1979).

Impaction is also favoured by the increased wind as it reduces the thickness of the boundary layer and increases turbulence around objects

(Little, 1979).

Wind strength is an important factor in determining the potential distance that a spray droplet will travel downwind (Johnstone et al.,

1977a), and may account for the detection of droplets with a VMD of 77 jum at 50 m downwind. For example in a wind of just 7 km/h, droplets of 100 jum and 50 Jum emitted one metre above the crop without any initial downward momentum would theoretically travel 7.4 and 24.4 m downwind respectively before being collected (Johnstone, 1974). Thus, in the wind velocities recorded of 15.5 km/h (the limit for Ulvamast spraying is 19 km/h), droplets in this size range are likely to travel considerable distances.

The temperature 1 - 4 m above the crop showed little change although wind velocity increased with height (Table 6) and in these cool, cloudy and windy conditions (tending to "neutral stability"), nearly all turbulence is likely to be caused by friction determined by the topography of the underlying surface as surface heating or cooling is probably negligible (Elliott and Wilson, 1983). The effect of evaporation is probably minimal, but the size of the water-based droplets exposed to the wind and turbulence will be reduced (page 42 ).

Differences in nozzles and operating conditions limit comparisons

84 with other drift measurements. Byass and Lake (1977) suggested that deposits 200 m downwind from a hydraulic spray were 0.1 - 0.03 per cent of the applied dosage, depending on the wind speeds, whereas the value derived here was 0.005 per cent at 150 m (Table 8). Minute droplets may have diffused beyond the 150 m sampling-point but magnesium oxide slides were not efficient at collecting these droplets.

85 Chapter 4

SPRAY DEPOSIT ASSESSMENTS

4.1 Introducti on

Substrates used to collect spray drifting downwind include Mylar acetate sheets (e.g. Yates et al., 1978), glass plates (e.g. Ware et al., 1969), aluminium foil sheets (e.g. Yuill and Secrest, 1966; Ware et al., 1975; Ware, Buck and Estesen, 1984), filter papers (e.g. Brazzel et al ., 1968), narrow polyethylene tubing (Lloyd and Bell, 1982), nylon cords (Johnstone et al., 1982), absorbent cotton piping or tape (e.g.

Byass and Lake, 1977; Nguyen and Symmons, 1984) and vertical plastic rods

(e.g. Nordby and Skuterud, 1975).

Many different tracer materials and techniques have been used to assess spray deposits quantitatively. Preliminary information was obtained by adding a suitable coloured dye to the spray liquids, which were recovered by washing the collecting-surface and measuring the amount of dye with a colorimeter (e.g. Yates and Akes.son, 1964). The dye used must be soluble and light-fast (Yuill and Secrest, 1966). Targets are often artificial as leaf washings may introduce substances which absorb light in the wavelength of the material being analysed (EPPO, 1982). The simultaneous use of different dyes possessing maximum optical densities at widely separated wavelengths has been demonstrated (Johnstone, 1977b). The

86 sensitivity of this technique varies from 10 - 100 ppm depending on the dye chosen (EPPO, 1982), and the speed of analysis has been estimated at

6 min/sample (Yuill and Secrest, 1966).

Conventional dyes were superseded by fluorescent materials which have been used as tracers since 1955 (Sharp, 1974). The measurement of spray deposits by fluorescence is widely reported in the literature (e.g.

Byass, 1969; Himel, 1973; Uk, 1977; Bryant et al., 1984), and can be 200 times more sensitive than the colorimetric measurement of coloured dyes at the same concentrations (Sharp, 1974). The detection limit is dependent _2 upon the fluorochrane used, for example, a fluorimeter can measure 10 >ug of the pigment Saturn Yellow (Byass, 1969; Sharp, 1974). The background fluorescence from chlorophyll and other plant constituents limits

detection from the plant surfaces to 5 or 10 times the dose for inert surfaces (Byass and Lake, 1977). The effect of the 'wash liquid', its temperature and pH should also be considered (EPPO, 1982), and there is the possibility of photolytic decay of the fluorescent dye (Maybank et al., 1978; Neisess, 1978). Fluorimetric analysis enables 25 measurements per hour (Sharp, 1974).

One of the most ideal and accurate methods of assessing the amount of spray deposit or drift is by direct analysis of the pesticide itself.

Gas-liquid chromatography offers a high degree of sensitivity, even at nanogram levels (EPPO, 1982), and is extensively used (e.g. Ware et al., 1975; Yates et al., 1978; Sundaram and Sundaram, 1982). However, the high cost of solvents and labour-intensive extraction techniques limit

87 its usefulness (Ambrus, 1978; Roberts, 1978). High pressure liquid chromatography is less sensitive and has similar drawbacks, but it enables the analysis of chemicals which are heat-labile or of very low volatility

(Roberts, 1978; EPPO, 1982; Nguyen and Symmons, 1984). Labelled pesticides (e.g. 2,4-D-l14 C) also require expensive solvent extraction, although spray drift deposits have been measured by scintillation spectrometry (Grover et al., 1972).

The use of metallic salts as tracers depends upon atomic absorption spectrophotometry (Akesson and Cowden, 1978). Although metallic salts have high detection sensitivities (e.g. strontium chloride, 2 x 10"4 jug), great care is required when handling the collecting-surfaces to avoid contamination. The wavelength of the light emission from the metallic anion can easily be confused with extraneous materials in the sample

(Akesson and Cowden, 1978). Artificial targets are the most appropriate substrates for sampling spray deposits, although recovery studies frcm foliage have been successful. The technique is restricted to aqueous sprays as the tracers are salts, and the possible phytotoxicity of certain tracers must be considered (EPPO, 1982).

Enzymatic assay has been used in the detection of organophosphorus compounds (Uk, 1977), and is valuable for the measurement of trace amounts of pesticides difficult to detect by chemical means. This method of analysis enables 30 samples per hour to be measured.

The extent of drift of herbicides can also be estimated by the

88 assessment of damage to sensitive plants (Nordby and Skuterud, 1975; Byass

and Lake, 1977; Yates e t a l ., 1978).

Neutron activation analysis was introduced to pesticide research

during the 1960's (Wilkes and Brusse, 1963). Samples are first bombarded

with neutrons and the induced radioactivity, which is characteristic of

the element in the pesticide or tracer, is subsequently measured. Several

different tracers have been used, including manganese sulphate (Wilkes and

Brusse, 1963), and europium (Takenaga, 1972). This analytical technique was also used to determine aluminium levels in suspension particles

(Smith et al., 1982). The long half-lives of the isotope europium (Eu)

and of manganese (9.2 h and 2.58 h respectively, Dams, 1981) precluded

their use. In the following trial, the rare earth, dysprosium ( 164Dy), was selected as a tracer to measure spray deposits on artificial and biological targets, particularly downwind from plots of winter wheat

treated conventionally and at ultra low volume.

When irradiated, 164Dy becomes activated to 165mDy, a shortlived radionuclide with a half-life of 1.26 min (Dams, 1981). The brief time required for the irradiation and counting of each sample reduces the cost of analysis and enables 25 - 30 samples to be analysed per hour. This technique is extremely sensitive due to the ability of dysprosium to absorb neutrons and beccme radioactive (neutron activation cross-section of 2100 barns) (Browne, Dairiki and Doebler, 1978). The low cost of dysprosium chloride (£l0/25g) minimised expenditure on tracer materials.

89 4.2 Materials and methods

4.2.1 Field Trial

The experimental site consisted of a 48.5 ha field of winter wheat

(cv. 'Bounty', growth stage 87 i.e. hard dough, (Tottman and Makepeace,

1979), on Lockinge Farm Estate, Oxfordshire. The southern section of the field was divided into three experimental 'blocks', separated by a 65 m untreated strip and the three plots (72 x 50 m), 25 m apart, comprising each block, were assigned treatments at random (Figure 11).

Plot numbers 1, 6 and 8 were treated with a conventional tractor-mounted hydraulic sprayer fitted with Chafer green hollow cone nozzles working at a pressure of 260 kPa and driven at 8 km/h to give an application of 215 1/ha. Each replicate plot was treated with 10 per cent permethrin (Ambush e.c., 0.375 g a.i./l) at dosage rate of 75 g a.i./ha.

Plot numbers 3, 5 and 7 were sprayed at ultra-low volume using the

Ulvamast Mk2. The spinning discs were operated at 12 V (7000-7500 rpm) and fed with 475ml/min to give an application rate of 2.5 l/ha at lOkm/h.

The spray tank was modified to enable small volumes of liquid to be fed to the atomiser at a constant pressure of 117 kPa. The extendable mast was adjusted to approximately 2m above the crop to give a suitable swath in the prevailing wind which gusted up to 24 km/h. 10 per cent permethrin

(Ambush e.c. 30 g a.i./l) was applied at a dosage rate of 75 g a.i./ha.

The spray was released as the tractor was driven along six successive

90 tram-lines at right angles to the prevailing wind direction. The distance between each track was 10m. The ensuing series of overlapping swaths achieved the correct dosage as the tractor-mounted sprayer moved upwind across each plot (Figure 12).

Plot numbers 2, 4 and 9 were left untreated as controls.

Dysprosium (Dy) was incorporated into the spray liquids of the conventional and ultra-low volume application equipment at a concentration of 1.3 g dysprosium chioride/1 (0.56 g Dy/1). To ensure complete solubility, dysprosium chloride was dissolved in a minimum volume of concentrated hydrochloric acid before dilution in water.

Wind velocity and direction were recorded throughout the sampling period using a wind vane and cup anemometer at 0.65 m above the crop, but due to failure of this equipment, the readings were supplemented with meteorological data from RAF Benson and AFRC Letcombe, both having weather stations close to the field site (Figures 13 and 14). The average wind velocity was 17.6 km/h and the ambient air temperature at the time of the spray application was 17.5°C. The prevailing wind direction was north - north-east and only 4.7 hours of sunshine were recorded. No rain fell six days before and seven days after the spray date.

Five canes, each 2 m apart, were placed within the plots and 10, 30 and 100 m downwind (Figure 11). Spray was collected on horizontal filter paper discs (Whatman No 7), 7 cm in diameter, which were attached to each

91

FIGURE 12 Field trial layout indicating the overlapping swaths (Ulvamast) and the location of the sampling points.

winter wheat wind direction ------> x sampling points

< ------overlapping swaths

X XX X

< ------3 0 ------>

< ------72*------> < ------1 0 0 ------>

Distance within (* ) or outside sprayed plots (m ) cane at 0, 0.45 and 0.75 m (crop height) above the ground. After treatment, filter papers were removed with the minimum of handling and stored individually between aluminium foil discs in petri dishes in a deep-freeze. Ten plants were harvested from each sampling-station and placed in polythene bags which were heat-sealed and stored in a deep-freeze.

4.2.2 Irradiation and counting

4.2.2.1 Filter papers

A dysprosium standard solution (10 jug Dy/ml) was prepared by dissolving a known amount of dysprosium chloride in a minimum volume of concentrated hydrochloric acid and making up the required volume with water. Standards of 1 jug dysprosium were prepared by spiking 100 jul of dysprosium chloride solution on to filter papers (Whatman No 1) which were allowed to dry before folding with tweezers and placing in specimen tubes

(type 3A). A blank correction was essential as filter papers were found to contain a mean dysprosium level of 5.33 x 10"4 - 7.39 x 10"5 jug/cm2 .

The samples were also folded into specimen tubes and were irradiated, with the standards and blanks, for one minute in the Cyclic Activation

System (CAS) of the Consort reactor (maximum power 100 kW) at the Reactor

Centre, Imperial College at Silwood Park, in a thermal flux of 1.29 x 1012 neutrons/ cm2 per second. The decay time and counting time were 1 second and 1 minute respectively. The irradiated samples were counted on a

Princeton Gamma Tech Ge (Li) Semiconductor Detector, nominal active volume

94 Relative humidity (%) -n Wind velocity (Km /h) temperature. and velocity wind hourly Mean 13 FIGURE GR 14 IGURE en ory eaie humidity. relative hourly Mean Time of day day of Time 95 (hour) 30 cm^ , with a detection efficiency of 4.9 per cent and a resolution of

1.69 keV at 1.33 MeV. Analysis was carried out using the ND6600

Multichannel Analysis (Nuclear Data Inc.) and associated computer programmes to determine the concentration of dysprosium in the samples.

The high activity of dysprosium on filter papers collecting spray

from conventional hydraulic treatments saturated the counting capacity of

the CAS system. To enable approximate values to be determined for these

samples, a number of dilutions were made. A dysprosium standard (1 jug) was used as an internal monitor for the recovery of dysprosium in the

samples by spiking each filter paper sample from the field with 125jul of

dysprosium chloride solution (8 jug Dy/ml). The filter papers were allowed

to dry before each was immersed in 100 ml of distilled water. Standards

and blanks were also soaked. Seventeen hours later, each filter paper was

removed and discarded, and the remaining solutions mixed thoroughly.

Aliquots of 50 jul were spiked on to fresh filter papers which were allowed

to dry before being placed into specimen tubes ready for irradiation.

4.2.2.2 Plant material

Individual wheat plants were divided into the ear, flag leaf and

remaining stem and leaves, and freeze-dried for 40 h. The awns were

carefully removed from each glume and ground for 40 s at high speed using

a Waring Blender. Replicate samples (each 160 mg) of the macerated tissue

was placed in CAS specimen tubes. The 50 ml container was cleaned between

each "grinding" with a small amount of 'Lipsol' liquid concentrate and

96 water, rinsed in hot water and dried, and finally rinsed in acetone.

The weighed flag leaves were ground in the same way and each leaf

sample placed in a CAS specimen tube for irradiation. The blender was

sterilised between each sample as described above. Irradiation and

counting procedures did not differ from those described earlier for

filter paper targets.

Since the activity of sections of the stems was below the detection

limit for dried material, it was necessary to concentrate the tissue using

an ashing technique. The samples were ground for 30 s, and put in a

muffle furnace pre-heated to 230°C for 16 h. The whole stem could then be

irradiated in a single specimen tube. The ashed samples were irradiated

under cadmium to reduce the high background produced by the concentration

of the dried material. This technique eliminates the thermal neutrons

usually used in standard irradiation and produces a neutron spectrum of

epithermal and fast (high energy) neutrons which reduce the amount of

activity from interfering elements such as sodium and chlorine.

Standards were prepared by mixing 1 g of ground stem or ear with 5 ml of dysprosium chloride solution (ljug Dy/ml), and the paste was

freeze-dried, homogenised and 200 mg removed for irradiation in a CAS tube. The ears and stems of plants harvested from the field prior to spray application were also irradiated as control 'blanks'.

97 4.2.3 Statistical analysis

The data from the filter papers and plant material were transformed using the mathematical function l o g ^ ( x + 1.0) and a'Genstat'programme was used to perform ANOVA on the transformed data.

4.3 Results

4.3.1 Filter papers

The detection limit of the neutron activation technique is defined by assuming a detectable peak area of twice the standard deviation of the background area under the 108.2 keV peak of 1®5 m Dy (Minski, M. pers. canm.). The dysprosium peak can be confirmed from two other peaks characteristic of Dy at 361.7 keV and 515.5 keV (Browne et al., 1978).

This detection limit, specific to a filter paper matrix, was found to be

1.62 x 10‘^jjg Dy.

The difference between the treatment means was highly significant

(P<0.001). The distance means differed significantly at P<0.001 and the overall variation between the mean values 0, 0.45 and 0.75 m above the ground was significant (P<0.001). The following interactions were significant: treatment and distance (PC0.001); treatment and sampling height (P<0.05). The amount of dysprosium collected within the conventional hydraulic and ULV sprays was significantly higher than

98 Table 9 The deposits of dysprosium on filter papers at 36m inside the

treated plots.

Treatment Sample height above the ground Dysprosium deposit

(m) (jug x 10“3/ cm2)

Mean S.E.

Conventional 0.75 830.0 +170.0 hydraulic 0.45 710.0 +150.0

0 850.0 +140.0

Ultra-low 0.75 2.19 +0.77 volume 0.45 3.48 +2.73

0 7.82 +3.28

Control 0.75 0.31 +0.05

0.45 0.41 +0.12

0 5.81 +4.72

99 The mean deposits of dysprosium (jug x 10'3/cm 2 ) on filter papers downwind from the hydraulic ffl and ULV U sprays and untreated □ plots.

FIGURE 15 0.75 m above the ground

FIGURE 17 Ground level

04

CO t o

O) R

(0 o a a> ■o >* a deposits 10 - 100 m downwind (P<0.001 and P<0.05 for all comparisons with the hydraulic and ULV sprays respectively) (Table 12, Figures 15 to 17).

No significant variation occurred between deposits outside the treated plots.

In general, deposits within and up to 100 m downwind from the untreated plots were not significantly different, although more dysprosium was collected at crop height 10 m downwind compared with deposits at other sampling-points (PC0.05 for all comparisons) and mid-crop deposits were significantly higher at 10 m than at 30 m and 100m downwind (P<0.005 for all comparisons).

Inside treated plots

(i) Samplina-height differences

The dysprosium deposits on filter papers 0 - 0.75 m above the ground

36m within the hydraulic spray were not significantly different (Table 9).

More dysprosium was collected on the ground within the ULV spray compared with deposits at crop height (PC0.05). The levels of dysprosium at the other sampling-heights were not significantly different (Table 9).

Deposits on the ground inside the untreated plots were approximately 14 and 19 times greater than levels at 0.45 m (P<0.005) and 0.75 m (P<0.005)

(Table 9).

101 (ii) Treatment differences

The amount of dysprosium collected within the hydraulic spray at sampling heights of 0.75 m and 0.45 m was significantly higher than deposits at the corresponding heights at 36 m inside the ULV and untreated plots (P<0.001 for all comparisons) (Figures 15 and 16). Deposits collected on the ground were 100 - 145 times higher within the hydraulic spray than deposits inside the ULV spray (P<0.001) (Figure 17). More dysprosium was collected at crop (P<0.05) and mid-crop (PC0.05) heights inside the ULV spray than within untreated plots (Figures 15 and 16), but the ground deposits were not significantly different (Figure 17).

10 m downwind

(i) Sampling height differences

The amount of dysprosium deposited 0 - 0.75 m above the ground downwind from the hydraulic spray and untreated plots were not significantly different (Figures 15 to 17), although outside the ULV spray more dysprosium was found at 0 m than at 0.75 m (P<0.05) (Figures 15 and

17).

(ii) Treatment differences

The amount of dysprosium collected at crop height downwind from the hydraulic spray was significantly higher than deposits outside the ULV

102 (P<0.001) and untreated (P<0.05) plots (Figure 15). More dysprosium was sampled outside the control plots compared with the ULV spray (P<0.05)

(Figure 15).

The mid-crop deposits downwind from the unsprayed plots were not significantly different from the amount collected downwind from the hydraulic and ULV sprays (Figure 16). However, three times more dysprosium was sampled from the hydraulic than the ULV spray (PC0.05)

(Figure 16). The deposits of dysprosium on the ground outside all treatments were not significantly different (Figure 17).

30 m downwind

(i) Sampling height differences

The deposits of dysprosium at each sampling height outside the

hydraulic spray were not significantly different. Downwind from the ULV

spray, deposits on the ground were significantly higher than at 0.45 m

(P<0.05) and at 0.75 m (P<0.05). The deposit of dysprosium on the ground

outside the untreated plots was 4 - 5 times higher than the amount at

0.45 m (P<0.05) and 0.75 m (PC0.05) (Figures 15 to 17).

(ii) Treatment differences

Dysprosium deposits at all sampling heights were significantly

higher outside the hydraulic spray compared with samples from outside the

103 ULV spray (crop height, P<0.01; mid-crop, PC0.05; ground, P<0.05) and untreated plots (crop height, P<0.01; mid-crop, PC0.05; ground, P<0.05)

(Figures 15 to 17). No significant variation occurred between deposits downwind from the ULV spray and untreated plots, irrespective of the sampling height. .

100 m downwind

(i) Sampling height differences

The amount of dysprosium collected on the ground was significantly higher than deposits at 0.45 m (P<0.05) and 0.75 m (PC0.05) downwind frcm all treatments (Figures 15 to 17).

(ii) Treatment differences

The amount of dysprosium at all sampling heights and downwind from each treatment did not differ significantly, apart from ground deposits which were higher outside the hydraulic spray than downwind from the untreated plots (P<0.05) (Figures 17 to 19).

104 Table 10 Volume of spray deposited on filter paper targets

(ml x 10"6/ c m 2 )

Treatment Sample height Distance downwind from edge of sprayed plot (m) above ground (m) In plot 10 30 100

Hydraulic 0.75 1480 2.72 2.21 1.23 0.45 1260 1.96 2.21 1.75 0 1510 3.18 3.54 5.66

Total 4250 7.86 7.96 8.64

LJlvamast 0.75 3.90 0.39 0.26 0.41 0.45 6.19 0.52 0.34 0.50 0 13.90 1.87 1.19 3.08

Total 23.99 2.78 1.79 3.99

Table 11 Drift deposits as a percentage of the total spray volume per cm^ within the treated plots.

Treatment In plot Distance downwind from edge of sprayed plot (m)

10 30 100

Hydraulic 100 0.18 0.19 0.20

Ulvamast 100 11.60 7.46 16.62

105 Volume calculations

One litre of spray liquid contained 0.56 g Dy, so 1.78 x 10'^ ml of spray contained 1 jug Dy. Assuming the application rates given on page 90 , P o p the expected volume of spray per cm would be 2.15 x 10 ml/cm and 2.5 x 10“5ml/cm^ for the hydraulic and ULV sprays respectively. The volume of spray deposited is shown in Table 10 and is expressed as a percentage of the total spray volume in Table 11.

Calculated deposits of perroethrin

The amount of dysprosium was converted into the amount of active ingredient (permethrin), assuming the same dosage per hectare (75 g a.i./ha) was applied for both methods of spray application, and therefore

1 ja g of dysprosium was equivalent to 0.67 jug and 53.5 jug of permethrin for the conventional and ULV treatments respectively (Table 12).

The amounts of dysprosium within the conventional treatments were equivalent to approximately 0.6 jug permethrin/cm2 , while the calculated amount of active ingredient present within the ULV treatments varied fran approximately 0.1 to 0.4 jug permethrin/ cm2 with decrease in sampling height. Conversely, at 0.75 m and 0.45 m above the ground, a 10 - 20 fold difference was apparent between the theoretical amounts of permethrin at the sampling distances downwind from both types of treatment. The

insecticide deposit on the ground was approximately 47 times greater at 10

106 and 100 m downwind from the ULV treatment than the levels outside the

conventional treatment. This difference declined to approximately 28-fold

at 30 m from the sprayed plots.

At the 100 m sampling-distance, the trace amounts of dysprosium on

the ground represented approximately 0.002 jug and 0.1 jug permethrin /cm2

downwind from the conventional hydraulic and ULV treatments respectively.

p p Table 12 Calculated mean deposits of permethrin (jug x 10 /cm ) based on actual deposits of dysprosium (Figures 15 to 17; Table 9) and assuming the same mass application rate.

Treatment Sample height Distance downwind from edge of sprayed plot(m) above ground (m) In plot 10 30 100

Hydraulic 0.75 55,.0 + 11..0 0..10 + 0..03 0..08 + 0,.05 0..05 + 0..03 0.45 48.,0 + 10..0 0..07 + 0..02 0..08 + 0..06 0..07 + 0..04 0 57..0 + 10..0 0..12 + 0..03 0..13 + 0..06 0..21 + 0..09

Ulvamast 0.75 12.,0 + 3..0 1..30 + 0..50 0..80 + 0..30 1..00 + 0.,40 0.45 20.,0 + 14..0 1..60 + 0..60 1..10 -f 0..40 1..60 + 0.,60 0 44.,0 + 0..24 5..70 + 2.,60 3..70 + 0..70 9..70 + 0.,60

4.3.2 Plant material

The difference between the treatment means was significant at P<0.01, * but the overall means for each part of the plant (glume, flag-leaf, stem and lower leaves) were not significantly different. No dysprosium was collected on tillers downwind apart from 10 m outside the hydraulic spray where deposits on glumes were 1.08 x 10"® + 9.90 x 10"4 mg/g plant material.

107 Glumes

The glumes collected 140 and 364 times more dysprosium within the hydraulic spray than inside the ULV spray (P<0.001) and untreated

(P<0.001) plots respectively (Table 13). More dysprosium was collected on glumes inside the ULV spray than on the untreated plots (PC0.05).

Table 13 Deposits of dysprosium (mg/g plant material) within the treated plots. (Mean values with standard errors)

Treatment Part of plant

Ear Flag Stem

Hydraulic Mean 1.17 1.89 13.98 2 r—1 o S.E. + 2.02 X + 0.09 + 0.64

ULV Mean 8.41 X 10‘3 1.61 x 10'2 6.0 x 10‘2 S.E + 1.01 X 10-3 + 1.0 x 10'2 + 6.0 x 10-2

Untreated Mean 3.21 X 10"3 4.73 x 10~3 7.0 x 101 S.E. + 3.21 X 10-3 + 4.60 x 10’3 + 4.0 x 10"2

Flag leaves

On flag leaves, 117 times more dysprosium was deposited within the hydraulic spray than inside the ULV spray (P<0.001) and levels were 400 times higher than deposits within the untreated plots (P<0.001). The difference between the amount of dysprosium within the ULV and untreated plots was significant at P<0.05 (Table 13).

108 Stem and lower leaves

A 200-fold difference was found between the deposits of dysprosium

within the the hydraulic spray and the amount on stems inside the ULV

spray (P<0.001) and untreated plots (P<0.001). Deposits inside the latter

two treatments were not significantly different.

Calculated deposits of permethrin

The amount of insecticide deposited was calculated from the deposits of dysprosium, assuming the same dosage rate (75g a.i./ha) for both

sprayers (Fi gure 18).

The theoretical amount of permethrin on the glumes and flag-leaves were similar irrespective of the method of insecticide application, but the level of permethrin was 3 times higher on the stem and lower leaves of plants treated conventionally than those sprayed at ULV.

The mean weight of the flag-leaves samples was 222.5 mg. The area of each flag leaf was determined using the Optomax Image Analyser and the mean area was calculated as 27.94 cm2. From these values, the amount of dysprosium/cm2 and the equivalent levels of active ingredient/cm2 were derived (Table 14).

109 FIGURE 18 Calculated deposits of permethrin on plants(m g /g ) based on actual deposits of dysprosium (Table 9) and assuming the same dose rate for hydraulic IP and ULV H3 sprays.

110 Table 14 Deposits of dysprosium and calculated deposits of permethrin (jjg/cm2f lag-leaf)

Treatment Sampling Dysprosium Theoretical permethrin surface deposit deposit (jug/cm2) (jug/cm2)

Hydraulic Filter paper 0.83 0.55 Flag leaf 15.05 10.08

ULV Filter paper 2.19 x 10'3 0.12 Flag leaf 0.13 6.95

Untreated Filter paper 3.10 x 10"4 _ Flag leaf 0.04

Approximately 18 times more dysprosium was collected on the flag-leaves than on filter papers at crop height within the hydraulic spray (Table 14). The difference increased to approximately 60 - fold within the ULV spray treatment and 129 - fold on samples inside the untreated plots (Table 14).

Spray distribution

The highest spray deposits were on the stem and lower leaves of the plants, irrespective of the method of application, although a greater proportion of spray was collected by the ears and flag-leaves when the insecticide was applied at ULV (Figures 19 and 20).

Ill Distribution of dysprosium on the tillers (as a percentage of the total amount of dysprosium detected).

FIGURE 19 Hydraulic spray

FIGURE 20 ULV spray

FIGURE 21 Untreated

112 The spray drifting on to the control plots deposited mainly on the

flag-leaves and stams/lower leaves, while trace amounts were detected on

the ears (Figure 21).

4.4 Discussion

Strong winds increase drift potential (e.g. Johnstone et al.,

1977a; Smith, Harris and Butler, 1981; Sharp, 1984) and, although

droplets below 100jum in diameter are liable to drift (e.g. Maybank and

Yoshida, 1969; Hartley and Graham-Bryce, 1980), Cowan (1983) considered

that all droplets less than 200 jjm in diameter are likely to drift in wind

speeds up to 24 km/h. As the wind speed increases, the stability of the

atmosphere increases and nearly all turbulence tends to be created by the

effects of surface friction (Pasquill, 1961; Johnstone et al., 1977a).

Droplets tend to drift further with increased turbulence (Akesson and

Yates, 1964; Elliott and Wilson, 1983). Considerable drift was

anticipated during the trial, especially as in an earlier trial droplets

from both sprayers were found on vertical glass slides up to 150 m downwind in similar meteorological conditions (Chapter 3, section 3.3).

4.4.1 Artificial targets (Filter papers)

The amounts of dysprosium detected refer only to the spray which sedimented on to the horizontal surfaces, chosen partly because of limitations imposed by handling and cost. Most of the spray would be

113 expected to be found at ground level as the collection efficiency of the

filter papers would be least affected by wind movement and turbulence

(Byass and Lake, 1977; Uk and Courshee, 1982; Nguyen and Symmons, 1984).

Even droplets below 40jum in diameter tend to sediment in close canopies

in which the wind velocity decreases (Bache and Uk, 1975).

Higher ground deposits would be expected within the hydraulic spray

as the nozzles impart downward velocity to the spray droplets (Western et al., 1985). This can lead to droplet reflection and/or shatter on impact with the leaves of the upper canopy and increased penetration and loss of spray to the ground (Bryant et al., 1984; Young, 1985). Retention of

large droplets with high velocities is poor on the waxy, steeply-sloping surfaces of cereal leaves and deposits are consequently higher within the canopy (Taylor, 1985).

Droplets were released frcm the spinning-discs 2 m above the crop and the proportion of droplets which are entrained by the wind to become airborne will be higher than droplets released at 0.5 m and evaporative loss between release and impaction increased (Johnstone et al., 1974;

Grover et al., 1978). The droplets possess little vertical velocity, relying on gravity to settle out, and canopy penetration was probably facilitated by turbulence and wind movement over the top of the crop

(Little, 1979).

114 4.4.2 Natural targets (wheat)

Inertial (wind-induced) collection becomes increasingly evident for

droplets below 100 -um diameter and is the dominant deposition mechanism

for droplets 50jum (EPPO, 1982). Strong winds favour impaction on to

vertical targets and can reduce long-distance contamination (Lloyd and

Bell, 1982). However, spray was only detected on ears 10 m downwind from

the hydraulic spray and NAA may not have been sensitive enough to detect

very low levels of spray on plant material, or droplets moving outside the

target area were too small to impinge on the plants and were deflected

around them in the airstream.

The collection efficiency of objects increases with decrease in diameter and stems and lower leaves may collect more spray through a

combination of sedimentation and impaction processes (Table 3). Spray

produced at high volume may "run-off" the plants and tend to concentrate

in the lower canopy, accounting for the higher levels (Table 13).

4.4.3 Artificial vs. natural taraets

The filter papers only give an estimate of the amount of spray arriving in the vicinity of the natural target and cannot imitate the movement, size and shape of the wheat crop. The horizontal filter paper discs were mainly sampling droplets settling out under gravity, while the plants presented vertical targets, collecting droplets predominantly by impaction or interception mechanisms and deposit densities will therefore

115 differ considerably (Table 17). Leaf venation, hairs and other minute

processes affect turbulence, and thus the deposition of small droplets, in

a complex way, and deposit density is strongly related to the crop form,

stage of development and foliage density (Uk, 1977; Little, 1979; Uk and

Courshee, 1982).

Lawson (1983), using an eddy diffusion model, predicted that deposits

96 m downwind from a hydraulic spray would be approximately 0.07 per cent

of the total applied dose (wind velocity 18 km/h) compared with a value of

approximately 0.2 per cent at 100 m downwind in a similar wind velocity (Table 11).

Lloyd and Bell (1982) reported sampling on filter papers at 80 - 120 m downwind and estimated that 0.1 - 0.7 ml of ULV spray and 0.1 - 0.8 ml of hydraulic spray was airborne and passing through an imaginary frame 11 x 1 m in area. Assuming that the sprays contained 0.56 g Dy/1, these values represent 0.5 - 3.56 x 10"® and 0.5 - 4 x 10’®jug Dy/cm2 respectively, which are similar to the data in Figures 15 to 17 at 100 downwi nd.

Deposits 7 - 10 m downwind were also comparable with the amounts of dysprosium collected at 10m (0.5 - 5 x 10~4 and 0.5 - 4.6 x 10"® jug

Dy/cm2 for the ULV and hydraulic sprays respectively; Lloyd and Bell,

1982).

116 P A R T T W O

SPRAYING IN RELATION TO THE CEREAL APHID PROBLEM

117 Chapter 5

CEREAL APHIDS AND THEIR NATURAL ENEMIES

5.1 Introduction

The biology and pest status of cereal aphids in the United Kingdom have been widely covered in the literature and extensively reviewed by

Vickerman and Wratten (1979) and Carter et al. (1980).

5.2 Cereal aphid species

Five species of aphid are commonly found on cereals in the U.K. between April and September, namely: the grain aphid (S. avenae F. ), the rose-grain aphid (Metopolophium dirhodum Wlk.), the bird-cherry aphid (Rhopalosiphum padi L.), the blackberry aphid (S. fragariae

Wlk.) and the grass aphid (M. festucae Theob.). The cereal-leaf aphid

(M. maidis Fitch.) has also been recorded occasionally on barley leaves.

The apple-grass aphid (R. insertum Wlk.) attacks the roots of cereals and may assume importance in drought conditions (George and Plumb, 1982).

In European countries the reduction in yields is mainly caused by

S . avenae and M. dirhodum, although R. padi can be important, in

118 particular as a vector of BYDV on autumn-sown cereals. All three species

can overwinter viviparously on cereals and grasses (Dean, 1974a; George,

1974) and also as eggs on hosts characteristic of each species. While R.

padi i s speci fi c to the bi rd-cherry (Prunus padus L.), M. di rbodum

returns to lay eggs on its primary host, Rosa spp. in October-November

and S .avenae, being monoecious on Graminae, oviposits on grasses and

stubble (Kolbe, 1969; George and Plumb, 1982). This aphid species can overwinter in areas close to the fields at risk from infestation, especially with the increase in the area of winter cereals grown.

5.3 Feeding-sites and damage

The feeding-site preferences of S. avenae, M. dirhodum and R. padi differ considerably and are important when considering the type and amount of damage caused by the aphids and the efficacy of control measures. Yield losses result from direct feeding or from viral infection spread by the aphids.

5.3.1 Direct damage

S. avenae probably causes the greatest crop loss on wheat as it colonises the upper leaves, moves to the ear and feeds at the base of the glumes as well as on the spindles (Dean, 1974b; Kolbe, 1969). On spring barley this species is found mainly on the leaves, with only low numbers reaching the ears (George, 1974).

119 Early attacks during flowering and before grain formation cause blindness or shrunken kernels, decreasing the number of grains or yield per ear respectively and yield losses of 20 - 25 per cent have been recorded (Kolbe, 1969; McLean, Carter and Watt, 1977; George and

Plumb, 1982). A reduction in the damage caused by S . avenae as the growth stage increases was reported by Lee et al., (1981).

Grain weight has been related to photosythesis mainly in the flag-leaf and ear (Dean, 1974b; Wratten, 1975; Wratten and Redhead, 1976) and S. avenae has been implicated in the reduction of grain size and associated changes in grain protein and decreases in grain nitrogen, factors important in determining grain quality (Wratten, 1978). High levels of S. avenae on winter wheat reduced the proportion of grain which could be extracted as flour and caused darkening of the flour

(Wratten, Lee and Stevens, 1979).

At the milky-ripe stage, seepage of grain contents from feeding punctures creates a suitable medium for the development of sooty moulds

(e.g.Cladosporium spp.) which discolour and lower the milling quality of grain and reduce the photosynthetic efficiency of the plant (Dean, 1974b;

Wratten, 1978; George and Plumb, 1982). Honeydew produced by the aphids encourages the growth of sooty moulds and attracts Dipterans including wheat bulb fly (George and Plumb, 1982).

Cereal infestation with M. dirhodum can be easily overlooked by farmers as feeding is usually confined to the leaves, moving up the plant

120 as the lower leaves senesce. Sometimes almost 100 per cent of the

population reaches the flag-leaf by plant maturity (Dean, 1974b; George,

1974). Direct feeding can cause similar levels of damage as for the grain

aphid, particularly as most of the carbohydrate stored in grain is derived

from the flag-leaf, ear, and, to a lesser extent, the pen-ultimate leaf

(Lowe, 1974).

Economically important yield losses from M. dirhodum colonisation of wheat occur from the end of flowering onwards (Kolbe, 1969; Lowe, 1974;

Holt, Griffiths, and Wratten, 1984).

In contrast, R. padi, which is rarely a pest on cereals in the

United Kingdom, colonises the stems and lower leaves although it can still cause considerable damage (Mclean et al., 1977).

5.3.2 Virus transmission

BYDV is the most important virus affecting cereals and grasses. All cereal-feeding aphids carry BYDV (Plumb, 1978),. but in Britain virulent strains are transmitted by S. avenae or R. padi (Plumb, 1974). The virus is usually introduced into a crop during the autumn by R. padi infesting the young cereals and S . avenae is more often responsible for within-crop spread (George and Plumb, 1982). The symptoms of BYDV vary according to the crop, the disease causing red discolouration of leaves in oats with occasional stiffening and ear blasting; leaf yellowing and heavy growth stunting in barley; and leaf reddening and yellowing with

121 associated necrosis and depressions of yields in wheat (Kolbe, 1969;

George and Plumb, 1982).

Plumb (1978) reconmended a delay in drilling autumn-sown crops to

increase the interval between crops and minimise the risk of virus infection.

5.4. Factors affecting aphid populations

The rate of build-up of an aphid population 'is predominantly governed by weather conditions although the numbers of alates invading, the time of their arrival with respect to the growth stage of the crop, and the effectiveness of the natural enemy populations also influence the extent of an aphid infestation.

5.4.1 Weather

The important period for the invasion of cereals, growth and reproduction of aphids is in May and June. Cold, wet weather then results in a slow increase in the populations of aphids and their natural enemies, whereas high temperatures and low rainfall, notably in June 1975 - 1977, favoured rapid multiplication (Jones, 1972, 1979; Jones and Dean, 1975).

Reduced aphid flight at lower temperatures may limit the establishment of infestations (Carter et al., 1980).

There is little information available on the impact of rainfall on

122 aphid populations, although Smith (1981) considered rain between October

and March to be a negligible cause of mortality. However, the numbers of

M. dirhodum and S. avenae were reduced by 65 and 80 per cent

respectively following a heavy rainstorm (Dean and Wilding, 1971).

Strong winds during May and June 1973 - 1975 were thought to have

prevented alate migration into cereal crops and dislodged aphids, in

particular M. dirhodum, from the leaves (Jones, 1979). S . avenae

would be less exposed on the developing ears. A decrease in the aphid

populations during the winter was attributed to wind velocity and

gustiness; S. avenae was more susceptible than the other species feeding

lower down the plant (Smith, 1981).

5.4.2 Polyphaaous predators

The influence of polyphagous predators on cereal aphid populations was first realised by Potts and Vioverman (1974, 1975), who found a significant inverse relationship between the number of apterous cereal aphids present in different fields and the proportion of predatory arthropods. They showed that certain species of Carabidae and

Staphylinidae had fed on aphids.

Later studies, including the gut dissection of polyphagous predators, revealed aphid predation by many species (Sunderland, 1975;

Vickerman and Sunderland, 1975; Sunderland and Vickerman, 1980).

123 Ground predator exclusion work has shown strong negative

correlations between populations of Araneae, Staphylinidae and Carabidae

and the number of cereal aphids (Edwards and George, 1977; Edwards et al., 1978; Edwards, Sunderland and George, 1979; Edwards and George,

1981; Chiverton, 1982; de Clercq and Pietraszko, 1983).

Studies to date suggest that the value of non-specialist feeders lies

in their ability to persist in crops during periods of low pest density,

particularly during aphid colonisation (Carter et al., 1982; Chambers et

al., 1982).

The main groups of predatory arthropods known to feed on aphids

include Staphylinidae, Carabidae, Araneae, Dermaptera and Opiliones

(harvestmen). The predominant carabid species with the highest

percentage occurrence of aphids in their diet and/or active enough in the

season to prey on early infestations have been shown by various workers to

be Demetrias atricapillus (L.) (Potts, 1977; Shires, 1980; Sunderland

and Vickerman, 1980), Agonum dorsale (Pont.) (Pollard, 1968; Potts and

Vickerman, 1974; Dunning, Baker and Windley, 1975; Sunderland, 1975;

Edwards and George, 1977; Edwards et al., 1978; Edwards et al 1979;

Shires, 1980; Sunderland and Vickerman, 1980; Edwards and George, 1981;

Griffiths, 1982), Bembidion spp. (Potts and Vickerman, 1974; Edwards

et al., 1979), Synuchus nivalis (Panzer) (Sunderland and Vickerman,

1980).

Pterostichus melanarius (111.) P. madidus (F.) and Harpalus

124 rufipes (Degeer) have all been trapped later in the season and therefore

have less impact on the established aphid populations (Edwards et al.,

1979), although a negative correlation between the numbers of aphids and

P. melanarius has been shown by Edwards and George (1977). Edwards et al. (1978) found that the only beetle species of importance during a season of large aphid numbers was P. melanarius, depressing populations by about 20 per cent. Chan (1982) demonstrated the voracity of P. melanarius, which consumed an average number of 42 Acrythosi phon pisum in twenty-four hours. Following experiments in the laboratory and field, Loughridge and Luff (1983) concluded that H. rufipes has potential as an aphid predator, but the aphid density and temperature limits its usefulness at the time of year when predation would be of the most benefit.

A few staphylinid species are active aphid predators, in particular the adults and larvae of Tachyporus spp. (Potts and Vickerman, 1974;

Sunderland, 1975; Potts, 1977; Sunderland and Vickerman, 1980). The maximum potential consumption of first instar S. avenae by the staphylinid Philonthus cognatus (Mannerheim) was found to be about 50/day under laboratory conditions (Wratten et al., 1984).

The dermapteran Forficula auricularia (L.) is efficient at finding aphids at low densities and is an active plant climber (Vickerman and Sunderland, 1975; Shires, 1980; Sunderland and Vickerman, 1980).

Linyphiid (money) spiders are the most abundant members of the

125 Araneae in cereal fields and have been shown to feed on cereal aphids in the field and laboratory (Sunderland and Fraser, 1980; Edwards and George,

1981: Carter et al., 1982).

In general, the proportion of predators feeding on aphids increases at higher aphid densities, but this response differs between species and

F. auricularia, A. dorsale and D. atricapillus were found to feed on aphids even at low field densities of aphids (Shires, 1980; Sunderland and

Vickerman, 1980; Griffiths, 1982). Sunderland and Vickerman (1980) attributed this response to the climbing ability of the predator, although

Griffiths (1982) showed that A. dorsale rarely climbed tillers, feeding almost entirely on the ground.

The method and time of sampling influence the data on the percentage number of predators which include aphids in their diet, but the degree of synchronisation between the life-cycle of the individual species of predator and the phenologies of the different cereal aphid species are clearly important factors (Sunderland and Vickerman, 1980). The sex and stage of sexual maturity may also influence feeding efficiency

(Sunderland, 1975; Mols, 1979).

Many of the polyphagous predators are active at night, in particular

Staphylinidae, Carabidae and F. auricularia (Vickerman and Sunderland,

1975).

126 5.4.3 Aphidophagous predators

The aphid-specific predators belong to the families Coccinellidae

(Coleoptera), Syrphidae (Diptera) and Chrysopidae (Neuroptera) although

Anthocoridae (Hemiptera) may also feed on aphids (Jones, 1972; Dean,

1974c; Jones and Dean, 1975). Their role in preventing aphid outbreaks varies with locality and from year to year and they were considered to be unimportant in aphid predation by Potts and Vickerman (1974).

Aphid population development can be split into three phases

(Chambers et al., 1983); an initial rapid growth phase; a divergence phase which coincides with an increase in the number of aphid-specific predators; and a decline phase caused by predation, parasitism, disease and emigration. Chambers et al., (1983) suggested that aphidophagous species were a major factor in determining the rate of aphid increase, therefore affecting the size of the aphid population peak. In certain conditions, aphid-specific predators can reduce aphid numbers to a level where economic damage is minimal (Chambers et al., 1982).

5.4.3.1 Coccinellidae

Phenological surveys during the last decade have shown that the larvae and adults of Cocci nella septempunctata (L.), C. 11-punctata

(L. ) Propylea quatuordecimpunctata (L.) and Adalia bipunctata (L.) are probably the most important aphidophagous predators in cereals (Dean,

1974c, 1975, 1982; Jones and Dean, 1975; Potts, 1977; Chambers et al,

127 1982).

Laboratory and field data presented by Carter et al. (1980) revealed that coccinellid larvae consume more aphids than adults, although adult predation early in the season is of great importance in suppressing aphid populations. The appearance of the voracious fourth instar larvae coincides with a considerable increase in aphid consumption (Carter et al., 1980). The authors attributed a decline in predation during July to pupation, and reduced numbers of fourth instar larvae to the death of early instars coinciding with a decline in the aphid population.

5.4.3.2 Syrphidae

Unlike the Coccinellidae, only the larval stages of Syrphidae are aphid predators, the adult hover-flies feeding on nectar and pollen, an activity essential for ovary maturation and successful egg-laying

(Schneider, 1969).

The most common species found in cereal crops are Episyrphus balteatus (De Geer), Metasyrphus corollae (F.) and Syrphus ribesii

(L.) (Dean, 1974c, 1975; McLean, 1980; Chambers et al., 1982).

In general, fewer larvae of Syrphidae than of Coccinellidae are found in cereal crops, implying that their role as aphid predators is less

(Carter et al., 1980), although their numbers are easy to underestimate

(Dean, 1974c; Chambers et al., 1983).

128 Under comparable conditions of temperature, Sundby (1966) found the consumption rates of Myzus persicae (Sulzer) by larvae of S. ribesii to be greater than that of the larvae of C. septempunctata and Chrysopa carnea (Steph.).

5.4.3.3 Chrysopidae

In general, only low numbers of Chrysopidae have been found in cereal crops (Dean, 1974c; McLean, 1980). The main species frequenting cereal crops is C. carnea. Only the larvae are aphidophagous and occasional heavy attacks against aphids have been recorded (Jones, 1972;

Dean, 1982). As the larvae are highly mobile and take a shorter time to consume aphids than C. septempunctata or S. ribesii (Sundby, 1966) they should be more effective at low aphid densities (Carter et al.,

1980).

5.4.3.4 Anthocoridae

The larvae and adults of Anthorcoris nemorum (L.) also feed on aphids in cereal crops but only at densities too low to have a severe effect on the aphid population (Jones, 1972, 1979).

5.4.4 Parasites

The primary parasites belong to two families of Hymenoptera, the

129 Aphidiidae and the Aphelinidae, and the main species listed by Vickerman

and Wratten (1979) are: Aphi di u s pi ci pes (Nees), A. uzbekistanicus

(Luzhetzki), A. ervi (Haliday), A. urticae (Haliday), A. equiseti-

cola (Stary), Praon volucre (Haliday), P. gallicum (Stary),

Lysiphlebus fabarum (Marshall), Ephedrus plagiator (Nees), Tri oxys

auctus (Haliday), Monoctonus cerasi (Marshall), Diaeretiella rapae

(M'lntosh) and Aphelinus varipes (Forster).

The biology of aphid parasites has been comprehensively reviewed by

Stary (1970). High levels of parasitism have been recorded (Jones, 1972), and Jones (1976) attributed a rapid decline in aphid numbers to heavy attack by hymenopterous parasites, parasitism reaching 100 per cent in the centre of the field.

Parasites are thought more likely to synchronise with and exert control over the immigrant aphid population in cereals than are predators

(Dean, 1974c; Jones, 1979), although their rate of development can be slow compared with the aphids (Ankersmit, 1983). A positive relationship between aphid and parasitoid densities has been found (Chambers et al.,

1982; Vickerman, 1982).

Hyperparasitism of the newly-emerged parasites by species of

Pteromalidae, Ceraphronidae, Cynipidae and Encyrtidae, of which

Dendrocerus carpenteri (Curtis) is the most common (Carter et al.,

1982), can have far-reaching consequences (Jones, 1972, 1976; Dean, 1974c;

Jones and Dean, 1975). By suppressing the build-up of primary parasites

130 and therefore reducing the total number overwintering, the level of

parasitism the following year could be reduced, increasing the likelihood

of a cereal aphid outbreak (Jones, 1972). Hyperparasitism can be

extensive, for example in 1978, McLean (1980) recorded an average level of

60 per cent in cereal fields in East Anglia.

There are many other factors influencing the primary parasitoid

population, including aphid and parasite abundance during the previous

year, weather and the overwintering mortality (Carter et al., 1980;

Powell, 1983).

5.4.5 Pathogens

Three species of the genus Entomophthora, E. planchoniana, E.

aphidis and E. thaxteriana, have been recorded infecting cereal aphids

at different levels from year to year (Dean and Wilding, 1971, 1973; Jones

and Dean, 1975). Dean and Wilding (1971, 1973) concluded that in 1970 and

1971 more cereal aphids were killed by Entcmophthora spp. than by

predators and hymenopterous parasites, with infection levels of 80 and

52-67 per cent in late July 1970 for S . avenae and M. dirhodum

respectively. The potential of Entomophthora spp. as an agent for

biological control is limited by the high relative humidity required for

sporulation (Wilding, 1969), and the establishment of disease so late in the season can only be important in minimising the numbers of viruliferous alatae which can infest subsequent early autumn-sown crops. However, high

levels of infestation at this time could also result in increased inoculum

131 levels the following spring and so increase the likelihood of subsequent epizootics (Vickerman and Wratten, 1979).

5.5 Causes of pest status

The increasing importance of cereal aphids since 1968 has coincided with the increased use of fertilizers and the application of pesticides

(Tables 15 and 16), and changing cultural practices e.g. the adoption of techigues such as direct-drilling. The effects of modern farming practices on the cereal ecosystem have been studied by Potts and Vickerman

(1974) and the impact on a range of insect taxa is shown in Table 17 and

Figure 22.

5.5.1 Fertilizers

There is little information of the effects of fertilizers on cereal aphid populations, although Baranyovits (1973) suggested that the pest status of cereal aphids was aggravated by increased use of fertilizers.

An enhanced supply of nitrogen in the soil would increase host-plant vulnerability to aphid attack by producing more tender growth and extending the growing period for fresh shoots and foliage (Baranyovits,

1973).

132 Table 15 Pesticide usage on cereals (British Agrochemicals Association, 1985)

Treatments x area in 000's hectares

AREA GRCWN 1982 - 1983 3904 1983 - 1984 3979

TREATMENT WITH HERBICIDES - Total 7221 Couch/stubble 302 Wild Oat/blackgrass 2290 Broad-leaved weeds 4629

TREATMENT WITH FUNGICIDES - Total 8161 Foliar sprays 7290 Seed treatment (Mildew control) 871

TREATMENT WITH INSECTICIDES - Total 1850 Foliar sprays 1844 Granules 6

OTHER TREATMENT Growth regulators 1277

Table 16 Types of pesticides used on cereals in 1974 and 1977, and estimated quantities of active ingredient (Royal Ccmmission on Environmental Pollution, 1979)

Tonnes of Pesticide Group Spray hectares active ingredient

1974 1977 1974 1977

Insecticides:- Organochlorine 0 1000 0 <1 Organophosphorus 41000 294000 17 107 Other 5000 272000 <1 43 Seed treatments 3309000 3358000 553 480 Fungicides 616000 978000 394 588 Herbicides 4475000 4408000 8727 8026 Other pesticides 67000 188000 84 263 Total 8513000 9499000

133 Table 17 Changes in the late June density of the adults and larvae of some insect taxa in cereal crops in Wsst Sussex 1970 - 1975 (mean number/m2 ) (from Potts, 1977).

Year

1970 1971 1972 1973 1974 1975

No. of fields sampled 135 110 98 148 149 141

Polyphagous predatory Coleoptera (adults) Pisophilus atricapillus 0.56 0.98 0.80 0.63 0.55 0.18 Bembidion lampros 1.19 0.73 0.80 0.75 0.79 0.42 Aqonum dorsale 0.26 0.11 0.03 0.10 0.06 0.05 Trechus quadristriatus 0.92 0.98 0.83 1.09 0.74 1.16 Notiophilus biquttatus 0.14 0.15 0.12 0.07 0.07 0.20 Paederus littoralis 0.06 0.06 0.07 0.10 0.04 0.03 Stenus spp 0.39 0.32 0.35 0.41 0.07 0.23

Apbidophagou s predator s (adults and larvae) Neuroptera 1.00 1.06 0.06 1.44 0.97 0.37 Syrphidae 0.24 1.22 0.12 1.67 2.61 0.48 Coccinellidae 1.21 0.71 0.18 0.73 3.91 3.78

Phytophagous Coleoptera and Diptera (adults) Gastrophysa polyqoni 1.26 0.38 0.00 0.28 0.64 0.94 Crepidodera transversa 0.43 0.58 0.06 0.37 0.16 0.06 Lema melanopa 0.47 0.07 0.09 0.09 0.38 0.57 Phyllotreta spp. 0.11 0.24 0.09 0.00 0.06 0.01 Chaetocnema spp. 0.27 1.29 0.12 0.04 0.04 0.06 Lonqitarsus spp. 0.05 0.15 0.12 0.04 0.04 0.03 Meliqethes spp. 0.42 0.53 0.65 0.00 0.04 0.06 Nephrotana spp. 1.60 1.10 0.51 0.54 0.66 0.62

Qnnivorous Coleoptera and Dermaptera (adults) Tachinus rufipes - 0.13 0.09 0.01 0.03 0.00 Forficula auricular!a 0.39 0.78 0.33 0.40 1.25 0.17

Mycetophagous Coleoptera (adults) Atomaria spp. 43.60 43.58 34.32 25.50 14.46 10.17 Stilbus testaceous 4.35 3.82 2.42 0.94 1.55 0.35 Enicmus spp. 2.27 10.87 12.91 7.74 8.14 3.13 Lathridius spp. 20.33 7.67 8.76 6.23 24.45 2.23 Stephostethus ladarius 1.00 3.88 1.29 0.37 1.31 0.43 Tachyporus spp. 11.56 10.81 8.86 5.64 1.74 1.60

134 FIGURE 22 The decline in the abundance of Tachyporus spp. adults

None 0 o o 0 EsnssnD Frequency %

135 Baran (1972) found a negative correlation between the potassium and phosphorus content of wheat seedlings and the fecundity of S. avenae, and Verijken (1975) reported a positive correlation between the level of nitrogen fertilizer and S . avenae performance in the laboratory, although field dressing had a negligible effect on aphid numbers.

According to Henderson and Perry (1978), greater aphid densities were associated with low nitrate concentrations in the plant sap during the early stages of crop growth, whereas increasing levels of nitrogen applied to spring barley were accompanied by an increase in the number of plants showing symptoms of BYDV (Plumb, 1978). Similar results were obtained when spring oats were treated with magnesium sulphate and Plumb

(1978) suggested that the fertilizers could have had a direct effect on host susceptibility or on aphid numbers.

5.5.2 Growth reoulators

Early work on the effects of plant growth regulators on aphids revealed their possible potential as dual-function agents affecting both plant characters and pest populations (van Emden, 1964; Smith, 1968).

Van Bnden (1964) found poor longevity, decreased fecundity and a depressed rate of increase of Brevicoryne brassicae (L.) on brussels sprouts treated with the growth retardant 'Cycocel' (2-chloroethyl trimethylammonium (chlormequat) chloride) and attributed this to a

136 nutritional rather than a toxic.effect.

Field experiments by Singer and Smith (1976) showed a reduction in

the density of Hyperomyzus lactucae to a level below which damage was

caused following the application of chlormequat chloride to blackcurrant

bushes. They suggested that this effect was mediated through aphid

reproduction rather than through mortality, migration or predation. No

immediate detrimental effect on the resident natural enemy population

(syrphids, coccinellids and anthocorids) was observed, although long-term

effects on the interactions between aphids, their host and the predators

were inevitable.

However, the results of research into the effects of chlormequat

chloride on cereal aphids have proved rather inconclusive. Although Hinz,

Daebeler and Giessmann (1973) found that this chemical inhibited the

development of populations of S. avenae, Rautapaa (1972) failed to find

any effect on host-plant selection and reproduction of S. avenae in the

laboratory.

Latteur (1976) also found that chlormequat chloride applied to crops

had no significant effect on the numbers of S. avenae, M. dirhodum and

R. padi, even at twice the normal dosage. Unpublished work by Singer

and Smith with R. padi and M. di rhodum showed that chlormequat

chloride applied to wheat had no apparent effect on aphid reproduction and

growth.

137 5.5.3 Herbicides

Baranyovits (1973) considered that one of the contributary factors to the recent worldwide upsurge of cereal aphids was the introduction and widespread use of herbicides. Since the introduction of MCPA and 2,4-D in

1946 there has been a great increase in the chemical control of weeds in arable crops (Woodford, 1964). Recent changes in crop rotation and stubble hygiene have aggravated the problem of monocotyledonous weeds.

For example, wild oats used to be 'rogued' in the early stages of infestation and grass rhizomes were killed by prolonged cultivation (Potts and Vickerman, 1975).

Grass weeds which have increased in abundance include wild oats

(Avena fatua L. and A. ludoviciana Dur.), blackgrass (Alopecurus myosuroides Huds.) and Poa trivialis (L.). The predominant species of rhizomatous grass weeds are Aaropyron repens (L.) and Aarosti s stolonifera (L.) (Potts and Vickerman, 1975; Vickerman, 1974).

New herbicides have been introduced to control dicotyledons as continued use of early compounds has led to the development of floras dominated by tolerant species which increased in importance accordingly, for example, chickweed (Stellaria media L. Vill.), redshank (Polygonum persicaria L.), black bindweed (P. convolvulus L.) and speedwells

(Veronica spp.) (Potts and Vickerman, 1974, 1975). The hectarage of cereals treated with herbicides is escalating rapidly with little or no information available on the repercussions on cereal aphids and beneficial

138 arthropods.

In the 1960's, Adams and Drew (1965, 1969) observed that populations of

R. padi and S. avenae increased after applications of 2,4-D-amine to oats. Initially they attributed this effect to the toxicity of

2,4-D-amine to coccinellid larvae, therefore reducing the predation pressure (Adams, 1960; Adams and Drew, 1965), but in later laboratory studies they found that herbicide treatments increased the longevity and decreased the reproduction of R. padi and caused a decrease in both longevity and reproduction of S. avenae (Adams and Drew, 1969).

Oka and Pimentel (1974) suggested that physiological changes stimulated by the activity of 2,4-D and the improved nutritional quality of the plants , may account for the increased aphid reproduction that they observed in R. maidis on 2,4-D-treated maize. This theory was supported by earlier work (Maxwell and Harwood, 1960), which showed that sub-lethal doses of 2,4-D dimethylamine on broad bean plants markedly increased the reproductive rate of pea aphids (A. pisum).

Maxwell and Harwood (1960) also noted that levels of various amino acids were higher in bean plants exposed to 2,4-D dimethylamine. The effects of a range of herbicides on host-plant selection and reproduction of S . avenae were investigated by Rautapaa (1972). Dinoseb decreased the reproduction rate of the aphids, but no other herbicides had any apparent effect.

139 Almost all of nine different herbicides tested by Muller (1971) had some toxic effect on small carabids of the genus Bembidion. 2,4-D and chlorpropham acted very rapidly and brought about a high rate of mortality, although the dosage was above normal field rates. The ingestion of contaminated food accentuated the effect of chlorpropham and some repellent action was recorded which could lead to the migration of species capable of flight, and result in . an alteration of the fauna

(Thiele, 1977).

Hedges and groups of trees in fields constitute reservoirs for a species-rich carabid population in agricultural areas (Thiele, 1977).

Pollard (1968a,b) simulated the effect of the spray drift into hedgerows on the carabid population by using repeated applications of a paraquat-diquat mixture to eliminate the ground flora in stretches of hawthorn hedges. Almost all carabid species showed a reduction in numbers on the treated areas, in particular Bembidion guttula (F.) and A. dorsale, both species overwintering in the hedge and active in the crcp during the summer (Pollard, 1968b). A. nemorum was also seriously depleted following spraying (Pollard, 1968a). Pollard (1968b) attributed this effect to the change in the micro-climate of the hedge bottom elicited by the herbicide mixture. The removal of the soil flora lowered the humidity and increased the amplitude of seasonal and diurnal temperature changes, all factors governing habitat preference in Carabidae

(Pollard, 1968b; Thiele, 1977), and so had a detrimental effect on potential predators of crop pests.

140 Thiele (1977) postulated that changes in the flora may have a greater role in manipulating the carabid populations on agricultural land than the toxic effect of the herbicide itself, especially as Pollard

(1968 a,b) found that the numbers of Bembidion obtusum and Trechus quadristri atus, both inhabitants of open fields, increased on herbicide-treated areas. Also cereal aphids were the only arthropods significantly more abundant on winter barley sprayed with metoxuron-simazine mixture (to remove the monocotyledonous weeds) than on plots treated with mecoprop (monocotyledons present) (Vickerman, 1974).

As fewer potential cereal aphid predators (Tachyporus adults and larvae) were found in the former treatment, this effect was attributable to reduced aphid predation in the metoxuron and simazine treatment

(Vickerman, 1974). Although seme arthropod species were probably reduced

in number by the virtual eradication of their host plant, the majority were apparently affected by the alteration in the crop environment. Weed

removal decreases the amount of cover, decaying plant material and

associated micro-organisms and changes the microclimate. Insects such as

Tachyporus spp. are fungus feeders, so the changes in micro-habitat may

explain the dramatic effect of the herbicide mixture on this species

(Vickerman, 1974).

According to Speight and Lawton (1976), the number of adult carabids

and staphylinids trapped was directly related to the frequency and density

of annual meadow grass (Poa annua L.), and that predation pressure of

carabids on artificial prey (Drosophila pupae) was greater in a "weedy"

field than in a "clean" field, indicating that weeds can protect predators

141 from extremes of climate, for example, insolation during the day and

dessication, both during the day and night. Similarly the adults and

larvae of the carabid species Loricera pilicornis (F.), A. dorsale and

Amara spp and larvae of Staphylinidae were more numerous in untreated winter wheat with dense ground cover than in areas treated with a number

of spring and autumn herbicides (Powell et al., 1981).

There was no apparent effect on the spider populations, although P. melanarius and P. madidus were found in larger numbers in the "clean" plots. Greenslade (1964a) found the highest catches of carabids, in particular Nebri a brevi col1i s, in litter, which offers the least resistance to beetle movement and this may have contributed to the effect of weed removal on Pterostichus spp.

From 1972 to 1974, in comparisons made between the arthropod fauna of undersown spring barley and spring barley fields, the higher number of

Aphididae (60 per cent) in the latter could be due to reduced predation as undersowing provided a greater diversity and density of arthropods

(especially Hymenoptera, Hemiptera, Coleoptera and Araneae). Populations of Staphylinidae (mainly Tachyporus hypnorum F. and T. chrysomelinus) and seme polyphagous Carabidae (for example, P. melanarius, H rufipes and A. dorsale) were all considerably higher in the undersown barley

(Vickerman, 1978) .

Powell (1983) advocated less intensive use of herbicides and undersowing with rye grass to allow a tolerable amount of weed growth

142 which may reduce aphid pest problems later in the season by encouraging

populations of Coccinellidae, Carabidae, Staphylinidae, Araneae, parasitic

Hymenoptera, Syrphidae and Chrysopidae. Also, with undersowing,

entomogenous fungi pathogenic to cereal aphids would be more likely to

proliferate in the more humid conditions.

The side effects of a range of herbicides on beneficial arthropods

were investigated by Hassan et al., (1983). Of those tested, dinoseb

was harmful to several parasitic Hymenopterous species, C. carnea and

Syrphus vitripennis (Meig.), while difenzoguat had similar effects, but

was non-toxic to C. carnea (Franz et al., 1980; Hassan et al, 1983).

5.5.4 Fungicides

The total number of foliar fungicides approved under the Agricultural

Chemicals Approval Scheme for use on cereals has increased from none in

1970 to eleven in 1980 (Vickerman, 1981).

The number of applications vary but, in addition to seed-transmitted fungal disease control (e.g. loose smut Ustilago nuda (Jens.) Rostr.), some crops may be treated four or five times against major leaf diseases such as yellow and brown rusts (Puccinia striiformis Westend. and P. hordei Otth.), powdery mildew (Erysiphe graminis DC. ) and leaf blotch

(Rhynchosporiurn secalis (Oudem.) J. J. Davis). Despite the introduction and widespread adoption of foliar application of fungicides (Tables 15 and 16), there is very little literature pertinent to their direct and

143 indirect effects on the cereal ecosystem.

Benomyl (200 mg a.i. per pot) applied to chrysanthemum plants infested with Myzus persicae and Aulacorthum circumflexum was aphicidal, reducing their numbers by 79 per cent, compared with a three-fold increase on control plants (Binns, 1970). The application of bencmyl and carbendazim (Sagenmuller, 1977; Vickerman, 1977) and thiophanate-methyl (Sagenmuller, 1977; Vickerman, 1981) to cereal plants decreased the survival and reproductive rate of Sitobion avenae and

Metopolophium dirhodum. Vickerman (1977) noted that bencmyl, in addition to toxicity at normal doses, may have an antifeedant or repellent effect although it did not affect aphid natural enemies in winter wheat

(Powell, Dean and Bardner, 1985). As the carbamate is known to possess anti-cholinesterase activity which has been exploited in the use of commercial carbamate insecticides, Partis and Bailiss (1980) thought it probable that the carbamate moiety of carbendazim was responsible for the aphicidal activity of fungicides which contain carbendazim as an active ingredient, or those with an active ingredient such as bencmyl which is converted to carbendazim. They based this hypothesis on experiments which showed a clear association between the mortality of Acrythosiphon pi sum and the concentration of methyl benzimidazole-2-yl carbamate (MBC = carbendazim) in the sap of plants treated with bencmyl and carbendazim.

In contrast, the triazole fungicide, triadimefon, had no effect on either S . avenae or M. di rhodum (Vickerman, 1977, 1981), whereas tridemorph (Sagenmuller, 1977; Vickerman, 1977, 1981) and

144 chloraniformethan (Sagenmuller, 1977) increased the reproductive rate of both species. Plants treated with tridemorph and ch1oraniformethan were found be be more attractive to cereal aphids than untreated plants

(Sagenmuller, 1977).

The possibility that fungicides may protect aphids from infection by

Entomophthora spp. has been studied by Nanne and Radcliffe (1971) who found an increase in Myzus persicae populations associated with a reduction in the incidence of diseased aphids on potatoes treated with dithane (zinc and maneb), captafol and Bordeaux mixture (copper sulphate pentahydrate and calcium dihydroxide). Also according to Wilding (1972), the development of Cephalosporium aphidicola, a fungal pathogen of

Aphis gossypii, was inhibited in vitro by the fungicides benomyl and triarimol. A number of fungicides was tested by Zimmermann (1976), who found that the germination of the cereal aphid pathogens, Entomophthora aphidis and E. thaxteriana was completely inhibited by tridemorph and chloraniformethan and was severely affected by both oxycarboxin and triforine. Benomyl and ethirimol inhibited the germination of E. aphidis only and thiophanate-methyl had little effect. The germ-tube growth of

E. thaxteriana was inhibited by all of the fungicides.

According to Potts (1977), there has been a marked decline in the numbers of mycetophagous species since 1970 (Table 17 and Figure 22) which coincides particularly with the increased use of foliar-applied fungicides. In particular, the fungicide tridemorph reduced the numbers of Tachyporus spp. by 73 per cent (Potts, 1977) and high mortalities of

145 the chrysomelid beetle, Gastrophysa polyqoni (L.) were attributed to the applications of benomyl, thiophanate-methyl and carbendazim as these

fungicides were toxic to all developmental stages (Vickerman, 1981). The larvae of G. polyqoni were adversely affected by laboratory treatment with bencmyl (1.0- 5.0 g a.i./l ), triademefon (0.5 g. a.i./l) and

thiophanate-methyl (1.0 g a.i./l) (Vickerman and Sotherton, 1983). As G. polyqoni is part of the staple diet of gamebirds, its removal may have

serious implications to gamebird populations (Vickerman, 1981).

The insecticidal activity of a range of fungicides (captafol,

carbendazim, propiconazole, pyrazophos, triadimefon and tridemorph),

applied at normal field concentrations, was determined using carabid and

staphylinid beetles (Sotherton and Moreby, 1984). Triadimefon did not

cause significant mortality, while the others were toxic to A. dorsale

and all except captafol and carbendazim caused considerable mortality of

D. atricapillus and T. chryscmelinus respectively.

Of a number of fungicides tested by Franz et al. (1980) and Hassan

et al. (1983), thiophanate-methyl was harmless to parasitic Hymenoptera,

C. carnea and S. vitripennis, although triadimefon and captafol were

slightly harmful to S. vitripennis only. Pyrazophos and ditalimfos were

toxic to most test species. The numbers of carabid and staphylinid

beetles, Coccinellidae and Syrphidae in cereals were reduced by normal

field rates of pyrazophos (Sotherton, 1985b).

146 5.5.5. Insecticides

The repercussions of the application of synthetic insecticides have been described by Coaker (1977), who attributed many of the short-term effects on pests immediately following pesticide treatment to the disruption of the natural enemy population by a variety of means.

. **

The responses of arthropod natural enemies to insecticides have been reviewed by Croft and Brown (1975).

5.5.5.1. Oraanochlorine insecticides

The susceptibility of adult carabid and staphylinid beetles to normal field rates of the soil-applied insecticides, aldrin and dieldrin, was found to vary frcm species to species and although the carabids H. rufipes and Pterostichus spp. were not affected, Aleochara spp., Bembidion spp. and T. quadristriatus were killed by the

insecticide residues (Coaker, 1966). Initial increases in the activity of

B. lampros and T. quadristriatus were probably a sub-lethal response

stimulated by the insecticide (Coaker, 1966). Ganma-HCH also increased the activity of B. lampros (Edwards et al., 1984) and in standardised

laboratory tests was shown to be harmful to most parasitic Hymenoptera and

S. vitripennis (Hassan et al., 1983), and was toxic to A. dorsale,

Pterostichus spp. and Nebria brevicol 1 is (F. ) at 5 and 0.2 x normal dose (Edwards and Wilkinson, 1983). The complex effects of pesticides on

Carabidae are exemplified by the susceptibility of H. rufipes to DDT

147 (Dempster, 1968). This species is very resistant to DDT, a characteristic attributed to its ability to convert DDT to the less toxic DDE. However, its rate of feeding can be substantially reduced by the presence of DDT at concentrations far lower than that required to kill it.

The application of DDT (at 1 kg a.i./ha) to spring wheat resulted in a slight reduction in the population of epigeal predators (Shires, 1980,

1985), and a significant recovery was observed within five weeks after treatment. DDT (1.28 kg a.i./ha) was lethal to all species of parasitic

Hymenoptera tested by Bartlett (1963), although a more diverse response was found among the Coccinellidae, with a great deal of variation in susceptibility between the immature stages.

5.5.5.2 Oraanophosphorus i nsecti ci des

Carabids were killed by soil treated with thionazin within dosage rates normally required for the satisfactory control of insect pests of cereals, i.e. 2.24-8.96 kg a.i./ha (Critchley, 1972a). Increased numbers of Carabidae were sometimes trapped in treatments with 2.24 or 8.96 kg/a.i./ha and Critchley (1972b) postulated that sub-lethal doses were increasing locomotor activity. The speed of kill was negatively correlated with adult size of carabid species that behaved similarly

(Critchley, 1972a). Smaller species such as B. lampros were more affected, while larger beetles such as Pterostichus vulgaris were less susceptible. Burrowing species were more susceptible than non-burrowing species of a comparable size, probably because they encountered more

148 insecticide (Critchleyf 1972a and b). For example, Asaphidon flavipes

(L.) suffered less than Harpalus aeneus (F.), a species which readily burrows. A similar effect was observed with newly-moulted or starved adults (Critchley, 1972a).

Several other soil-applied organophosphorus insecticides were tested by Critchley (1972a) who found that phorate (applied at 36 kg a.i./ha) was more toxic to Carabidae than equivalent rates of thionazin. Phorate was particularly toxic to P. melanarius (Edwards et al., 1984).

Disulfoton was not appreciably toxic at 75 kg a.i./ha although Edwards et al. (1984) recorded a severe decline in the activity of

P.melanarius after treatment with disulfoton (9 kg a.i./ha). Menazon was non-toxic to all species of Carabidae (Critchley, 1972 a).

Phorate (at 1.7-6.7 Kg a.i./ha) was also toxic to all stages of development of Anthocoris confusum (Reut.) and A . nemorum (Elliott,

1970). The survival of nymphs on plants treated with menazon at 1.7 kg a.i./ha was not affected (Elliott, 1970). Field applications of carbofenothion (9 kg a.i/ha) decreased the numbers of predatory beetles trapped in spring wheat by about 50 per cent (Edwards and Thompson, 1975) and depressed the activity of P. melanarius (Edwards et al., 1984).

The broad spectrum soil insecticide fonophos was found to be extremely toxic to the carabids P. melanarius, P. madidus and H. rufipes

(Edwards and Thompson, 1975; Edvrards et al., 1984).

Normal rates of treatment of cereal crops with parathion-ethyl (125

149 g a.i./ha) had a detrimental effect on all carabid species including B.

laropros, A. dorsale, P. melanarius and Loricera pilicornis,

staphylinids (especially Tachyporus hypnorum) and lycosids (Basedow,

Borg and Scherney, 1981). The timing of insecticide application determined the extent of the reduction in the numbers of Carabidae

(Basedow, Borg and Scherney, 1976). Only species which actively climb plants (in particular, staphylinids and A. dorsale) were susceptible to

treatments of methyl-parathion dust (at 200 g a.i./ha) (Basedow et al.,

1976). However, the application of methyl-parathion (1000 g a.i./ha) to

spring wheat brought about a rapid and severe reduction in the numbers of

epigeal predators (Shires, 1980, 1985), although Carabidae were less

affected in comparison with the decline in the Araneae population. A

secondary decline in the epigeal population was attributed to the virtual

removal of cereal aphids, thereby depriving the predators of a vital food

source (Shires, 1980, 1985). Aphid numbers escalated on plots sprayed

with methyl-parathion (Brown, 1982), probably due to the depletion of

polyphagous predators. A 70-80 per cent decline in trap catches was

recorded after treatment of cereals with methyl-parathion and phosalone,

the most affected groups being Carabidae, Staphylinidae and Hymenoptera

(Chambon, 1982).

Malathion and parathion (0.64 kg a.i./ha) were toxic to parasitic

Hymenoptera tested by Bartlett (1963), while the effect of malathion and

demeton-S-methyl on Aphidius ervi parasitising the pea aphid,

Acyrthosi phon pi sum, was determined by Obrtel (1961). In the laboratory

'mummies' exposed to these insecticides at normal field dosages showed a

150 significantly higher level of mortality (58-87 per cent) than in controls

(12 per cent), but these results were not reproduced in 'mummies' collected from fields sprayed with the insecticides.

Demeton-S-methyl is lethal to many other species of parasitic

Hymenoptera (Hassan et al., 1983; Stevenson, Smart and Walters, 1983;

Inglesfield, 1984), C. carnea and S. vitripennis (Hassan et al,

1983) and to Carabidae (Basedow et al., 1981; Dunning et al., 1982), thus foliar sprays at 110 g a.i./ha or with parathion in a mixture (84 g a.i./ha and 140 g a.i./ha respectively) applied to grain sorghum eliminated 88-100 per cent of the mobile instars of the coccinellid and syrphid predators (Van Rensburg, 1978). In field tests, oxydemeton-methyl applied to winter wheat was highly toxic to coccinellids and syrphids, but had no significant effect on the chrysopid population (Hellpap, 1982).

Vickerman and Sunderland (1977) noted reductions in the populations of T. quadristriatus, B. lampros and D. atricapillus of 67, 42 and

86 per cent respectively after a dimethoate spray and emerging adults were still affected 3 - 4 weeks later. Numbers of staphylinids (especially adults and larvae of Tachyporus spp.,) and two common species of predatory Diptera (Platypalpus pallidiventris Meig., Bnpididae and

Sciopus platypterus F. Dolichopodidae) were also suppressed by insecticide treatment. Adults and larvae of C. septempunctata,

Propylea 14-punctata and Syrphidae (mainly Melanostcma mellinum L.) were sensitive to dimethoate and found dead on the soil surface after spraying. The number of Araneae (adults and immature stages) were still

151 reduced by 90 per cent 7 days after treatment, and a depletion in populations of parasitic Hymenoptera (in particular Aphidius avenae

Haliday) was still apparent six weeks post-application (Vickerman and

Sunderland, 1977).

Dimethoate (340-400 g a.i./ha) reduced the numbers of Carabidae

(Basedow et al., 1981; Chambon, 1982; Edwards and Wilkinson, 1983; Cole and Wilkinson, 1984a and b; Feeney, 1983; Powell et al., 1985),

Staphylinidae (Powell et al., 1981; Chambon, 1982; Cole and Wilkinson,

1984a and b; Powell et al, 1985), Araneae (Powell et al, 1981; Cole and Wilkinson, 1982, 1984 a and b; Powell et al., 1985) and parasitic

Hymenoptera (Bartlett, 1963; Chambon, 1982; Powell et al., 1985). In field trials, numbers generally increased 2-4 weeks later. Some contact toxicity of dimethoate to Anthocoridae has been reported (Elliott, 1970).

Fenitrothion is less harmful to Carabidae than other insecticides and at normal field dosages affected the abundance of P. vulgaris and

P . niger only for a short period (Basedow et al., 1976) while the activity of P. melanarius was reduced for up to 14 days post-treatment

(Chiverton, 1984).

Aphidophagous and polyphagous species are very susceptible to most modern, broad-spectrum organophosphorous insecticides, but these chemicals are generally less persistent than chlorinated hydrocarbons such as DOT and HCH and the rapid disappearance of toxic residues (3-4 days) increases the chance of natural enemy survival (Van Rensburg, 1978).

152 5.5.5.3 Carbamate insecticides

Pirimicarb is widely recommended for aphid control and, at normal field rates, has little impact on beneficial arthropods (Powell et al.,

1981; Dunning et al., 1982; Cole and Wilkinson, 1984a,b) although toxic to some species of parasitic Hymenoptera (Powell et al., 1981; Hassan et al., 1983; Powell et al., 1985), and the larvae of Syrphidae

(Hellpap, 1982; Hassan et al., 1983),

Ethiofencarb (125 mg a.i./l) is non-toxic to P. melanarius and other carabid species (Basedow et al., 1981; Dunning et al., 1982).

5.5.5.4 Pyrethroid insecticides

Cypermethrin applied to spring wheat at lOOg a .i./ h a suppressed the population of ground-dwelling predators for up to four weeks (Shires,

1980, 1985),while secondary decline in the predator numbers was attributed to the almost complete removal of cereal aphids by cypermethrin.

Commercial rates of cypermethrin depleted populations of Araneae (Brown,

1982; Cole and Wilkinson, 1984a; Stevenson, Smart and Walters, 1983,

1984), Staphylinidae (Stevenson et al., 1984), Carabidae (P. cupreus, A. dorsale, N. brevicollis, T. quadristriatus) (Feeney,

1983; Edwards, pers. canm.) and predatory larvae of Carabidae,

Coccinellidae and Staphylinidae (Stevenson et al., 1983).

Permethrin (50g a.i./ha) had no significant effect on carabids and

153 staphylinids (Cole and Wilkinson, 1984a) although the number of T. chrysomelinus was reduced following treatment and the populations of

Linyphiidae were depleted for up to four weeks (Cole and Wilkinson, 1982,

1984b).

A six-fold increase in the numbers of Aphis fabae after permethrin application was probably due to the mortality of the predominant aphid predators, the Coccinellidae (Dunning and Winder, 1975). In standard laboratory tests, normal rates of permethrin and fenvalerate were harmful to many species of parasitic Hymenoptera, S. vitripennis and C. carnea (Hassan et al., 1983). The third instar larvae of C. carnea have exhibited a marked pyrethroid tolerance (Shour and Crowder,

1980), although high dosages of permethrin (1000 Aig/g) decreased female longevity and the same level of fenvalerate affected larval survivorship, adult emergence and fecundity. P. melanarius activity diminished after fenvalerate (lOOg a.i./ha) was applied, but numbers recovered within two weeks (Chiverton, 1984).

Braconid Ichneumonoidea in winter wheat were reduced by the application 'Fastac' (15g a.i./ha) (Inglesfield, 1984). Deltamethrin (17 mg a.i./l) was toxic to melanarius when applied to the soil, but had no effect when the beetles consumed food contaminated with the insecticide (Dunning et al., 1982). The number of T. quadristriatus was severely reduced by deltamethrin applied to cereals (Feeney, 1983).

In addition to the direct toxic effects of an insecticide,

154 persistence in the environment is important, for example, the rates of evaporation, photolysis, biodegradation and sorption of the pesticide

(Shires, 1980).

Potts (1977) claims that the abundance of mainly polyphagous predators present before aphid immigration is the principal factor affecting pest populations. The potential value of these predators is being reduced by the widespread use of herbicides, fungicides and insecticides.

5.5.6 Cultural practices

Stubble and straw-burning was widely practised to minimise the carry-over of disease on crop residues and to aid stubble hygiene generally (Potts, 1977). Despite the use of desiccants and pesticides, trends towards minimal cultivation, direct-drilling and the reduction of straw-burning probably have, in general, less dire consequences on the crop fauna.

Direct drilling has been shown to encourage more serious attacks by several pests, for example, slugs and wire-worms (Edwards, 1975), and although the number of stem-borers (especially dipterous belonging to the

"frit" complex) was higher in ploughed fields, Edwards (1975) considered that cereal aphids, leatherjackets, chafers and cereal cyst eelworm may all be more troublesome in direct-drilled crops due to the lack of mechanical damage and carry-over in weeds. Populations of soil

155 arthropods, in particular Symphyla and beetle larvae, were more numerous

in direct-drilled plots, while fly larvae and carabid and staphylinid

beetles were less cannon (Edwards, 1975).

Yarham (1975) noted that certain pathogens ( Rhynchosporiurn spp.,

Septoria spp. and Pseudocercosporella) were all favoured by

direct-drilling and may demand fungicide application with additional

side-effects on the beneficial fauna. The change to non-ploughing had no

effect on diseases such as rusts, viruses and mildew (Yarham, 1975).

Changes in crop rotation and stubble hygiene (e.g. wild oats used to

be "rogued" in the early stages of infestation and grass rhizomes were

killed by prolonged cultivation), have led to increases in monocotyledonous weeds (Potts and Vickerman, 1975) and an associated rise in the use of herbicides (page 138).

The absence of undersowing was found to result in a 27 per cent decrease in the faunal diversity of cereal fields, accompanied by a 15.2 per cent reduction in the proportion of predatory insects (Potts and

Vickerman, 1975). The disappearance of undersowing was exemplified by

Potts (1970) who discovered only 3 per cent of cereals in East Anglia to be undersavn in 1970, compared with a figure of 30 per cent twenty years earlier.

The number of insect taxa on modern arable farms has been recorded as much smaller than on traditional ley farms (Vickerman, 1974). With the

156 decline of mixed farming during the 1960's, farmers are becoming more specialised and the main cereal growing areas are relatively separated from grassland areas (Potts, 1977). The trend towards large areas of monoculture is tending to favour the breeding of cereal aphids rather than their predators and parasites (Baranyovits, 1973) and, with the advent of bigger, improved farm machinery, hedgerows and scrubland have been removed, resulting in a reduction in the number of refuges available to epigeal predators. In Norfolk alone 50 per cent of the hedges were cut down between 1946 and 1970 (Potts, 1977). The creation of larger fields increases the distance between the remaining hedgerows and the middle of the crop and can limit the numbers of predators invading from the field perimeters from reaching the central areas (Shires, 1980).

Field boundaries are important as overwintering sites for polyphagous predators (Sotherton, 1982, 1983, 1984, 1985), and hedgerow removal or drift of pesticides into field boundaries may have serious repercussions on the populations of beneficial arthropods.

5.6 Control of cereal aphids

Since severe and widespread cereal aphid infestations in 1968, the application of insecticides to cereals is becoming a routine procedure, and in 1976, when aphid numbers reached 'epidemic' proportions, well over half of the total wheat hectarage in England was sprayed (Stone, 1977).

157 Farmers are now encouraged to spray only in relation to the economic

thresholds established by George (1975), who recommended treatment if the

mean aphid populations on wheat ears at the beginning of flowering (Growth

Stage 10.5.1) are five or more, and further counts 1-2 days later reveal

that the population is increasing. This advice was substantiated in 1976

with yield increases of 13-33 per cent (Stone, 1977). A diagrammatic

version of the use of thresholds is shewn in Figure 23 (Hancock,1983).

George (1975) and George and Gair (1979) found little justification

for applying single sprays after the end of flowering especially as there

is little aphid immigration into the crop after this stage, and there is no significant increase in yield following insecticide treatment beyond

G.S. 11.1 - 11.2 (Wratten et al., 1979). Several other European workers have attempted to define thresholds of aphid damage. Kolbe (1973) found that infestation levels of 20-30 aphids/ear could cause yield losses of up to 10 per cent unless control measures were timely applied and he considered spraying to be profitable when the aphid density was in excess of 20 individuals/ear at flowering time. In order to obtain a return of twice the cost of insecticide application, Latteur (1976) suggested the minimum infestation to be 10-25 S. avenae /stem, while Fautapaa and

Uoti (1976) concluded that the cost of two insecticide treatments against

R. padi would be recovered if the maximum number of aphids per main stem exceeded 25. The monitoring procedures and the economic injury criteria for cereal aphids in Europe are summarised by Way and Cammell (1979).

158 FIGURE 23 The use of threshold levels (from Hancock,1983).

159 With a view to forecasting crop infestations, a co-operative project

between the National Agricultural Advisory Service (NAAS) and Rothamsted

Experimental Station attempted to relate the incidence of alate aphids in

widely distributed 'survey' suction traps operating at 1 2 .2 m above the

ground to numbers found in weekly surveys of wheat fields (Taylor,

et al., 1971), but usually alates were found in traps without being

present in the crops. Dean and Luuring (1970) noted several species on

cereals within three weeks of their first alatae being caught in survey

suction traps, but their aerial abundance and densities on the crops

during June were not related. No apparent relationship has been found

between the size of the aphid infestation and numbers of alatae caught in

the suction trap (Dean, 1973, 1974 a, b). However, a comparison of field samples and suction trap catches (George, 1974) suggested that survey suction traps can give adequate warning of the first appearance of cereal aphids in the spring.

A simulation model has been developed to predict cereal aphid outbreaks by studying the population dynamics of S. avenae. It can be split into three components: the crop, the aphid (S. avenae) and its natural enemies (coccinellids and parasites of the genus Aphidius)

(Carter et al., 1980). The predictions of the model showed that the timing and the size of the aphid immigration relative to the crop growth stage affect the peak aphid density achieved (Walters and Carter, 1981).

The current cereal aphid model incorporates the effects of predation by species such as the carabids, D. atricapillus and A. dorsale, staphylinids of the genus Tachyporus and the common earwig,

160 auricularia (Carter, 1983). Carter (1983) pointed out that no allowances have been made for the age-structure of the aphid population and predator phenology, and predator phenology and predator densities are not corrected for either diurnal rhythm or D-vac efficiencies (data cane from monitoring schemes using D-vac suction samples). Although the advantages of the integration of data and information from several sources are apparent, factors such as crop micro-climate and vigour (influenced by cultivar, soil type, husbandry, etc.) must vary dramatically from one field to another. The abundance of epigeal predators and species diversity are also extremely variable and the type of field boundary probably exerts an effect (e.g. shelterbelt). The complex inter-actions within any cereal ecosystem cast doubt on the success of a simulation model.

Until recently, many farmers preferred aerial application because of the damage caused to full-grown cereal crops by ground-spraying (McLean et al., 1977). However, the high demand for aircraft when farmers in an area are all simultaneously faced with a pest problem can make it difficult to hire an aerial spraying contractor, resulting in delayed spraying which is no longer worthwhile or booking in advance and spraying regardless of an aphid attack. Tractor-mounted equipment is also now very widely used and "wheeling-losses" of 2-4 per cent (100-150 kg per ha)

(Kolbe, 1969), can be eliminated or reduced by the use of tram-lines which decrease the cost of spraying to approximately 2 .6 per cent of the yield

(George and Gair, 1979).

The new methods of pesticide application offer a more rapid means of

161 treatment by using lower volumes of spray. One significant aspect of

"Controlled Droplet Application" is that manufacturers suggest a dosage rate of between 10 and 50 per cent of that recommended for conventional hydraulic nozzles. Whittles (1977) reconmended cereal aphid control at the 'establishment phase' when BYDV is normally transmitted, and again after the flag-leaf emergence to minimise yield reduction. The following insecticides are approved by the Ministry of Agriculture,

Fisheries and Food for cereal aphid control during the late spring and

summer (George and Plumb,1982).chlorpyrifos, demeton-S-methyl, dimethoate,

formothion, heptenphos, oxydemeton-methyl, phosalone, thiometon and pirimicarb. Those recormended for the control of aphids on early sown crops in the autumn are demeton-S-methyl and permethrin. Autumn treatment of winter barley with permethrin against bird-cherry aphid vectors of BYDV was found to increase yields by up to 25 per cent and the Agriculture and

Development Advisory Service (ADAS) advise a September spray application with a cheap, conventional insecticide such as pirimicarb or dimethoate, backed up by the standard pyrethroid treatment eight weeks later (Anon,

1983). Horellou and Evans (1979) found permethrin to be more effective

than dimethoate in terms of the control of R. padi. Although permethrin has poor fumigant and translaminar activity (Ruscoe, 1979), the aphids are fairly exposed to its contact toxicity as the insecticide is applied at

the 2-3 leaf stage. A high level of persistence, negative temperature coefficient (i.e. more lethal to some insects at lower temperatures) and an anti-feedant or repellant activity against insects may all be

significant in the control of alates migrating into the crop and protecting early crops at risk from BYDV (Horellou and Evans, 1979;

162 Ruscoe, 1979). However, aphid-specific insecticides such as pirimicarb, although often more expensive and less persistent, are less harmful to beneficial insects.

The prospects for varietal resistance are being assessed (Lowe,

1974). Although their value to farmers in suppressing cereal aphid population must not be underestimated, McLean et al (1977) considered

that the "artificial release of natural enemies is unlikely to be

successful ” as they could be too expensive to rear and release in

sufficient numbers and wauld tend to leave fields with low aphid densities

at the threshold level where control is crucial.

Carter et al. (1980) considered that breeding for resistance of plants to cereal aphids is more likely to result in the control of aphids

than the use of natural enemies, and suggested that resistant varieties might enable predators and parasites to exert a greater degree of control.

163 Chapter 6

THE EFFECT OF CYPERMETHRIN ON BENEFICIAL ARTHROPODS WITHIN AND DOWNWIND

FROM THE HYDRAULIC AND ULV SPRAY TREATMENTS

6.1 Introduction

Arable crops such as winter wheat can harbour many species of aphid predators and parasites. The role of aphid-specific and polyphagous predators in reducing populations of cereal aphids has recently been investigated (e.g. Potts and Vickerman, 1974; Edwards et al., 1979;

Chambers et al., 1983). Continued widespread use of aphicides and fungicides is a threat to these species and information on the effects of spray drift on the arthropod fauna of hedgerows and adjacent land is limited. For example, the decline in the populations of grey partridge

(Perdix perdix) has been attributed partly to a drastic reduction in the abundance of the arthropod food (e.g. cereal aphids, larvae of cereal leaf-eating sawflies, larvae of Chrysomelidae) component of the partridge chicks' diet (Potts, 1970, 1977, 1982; Rands and Sotherton,

1985). The effect of the broad spectrum insecticide, cypermethrin, on epigeal and aerial arthropod populations within and downwind from plots sprayed conventionally and at ULV was assessed using several sampling techniques.

164 J

PLATE 1 Hawthorn hedgerows at the edge of the

cereal crops.

165 6.2 Materials and methods

6.2.1 Spray application

This was carried out across two fields of winter wheat (23.8 and

48.5 ha respectively) on Lockinge Farm Estate, Oxfordshire (Appendix 3).

The boundary (running east-west) comprised two hedgerows 1.8 - 2.0m high and 0.8 - 1.0m thick. The dominant shrub was hawthorn (Crataecrus monocryna) with seme ash (Fraxi nus exce 1 s i or) and elder (Sambucus niora). Bottom growth consisted mainly of stinging-nettles (Urtica dioica), white dead-nettle (Lamium album), couch grass (Aaropyron repens) with some dog rose (Rosa canina), field scabious (Knautia arvensis), bush vetch (Vicia sepium), cow parsley (Athriscus sylvestris). The hedges were separated by a 4.5 - 5.0m band of grass

(Plate 1).

On 7th July, 1981, an 85 x 80 m plot within the smaller field (cv.

Bounty, growth stage 83, i.e. early dough-Zadoks decimal code, Tottman and

Makepeace, 1979) was treated using the Ulvamast Mk 2 sprayer to apply cypermethrin (Cymbush e.c., 20 g a.i./l). A full description of the equipment and its operation is given in Chapter 3, 3.3.1.1. Modification of the spray tank using a 10 1 Cornelius tank enabled small volumes of liquid to be fed to the atomizer at a constant pressure of 117 kPa. The disc was 2.75 m above the crop so that spray covered a swath of 12 m in the light south-westerly wind which gusted up to 18 Km/h.

166 A similar plot was sprayed hydraulically with cypermethrin at the same

dosage rate. The tractor-mounted hydraulic sprayer (Chafer T2000) was

fitted with Chafer green hollow cone nozzles working at a pressure of 205

kPa to give an application rate of 200 1/ha at a speed of 10 km/h. The

boom was adjusted to 0.1-0.15 m above the crop.

Both fields had not received any other pesticide treatment between

March and July 1981.

The average wind velocity during spray application was 6.5 km/h and

the ambient air temperature was 22°C (at crop height). Weather conditions

from May-July,1981 are summarised in Appendices 4 to 9.

6.2.2 Insect sampling

The number of aphids per ear and flag-leaf of 25 tillers at 75, 10

and 1 m within the sprayed plots was recorded 3 days before insecticide

treatment and 1,3,7,14 and 20 days afterwards. Visual counting of aphids

on the crop has since been shown to be the most accurate method of

estimating aphid numbers at densities of 0.5-20 per tiller (Dewar, Dean

and Cannon, 1982).

White water traps were used to sample aerial arthropod populations

moving within and over the crop (Taylor and Palmer, 1972; Southwood,

1978). These were preferable to standard yellow traps as they are less

attractive to Syrphidae and would not draw insects over a large area.

167 Three traps, 20 m apart to avoid interference, were placed 0.15 m above the ground at distances of 75 and 10 m within the sprayed plots and 10,

30, 50, 75, 120 and 200 m downwind into the adjacent field (Figure 24).

The bottom of each trap was covered with a solution of water and detergent.

Townes Malaise traps were used to measure the patterns of activity and movement of flying insects (VJaaae, 1980). Brown traps were used as the possible long range stimulus of white Malaise traps has been shown to be attractant (Nyambo, 1980). Two traps, 25 m apart, were erected 5 m within the treated plots and at 5 m and 120 m downwind (Figure 24). The collecting baffles and net entrance level were approximately 2 m and 0 .8 m respectively above the ground. Each collecting-bottle contained 100 mis of detergent solution.

Beetles and other epigeal arthropods were collected in plastic pitfall traps, 7 cm in diameter and 9 cm deep. Preservatives such as formalin were not used as repellent and attractive properties, varying according to the species and sex, have been reported (Luff, 1968;

Skuhravy, 1970). As dry traps encourage predation (Luff, 1968) and small winged beetles may escape (Southwood, 1978), a small volume of detergent solution was added to each trap. Five pitfall traps, at 2 m intervals

(Greenslade, 1964b) were situated 75 m and 10 m within the sprayed plots, at 1 m to each side of the hedgerows, and 10, 30, 50, 75, 120 and 200 m downwind (Figure 24). The lip of each trap was level with the soil

surface to minimise differential trapping efficiency (Greenslade, 1964b).

168

water trap * within spray . . pitfall trap o o AMalaise trap H*andH, H*andH, m

H* H H* hedgerows Distance from hedgerows CHALKHILL WEST BARROW HILL FIGURE 24 Trial layout.

169 Transparent plastic lids were used to cover the traps when sampling was

not in progress. The traps were left covered for several days before

sampling commenced as disturbances due to the 'digging-in' of traps can

result in increased activity of surface-dwelling Collembola (Joose and

Kapteijn, 1968) which may influence the behaviour of other arthropods.

All of the traps were anptied twice daily (9 am and 4 pm), three

days both spraying and 1,3,7,14 and 20 days after the cypermethrin spray.

The catches were preserved in 75 per cent alcohol for later

identification.

6.2.3 Statistical analysis

'Genstat' (Alvey et al., 1982; Rothamsted Experimental Station,

1977 ) was used to perform analysis of variance (ANOVA) on the

untransformed data, but as treatments were not replicated, the ANOVA

tables were used to determine the relative importance of various factors

(for example, distance from hedgerow, time of sample, number of days

pre-or post-treatment, method of spray application), and their interaction

in influencing insect and spider densities.

170 6.3 Results

6.3.1 Pitfall trap catches

Carabidae

Carabidae, in particular P. melanarius, dominated pitfall trap catches and were identified to species (Table 18). The distribution of

Carabidae during the sampling-period is represented in Figures 25 to 28.

P. melanarius and P. madidus were more abundant inside the crop although this was less evident in the ULV treatment. Species diversity increased with proximity to the hedgerows and Clivina fossor (L.) and isolated catches of Amara plebeja (Gyll.), Calathus melanocephalus

(Goeze) and A. dorsal e were only present in hedgerow samples. H. rufipes, other harpalid species (H. aeneus F., H. tardus P. and H. rufibarbis F.), Bembidion lampros (Herbst.) and B. harpaloides

(Serville) were also more common in hedgerow samples, while Notiophilus biguttatus (Fab.) and Leistus spinibarbis (F. ) were recorded inside the crop and at the field boundaries.

More carabids/hour were collected at night (0.1/trap) compared with the day samples (0.04/trap) and there was little change in the numbers trapped during the day (Figure 29).

171 Table 18 Species list. (Carabidae)

1. Pterosti chus - P. melanarius (111.)

- p. madidus (F.)

2. Harpalus - H. rufipes (Deq.)

- H. rufibarbis (F.)

- H. tardus (Panz.)

- H. aeneus (F.)

3. Leistus - L. spinibarbis (F.)

4. Demetrias - D. atricapillus (Linn)

5. Bembidion - B. lampros (Herbst.)

- B. harpaloides (Serville)

6 . Lori cera - L. pilioornis (F.)

7. Amara - A. plebeia (Gyllenhal)

8 . Calathus - C. melanocephalus (Linn.)

9. Clivina - C. fossor (L.)

10. Aqonum - A. dorsale (Pont.)

1 1 . Notiophilus - N. biquttatus (F.)

172 Beetle no. Beetle no. outside the HYDRAULIC SPRAY from 29 June to 27 July 1981. (*)and grass Distance from hedgerow, H (m ) FIGURE 25 Total captures of Carabidae E2 within L.spinibarbis 173

Z o z o

z p f 9 5 ^ 5 0 0 0 10 i5 i 5 n 5 1 pi pi SL within within (* ) and outside the HYDRAULIC SPRAY from 29 June to 27 July 1981. E3 E3 M. I m 0 JZL ______M. . . n n n n n 1 ra 0 ra FIGURE 26 Total captures of less common Carabidae

N.biguttatus B. harpaloides B. B. lampros B. C.fossor P. P. madidus Cmelanocephalus H. rufipesH. A.dorsale H.aeneus A. plebeia

174 Beetle no. Beetle no. ’ 1861- ^|np ^|np 1861-’ iz oi eunp 63 63 eunp oi wojj Vd All m psn pe ujiUjM ) * { pue ep|s*no om lfl A AVUdS % % aepjqejeo jo sejnideo |eioj. |eioj. sejnideo jo aepjqejeo LZ 3driOld snueueieui'd snpipeui d snpipeui

175 Z z o o o in___ o in ___ o m o in __ o in___ o in___ o m S 5 22L . 0 . 120 200 75 JL -EL K n J3L EL .13. EL grass EL R ..fjinny ___ __ &>A.A JB EL H CT 10* 1* 1 1 1 10 30 50 1 R 75 FIGURE 28 Total captures of less common Carabidae E l within (*) and outside the ULV SPRAY from 29 June to 27 July 1981.

N. N. biguttatus A.plebeia L.spinibarbis B.harpaloides H.rufibarbis H.rufipes aeneus H. B.lampros H. tardusH.

176 The number of carabids declined 1-3 days after spraying (Table 19),

although their density increased later (Figures 29 and 30).

Table 19 Pre and post spray variation in overall carabid density.

Time (pre (-) or post (+) spray)

-3 + 1 + 3 + 7 + 14 + 20

0.56 0.42 0.49 0.64 1.61 2 .0 1

The number sampled in the hydraulic spray treatment was

signifi cantly higher (1.16/trap) than the density in the ULV treatment

(0.75/trap).

Populations were low at the field boundaries and inside the treated

plots (Table 20) and the greatest post spray decline in numbers occurred

inside the hydraulic spray and up to 1 m downwind from the ULV spray

treatment (Table 20).

Table 20 Variation in carabid density within and downwind from the treated plots.

Method of Distance from hedgerow, H (m) application 75*& 10* 1*& 1*(H) 1(H) & 1 10 & 30 50 & 75 120 & 200

Hydraulic 1.55 0.53 1.18 1.96 3.95 4.77 ULV 1.35 1.07 1.23 2 .2 2 1.62 1.48

* indicates sprayed plots

1. Here and on subsequent pages, for density read number / trap.

177 FIGURE 29 Pre and post spray variation in overnight (a ) and

daytime ( a ) trap catches of Carabidae.

(0a

Aa> E C3 •u A (0w CO o c <0

Days pre (-) or post spray, s

FIGURE 30 Pre and post spray variation in the trap catches of Carabidae within and outside the hydraulic ( • ) and ULV(°) sprays. Table 21 The general trend in the pre and post spray abundance of Carabidae within and downwind from the sprayed plots

Di stance Time (days pre (-) or post (+) spray) from hedgerow, H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 0.80 0.28 1.50 5.36

* 1.0 - 1.0*(H) 0.20 • 0.18 0.42 2.33

1.0 (H) - 1.0 0.45 0.48 0.82 1.72

10.0 - 30.0 0.35 0.57 1.92 3.38

50.0 - 75.0 0.45 1.12 4.02 3.59

120.0 - 200.0 0.70 1.05 5.22 4.98

ULV

* 75.0 - * 10.0 0.90 0.32 1.10 3.44

* 1.0 - 1.0*(H) 0.75 0.30 0.77 2.58

1.0 (H) - 1.0 0.70 0.20 1.20 6.00

10.0 - 30.0 0.30 0.60 2.27 3.79

50.0 - 75.0 0.60 0.62 1.20 1.93

120.0 - 200.0 0.50 ‘ 0.48 1.25 2.60

* indicates sprayed plot.

The increase in beetle density 14-20 days after spraying was higher outside the hydrauli c spray than the ULV treatment. Outside the sprayed plots, numbers increased 1-20 days after treatment (Table 21).

179 Numbers within the treated plots

The number of carabids at 75 m and 10 m declined by 100 per cent and

72-100 per cent 1-3 days after the hydraulic spray and ULV treatments

respectively (Figures 31 and 32). Numbers increased one week post spray

but the subsequent rate of increase was higher inside the hydraulic spray.

The carabid density 1 m from the hedgerow was unaffected by the hydraulic

spray although an 84 per cent reduction in numbers occurred within the ULV

treatment with little subsequent increase (Figure 33).

Numbers in hedaerows

Few carabids were collected close to the hedgerows (*l(H)m and

l(H)m) but no decline in density was apparent after spraying (Figures 34 and 35).

Numbers 1-200 m downwind

Immediately after spraying, numbers 1 m downwind from the hydraulic spray and ULV treatments declined by 48 and 80 per cent respectively.

Outside the hydraulic spray, their density increased 2 days later but numbers did not return to pre spray levels until 14 days after the ULV spray (Figure 36).

180 Pre and post spray trap catches of Carabidae within (*) and outside the hydraulic (•) and ULV (° ) sprays.

FIGURE 31 75 m * FIGURE 32 10m*

Days pre(-) or post spray,s Days pre(-) or post spray ,s

FIGURE 33 1m * FIGURE 34 1m to lee of hedge 1 (H)*m

Days p re (-)o r post spray,s Days pre (-) or post spray, s 181 Pre and post spray trap catches of Carabidae outside the hydraulic (•) and ULV (°) sprays.

FIGURE 35 1m to windward of FIGURE 36 1m downwind hedge , 1 (H)m

Days pre(-) or post spray, s Days p re(-)o r post spray,s

FIGURE 37 10m downwind FIGURE 38 30m downwind

a (0

© JQ E 3 C TJ S(0 flj o

Days pre(-) or post spray,s Days pre(-) or post spray, s 182 Pre and post spray trap catches of Carabidae outside the hydraulic (•) and ULV (°) sprays.

FIGURE 39 50m downwind FIGURE 40 75 m downwind

Days p re (-) or post spray,s Days pre (-) or post spray,s

FIGURE 41 120m downwind FIGURE 42 2 00 m downwind

Days pre ( - ) or post spray,s Days pre ( - ) or post spray,s 183 The number of Carabidae 10-200 m downwind were not adversely affected by the insecticide spray and beetle density increased 7-20 days post-treatment (Figures 37 to 42). This effect was most marked 50-200 m outside the hydraulic spray (Figures 39 to 42).

Pterostichus melanarius (1 1 1 )

The number of male and fenale P. melanarius was recorded and sexual dimorphism of the anterior tarsal segments facilitated rapid differentiation between sexes. In the male there is a dilation of the tarsi which appears as a "pad-like" structure and is not apparent in the female (Holliday, 1977; Jepson, 1981 pers. ccmm.).

More P. melanarius were collected in the hydraulic spray

(0.88/trap) compared with the ULV treatment (0.47/trap). Numbers of P. melanarius decreased 1-3 days after spraying (Table 22) but their density increased subsequently (Figures 43 and 44).

Table 22 Pre and post spray variation in the overall density of P. melanarius

Time (pre(-) or post (+) spray)

- 3 + 1 + 3 + 7 + 14 + 20

0.31 0.20 0.23 0.42 1.30 1.58

184 The lowest populations occurred inside the sprayed plots and in the hedgerows (Table 23) and the greatest decline in density was within the treatments and up to 1 m downwind from the ULV spray (Table 24). The subsequent rate of increase in numbers was higher for the hydraulic spray than the ULV treatment (Table 24). CXitside the treated areas (1-200 m downwind), there was little change in the number of P. melanarius 1-3 days after spraying and populations increased later (Table 24).

Table 23 Variation in the overall density of P. melanarius within and downwind from the hydraulic and ULV spray treatments.

Method of Di stance from hedcrerow, H (m) application 75*& 10* 1*& 1*(H) 1(H) & r 10 & 30 50 & 75 120 & 200

Hydraulic 0.42 0 .10 0.32 0.67 1.69 2.09 ULV 0.42 0.27 0.36 0.77 0.51 0.52

* indicates sprayed plots Slightly more fanale P. melanarius (0.82/trap) were sampled compared with the number of males (0.53/trap). The femalermale ratio for both treatments was not significantly different (approximately 1.5), but

twice as many male and female beetles were collected in the hydraulic

spray treatment (Table 24).'

Table 24. Overall density of male and fanale P. melanarius for each spray treatment.

Method of application Sex Male Female

Hydraulic • 0.69 1.07 ULV 0.37 0.57

185 Mean number of P. melanarius per trap 2 Mean number of P. melanarius per trap of catches trap in variation spray post and Pre 3 4 FIGURE UE 4 4 GURE r ad ot pa vrain n rp ace of catches trap in variation spray post and Pre ae n fml □ P melanarius P. □ female and H male .mlnru wti ad usd te yrui (•) sprays. ) hydraulic (° the ULV outside and and within P. melanarius 186

Table 25 The general trend in the pre and post spray abundance of P. melanarius within and downwind from the hydraulic and ULV spray treatments •

Di stance Time (days pre (-) or post ( + ) spray) from hedgerow, H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 0.40 0.05 0.67 13.40

* 1 .0 - 1 .0 *( H) 0 .0 0 .1 0 0.13 1.30

1.0 (H) - 1.0 0 .10 0.15 0.50 3.33

10.0 - 30.0 0.30 0 .2 2 1 .1 0 5.00

50.0 - 75.0 0.40 0.45 2.95 6.55

1 2 0 .0 - 200.0 0.55 0.50 3.67 7.34

ULV

* 75.0 - * 10.0 0.70 0 .1 2 0.52 4.33

* 1.0 - 1.0*(H) 0.35 0.17 0.32 1 .8 8

1.0 (H) - 1.0 0.15 0.07 0.62 8 .8 6

10.0 - 30.0 0 .20 0.25 1.27 5.08

50.0 - 75.0 0.40 0.27 0.70 2.59

1 2 0 .0 - 200.0 0 .2 0 0.25 0.80 3.20

* indicates sprayed plot.

187 Table 26 Variation in the overall densities of male and female P. melanarius within and outside the sprayed area.

Distance from hedgerow, H (m) Sex 75*& 10* 1*& 1*(H) 1(H) & 1 10 & 30 50 & 75 120 & 200

Male 0.41 0.18 0.23 0.53 0.84 0.97 Female 0.42 0.19 0.44 0.89 1.34 1.63

* indicates sprayed plots

The sex ratio was close to unity inside the sprayed areas (Table

26), but the number of females was higher 1 - 200 m downwind. Within the treatments numbers of male and fenale P. melanarius declined 1 - 3 days after spraying (Table 27) and, although numbers increased subsequently the male density remained low up to 3 and 7 days after the hydraulic and ULV treatments respectively (Figures 45 and 46).

Numbers within treated plots

Male P. melanarius disappeared from traps at 10 and 75 m 1 -3 days

post treatment but numbers increased 7 and 20 days after the hydraulic

spray and ULV treatments respectively (Figures 47 to 50). Males were not present in samples at 1 m up to 20 days after the hydraulic spray (Figure

51) although their density declined by 67 per cent inmediately after the

ULV spray and none were found 2 days later (Figure 52). Numbers recovered to pre spray levels 14 days post ULV treatment (Figure 52).

188 Table 27 The general trend in the pre and post spray abundance of male and female P. melanarius within and downwind from the sprayed plots.

Distance Time (days pre (-) or post (+) spray) from hedgerow,H (m) -3 (Tl) 41,3,7 (T2) 414,20 (T3) Ratio T3/T2

MALE

* 75.0 - * 10.0 0.65 0 .1 2 0.52 4.33

* 1.0 - 1.0*(H) 0.25 0 .1 0 0 .2 2 2 .2 0

1.0 (H) - 1.0 0.15 0.07 0.37 5.28

10.0 - 30.0 0.15 0 .2 2 0.87 3.95

50.0 - 75.0 0.40 0.15 1.48 9.87

12 0 .0 - 200.0 0.15 0.27 1.72 6.37

FEMALE

* 75.0 - * 10.0 0.45 0.05 0.67 13.40

* 1.0 - 1.0*(H) 0 .1 0 0.17 0.23 1.35

1.0 (H) - 1.0 0 .10 0.15 0.75 5.00

10.0 - 30.0 0.35 0.25 1.50 6 .0 0

50.0 - 75.0 0.40 0.57 2.17 3.81

1 2 0 .0 - 200.0 0.60 0.47 2.75 5.85

* indicates sprayed plot.

189 IUE 45 FIGURE Mean no. of P. melanarius /trap £ Mean no. of P. melanarius / trap 6 r ad ot pa vrain n rp ace of catches trap in variation spray post and Pre 46 ae 1ad eae .mlnru wti and within P.melanarius □ female and 11 male r ad ot pa vrain n rp ace of catches trap in variation spray post and Pre usd te YRUI SPRAY. HYDRAULIC the outside male male usd h UV SPRAY. ULV outside the IS IS n fml □ P eaais ihn and within melanarius P. □ female and 190

trsihs eaais 5 ad 0 wti te hydraulic the within 10m and sprays. ULV 75m and melanarius Pterostichus r ad ot pa ta cths f ae n fmae □ ale fem and H male of catches trap spray post and Pre Mean no. of P. melanarius / trap ti Mean no. of P. melanarius / trap spray HYDRAULIC 47 FIGURE UE 9 YRUI spray HYDRAULIC 49 SURE as r (-) o ps spray,s post or ) - ( pre Days as r () r ot spray,s post or (-) pre Days 0m* 10 m 5m* m 75

191

5 JO ’C CL a> CO c c 6 O a> c CO E (0 3 2 CO a IUE 0 L spray ULV 50 FIGURE JO Ql 'C © CO c c O* O E CO

Pre and post spray trap catches of male S and female 0 Pterostichus melanarius 1m within and outside the hydraulic and ULV sprays.

FIGURE 51 HYDRAULIC spray FIGURE 52 ULV spray 1m * 1m*

a. a (0

(0 3 C CO (0c

a.*

o o c c

s Days pre ( - ) or post spray,s Days pre ( - ) or post spray,s

FIGURE 53 HYDRAULIC spray FIGURE 54 ULV spray 1m to lee of hedge 1m to lee of hedge

a (0

Days pre (-) or post spray, s Days pre (-) or post spray, s 192 One to three days after the hydraulic spray, no fanale beetles were trapped at 10 m and 75 m although numbers increased one week post treatment (Figures 47 and 49). No insecticidal effect was recorded

75 m inside the ULV spray (Figure 48), but at 10 m the number of females declined by 80 per cent one day after treatment and disappeared 2 days later (Figure 50). Females were found in catches 7 days post spray

(Figure 50). The numbers 1 m fron the edge of both treatments were not significantly different from zero throughout the trial (Figures 51 and 52).

Numbers in hedaerows

Captures of male and female P.melanarius were low or zero throughout the sampling-period and no insecticidal effect was apparent

(Figures 53 - 56).

Numbers 1-200 downwind into the untreated field

Three days after the hydraulic spray, male beetles were absent from traps at 1 m but reappeared 4 days later (Figure 57). Numbers 1 m downwind from the ULV spray remained low up to 20 days post treatment

(Figure 58). No males were present in pre spray samples 10 m downwind from both sprays, but were sampled 1 and 7 days after the ULV and hydraulic sprays respectively (Figures 59 and 60). In general, the numbers of males 30-200 m downwind were not significantly affected by the hydraulic spray and their density increased 7-20 days post treatment, notably 50-100 m downwind (Figures 61,63,65,67, and 69). The male density

193 30-200 m outside the ULV spray was lower and significant increases, if any, occurred 2 weeks after spraying (Figures 62, 64, 6 6 , 6 8 , and 70).

Following spray application, the number of female P. melanarius did not decline significantly 1-200 m downwind (Figures 57 to 70).

Initial trap captures were low but numbers increased 7-20 days after the hydraulic spray, in particular 50-200 m downwind (Figures 63, 65, 67, and

69). The number of females also increased 14-20 days after the ULV spray

(Figures 58, 60, 62, 64, 6 6 , 6 8 , and 70) although little significant change in density occurred 50-200 m downwind (Figures 64, 6 6 , 6 8 , and 70).

Staphylinidae

The staphylinid activity per hour was similar at night (0.03/trap) and during the day (0.02/trap). Populations decreased 1-3 days after spraying (Table 28) and increased slightly later (Figures 71 and

72).

Table 28 Pre and post spray variation in staphylinid density

Time (pre (-) or post (+) spray)

-3 +1 +3 +7 +14 +20

0.50 0.27 0 .20 0.23 0.33 0.35

194 Pre and post spray trap catches of male fH and female □ Pterostichus melanarius 1m on both sides of the hedge bordering the unsprayed field.

FIGURE 55 HYDRAULIC spray FIGURE 56 ULV spray 1 (H )m 1 (H)m

a a TO TO

(0 3 (0 l . TO TO c C TO TO 0) O E E CL CL

O o c

Days p re (-) or post spray,s Days p re (-)o r post spray, s

FIGURE 57 HYDRAULIC spray FIGURE 58 ULV spray 1 m downwind 1m downwind

a TO

Days pre (-) or post spray, s Days pre ( - ) or post spray, s 195 Pre and post spray trap catches of male U and female i _ i Pterostichus melanarius 10m and 30m outside the hydraulic and ULV sprays.

FIGURE 59 HYDRAULIC spray FIGURE 60 ULV spray 10 m downwind 10 m downwind

Days p re (-)o r post spray,s Days pre (-) or post spray, s

FIGURE 61 HYDRAULIC spray FIGURE 62 ULV spray 30 m downwind 30m downwind

a(0

(0 u <0c iS o E al o d c (0c 0) 2 Pre and post spray trap catches of male H and female D Pterostichus melanarius 50m and 75m outside the hydraulic and ULV sprays.

FIGURE 63 HYDRAULIC spray FIGURE 64 ULV spray 50m downwind 50m downwind

a TO

W TO C TO TO 6 a

o

oc c TO to 5

Days p re (-)o r post spray,s Days pre ( - ) or post spray, s

FIGURE 65 HYDRAULIC spray FIGURE 66 ULV spray 75 m downwind 75 m downwind

a a TO ra

(0 3 u TO C TO TO E a

o o c

Days p re (-)o r post spray,s Days p r e (-) or post spray,s 197 Pre and post spray trap catches of male E l and female □ Pterostichus melanarius 120m and 200 m outside the hydraulic and ULV sprays.

FIGURE 67 HYDRAULIC spray FIGURE 68 ULV spray 120 m downwind 120 m downwind

Days p re (-)o r post spray, s Days pre ( - ) or post spray, s

FIGURE 69 HYDRAULIC spray FIGURE 70 ULV spray 200 m downwind

a(0

(0 'S ‘C c(0 J2 a> E ol

o

6c

Days p re (-) or post spray,s 198 Days p re (-) or post spray,s The number of staphylinids trapped in the hydraulic spray (0.43/trap) was twice the density in the LJLV (0.20/trap) treatment. The highest populations occurred within the treated plots (Ikble 29) and 1-3 days after spraying numbers declined at all distances apart from 1 m to both sides of the hedge bordering the hydraulic spray (Table 30). Numbers increased slightly 7-20 days post-spray (Table 30).

Table 29 Variation in staphylinid density within and downwind from the treated plots.

Method of Distance from hedgerow, H (m) application 75*& 10* 1*& 1*(H) 1(H) & 1 10 & 30 50 & 75 120 & 200

Hydraulic 0.49 1.27 0.20 0.14 0 .2 2 0.24 ULV 0.47 0.36 0.08 0 .10 0.09 0 .1 1

* indicates sprayed plots

199 Mean staphylinid number/trap m Mean staphylinid number/trap 71 FIGURE GR 7 r ad ot pa vrain n h ta catches trap the in variation spray post and Pre 72 IGURE r ad ot pa vrain n vrih and overnight in variation spray post and Pre atm () rp ace o Staphylinidae. of catches trap (^) daytime f tpyiia wti ad usd the outside and within Staphylinidae of yrui ad L spray. ULV and hydraulic 200

Table 30 The general trend in the pre and post spray abundance of Staphylinidae within and downwind from the sprayed plots

Di stance Time (days pre (-) or post. (+) spray) from hedgerow, H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 1.45 0.30 0.30 1 .0 0

* 1.0 - 1.0*(H) 0.95 1 .2 2 1.40 1.17

1.0 (H) - 1.0 0.15 0 .1 2 0.27 2.14

10.0 - 30.0 0.30 0.07 0.13 1.77

50.0 - 75.0 0 .10 0 .20 0.28 1.41

1 2 0 .0 - 200.0 0.45 0.07 0.28 3.77

ULV

* 75.0 - * 10.0 1.50 0.25 0.27 1.08

* 1.0 - 1.0*(H) 0.40 0 .2 2 0.43 1.91

1.0 (H) - 1.0 0.30 0.05 0.03 0.60

10.0 - 30.0 0.15 0.05 0 .1 2 2.40

50.0 - 75.0 0.30 0.05 0.05 1 .0 0

1 2 0 .0 - 200.0 0 . 0.17 0 .1 0 0.57

* indicates sprayed plot.

201 Numbers inside the treated plots

Immediately after the hydraulic spray, the number of Staphylinidae at 75 m and 10 m declined by 60 and 74 per cent respectively (Figures 73 and 74) and 2 days later numbers at 1 m decreased by 75 per cent (Figure

75). One day after the ULV spray, a 67-86 per cent decline in numbers was recorded at 75 m and 10 m (Figures 73 and 74) while no staphylinids were found at 1 m (Figure 75). No significant recovery occurred subsequently.

Numbers in hedaerows

Populations of Staphylinidae 1 m to the lee of the hedgerow (*1(H) m) increased 1-14 days after the hydraulic spray (Figure 76). An initial increase immediately after the ULV spray preceded a decline in density to pre-spray levels although numbers increased slightly later (Figure 76).

Pre and post spray numbers of staphylinids collected 1 m to the windward of the hedgerow bordering the untreated field were not significantly different up to 14 days after the hydraulic spray and numbers downwind from the ULV spray remained low throughout the trial

(Figure 77).

Numbers downwind into the untreated field

The number of staphylinids 1-200 m downwind declined and disappeared

1-3 days after the hydraulic spray (Figures 78-84) apart from at 75 m

202 where their density increased up to 14 days post-treatment (Figure 82).

After the ULV spray, no staphylinids were trapped 1-120 m downwind

(Figures 78 to 83), although numbers at 200 m increased 1-3 days

post treatment (Figure 84). Populations at all distances showed little

variation subsequently (Figures 78-84).

Coleopteran larvae

The number of larvae sampled per hour was 0.02/trap at night and

during the day but the low numbers necessitated combining the data. The

number of coleopteran larvae decreased 1-3 days after spraying (Table 31)

and only a slight increase in their density was apparent later (Figures 85

and 8 6 ).

Table 31 Pre and post spray variation in the density of coleopteran larvae

Time (pre(-) or post ( + ) spray)

-3 + 1 +3 +7 +14 +20

0 .8 8 0.16 0.05 0.08 0.14 0.07

Numbers collected in the hydraulic spray (0.23/trap) and ULV (0.24/trap) treatments were not significantly different. The lowest populations occurred next to the hedgerows (Table 32) but numbers declined at all distances 1-3 days post spray and further decreases were evident within and 50-200 m downwind 7-20 days after spraying (Table 33).

203 Pre and post spray trap catches of Staphylinidae within (*) and outside the hydraulic (•) and ULV (°) sprays.

FIGURE 73 75 m* FIGURE 74 10 m*

FIGURE 75 1m* FIGURE 76 1m to lee of hedge

FIGURE 77 1m to windward of FIGURE 78 1m downwind Pre and post spray trap catches of Staphylinidae outside the hydraulic (•) and ULV (°) sprays.

FIGURE 79 10m downwind FIGURE 80 30m downwind

a to

>% x: a CO (/> c 0<0) S

FIGURE 81 50m downwind FIGURE 82 75 m downwind

FIGURE 83 120 m downwind FIGURE 84 200 m downwind Table 32 Variation in the density of coleopteran larvae within and downwind from the treated plots

Method of Distance from hedgerow, H (m) application 75*& 10* 1*& 1*(H) 1(H) & 1 10 & 30 50 & 75 120 & 200

Hydraulic 0.23 0.27 0.07 0.17 0.32 0.30 ULV 0.32 0 .20 0 .1 2 0.27 0.27 0.25

* indicates sprayed plots

Numbers inside treated plots

The number of Coleopteran larvae at 75 m decreased by 94 and 83 per

cent immediately after the hydraulic spray and ULV treatments respectively

(Figure 87). No larvae were collected in subsequent samples within the

hydraulic spray, although numbers increased significantly 14 days post

ULV treatment (Figure 87).

Populations 10 m inside the hydraulic spray did not vary

significantly after treatment, while a 67 per cent decline in density

occurred 3 days after the ULV spray and numbers did not increase later

(Figure 83).

Larvae disappeared from traps at 1 m 3 days after both sprays

(Figure 89). Numbers increased significantly one week post hydraulic

spray but little significant change in density was apparent inside the ULV

spray (Figure 89).

206 Mean no. of coleopteran larvae /trap 33 Mean no. of coleopteran larvae /tra p overnight in variation spray post and Pre 5 8 FIGURE UE 86 GURE r ad ot pa vrain n rp ace of catches trap in variation spray post and Pre oepea lra wti ad usd the outside and within larvae coleopteran hydraulic ( • ) and and ) • ( hydraulic larvae. and daytim e e daytim and 207 ( a ) rp ace o coleopteran of catches trap ULV(o) sprays.

( a )

Table 33 The general trend in the pre and post spray abundance of coleopteran larvae within and downwind from the sprayed plots.

Di stance Time (days pre (-) or post (+) spray) from hedgerow,H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 0.95 0.17 0.03 0.18

* 1.0 - 1.0*(H) 0.15 0.12 0.42 3.50

1.0 (H) - 1.0 0.30 0 0.03 inf.

10.0 - 30.0 0.80 0.02 0.05 2.50

50.0 - 75.0 1.35 0.15 0.08 0.53

120.0 - 200.0 1.50 0.12 0.02 0.17

ULV

* 75.0 - * 10.0 0.65 0.35 0.18 0.51

* 1.0 - 1.0*(H) 0.45 0.05 0.07 1.40

1.0 (H) - 1.0 0.65 0.02 0.20 1.00

10.0 - 30.0 1.20 0.07 0.08 1.14

50.0 - 75.0 1.45 0.07 0 0

120.0 - 200.0 1.15 ‘ 0.12 0.03 0.26

* indicates sprayed plot.

208 Numbers in hedaerows

One day after the ULV spray, the number of larvae declined by 75 per

cent 1 m from the hedge next to the sprayed plots (*1(H) m) and none were

trapped 3 days after both sprays (Figure 90). The subsequent rate of

increase was lower next to the ULV spray and numbers declined in the final samples from both sprays (Figure 92).

Larvae disappeared from samples 1 m outside the untreated field

(1(H) m) immediately after both treatments and did not increase subsequently (Figure 91).

Numbers 1-200 m downwind into the untreated field

No beetles were trapped 1-3 days after both sprays (Figures 92-98) and no subsequent increase in numbers occurred downwind from the hydraulic spray although a slight increase was apparent 10 m, 30 m, and 200 m downwind from the ULV spray (Figures 93, 94 and 98).

209 Pre and post spray trap catches of Coleopteran larvae within (*) and outside the hydraulic (•) and ULV (°) sprays.

FIGURE 87 751^ FIGURE 88 10 m*

a a (0 CO

0> o> 5 w5 « JS 2 a>2 •*->a> ** a a o a> s o O 6c (0c 0) 2

FIGURE 89 1m* FIGURE 90 1m to lee of hedge

a co

a> CO u> . ro co o a o a> o O 6 c c CO 0) 2

FIGURE 91 1 m to windward of FIGURE 92 1m downwind

210 Pre and post spray trap catches of Coleopteran larvae outside the hydraulic (•) and ULV (®) sprays.

FIGURE 93 10 m downwind FIGURE 94 30 m' downwind

a a. CO (0

a> o(0 >(0 > k . k - i2 i5 2 (0 a. Q. o O a> 0) o O O o 6c 10c a>

FIGURE 95 50m downwind FIGURE 96 75m downwind

a a to to

o 5 aj to 2 k _ a> a a. o o JJJ _a) o o O O o c 6c (0c c 0) (0a>

FIGURE 97 120 m downwind FIGURE 98 200 m downwind

a CO

0) >CO .2k . 2 a> •4- o O

211 Araneae

Spiders, predominantly members of the Linyphiidae and Lycosidae,

were very numerous in the pitfall traps. No differentiation was made

between adult and immature individuals.

Slightly more spiders/hour were collected during the day (0.17/trap)

compared with the night samples (0.09/trap). Numbers of spiders decreased

1-3 days after spraying (Table 34), but their density increased

subsequently (Figures 99 and 100).

Table 34 Pre and post spray variation in the overall density of Araneae

Time (pre (-) or post(+) spray 1) days

-3 +1 +3 +7 +14 +20

1.39 1.05 1.15 1.39 1.63 1.85

The number sampled in the hydraulic spray (1.32/trap) and ULV

(1.50/trap) treatments was- not significantly different, with the lowest populations and greatest decline in density occurring inside the treated plots (Tables 35 and 36). CUtside the treated areas (1-200 m downwind) there was little change in the number of spiders immediately after the spray, although numbers increased slightly later (Table 36). The increase in density 7-20 days after spraying was highest inside the ULV treatment (Table 36).

212 Table 35 Variation in the overall density of Araneae within and downwind from the treated plots

Method of Di stance from hedaerow, H (m) application 75*& 10* 1*& 1*(H) 1(H) & 1 10 & 30 50 & 75 120 & 200

Hydraulic 0.50 0.98 2.01 1.43 1.25 1.74 ULV 1.02 1.82 2.12 1.11 1.22 1.68

* indicates sprayed plots

Numbers within treated plots.

More detailed analysis showed that the density of spiders declined by 33 - 80 per cent immediately after both sprays (Figures 101 to 103), although no decrease was evident 10 m within the ULV spray until 2 days later when numbers were reduced by 58 per cent (Figure 102). Further depletion of populations occurred 2 days after the hydraulic spray and the number of spiders at 10 m and 1 m declined by 100 and 80 per cent respectively (Figures 102 and 103). Their density at 10 m and 1 m within the hydraulic spray increased one week post treatment (Figures 102 and

103), while no significant recovery was apparent at 75 m up to 20 days after spraying (Figure 101). The rate of increase was higher inside the

ULV spray (Figures 101 and 102) apart from numbers sampled close to the 4 hedge which did not return to pre spray levels until 14 days after treatment (Figure 103).

213 FIGURE 99 Pre and post spray variation in overnight (a ) and daytime (a ) trap catches of Araneae.

a to

5

FIGURE 100 Pre and post spray variation in trap catches of Araneae within and outside the hydraulic (•) and ULV ( o) sprays .

a TO

a> TO a> c TO < 1 O k_ 0 JD E

0 i------1------1------r ~ —I ▲ -3 s 1 3 7 14 20 Days pre (- ) or post spray, s 214 Table 36 The general trend in the pre and post spray abundance of Araneae within and downwind from the sprayed plots

Di stance Time (days pre (-) or post (+) spray) from hedge row, H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 0.95 0.20 0.55 . 2.75

* 1.0 - 1.0*(H) 1.20 0.80 1.03 1.29

1.0 (H) - 1.0 2.15 2.00 1.97 0.98

10.0 - 30.0 0.80 1.12 1.85 1.54

50.0 - 75.0 0.45 0.52 2.00 3.85

120.0 - 200.0 1.45 1.35 2.10 1.55

ULV

* 75.0 - * 10.0 0.60 0.22 1.68 7.64

* 1.0 - 1.0*(H) 2.45 1.55 1.80 1.16

1.0 (H) - 1.0 2.60 2.10 1.98 0.94

10.0 - 30.0 1.05 1.02 1.18 1.16

50.0 - 75.0 1.05 1.12 1.35 1.20

120.0 - 200.0 1.90 1.15 1.97 1.71

* indicates sprayed plot.

215 Pre and post spray trap catches of Araneae within (*) and outside the hydraulic (•) and ULV (°) sprays.

FIGURE 101 75 m* FIGURE 102 10 m*

Days pre(-) or post spray,s Days pre (-) or post spray,s

FIGURE 103 1m* FIGURE 104 1m to lee of hedge

Days p re (-) or post spray,s Days pre ( - ) or post spray,s

216 Numbers in hedgerows

The spider populations 1 m leeward of the hedgerow (*1(H) m) next to the hydraulic spray showed little significant change throughout the trial whereas numbers declined by 43 per cent immediately after the ULV spray but increased one week later (Figure 104). The number of spiders 1 m from the hedge bordering the untreated field (1(H) m) decreased by 80 per cent

3 days after the hydraulic spray and 38 per cent 1 day post ULV treatment

(Figure 105). The density outside the hydraulic spray increased later but did not return to pre spray levels, while numbers increased 3 days after the ULV spray but declined 11 days later (Figure 105).

Numbers 1-200 m downwind into the untreated field

The density of spiders 10 m, 120 m and 200 m downwind declined 1-3 days after the hydraulic spray but increased 2-4 days later (Figures 107,

111 and 112). Numbers collected 1 m, 30 m, 50 m, 120 m and 200 m downwind

also declined slightly 1-3 days after the ULV spray (Figures 106, 108,

109, 111 and 112). Populations returned to pre spray levels 7-20 days

post treatment although considerable variation in catches occurred

subsequently at 50 m, 120 m and 200 m (Figures 109, 111 and 112).

The number of spiders at other distances outside the ULV spray

showed little significant variation during the trial (Figures 107 and 110) while populations 1 m, 30 m, 50 m, and 75 m, downwind from the hydraulic

spray increased 3-20 days post treatment (Figures 106, 108 , 109 and 110).

217 Pre and post spray trap catches of Araneae outside the hydraulic ( • ) and ULV (°) sprays.

FIGURE 105 1m to windward of hedge FIGURE 106 1m downwind

a (0

a> .o E 3 C

Days p re (-) or post spray, s Days pre (-) or post spray, s

FIGURE 107 10m downwind FIGURE 108 30m downwind

a (0

o

5

Days pre (-) or post spray, s Days pre(-)or post spray,s

218 Pre and post spray trap catches of Araneae outside the hydraulic (•) and ULV (°) sprays.

FIGURE 109 50m downwind FIGURE 110 75 m downwind

a co

a> co ) c0 CO <

0) JQ E 3 C

Days pre (-) or post spray, s Days pre (-) or post spray,s

FIGURE 111 120m downwind FIGURE 112 200 m downwind

8 r

Q. CO

0) CO a> c COW < o k- ) A0 E 3 C C CO a>

— i-- n r “ i— “ l - 3 A1 3 14 20 s Days pre (-) or post spray,s Days pre (-) or post spray, s

219 6.3.2 Water trap catches

Total catches

Water traps in the winter wheat crops sampled flying and crawling arthropods, predominantly Ichneumonidae, Braconidae, Chalcidoidea and

Proctotrupoidea. The most cannon species trapped was Pirene penetrans, a parasite attacking wheat blossom midge larvae (Contarinia tritici).

Aphids, Cecidomyiidae, Empididae, Apoidea, Arachnida and Staphylinidae

(principally Tachyporus spp.) were also trapped but numbers were so low that data for individual genera were not analysed. Some traps occasionally contained larvae, e.g. wheat blossom midge, coccinellid and chrysopid larvae, which probably fell off wheat plants. Thysanoptera,

Anthomyiidae, Opcmyziidae and Drosphilidae (probably Scaptomyza spp.) were frequently trapped but the data were not relevant to the natural enemy survey. Small numbers of Syrphidae were also found; the main species present in the crop were: Platycheirus peltatus

(Meig.), Episyrphus balteatus (Deg.), Metasyrphus corollae(F.)

Melanostoma spp. and Heliomyza spp.

Fewer arthropods/hour were sampled overnight (0.39/trap) compared with daytime samples (1.47/trap). More arthropods were collected 1-3 days after spraying (Table 37) but numbers declined later (Figures 113 and

114).

220 Table 37 Pre and post spray variation in overall water trap catches.

Time (pre (-) or post (+) spray)

-3 + 1 + 3 + 7 + 14 + 20

8.13 10.62 11.55 7.28 6.78 6.22

The number sampled in the hydraulic spray (8.22/trap) and ULV

(8.64/trap) treatments were not significantly different. The lowest populations and the smallest increase in density 1-3 days post spray were inside the ULV treatment and on the windward side of the hedgerow next to the sprayed plots (Tables 38 and 39).

Table 38 Variation in water trap catches within and downwi nd from the treated plots.

Method of Di stance from hedcrerow, H (m) applicatior) 75* 10* 10 30 " 50 75 120 200

Hydraulic 7.89 5.06 10.81 10.22 10.61 6.69 8.44 6.04 ULV 5.25 4.39 13.80 13.47 9.14 9.67 5.42 8.00

* indicates sprayed plots

Outside the treated areas (10-200 m downwind), the highest populations were 10 m and 30 m downwind (Table 38) and the number of arthropods increased after spraying, but their density decreased later

(Table 39).

221 FIGURE 113 Pre and post spray variation in overnight overnight in variation spray post and Pre 113 FIGURE Mean arthropod number / trap 3 Mean arthropod number / trap GURE 114 Pre and post spray spray post and Pre 114 GURE 10 12 14 0 8 0 8 - - -3 -3 T ace wti ad usd te yrui (•) hydraulic the outside and within catches n UV ° sprays. (°) ULV and and daytime daytime and s 1 — 3 7 14 7 3 1 S T as r -) o ps sry, s , spray post or ) (- pre Days as e- o ps sry s spray, post or re(-) p Days ------T 3 A ------1------1- 1------1------1 ( a ) 7 ae ta catches. trap water aito in variation 14 ae trap water

(

a

20 20 <1 ◄ <1 )

Table 39 The general trend in the size of water trap catches before and after treatment and within and downwind from the hydraulic and ULV sprays.

Distance Time (days pre (-) or post ( + ) spray) from hedgerow,H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 7.75 8.46 4.72 0.56

10.0 - 30.0 11.42 13.08 8.50 0.65

50.0 - 75.0 7.25 10.12 8.14 0.80

120.0 - 200.0 7.45 8.00 6.67 0.83

ULV

* 75.0 - * 10.0 5.08 5.79 4.08 0.70

10.0 - 30.0 15.00 19.85 9.03 0.45

50.0 - 75.0 6.00 15.04 6.78 0.45

120.0 -- 200.0 5.08 8.33 6.17 0.74

* indicates sprayed plot. Numbers inside treated plots

One day after spraying, the number of arthropods trapped 75 m and 10 m within the hydraulic spray increased by 49 and 25 per cent respectively, although their density declined subsequently (Figures 115 and 116).

Numbers collected inside the ULV spray were not significantly different throughout the sampling-period (Figures 115 and 116).

Numbers 10-200 m downwind into the untreated plots

The number of arthropods sampled 10 m and 30 m downwind from the ULV spray increased by 77 and 67 per cent respectively 3 days after treatment but numbers in subsequent captures declined (Figures 117 and 118). No significant variation in arthropod density occurred 10-30 m outside the hydraulic spray 1-3 days post treatment, although numbers declined 4 days later (Figures 117 and 118).

Numbers trapped 50-120 m downwind doubled inmediately after the ULV spray (Figures 119 to 121). Further increases were recorded at 50 m, 75 m <• and 200 m 2 days later (Figures 119, 120 and 122) but numbers declined subsequently. The density of arthropods 50-200 m outside the hydraulic spray showed little significant fluctuation during the sampling-period

(Figures 119 to 122).

224 Pre and post spray water trap catches of arthropods within (*) and outside the hydraulic (•) and ULV (°) sprays.

FIGURE 115 75 m* FIGURE 116 10 m'

FIGURE 117 10 m downwind FIGURE 118 30 m downwind Pre and post spray water trap catches of arthropods outside the hydraulic ( • ) and ULV(<>) sprays.

FIGURE 119 50m downwind FIGURE 120 75m downwind

FIGURE 121 120m downwind FIGURE 122 200m downwind

226 Parasitic Hymenoptera

More parasitic Hymenoptera were collected in the day (4.63/trap)

samples than at night (2.41/trap) and as there was little variation in overnight captures with time (Figure 123), the data were combined. Numbers decreased 1 day after spraying (Table 40) and, although their density

increased 2 days later, numbers declined subsequently (Figures 123 and

124).

Table 40 Pre and post spray variation in the number of parasitic Hymenoptera.

Time (pre (-) or post (+) spray)

-3 + 1 + 3 + 7 + 14 + 20

4.55 3.20 5.44 2.64 2.70 2.61

Slightly more parasitic Hymenoptera were sampled in the ULV spray

(3.97/trap) compared with the hydraulic spray (3.08/trap) treatment and the lowest populations occurred inside the sprayed plots (Table 41). High numbers were trapped 10 - 30 m downwind, to the leeward of the hedgerow

(Table 41). Outside the hydraulic spray treatment captures declined

(Table 42), while parasitic Hymenoptera were more abundant 1-3 days after the ULV spray although their density decreaed subsequently (Table 42).

227 Table 41 Variation in the number of parasitic Hymenoptera within and downwind from the treated plots

Method of Distance from hedaercw, H (m) application 75*& 10* 10 & 30 50 & 75 120 & 200

Hydraulic 1.76 4.28 3.08 3.18 ULV 1.54 6.12 4.32 3.90

* indicates sprayed plots

Table 42 The general trend in the abundance of parasitic Hymenoptera before and after treatment and within and downwind from the hydraulic and ULV sprays.

Di stance Time (days pre (-) or post (+) spray) from hedgerow ,H (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

* 75.0 - * 10.0 2.50 1.96 1.39 0.71

10.0 - 30.0 7.83 5.21 2.47 0.47

50.0 - 75.0 3.41 3.21 2.89 0.90

120.0 - 200.0 3.32 3.17 3.14 0.99

ULV

* 75.0 - * 10.0 1.08 1.96 1.42 0.72

10.0 - 30.0 11.25 7.21 3.66 0.51

50.0 - 75.0 4.00 7.04 2.61 0.37

120.0 - 200.0 3.00 4.79 3.61 0.75

* indicates sprayed plot.

228 FIGURE 123 Pne and post spray variation in overnight (▲) and daytime (^ ) water trap catches of parasitic Hymenoptera.

a CD

2 aa oc a> E > x o (/) %—CD CD a

co c CD CD

FIGURE 124 Pre and post spray variation in water trap catches of parasitic Hymenoptera within and outside the hydraulic (•) and ULV (o) sprays. a CD k.CD a a co * x o '53 u.CD CD a o c c CD 0)

229 Numbers inside treated plots

The number of parasitic Hymenoptera increased slightly one day after the ULV spray, whereas there was no immediate significant change in the numbers collected inside the hydraulic spray (Figures 125 and 126). Apart from a slight decline in density 3-7 days post treatment, little fluctuation in catches occurred later.

Numbers 10-200 m downwind into the untreated field

The high pre spray numbers of parasitic Hymenoptera 10-30 m downwind decreased by 52-68 per cent immediately after the hydraulic and ULV spray treatments (‘Figures 127 and 128). The density increased 2 days later but numbers declined subsequently.

Populations at 50-200 m downwind from the hydraulic spray showed little significant variation throughout the trial (Figures 129 to 132) although the density of parasitic Hymenoptera increased at 50-120 m 3 days after the ULV spray (Figures 129 to 131) and numbers decreased later. At

200 m downwind, no significant change in the numbers occurred after the

ULV spray (Figure 132).

230 Pre and post spray water trap catches of parasitic Hymenoptera within (*) and outside the hydraulic (•) and ULV (°) sprays.

FIGURE 125 75m* FIGURE 126 10 m*

FIGURE 127 10 m downwind FIGURE 128 30m downwind

231 Pre and post spray water trap catches of parasitic Hymenoptera outside the hydraulic (•) and ULV (°) sprays.

FIGURE 129 50m downwind FIGURE 130 75 m downwind

FIGURE 131 120m downwind FIGURE 132 200m downwind

232 6.3.3 Malaise trap catches

Total catches

The Malaise traps were used to determine whether the insecticide sprays affected the overall density of flying insects including parasitic

Hymenoptera, Cecidomyiidae, Empididae, Lepidoptera and Thysanoptera.

Syrphids were caught regularly but numbers were too low for analysis. The following species (predominantly females) were sampled:- Metasyrphus corollae (F.), Syrphus vi tri penni s (Meig.), Episyrphus balteatus

(Deg.), Platycheirus manicatus (Meig.), Melanostoma mellinum (L.) and

S . ribesii (L.). The diversity and abundance of Syrphidae generally increased in traps next to the hedgerows.

Only a number of Malaise traps were available which restricted statistical analysis. The highest numbers of insects occurred in day samples and overnight catches were combined with these data (Figures 133 to 135). One day after spraying, the number of insects increased at all distances (Figures 133 to 135) and this effect was most marked 5 m inside the untreated field where 30 and 10 - fold increases in density occurred downwind from the hydraulic spray and ULV treatments respectively (Figure

134). Numbers declined 2-6 days later and showed no significant variation subsequently (Figures 133 to 135).

233 Pre and post spray Malaise trap catches of arthropods within (*) and outside the hydraulic (•) and ULV (°) sprays.

i FIGURE 133 5m* FIGURE 134 5m downwind

FIGURE 135 120 m downwind

234 Pre and post spray Malaise trap catches of parasitic Hymenoptera within (*) and outside the hydraulic ( • ) and ULV(°) sprays.

FIGURE 136 5m* FIGURE 137 5 m downwind

FIGURE 138 120m downwind

235 Total Parasitic Hymenoptera

The total trap catches of parasitic Hymenoptera (predominantly

Chalcidoidea and Proctotrupoidea) followed a similar pattern (Figures 136 to 138). Immediately after spraying, a 37 and 79-fold increase in numbers was evident 5 m downwind from the hydraulic spray and ULV treatments respectively (Figure 137) and was concomitant with a 7-9 fold increase inside the sprayed areas and 14-16 fold increase 120 m downwind (Figures

136 and 138). Populations decreased 2-6 days later and no significant variation occurred later (Figures 136 to 138).

6.3.4 Aphid Observations.

The predominant cereal aphid was S. avenae although some M. dirhodum were found and counts on ears and flag-leaves were combined.

The number of aphids increased slightly one day after spraying (Table 43) but decreased subsequently (Figures 139 and 140).

Table 43 Pre and post spray variation in aphid numbers.

Time (pre (-) or post (+) spray)

-3 4 1 4 3 + 7 + 14 4 20

5.70 6.54 5.08 2.89 1.73 1.60

The lowest populations and the greatest decline in numbers occurred at 75 m 1-3 days after the hydraulic spray (Tables 44 and 45) although a

236 FIGURE 139 Pre and post spray variation in the number of aphids on tillers within the hydraulic (•) and ULV (<>) sprays.

FIGURE 140 Pre and post spray variation in the number of aphids on tillers 75m (■), 10m (□), and 1m (a) within the sprayed plots.

237 slight decrease in density was apparent next to the hedgerow in both

treatments. The number of aphids at all distances declined 7-20 days

post spray (Table 45).

Table 44 Variation in aphid numbers within the treated plots •

Method of Distance inside treated plots (m) application 75 10 1

Hydraulic 1.82 4.54 4.19 ULV 3.53 5.24 4.22

Table 45 Pre and post spray variation in the? number of aphids within the hydraulic and ULV sprays.

Di stance Time (days pre (-) or post ( + )spray) inside treated plot (m) -3 (Tl) +1,3,7 (T2) +14,20 (T3) Ratio T3/T2

HYDRAULIC

75* 3.50 2.47 0.83 0.34

10* 5.90 6.32 2.90 0.46

1.0* 5.90 5.07 3.03 0.60

ULV

75* 3.75 6.30 1.62 0.26

10* 7.20 8.02 2.73 0.34

1.0* 7.95 6.67 1.33 0.20

238 Pre and post spray variation in the number of cereal aphids on tillers within the hydraulic (•) and ULV (<>) sprays.

FIGURE 141 75 m *

FIGURE 143 1m*

239 More detailed analysis showed that populations at 75 m declined 1-7 days after the hydraulic spray, but increased 20 days post treatment

(Figure 141). Numbers at 10 m and 1 m were not significantly lower until

7 days after spraying (Figures 142 and 143). Conversely one day after the

ULV spray, aphid counts at 75 m and 10 m increased by 60 and 34 per cent

respectively (Figures 141 and 142) although their density at 1 - 75 m declined 3-14 days post spray (Figures 141 to 143).

6.4 Discussion

The use of cypermethrin to control cereal aphids in winter wheat

resulted in changes in the abundance of the non-target arthropod fauna within the hydraulic spray and ULV treatments. Some arthropod groups were

affected to the leeward of the hedgerow bordering the untreated cereal

crop.

6.4.1 Epigeal predators

Pitfall trap catches are determined by both the size of the

population and the level of activity and provide a measure of the

"effective abundance" of ground predators (den Boer, 1970). Catches are

influenced by a wide range of other factors (Adis, 1979): movement of

arthropods is affected by temperature, moisture and other weather conditions ( e.g. Mitchell, 1963); food supply (Briggs, 1961); type

240 of habitat ( e.g. weedy cover encourages some species but impedes the movement of others, Speight and Lawton, 1976); the sex and physiological state of the individuals (Sunderland, 1975; Mols, 1979) and variations in avoidance behaviour (Greenslade, 1964b), e.g. Demetrias spp. and

Tachyporus spp. were poorly represented in 7 cm diameter pitfall traps

(Sunderland and Vickerman, 1980). Pitfall trap efficiency may also depend on the size and shape of the material from which it is made. For example,

Luff (1975) showed that in general, smaller traps seemed to have higher efficiencies for smaller beetles, while the larger traps caught a high proportion of the larger beetles, due to their greater weight and faster running speed (Adis, 1979).

Most species trapped have been shown to feed on cereal aphids

(Chapter 5; Sunderland, 1975; Vickerman and Sunderland, 1975; Potts, 1977;

Luff and Loughridge, 1980; Sunderland and Vickerman, 1980; Wratten et al., 1984). The field consumption rates are affected by several factors, for example, predator species; aphid density (e.g. N. biguttatus and A. plebeja only feed on aphids when they are particularly abundant,

Sunderland and Vickerman, 1980); the sex and stage of sexual maturity of the predator (females may eat more than males, Sunderland, 1975; non-gravid more than gravid females, Mols, 1979); the temperature range over which the predators remain active (Sunderland and Chambers, 1983); preference for certain prey (e.g. the main food of P. melanarius in cereals was adult Coleoptera, Sunderland, 1975, but it will also feed on carabid larvae, earthworms, slugs and spiders). Searching efficiency is related to climbing ability (e.g. Staphylinidae and Araneae were found in

241 high numbers on vegetation at night, Griffiths, 1982), and the ability to aggregate to prey (Bryan and Wratten, 1984; Wratten et al'., 1984).

Aphids cane into contact with non-climbing predators and web-building spiders through movement and the action of wind, rain and climbing predators (Sunderland and Chambers, 1983). The degree of synchronisation between the life-cycle of the predator and phenologies of the cereal aphid species is important, for example, although P. melanarius can' 'consume high numbers of aphids, their density is very low during the aphid increase phase (Sunderland and Vickerman, 1980). The increase in the number of P.melanarius during this trial coincided with the decline in aphid populations as alatae left the mature crop.

P. melanarius and P. madidus are classified as "field-dwelling" species with little association with hedgerows (Pollard, 1968b), and this is reflected in their distribution across the field (Figures 25 to 27, 56 to 70). The adults of both species of Pterostichus usually emerge in late June - early July (Briggs, 1965; Luff, 1973; Hurka, 1975) and they appeared in trap catches from this time onwards. Peak activity of B. lampros (Wratten et al., 1984), N.biguttatus, A. dorsale (Jones,

1979) and C.fossor (Jones, 1979; Edwards et al., 1979) did not coincide with the time of the trial and, in general, periods of maximum abundance of small carabids are not concomitant with those of larger beetles (Jones, 1979). L.spinibarbis was found in low numbers throughout the field and field boundaries (Figures 25 and 27). Little information is available on its seasonal activity although it was thought to be a "hedgerow" species not usually found far into the crop (Pollard,

242 1968b).

The high temperatures and low relative humidities recorded during

July (Appendices 8,9) diminish the activity, and therefore catches of all species on the soil surface, particularly small beetles which are very susceptible to desiccation. Large species such as P. melanarius and P. madidus tend to be nocturnal and are less affected, while smaller beetles are often diurnal and more vulnerable to changes in the weather (Luff,

1978; Jones, 1979).

The adverse effects of field rates of cypermethrin on Carabidae

(Feeney, 1983; Cole and Wilkinson, 1984a; Shires, 1985), Sta'phylinidae

(Cole and Wilkinson, 1984a; Stevenson et al, 1984) and Araneae (Brown,

1982; Cole and Wilkinson, 1984a) are well-documented and it is likely that the hydraulic and ULV applications of cypermethrin resulted in the

reduction in the number of epigeal predators in the crop 1-3 days after

spraying. Recovery of Carabidae and Araneae occurred less than one week

later and as cypermethrin is reported to have a low persistence of 5-10

days (ICI, 1978) and a high initial knock-down but low mortality rate for

carabids (Edwards, pers.comm.), the subsequent increase in carabid numbers was probably attributable to adult emergence of P. madidus andVP. melanarius (Briggs, 1965; Luff, 1973; Hurka, 1975; Ericson, 1978).

Carabidae may also be less affected by the insecticide as nocturnal

species hide in crevices or under stones during the day and immediate

contact with the insecticide may have only resulted from disturbance of

the crop and soil surface during spraying. The proportion of male and

243 female P. melanarius were recorded to determine any differences in susceptibility to insecticide arising from the highly active and more voracious fenales (Sunderland, 1975; Ericson, 1978; Mols, 1979), therefore having greater contact with insecticide residues and a high intake of contaminated prey. Captures of females were low and they were slow to appear in samples from both sprays. However, sex ratios in pitfalls are difficult to interprete as changes in catch reflect either differential activity of equal numbers of each sex or the real sex ratio in the habitat. Other factors such as irritation and repellence (ICI, 1978) might stimulate activity and increase trap catches of both sexes.

Staphylinids are normally active throughout the summer and reach a peak between the end of July-September (Dean, 1974d, 1975). Staphylinids showed little subsequent increase after spraying and beetles may have left the unfavourable micro-climate of the maturing crop where food was becoming depleted. — .

Larval activity during the summer is low to avoid desiccation and competition with adult beetles for food and space (Jones, 1979). The removal of surface-active instars may have coincided with seasonal changes in larval behaviour associated with moulting.

6.4.2 Aerial arthropods

Increases in the abundance of insects flying above and moving within the crop immediately after spraying may be attributable to disturbance

244 following spray application or increased activity caused by the repellent effect of sub-lethal levels of cypermethrin which has been reported for many insect species (ICI, 1978).

Braconid parasites of cereal aphids and hyperparasites (species of

Ptercmalidae, Ceraphronidae, Cynipidae and Encyritidae) are particularly active from May to September (Potts and Vickerman, 1974; Dean 1975;

Vickerman, 1982), and although another synthetic pyrethroid, 'Fastac', was found to reduce the number of braconids in D-vac and water trap samples

(Inglesfield, 1984), no detrimental insecticidal effect was observed and the catches followed a similar pattern of increase as recorded for the total arthropod fauna.

Small, weakly flying insects are deposited in the lee of hedges and more strongly flying insects tend to congregate in this area of calmer air

(Lewis, 1965a,b; Lewis, 1969a,b; Lewis, 1970) and more arthropods were trapped 5-10 m to the leeward of the hedgerow, although this increase is probably less marked in the light winds (Lewis, 1969a).

The hedgerows evidently contributed to the diversity of carabid

species and the number of Araneae, and they encourage adult insects, for example, adult parasitic Hymenoptera and Syrphidae which depend on pollen and nectar from flowers for the maturation of ovaries (van Emden, 1965;

Schneider, 1969; Pollard, 1971). As hedgerows interfere with the flow of

air (e.g. Lewis and Dibley, 1970), the effects on spray droplets drifting downwind will be complicated and many small droplets will be filtered out

245 by the stems and foliage.

The effect of cypermethrin was mainly apparent within and up to 1 m downwind into the adjacent cereal crop. The drift of spray might be expected to be low and the impact on arthropods downwind minimal as the horizontal movement of droplets is much reduced in low wind-speeds.

However, warm, sunny days with light winds give unstable atmospheric conditions, wind direction can be variable and air turbulence is created by conventional movement of air (Elliott and Wilson, 1983).

6.4.3 Aphids

Neither hydraulic or ULV spray applications of cypermethrin gave immediate control of cereal aphids and the increase in aphid density within the ULV spray (Figures 141 and 142) may have arisen through reduced predation pressure and temperatures favourable to reproduction. The subsequent decline probably corresponded to the production of alatae in response to the change in the nutritional quality of the ripening grain and drying leaves (Sunderland, 1976; Carter et al., 1980; Chambers et al., 1983). The alates of S.avenae leave the crop in July to colonise late maturing hedgerow grasses or volunteer cereals (Dewar and Carter,

1984).

246 Chapter 7

THE EFFECT OF PERMETHRIN ON CARABIDAE WITHIN AND DCWNWIND FROM

HYDRAULIC AND ULV SPRAYS AND UNTREATED PLOTS.

7.1 Introduction

Studies in 1982 were restricted to the epigeal predator population and the effects of another pyrethroid, permethrin, recently approved for use against cereal aphids, were investigated.

Pitfall trapping provided a valuable estimate of the ground-dwelling populations, so a grid of traps was enclosed within 5 x 5 m barriered areas to prevent beetle migration and immigration (e.g. Edwards et al.,

1979; Shires, 1980). Experiments using "mark and recapture" techniques showed that there was less than 5 per cent ingress or egress of most carabid species except for Trechus quadristriatus which could fly in

(Edwards and Thompson, 1975). The enclosed areas were situated within and up to 100 m downwind from the treated plots.

The amount of spray deposited at each distance was determined using a neutron activation analysis (NAA) technique with dysprosium (Dy) and the deposits of permethrin on the ground and on plants were estimated from the data (Chapter 4) and related to beetle and aphid density. The efficacy of hydraulic and ULV spray application methods was assessed by recording the

247 pre and post spray numbers of cereal aphids on the tillers.

7.2 Materials and Methods

7.2.1 Field trial

A detailed description of the experimental site and treatments

(Figure 11) is given in Chapter 4 (page 92). At the end of June, a 5 x 5 m area inside each plot and at 10, 30, and 100 m downwind was enclosed by

0.45 m wide standard gauge polythene tubing, buried to a depth of approximately 10 cm and supported by wooden stakes (Plate 2), A one m strip was cleared around each barriered area to prevent access via overhanging plants. Five plastic beakers, 7 cm diameter and 9 cm deep, were buried to soil level 1 m apart (Adis, 1979) in each enclosed area

(Figure 144) and following severe thunderstorms, several small holes

(uniform in size and number) were punched in the base of the traps to allow drainage. The number of Carabidae collected over 18 hour periods (4 pm - 10 am) was recorded 3 and one day before spray application and 1, 3,

5, 8, 10 and 14 days later. The species and sex were identified and the beetles released into the barriered areas. The traps were covered with plastic lids when inoperable. One day pre and post spray, the number of cereal aphids on the ears and flag-leaves of 20 tillers (selected at random) was determined within and up to 100 m downwind from the treatments.

Spraying was delayed until the wind direction was

248 PLATE 2 Areas enclosed with polythene tubing.

249 appropriate relative to the position of the plots. Meteorological conditions before and after insecticide application are shown in

Appendices 10 to 17.

7.2.2 Statistical analysis

The transformation (x+0.5) was applied to the data (predominantly small numbers and zeros) to change the scale of the captures, normalize the data and make the analysis more valid. 'Genstat' (Alvey et al.,1984; Rothamsted Experimental Station, 1977) was used to perform

ANOVA on the transformed data. The F-values were derived from the ANOVA tables and used as a measure of the level of significance of each factor in the analysis. An example is given in Appendix 18.

7.3 Results

The holes in the base of each trap facilitated the escape of most

small Carabidae, Coleoptera larvae, Staphylinidae and Araneae. Occasional

individuals of Bembidion spp., N. biguttatus, L. spinibarbis, A. dorsale, Staphylinidae and Linyphiidae were recorded, but numbers were

too low to allow separate analysis. P. melanarius was the predominant

species of carabid sampled, although P. madidus (F) was also ccmmon.

A large syrphid population (adults and larvae) was present in the

crop before spraying. Immediately after hydraulic spray treatment,

several dead adult P. peltatus, adult Coccinellidae and geometrid

250 FIGURE 144 Diagram of the barriered area.

O : plastic pitfall traps

: polythene barrier

251 Pre spray distribution of Carabidae across the field

FIGURE 145 Within plot

a

o c 2 n a a a c (0 ® S

Plot number

FIGURE 146 10m downwind

Plot number

FIGURE 147 30m downwind

a <0 ** \ o c 2 .Q 2 (0 a c (Q S

Plot number

FIGURE 148 100m downwind

Plot number 252 caterpillars were observed in plot one. Plot 5 contained dead P. peltatus after ULV spray treatment and, although plots 2 and 9 were unsprayed, dead caterpillars and adult Syrphus corollae (F.) were found which suggested lateral insecticide drift.

7.3.1 Carabidae

Figures 145 to 148 (page 252) show the pre spray variation between the number of carabids/trap inside and up to 100 m downwind from plots 1-9 and the uneven distribution of beetles across the field at each sampling-distance. The overall treatment means were not significantly different but carabid numbers differed with time (P<0.001) and distance

(P<0.001).

Variation in carabid density with time

(i) Inside treated plots

One day post spray, the number of carabids inside the hydraulic spray and ULV treatments declined by 84 (PC0.05) and 72 per cent (PC0.05) respectively and beetles disappeared frcm the ULV plots 2 days later

(Figures 149 and 150). Numbers increased significantly 5 days after both sprays (PC0.05) although no change in density occurred later. The number of Carabidae within the untreated plots did not differ significantly until

8 days after spraying when their density increased (P<0.05) (Figure 151).

253 Pre and post spray trap catches of Carabidae within the hydraulic (•) and ULV (°) sprays and untreated ( ^ j plots. FIGURE 149 HYDRAULIC SPRAY

a (0

aa>

•Q (0I- o(0 c CO0) 5

FIGURE 150 ULV SPRAY

a <0

a0) 6 c ■o 2 & a o c 0)CO s

FIGURE 151 UNTREATED PLOTS

254 (ii) lOmdownwind

The number of carabids/trap were not significantly different until 10 days after the hydraulic spray, whereas numbers decreased by 72 per cent immediately after ULV treatment (P<0.05) and did not increase later

(Figures 152 and 153). The carabid density downwind from the untreated plots increased slightly one day after spraying (PC0.05) but there was no

significant variation subsequently (Figure 154).

(iii) 30 m downwind

Populations of Carabidae downwind from the untreated and hydraulic

spray plots increased significantly 3 days after treatment (P<0.05) but declined later (Figures 155 and 157), while pre and post spray numbers downwind from the ULV plots were not significantly different (Figure 156).

'(iv) 100 m downwind

Immediately after the hydraulic spray, the number of carabids

increased 2-fold (P<0.05) and declined 2-4 days later (P<0.05) (Figure

158). No post spray fluctuation in density occurred downwind from the untreated plots or up to 5 days after the ULVspray (Figures 159 and 160).

255 Pre and post spray trap catches of Carabidae 10m outside the hydraulic ( • ) and ULV (°) sprays and untreated (▲) plots.

FIGURE 152 HYDRAULIC SPRAY

a®

~o 2 2 8 c CO a> 5

FIGURE 153 ULV SPRAY

a co

0)a 6 c T3 !a CO2 o c a>CO

FIGURE 154 UNTREATED PLOTS Pre and post spray trap catches of v^arabivae 3~m outside the hydraulic (*)and ULV (°) sprays and untreated (^ ) plots.

FIGURE 156 ULV SPRAY

a (0

0)a 6 c ■g Id (0k. (0 o c <0 V 2

Days pre ( - ) or post spray, s

FIGURE 157 UNTREATED PLOTS

a to

a0) 6 c a (0i. (0 o c (0 a> 2

Days Pre (-> 2 gf post spray , s Pre and post spray trap catches of Carabidae 100m outside the hydraulic (*)and ULV (°) sprays and untreated (^) plots.

FIGURE 158 HYDRAULIC SPRAY

a a

a o 2 2

S

Days pre(-) or post spray, s

FIGURE 159 ULV SPRAY

a (0

a0) cd 2 2 l(0. (0 a c (0 0) S

Days p r e ( - ) or post spray , s

FIGURE 160 UNTREATED PLOTS

a (0

a> a c6 T3 2(0 3 C a>CO 5

Days p r e ( - ) or post spray , s 2 5 8 Variation in carabid density with distance

Hydraulic spray

Five days before spraying, more carabids were collected at 30 m than at 10 m (PC0.05) but other pre spray catches were not significantly different (Figures 161 and 162). One to 3 days after treatments, changes in the rate of capture were evident. Populations within the hydraulic spray and at 10 m did not differ significantly but more beetles were found in samples at 30 m and 100 m than inside the treated plots (PC0.001) and at 10m (P<0.05) (Figures 163 and 164). Five days post spray, the numbers of carabids within the sprayed plots and at 10 m and 100 m were net significantly different, although their density was significantly higher at 30 m (PC0.01) (Figure 165). Populations recovered and were not significantly different 3 days later (Figure 166) and little variation occurred subsequently (Figures 167 and 168).

ULV spray

The pre spray samples of Carabidae within and up to 100 m downwind from the ULV treatments did not differ significantly (Figures 169 and

170). One day after spraying, more carabids were collected at 10 m and 30 m than inside the ULV plots (P<0.05) (Figure 171). Two days later, no beetles were trapped within the ULV spray and numbers were significantly higher at 10-100 m downwind (P>0.05) (Figure 172). Populations recovered

5-8 days after the ULV spray and numbers of carabids at each

259 sampling-distance were not significantly different (Figures 173 and 174).

Little significant variation between samples occurred subsequently

(Figures 175 and 176).

Untreated plots

The density of Carabidae did not fluctuate significantly throughout

the trial (Figures 177 to 184).

7.3.2 Pterostichus melanarius (111)

The pre spray distribution of P. melanarius across the crop

within and up to 100 m downwind from plots 1-9 (Figures 185 to 188)

indicated considerable variation in density so these data were included in

analysis.

No significant difference occurred between the treatment means, while numbers of P. melanarius were significantly influenced by distance

(P<0.001), time (PC0.001) and sex (PC0.001). Significant interactions were: distance and time (PC0.05), treatment and sex (PC0.001), distance and sex (PC0.01), time and sex (P<0.001) and treatment, distance and sex

(P<0.05).

260 Pre and post spray variation in trap catches of Carabidae within (*) and downwind from the HYDRAULIC SPRAY (•).

FIGURE 161 5 days pre-spray FIGURE 162 3 days pre-spray

Distance within (*) or downwind Distance within (*) or downwind from sprayed plots (m) from sprayed plots (m)

FIGURE 16 1 day post spray FIGURE 164 3 days post spray

Distance within (*) or downwind Distance within (*) or downwind from sprayed plots (m) from sprayed plots (m )

FIGURE 165 5 days post spray FIGURE 166 8 days post spray

Distance within (*)or downwind Distance within (*) or downwind from sprayed plots (m) from sprayed plots(m)

FIGURE 167 10 days post spray FIGURE 168 14 days post spray

Distance within (*)or downwind Distance within (*) or downwind from sprayed plots (m) from sprayed plots (m) Pre and post spray variation in trap catches of Carabidae within (*) and downwind from the ULV SPRAY (°).

FIGURE 169 5 days pre-spray FIGURE 170 3^lays pre-spray

Distance within (*) or downwind Distance within (*)or downwind from sprayed plots (m) from sprayed plots ^n)

FIGURE 171 1 day post spray FIGURE 172 3 days post spray

Distance within (*)or downwind Distance within (*) or downwind from sprayed plots (m) from sprayed plots (m)

FIGURE 173 5 days post spray FIGURE 174 8 days post spray

Distance within (*) or downwind Distance within (*) or downwind from sprayed plots (rr) from sprayed plots (rj

FIGURE 175 10 days post spray FIGURE 176 14 days post spray

Distance within (*) or downwind from sprayed plots Jtt) Pre and post spray variation in trap catches of Carabidae within ( * ) and downwind from the UNTREATED PLOTS (A ) .

FIGURE 177 5 days pre-spray FIGURE 178 3 days pre-spray

Distance within (*)ordownwind Distance within (•) or downwind from untreated plots (m) from untreated plots (m )

FIGURE 179 1 day post spray FIGURE 180 3 days post spray

a. Q. CO CO

o O c c -o TJ !5 !o CO COk. (0 oCD o c c (0 a> oCO

Distance within (*)or downwind Distance within (*)o r downwind from untreated plots (m) from untreated plots (m )

FIGURE 181 5 days post spray FIGURE 182 8 days post spray

Distance within (*)o r downwind Distance within (*)o r downwind from untreated plots (m) from untreated plots (m )

FIGURE 183 10 days post spray FIGURE 184 14 days post spray

a CO

o c -o !5 2 8 c a>CO S

Distance within (* ) or downwind Distance within ( *)o r downwind from untreated plots (m) 263 from untreated plots (m) Variation in density of P. melanarius with time

(i) Inside treated plots

Pre spray densities of male and female P. melanarius within all plots were not significantly different.

Hydraulic spray

One day after spraying, no female beetles were caught and the number of males per trap declined significantly (P<0.05)(Figure 189). Females reappeared in traps 2 days later, but numbers did not increase

significantly in subsequent samples. The number of male beetles increased

3.6-fold 5 days after spraying (P<0.05), although no further significant

increase occurred. The sex ratio was not significantly affected apart

from one and 14 days after treatment when males predominated.

ULV spray

The low number of P. roelanarius throughout the sampling-period

precluded any obvious trends in male and female densities (Figure 190).

However, male beetles disappeared immediately after spraying and were not

present in samples until 4 days later, with no subsequent variation in

abundance (Fi gure 190).

264 Pre spray distribution of male i H and female Pterostichus melanarius across the field.

FIGURE 185 Within plot a k.© \ 6 c © 4-> n8 c ©

Plot number

FIGURE 186 10m downwind

a fc-© \ o c

© 2 c ©

Plot number

FIGURE 187 30 m downwind

a © *->k. \ 6 c

© n© c © ©

Plot number

FIGURE 188 100m downwind

a ©

© © ©

C © S

Plot number 265 Pre and post spray trap catches of male H and female C Pterostichus melanarius within the hydraulic and ULV sprays and untreated plots.

FIGURE 189 HYDRAULIC spray

Days pre ( - ) or post spray, s

FIGURE 190 ULV spray

Days pre ( - ) or post spray , s -n

FIGURE 191 UNTREATED

Days pre(-) or post spray, s 266 Untreated plots

No significant changes in the numbers of male and female beetles was apparent until 8 days after spraying when their densities increased 2.5 and 4-fold respectively (P<0.05), but numbers declined subsequently

(Figure 191).

(ii) 10 m downwind

Hydraulic spray

The number of fenale beetles did not vary significantly and no significant change in the male P. melanarius population was evident 1-3 days after spraying (Figure 192). Male and female numbers increased significantly 5 and 8 days respectively post treatment (PC0.05), but declined subsequently. Male beetles dominated samples 3-8 days after

Spraying (P<0.05), but the sex ratio returned to unity 10 days post spray.

ULV spray

The densities of female and male P.melanarius declined significantly (P<0.05) one day after the ULV spray (Figure 193). No females were trapped 5-10 days post treatment, whereas the number of males increased slightly 8 days after the spray before disappearing frcm samples.

267 Pre and post spray trap catches of male O and female □ Pterostichus melanarius 10m outside the hydraulic and ULV sprays and untreated plots.

FIGURE 192 HYDRAULIC spray a CO co

© 0) c o(0 S

Days p r e (-) or post spray, s

FIGURE 193 ULV spray a CO co ©

Days pre ( - ) or post spray, s

FIGURE 194 UNTREATED

Days p r e (-) or post spray, s 268 Untreated plots

The number of fenale P. melanarius showed no significant variation

during the trial, while a 4-fold increase in male density (PC0.05) was

recorded immediately after spraying in the adjacent plots (Figure 194).

The number of males in subsequent samples did not differ significantly.

(iii) 30 m downwind

Hydraulic spray

No significant change in the number of male and female P.

melanarius occurred immediately after spraying, but their densities 3

days post spray were significantly higher than pre spray catches (P<0.05)

(Figure 195). Little further significant variation in number occurred.

ULV spray

The number of male or female beetles did not vary significantly during the trial and the sex ratio did not differ significantly from unity

(Figure 196).

Untreated plots

The populations of female P. melanarius remained stable until the final sample when numbers declined significantly (P<0.05) (Figure 197).

269 Pre and post spray trap catches of male fES and female I I Pterostichus melanarius 30m outside the hydraulic and ULV sprays and untreated plots.

FIGURE 195 HYDRAULIC spray

Days pre ( - ) or post spray , s

FIGURE 196 ULV spray

a to

oc a ao c (0 a> S

Days pre ( - ) or post spray , s

FIGURE 197 UNTREATED

a

co a> *-»a> Ao a>c ® 5

14

Days pre(-) or post spray, s 270 The number of males increased 5-fold (PC0.05) one day after the sprays, but declined slightly one week later. The male : female ratio remained close to unity for all samples.

(iv)100 m downwind

Hydraulic spray

. Immediately after treatment, the number of female P. melanarius did not differ significantly from pre spray samples and their density did not increase until 10 days later (P<0.05)(Figure 198). The number of male beetles increased 3.6-fold one day after spraying (PC0.001) and showed little significant variation subsequently until 9 days later when numbers declined to pre spray levels (Figure 198).

The sex ratio increased from approximately 1.0 to 3.7 (P>0.001) immediately after the spray although it returned to unity 2 days later.

ULV spray

Densities of male and female P. melanarius ranained low during the trial and females were absent from traps 5 days after spraying (Figure

199). Females dominated pre spray samples, but the post spray sex ratio was approximately 1.0.

271 Pre and post spray trap catches of male 111 and female □ Pterostichus melanarius 100m outside the hydraulic and ULV sprays and untreated plots.

FIGURE 198 HYDRAULIC spray

Days pre(-) or post spray, s

FIGURE 199 ULV spray

Days pre(-) or post spray, s

FIGURE 200 UNTREATED

a (0

£ o o a> -Q c (0 0) 35

Days pre ( - ) or post spray, s 272 Untreated plots

The number of female beetles fell by 42 per cent immediately after spraying (P<0.05), but did not differ significantly in subsequent samples until 10 days post treatment when a further decline was evident (Figure

200). The male density in all samples showed little significant fluctuation (Figure 200).

Variation in density of P. melanarius with distance

(i) Hydraulic spray

Pre spray catches of male and female P. melanarius at all sampling-distances were not significantly different (Figures 201 and 202).

Males

Immediately after spraying, the numbers caught within and 10 m outside the sprayed plots were not significantly different (Figure 203) although 2 days later, the male density was significantly higher at 10 m

(P<0.05) (Figure 204). Little variation in numbers occurred subsequently

(Figures 205 to 208).

273 Pre and post spray trap catches of male till and female □ Pterostichus melanarius within and downwind from the HYDRAULIC SPRAY.

FIGURE 201 5 DAYS PRE-SPRAY

Distance within ( * ) and downwind from sprayed plots (m)

FIGURE 202 3 DAYS PRE-SPRAY

Distance within ( * ) and downwind from sprayed plots (m )

FIGURE 203 1 DAY POST SPRAY

FIGURE 204 3 DAYS POST SPRAY

Distance within ( * ) and downwind from sprayed plots (m ) 274 Pre and post spray trap catches of male 1:111 and female □ Pterostichus melanarius within and downwind from the HYDRAULIC SPRAY.

FIGURE 2 0 5 5 DAYS POST SPRAY 2 a (0

a> na> c co a) k i . *3 6 10 30 100 Distance within ( * ) and downwind from sprayed plots (m)

FIGURE 206 8 DAYS POST SPRAY

FIGURE 207 10 DAYS POST SPRAY

FIGURE 208 14 DAYS POST SPRAY

Distance within ( * ) and downwind from sprayed plots (m) 275 One to three days after the spray, male numbers were lower inside the hydraulic spray than at 30 m (P<0.001) and 100 m (P<0.001) downwind (Figures 203 and 204), athough 5-10 days post spray, their densities were not significantly different (Figures 205 to 208).

Males were also more abundant at 30 m and 100 m than at 10 m downwind (P<0.05) one and three days post spray (Figures 203 and 204), but were not significantly different in later samples (Figures 205 and 208).

No significant difference occurred between the number of males at 30 m and 100 m until 3-5 days post spray (Figures 204 and 205) when males were more abundant at 30 m (P<0.05) and little subsequent variation was apparent (Figures 206 to 208).

Females

One and three days after spraying, numbers of female P. melanarius were significantly higher at 30 m and 100 m than inside the treated plots

(P<0.05 for all comparisons) (Figures 203 and 204) but no further difference in density occurred subsequently (Figures 205 to 208). Numbers within and 10 m from the treated plots were not significantly different

(Figures 203 to 208).

Eight to thirteen-fold differences between the number of females at

30 m and 10 m were apparent 1-5 days post spray (PC0.05) (Figures 203 to

205) and female density remained low at 10 m. More females were also

276 found at 100 m than 10 m one (P<0.05) and 3 (PC0.05) days after spraying

(Figures 203 and 204), but numbers were not significantly different in subsequent samples (Figures 205 to 208). The number of females at 30 m and 100 m did not differ significantly up to 5 to 8 days post spray when their density was higher at 30 m (P<0.05) (Figures 205 and 206).

(ii) ULV spray

Pre spray catches of male and female P. melanarius within and up to 100 m downwind from the ULV spray were not significantly different

(Figures 209 and 210).

Males

One to three days after spraying, more males were collected at 10 m, 30 m and 100 m compared with catches inside the treated plots (PC0.05)

(Figures 211 and 212). Two days later, the number of males was still significantly higher at 3 0 m (P<0.05) (Figure 213), but no subsequent difference in densities was apparent (Figures 214 to 216).

Immediately after spraying, five times more males were caught at 30 m than 10 m (P<0.05) (Figure 211) although no difference between captures occurred 2-11 days later (Figure 211 to 215). Numbers at 10 m and 100 m were not significantly different up to 5 days post spray when no males were found at 10 m (Figure 213). Male P. melanarius were more abundant at 30 m than 100 m (P<0.05) one day post spray (Figure 211), but numbers

277 Pre and post spray trap catches of male H I and female u Pterostichus melanarius within and downwind from the ULV SPRAY.

FIGURE 209 5 DAYS PRE - SPRAY

FIGURE 210 3 DAYS PRE - SPRAY

a

© ■4-> a © S i c (0 © 5

FIGURE 211 1 DAY POST SPRAY

a (0 2 © 8 S i c ©CO 5 Pre and post spray trap catches of male and female □ Pterostichus melanarius within and downwind from the ULV SPRAY.

FIGURE 213 5 DAYS POST SPRAY

FIGURE 214 8 DAYS POST SPRAY

FIGURE 215 10 DAYS POST SPRAY 2 r

o c <0 1 - zo> : 0) .Q c oCO —r~ *36 10 30 100 Distance within and downwind from sprayed plots (m)

FIGURE 216 14 DAYS POST SPRAY

Distance within (*) and downwind from sprayed plots (m ) 279 were not significantly different 2 days later (Figure 212).

Females

Female P.melanarius disappeared from traps within the ULV spray 3

days post treatment and significantly more were collected 10-100 m

downwind (P<0.05 for all comparisons) (Figure 212). Numbers at 10-100 m

showed little significant variation during the trial (Figures 211 to 216).

(iii) Untreated plots

Little significant fluctuation between numbers of male and female

beetles occurred 3-5 days before spraying (Figures 217 and 218)

Males

One to three days after the sprays, more males were trapped 10 m and

30 m downwind canpared with numbers recorded at 100 m (PC0.05) (Figures

219 and 220) but little significant variation occurred in subsequent

samples from all distances (Figures 221 to 224).

Females

Five days after spraying, the number of females was significantly

higher at 30 m than within and 10 m from the untreated plots (P<0.05)

(Figure 221), but their densities were not significantly different 3 days

280 Pre and post spray trap catches of male fill and female □ __Pterostichus melanarius within and downwind from the UNTREATED PLOTS.

FIGURE 217 5 DAYS PRE-SPRAY

a

a> s o a> JQ c <0 a>

FIGURE 218 3 DAYS PRE-SPRAY

FIGURE 219 1 DAY POST SPRAY

FIGURE 220 3 DAYS POST SPRAY

Distance within ( * ) and downwind from untreated plots (nrA 281 ' ' Pre and post spray trap catches of male | and female Pterostichus melanarius within and downwind from the UNTREATED PLOTS .

FIGURE 221 5 DAYS POST SPRAY « 2

= 1

ill p sl i l i __ Ik □ *36 10 30 100 Distance within ( * ] and downwind from untreated plots (m)

FIGURE 222 8 DAYS POST SPRAY

FIGURE 2 2 3 10 DAYS POST SPRAY

Q. 2 r-

- 1 a> a> a c re o i i 2 l ± L *36 10 30 100 Distance within ( * ) and downwind from untreated plots (m)

FIGURE 224 14 DAYS POST SPRAY

a 2 r 2 — 2 £ 1 - T A2

O *36 10 30 100 Distance within ( * ) and downwind from untreated plots (m) 282 later (Figure 222) and little fluctuation between samples occurred subsequently (Figures 223 and 224).

7.3.3 Aphi ds

The predominant aphid species on the heads of winter wheat was S. avenae, while M. dirhodum was prevalent on the flag-leaves. The mean number of aphids per head and flag-leaf prior to insecticide application was calculated for plots 1-9 (Figures 225 to 232, pages 256 and 257). The aphid distribution across the crop (east to west) at each sampling-distance indicates the variation in density between plots and distances. The patchiness was particularly marked inside the plots to be sprayed (Figures 225 and 229) and necessitated the incorporation of these data in the statistical analysis.

7.3.3.1 Heads

No significant difference occurred between the treatment means, but the aphid numbers were significantly affected by time (PC0.001) and sampling-distance (P<0.001). The interaction between time and distance was significant at P<0.01.

283 Pre spray distribution of aphids on ears across the field.

FIGURE 225 Within plot

c (0 0) 2

Plot number

FIGURE 226 10 m downwind

o c c re re 2

Plot number

FIGURE 227 30m downwind

o c c re re 2

Plot number

FIGURE 228 100m downwind

c re re 2

Plot number

284 Pre spray distribution of aphids on flag - leaves across the field.

FIGURE 229 Within plot

FIGURE 2 30 10m downwind

Plot number

FIGURE 231 30m downwind

Plot number

FIGURE 232 1 0 0 m downwind

O) (0

o c

5

Plot number

285 Hydraulic spray

Prior to spraying, populations of aphids at all sampling-distances were not significantly different (Figure 233). One day post spray, the number of aphids decreased by 94 per cent (P<0.001) inside the treated plots, but pre and post spray counts 10 m downwind did not differ significantly (Figure 233). However, the aphid density declined

significantly at 30 m (P<0.005) and 100m(P<0.05) downwind (Figure 233).

The post spray numbers at 10 m were significantly higher than the densities recorded inside and 100 m downwind from the treated plots

(P<0.05 for all comparisons). No other significant differences occurred.

ULV spray

One day before spraying, more aphids were found within the plots

than 10 m (P<0.01), 30 m (P<0.01) and 100 m (PC0.001) downwind (Figure

234). One day post ULV spray, numbers inside and 10 m from the treated

plots declined significantly (P<0.001 and P<0.05 respectively), while no

significant change occurred in the aphid density at 30 m (Figure 234).

Aphids disappeared from ears 100 m downwind (Figure 234). Populations at

30 m were significantly higher than numbers within and 10 m downwind from

the ULV spray (PC0.05 for both comparisons).

286 Pre □ and post ^ spray numbers of aphids on ears within and downwind from the sprayed and untreated plots.

FIGURE 233 HYDRAULIC spray 5 r

Q. <0 [It 0) T S

*3 6 10 30 100 Distance within ( * ) and downwind from sprayed plots (m)

FIGURE 234 ULV spray

FIGURE 235 UNTREATED

5 r T

(0 0)

O r i t *36 10 30 100 Distance within and downwind from untreated plots (m) 287 Untreated plots

Before spraying, more aphids were found within the untreated plots compared with the numbers 10 m (P>0.05), 30 m (P<0.005) and 100 m

(PC0.001) downwind (Figure 235).

One day after the sprays, the aphid density declined by 55 and 46 per cent within (P<0.001) and 10m (P<0.05) outside the untreated plots respectively, whereas pre and post spray numbers at 30 m were not significantly different and no aphids were found at 100 m (Figure 235)*

No significant variation occurred between the number of aphids downwind and up to 30 m from the control plots.

As discussed earlier, no overall significant difference was found between the treatment means, although the post spray number of aphids was

significantly higher within the untreated plots than inside the hydraulic

spray (PC0.05) and ULV spray (P<0.05).

More aphids were recorded after the ULV spray compared with counts after the hydraulic spray (P<0.05).

7.3.3.2 Flaa-leaves

Distance and time had a significant effect on the aphid populations

(PC0.001 and P<0.01 respectively) while the overall treatment means were

288 not significantly different.

Hydraulic spray

Prior to spraying, aphids were more abundant at 30 m compared with numbers within (PC0.01), 10 m (P<0.05) and 100 m (P<0.005) downwind from the treated plots (Figure 236). Pre and post spray aphid counts within and 10 m downwind from the hydraulic spray did not differ significantly

(Figure 236). However, after spraying, aphid numbers declined by 50 and

87 per cent at 30 m (P<0.05) and 100 m (P<0.05) (Figure 236).

One day post treatment, more aphids were found at 10 m (P<0.005) and

30m (PC0.01) than at 100 m, but numbers within and up to 30 m outside the sprayed plots were not significantly different.

ULV spray

Pre spray aphid counts at all sampling-distances were not significantly different (Figure 237). One day after spraying, no significant change in aphid density occurred within or up to 30 m downwind from the treatments, although no aphids were present at 100 m (Figure

237).

289 Pre ED and post ^ spray numbers of aphids on flag leaves within and downwind from sprayed and untreated plots.

FIGURE 236 HYDRAULIC spray

5 r

o> (0

a (0 V' c s A 5 I * 3 6 10 30 100 Distance within ( * ) and downwind from sprayed plots (mj

FIGURE 237 ULV spray

Distance within ( * ) and downwind from sprayed plots (m)

FIGURE 238 UNTREATED

5 i-

o> (0

co ■o 33 a !| (0 53 A c U a>CO I 5 1 *36 10 30 100 Distance within ( * ) and downwind from untreated plots (mj

290 Untreated plots

One day before spraying, the number of aphids within and up to 30 m downwind from the control plots were not significantly different, but aphid numbers were higher at 10 m (PC0.05) and 30 m (P<0.05) than at 100 m

(Figure 238). Populations did not fluctuate significantly after spraying apart from 100 m downwind where numbers declined by 78 per cent (PC0.05) and were significantly lower than densities at the other distances (PC0.05 for all comparisons) (Figure 238).

7.3.4 Permethrin deposits

Carabid numbers

No clear inverse relationship was found between the number of carabids and the amount of permethrin deposited on the ground (Figures 239 and 240). Inside the sprayed plots, the level of permethrin was high and corresponded with a low beetle density, but the dramatic decline in the amount of insecticide 10 m downwind was concomitant with only a slight increase in the number of Carabidae (Figures 239 and 240). Populations were also small 100 m outside the ULV spray although deposits of permethrin were low (Figure 240), whereas numbers 30 - 100 m downwind from the hydraulic sprayer were considerably higher (Figure 239).

291 FIGURE 239 The relationship between the deposits of permethrin (+) and the number of carabids (•) within and downwind from the hydraulic spray. en aai nme / ta Ma crbd ubr/ trap / number carabid Mean trap / number carabid Mean

FIGURE 240 The relationship between the deposits of permethrin (^) and the number of carabids (o) within and downwind from the ULV spray.

Distance within (*) or downwind from ULV spray (m) 292 FIGURE 241 The relationship between the deposits of permethrin M and the number of aphids per ear (•) within and downwind from the hydraulic spray. en pi no.ear en pi no.fag leaf g ./fla o n aphid Mean r a ./e o n aphid Mean

hydraulic spray (m)

FIGURE 242 The relationship between the deposits of permethrin W and the number of aphids per flag leaf (o ) within and downwind from the hydraulic spray.

hydraulic spray (m) 293 FIGURE 243 The relationship between the deposits of permethrin (^) and the number of aphids per ear (•) within and downwind from the ULV spray.

Distance within (*) and downwind from the ULV spray (m)

FIGURE 244 The relationship between the deposits of permethrin (^) and the number of aphids per flag leaf (o) within and downwind from the ULV spray.

Distance within (*)and downwind from the ULV spray (nr)

294 Aphid numbers

High levels of insecticide coincided with low numbers of aphids on

the heads and flag-leaves within the hydraulic spray (Figures 241 and

242). Aphid density increased 10 m and 30 m downwind where spray deposits

were much reduced, but declined at 100 m (Figures 241 and 242).

However, high deposits of permethrin on flag-leaves within .the ULV

spray were not associated with low aphid numbers (Figure 244), although

populations on heads were smaller than at 10 m and 30 m (Figure 243).

Aphids disappeared at 100 m but this was not due to the effects of

permethri n.

7.4 Discussion

The use of permethrin to control cereal aphids on the ears and

flag-leaves of winter wheat had serious repercussions on adult Syrphidae within the hydraulic and ULV sprays. Syrphids moving inside and above the untreated crop, adjacent to the sprayed plots were also killed and spray deposits found on the plants and soil surface indicated considerable

lateral movement of spray droplets ( Chapter 4). Permethrin (1-2 mg/cm2 ) was found to be very harmful to S. vitripennis (Hassan et al.,

1983) although levels detected on filter papers were much lower than this

(Table 12).

Considerable reductions in the populations of Carabidae within the

295 hydraulic and ULV sprays coincided with high levels of permethrin reaching

the ground (0.4-0.6 mg/cm2 filter paper, Table 12). A direct contact effect of the insecticide is unlikely as nocturnal carabid species such as

P. melanarius hide under stones and in soil crevices during the day

(Dunning et al., 1982), although tractor disturbance of the crop and

soil may stimulate activity after spraying. Recovery was apparent 5 days after both sprays (Figures 149 and 150).

Beetles inside the untreated plots were not affected by the spray deposited on the ground (Figure 151). P. melanarius is an active climber of sugar beet plants (Dunning, Baker and Windley, 1975).

Consequently, this species may have increased contact with the high levels of insecticide on the sprayed foliage (Figure 18) compared with the lower

deposits in the untreated plots (Table 13).

Lower levels of permethrin (50 g a.i./ha) caused a decline in the

number of adult Carabidae in cereals 2 weeks post spray ( Cole and

Wilkinson, 1984b), although other work reported little effect apart from a

short-term (one week) reduction in the number of P. melanarius (Cole and

Wilkinson, 1984b) and another pyrethroid, 'Fastac', had no obvious effect

on Carabidae (Inglesfield, 1984).

Brown (pers. ccmm.) reported a high knockdown of adult carabids at

sub-lethal levels of permethrin, but low subsequent mortality, with

recovery in 4-5 days. In the field, moribund beetles may be eaten before

they recover, so the effect of permethrin is probably more marked.

296 Conversely, hyperactivity and disorientation following contact with permethrin could increase catches (Brown, pers. ccrnm.) and data must be interpreted with care.

The detrimental effect of permethrin extended 10 m downwind from the

ULV spray only (Figure 153) where the theoretical amount of peynethrin/cm2 -2 * . o falter paper was 5.7 x 10 jug on the ground compared with 1.2 x 10 jug at the same distance outside the hydraulic spray (Table 12)-. .-Although deposits were detected 3 0 m and 100 m downwind (Figures 15 to 17, Table

12), no decline in carabid density was apparent (Figures 155 to 160).

A similar pattern was evident for P. melanarius, a catholic feeder

(Sunderland, 1975), which thrives throughout Europe (Basedow et al.,

1976) on a range of crops (Pietraszko and de Clercg, 1981), on various soils (Baker and Dunning, 1975) and under many farming conditions. Male and female beetles within both the hydraulic and ULV sprays were depleted

1-3 days after treatment, but this effect was confined to the hydraulic spray, while numbers also declined 10 m outside the ULV spray and subsequent recovery was slow (8-10 days).

Interpretation of sex ratios is difficult. Higher catches of females were anticipated due to increased mobility stimulated by hunger

(Sunderland, 1975; Mols, 1979). However, numbers remained lower than the male density at most sampling-distances. Male activity may have increased to mark the start of the mating-period (Ericson, 1978). Low post spray densities of females within and 10 m downwind from both sprays may be

297 attributable to more contact with insecticide residues through higher levels of activity, but these results are rather inconclusive.

No insecticidal effect was found at 30 m and 100 m although spray deposits were detected. Correlation of carabid numbers and spray deposits

is problematic as pitfall catches are influenced by a wide^ range of

factors other than population size and activity (page 40).

The hydraulic spray gave improved control of aphids on ears (Figure

233). A reduction in aphid populations occurred 10 m downwind from the

ULV and untreated plots (Figures 234 and 235) but no spray deposits were detected on plant material outside the sprayed plots.

Neither method of spray application controlled cereal aphids on the

flag-leaves (Figures 236 and 237), and although spray deposits were found on the leaves, poor coverage may have favoured aphid survival.

As a cereal crop matures and the aphid density increases, the proportion of S . avenae and M. dirhodum developing into alatae

increases (Dewar and Carter, 1984). This coincides with changes in the nutritional quality of the ripening crop and emigration to alternative and overwintering sites e.g. late-maturing hedgerow grasses (Jones and Dean,

1975; Carter et al., 1980; Chambers et al.,1982; Chambers et al^,1983). This probably accounts for the decline in aphid numbers at

100 m (Figures 233 - 238).

298 The uptake of a contact chemical such as permethrin is reduced in a ripe, 'dried out' crop, and insecticidal activity may be affected. A systemic insecticide (e.g. pirmicarb) would offer improved aphid control at this growth stage.

V J

299 Chapter 8

GENERAL DISCUSSION

The effects of herbicide drift have been well documented (Elliott and Wilson, 1983), but few studies have examined the impact ofinsecticide drift using different spraying machines. This project was concerned primarily with evaluation of the effects of spray deposits on the natural enemies of cereal aphids, so two sprayers were used to apply different volumes with distinctive droplet spectra to winter wheat. The study was confined to the effect of a single insecticide application which would normally be sufficient for aphid control. However, in relation to pesticide sprays in general, there is the possibility that several sprays applied throughout the season would have different or greater effects in the ecosystem.

Laser analysis of the spray droplet spectra from both types of nozzle indicated a wide range of droplet sizes (Table 4). In particular the hydraulic (hollow cone) nozzle produced 13 per cent of the total volume in droplets less than lOOjum in diameter, and thus liable to drift, while 27.5 per cent of the total volume was in droplets larger than 300^um in diameter and likely to "run-off". The latter increased the level of soil contamination, exacerbating the effect of spray on the epigeal arthropod fauna.

The spinning-discs reduced the large droplet component of the spray,

300 increasing the liklihood of droplet retention on the target plants, but

they produced approxiirately three times more "driftable" droplets (Table

5).

The sensitivity of neutron activation analysis (NAA) made this

method very suitable for the pesticide deposition studies, and, in v particular, for the investigation of spray drift which necessitated the

detection of small quantities of spray. Amounts of dysprosium as low as

1.75 to 3.20 x 10~3jug/cm2 on filter paper were found at ground'level 100m

downwind from both types of sprayer (Figure 17), while minimum deposits of

1.08 x 10"3 mg dysprosium/g plant material were detected on glumes 10m

outside the hydraulic sprayed area (see page 107). Differences between the

droplet sampling efficiences of "artificial" and "natural" targets are

discussed on pages 113 and 115.

Neutron activation analysis allowed much more rapid processing, so

that a larger number of replicates could be sampled. The use of stable

isotopes as tracers enabled samples to be stored for a considerable time without degradation, in contrast to the risk of photolytic decay of

fluorescent and other tracers.

Deposition on plant surfaces was predominantly on the lower part of

the canopy (stems and lower leaves, Figures 18 - 24), and most of the

spray in the treated plots moved completely through the canopy and 36 and

58 per cent of the total spray recovered within the hydraulic and ULV treatments respectively had reached the ground (from Table 10). Losses of

301 this magnitude to the soil ("endodrift", Himel, 1974) have been reported

in other studies in wheat, for example by Shires (1985), although Bryant

et al., (1984) recovered only 2-10 per cent of the spray at ground level

(applied at rates of 50-200 1/ha), presumably the density of crop foliage

affecting penetration of spray.

The high levels of permethrin deposited on the soil within both

treatments severely depleted populations of Carabidae (Figures 149, 150,

163, 171, 189, 190, 203 and 211) and preliminary trials showed a reduction

in the number of epigeal predators also following hydraulic and ULV spray

applications of cypermethrin (Figures 31 to 33 and 47 to 54). These

effects were short-term and recovery was apparent 5 - 8 days after

spraying, confirming previous published work (e.g. Cole and Wilkinson,

1984a; Feeney, 1983; Powell et al., 1985; Shires, 1980, 1985; Stevenson

et al., 1984). However, harmful effects of insecticides on non-target

species were restricted to within and up to 10m outside the hydraulic and

ULV sprayed areas and carabid populations 30m and 100m downwind were

apparently unaffected. This coincided with a dramatic decline in the

amount of spray deposited downwind, irrespective of the method of spray

application, although little significant variation occurred between

deposits 10 - 100m outside the treated areas (Figures 15 to 17; Tables 9

to 11). Small amounts of spray were detected within and downwind from

the untreated plots, which suggests that under the prevailing conditions of variable wind direction, the distance between plots was insufficient and facilitated their contamination with pockets of airborne droplets.

302 The filtering surface of the crop canopy would be expected to remove

spray droplets through impaction, although droplets less than 50 jum in

diameter would tend to settle out by gravity, once in the canopy and no

longer subject to the effect of a crosswind, and thus increase ground

deposits. Large droplets ( >300jum) with high velocities (as produced by

the hydraulic spray nozzles) are poorly retained on plants and also

exacerbate chemical wastage within the sprayed plots.

The fraction of spray still airborne was not measured, but with

the Ulvamast, if the same mass application rate had been applied, there

was a significant increase (x 47) in contamination on the ground at 100m

downwind, compared with the conventional hydraulic spray. Furthermore

environmental hazards can be increased by higher concentration of active

ingredient in a spray, but in theory there is seme potential reduction in

the dosage applied in ULV sprays, thus the manufacturers recommended using as little as one fifth of the recommended dosage (page 72). Oil based

formulations reduced the width of the droplet spectrum produced by the spinning discs and minimised the proportion of the smallest droplets most subject to drift (Table 4). Spinning discs are supposed to produce droplets of a controlled size, enabling the application of the optimum droplet size to increase the proportion of pesticide that reaches the target plants, but this can only be achieved if flow rate is regulated in relation to rotational speed. In practice, the actual formulation applied and operating conditions failed to achieve the degree of control that was i ntended.

303 Spray drift may also be reduced by lowering the boon height of

hydraulic sprayers (e.g Nordby and Skuterud, 1975; Byass and Lake, 1977)

or reducing the hydraulic pressure (e.g. Maybank et al., 1974), although

the subsequent increase in droplet size results in increased spray

deposits reaching the ground.

Hedgerows act as windbreaks, lessening the wind velocity to the

leeward and affecting radiation and precipitation at ground level, while

modifying the temperature and relative humidity of the air nearby (Lewis,

1965b). The hedgerow barrier interferes with the free movement of air to

an extent determined by the height and density (permeability) and the

angle and velocity of the incident wind (Lewis, 1970). Thus, spray

droplets carried downwind may be deflected with an air stream or impinge on

foliage and stems.

The whole ecology of the adjacent crops is influenced in a complex way by hedgerows. They act as reservoirs for some pest species (Van

Emden, 1965) and interact with many groups of natural enemies. For example, hedgerows provide important overwintering cover for predatory

Carabidae and Staphylinidae (Pollard, 1968b; Sotherton, 1984, 1985a) and provide valuable sources of food for the adult stages of natural enemy species including parasitic Hymenoptera and Syrphidae (Pollard, 1971;

Schneider, 1969; van Emden, 1965).

Preliminary trials showed an increase in carabid diversity in close proximity to the hedgerows (Figures 26 and 28). An increase in the

304 airborne fauna was found in the sheltered zone near to the windbreak and substantiated earlier work (e.g. Lewis, 1965,a,b, 1969a; 1970; Lewis and

Dibley, 1969). Later trials (Chapters 4 and 7) involved spray application in an "open field" situation, with no interference to air movement by hedgerows. As no adverse effects on populations of Carabidae occurred beyond 10m outside the hydraulic and ULV sprayed areas, an unspr

(1985) found that partridge chick survival was 40 per cent lower in areas treated with demeton-S-methyl, which is used frequently to control cereal aphids in this country, compared with unsprayed areas. This effect was attributed to a reduction of 40-80 per cent in preferred chick food items within the treatments. The Game Conservancy advocate that a 6m strip around each field is left unsprayed with any pesticide from 1st January each year. This has been shown to increase gamebird survival and brood size, with a three-fold increase in cereal arthropods (Rands, 1985; Rands and Sotherton, 1985). Yield reduction is not significant, although the problem of the contamination of grain by weed seeds is now being investigated (Rands, 1985).

The impact of fungicides and herbicides on arthropod populations may be as serious as that of insecticides. Few herbicides currently used are directly toxic to invertebrates but a reduction in arthropod numbers arises from the removal of host plants and ground cover, thus influencing the micro-climate (Potts, 1970; Vickerman, 1974). The decline of mycetophagous species (Table 17) coincides with the increased use of

305 herbicides and foliar-applied fungicides (Potts, 1977). Seme fungal feeders, for example, certain species of Tachyporus are also cereal aphid predators (Sunderland, 1975; Vickerman and Sunderland, 1975), and their continued decrease (Figure 22), attributed to an increase in the number of fungicide applications, could affect the balance of the pest/natural enemy ccmplex. Some fungicides are directly ^ toxic to

Carabidae, Staphylinidae, aphid-specific predators and insect species which form the principal constituents of pheasant and partridge chicks' diets (Sotherton and Moreby, 1984; Sotherton, 1985b; Vickerman and

Sotherton, 1983), and gamebird survival is greatly improved where chicks' vital food has not been reduced by pesticides (Rands, 1985).

Aphid control achieved by hydraulic and ULV spray applications of permethrin and cypermethrin was disappointing (Figures 141 to 143; 233 to

238) and a systemic insecticide may have given improved control when applied late in the season (trials were delayed until the wind velocity and direction were suitable for the use of the Ulvamast drift type sprayer with the relatively small plots to be treated). A more specific insecticide, such as pirimicarb also reduces the risk to non-target arthropods through spray drift, but was not used in these experiments as it was hoped that by using a broad-spectrum pyrethroid any small differences between sprayers might be detected.

These trials confirmed that losses of spray to the soil are high, even with the ULV spray and changes in the droplet spectra are necessary with an additional force to improve impaction on the target plants.

306 Recently attention has been given to the electrostatic charging of droplets (e.g. Arnold and Pye, 1981; Coffee, 1980; Hislop, Cooke and

Hannan, 1983). This improves deposition at the top of plants but less penetration of the canopy occurs and this reduces the levels of pesticide reaching the ground (Endacott, 1983). Consequently 'endo' and

'exo' drift are reduced and the effects on non-target organisms within the crop and hedgerows are minimised. Further studies are needed to determine how to develop a system of applying pesticides to.cereals to exploit any advantage with electrostatic forces to minimise effects on non-target species.

307 Summary

1. The VMD of aqueous sprays from the hollow cone nozzle measured by

laser analysis, was 223+2.4jum compared, with VMDs of 130+1.3jum

and 116+0.7 ^um for the spinning-discs operating at 5750 and

6215 rpn respectively. , i 2. The volume of small droplets (< 103 jum) liable to drift was 32 and 41

per cent by volume at disc speeds of 5750 and 6215 rpm respectively

and 13 per cent from the hollow cone nozzle.

3. Approximately 28 per cent of the spray volume from the cone nozzle

comprised droplets larger than 300 jum which were unlikely to be

retained on the target plant. The volume of large droplets in the

spray cloud from the spinning-discs varied from 0.3 - 0.6 per cent,

depending on the disc speed.

4. A reduction in the operational voltage and rotational speed of the

spinning-discs increased the VMD and reduced the proportion of small

droplets.

5. Both nozzle types, in particular the hollow cone nozzle, produced a

wide range of droplet sizes (VMD:NMD ratio of 34 and 15-22 for the

cone nozzle and spinning-discs respectively).

6. Spray additives (emulsifying agents) reduced the width of the droplet

spectrum from the spinning-discs.

7. Relating volume outputs and the concentration of pesticide in the

hydraulic spray, the drift potential ratio, expressed in chemical

terms, was 2.5 : 1 (Ulvamast : hydraulic).

8. The mean VMDs of droplets collected on vertically positioned,

308 magnesium oxide-coated slides were 119+3.0 jum and 4&+3.0 jum. 5 m

outside the hydraulic and LJLV spray treatments respectively. These

values declined to 42+6.5 jum and 31+3.0 jum respectively 150 m

downwind. No droplets were found 200 m downwind.

9. Estimated levels of chemical 75 - 150 m downwind from the ULV spray

were 2-10 times higher than the corresponding values for the

V j hydraulic spray.

10. The amount of dysprosium collected on horizontally positioned filter

papers and determined by neutron activation analysis was significant­

ly higher within the hydraulic and ULV sprays than the levels

detected 10 - 100 m downwind.

11. No significant variation occurred between deposits outside the

treated plots.

12. In general, more dysprosium was collected on the ground than at 0.45

m and 0.75 m sampling heights.

13. The volume of spray deposited 100 m downwind and expressed as a p percentage of the total spray volume/cm within the treated plots

was 0.2 and 16.6 for the hydraulic and ULV sprays respectively.

14. The amount of dysprosium within the conventional hydraulic spray was p equivalent to approximately 0.6 jug permethrin/cm compared with

0.1 - 0.4jug permethrin/cm2 inside the ULV spray treatment.

15. The theoretical insecticide deposit on the ground was 28-47 times

higher 10-100 m downwind from the ULV spray than the amounts

collected outside the hydraulic spray.

16. No dysprosium was detected by neutron activation analysis of plant

material downwind from the treatments apart from on glumes 10 m

309 outside the hydraulic spray.

17. The amount of dysprosium collected on glumes, flag-leaves and the

stems/lower leaves was 117 - 200 times higher within the hydraulic

spray than within the LJLV spray.

18. The calculated deposits of permethrin on the glumes and flag-leaves

were similar irrespective of the method of application although 3

V J times more chemical was collected on the stem and lower leaves of

plants treated conventionally compared with those sprayed at ULV.

19. The flag-leaves within the hydraulic and ULV sprays collected 18 and

60 times more dysprosium respectively than filter papers 0.75 m

above the ground (crop height).

20. ULV spray application gave improved spray deposition on the ears and

flag-leaves but the highest spray deposits were on the stems and

lower leaves, irrespective of the treatment.

21. Trace amounts of dysprosium were detected within and downwind

from the untreated plots and indicated considerable lateral movement

of spray droplets and inadequate distance between each plot.

22. Pitfall trap catches in winter wheat were dominated by Carabidae, in

particular P. melanarius.

23. The number of epigeal predators declined 1 - 3 days after the

hydraulic and ULV spray application of cypermethrin. Recovery of

Carabidae and Araneae occurred less than one week later.

24. The water trap and Malaise trap captures of aerial arthropods,

including parasitic Hymenoptera, increased inmediately after spray­

ing and this was attributed to disturbance following spray

application or increased activity caused by a repellent effect of

310 sub-lethal levels of cypermethrin.

25. The effect of cypermethrin was mainly apparent within and up to 1 m

downwind into the adjacent cereal crop.

26. The hedgerows contributed to the diversity of Carabidae and the

number of Araneae and encouraged adult insects (for example, adult

parasitic Hymenoptera and Syrphidae). They also offered shelter and , i more arthropods were trapped 5 - 10 m to the leeward' of the

hedgerows.

27. Conventional hydraulic and ULV spray applications of permethrin had

serious repercussions on adult Syrphidae within both sprays.

Considerable reductions in the number of Carabidae inside the

hydraulic and ULV sprays coincided with high levels of permethrin

reaching the ground (0.4 - 0.6 mg/cm2 filter paper). Recovery was

apparent 5 days later.

28. The detrimental effect of permethrin extended 10 m downwind from the

ULV spray only, where the theoretical amount of permethrin/cm2 o -2 filter paper was 5.7 x 10 jug canpared with 1.2 x lOjig outside

the hydraulic spray.

29. No insecticidal effect was found 30 - 100 m downwind and an unspray­

ed swath of 10 - 12 m around the field edge is reccmmended to

protect beneficial arthropod species.

30. Neither hydraulic or ULV spray applications of cypermethrin gave

immediate control of cereal aphids in winter wheat. The hydraulic

spray application of permethrin gave improved control of aphids on

ears but cereal aphid control on flag-leaves was poor within both

the hydraulic and ULV sprays.

311 Acknowledgements

Thanks are due to Dr. G. A. Matthews for the supervision of the project and his valuable comments on the manuscript. The assistance of all staff and former students of the International Pesticide Application Research

Centre, Silwood Park is gratefully acknowledged, in particular thanks to

Mr.A. Arnold and Mr. C. Endacott for their advice.

I am indebted to the Director, Mr. M. Kerridge, Miss M. Minski and the staff of the Reactor Centre, Imperial College at Silwood Park for the use of facilities and assistance given throughout the work.

Thanks are also extended to the following: Mr. J. Haigh (CDA Ltd) and his staff for the provision of the sprayers and field-site; the Plant

Protection Division of I.C.I. for supplying the spray formulations; Dr. J.

Gilmour (East of Scotland College of Agriculture), Dr. M. Franklin (ARC

Statistics Unit, University of Edinburgh) and Dr. S. Young (Imperial

College at Silwood Park) for assistance with statistical analysis; Mrs. M.

Matthews for typing the manuscript. The work was funded by a Ministry of

Agriculture, Fisheries and Food postgraduate studentship. Finally, a special thanks to my parents for their continuous encouragement and support.

312 REFERENCES

ADAMS, J. B. (1960) The effects of spraying 2,4-D amine on coccinellid larvae. Canadian Journal of Zoology, 38, 285 - 288.

ADAMS, J. B. and DREW, M. E. (1965) Grain aphids in New Brunswick. III. Aphid populations in herbicide treated oat fields. Canadian Journal of Zoology, 43, 789 - 794.

ADAMS, J. B. and DREW, M. E. (1969) Grain aphids in New Brunswick. IV. Effects of malathion and 2,4-D amine on aphid populations and yields of oats and barley. Canadian Journal of Zoology, 47, 423 -^ 426.

ADAMS, R. J. (1978) Meteorological aspects of changes in spraying techniques. Proceedings 1978 British Crop Protection Conference - Weeds, 2, 625 - 632.

ADAMS, R. J. (1980) Towards an objective method of categorising a given season in terms of suitability for spraying with special reference to the 1978 - 79 season. 16th Review of Herbicide Usage. Croydon: BCPC.

ADAMS, R. J. (1981) 'Spray Days' analysis - July 1979 to June 1980. 17th Review of Herbicide Usage. Croydon: BCPC.

ADIS, J. (1979) Problems of interpreting arthropod sampling with pitfall traps. Zoolgischer Anzeiger, Jena 202 (3/4), 177 - 184.

AKESSON, N. B. and COWAN, R. (1978) . Metallic salts as tracers for spray application. In: Methods for Sampling and Assessing Deposits of Insecticidal Sprays Released over Forests, p.107 (ed. by J.W.Barry, R.B.Ekblad, G.P.Markin and G.C.Trostle). U.S. Department of Agriculture Technical Bulletin No. 1596. Washington: U.S.A.

AKESSON, N. B. and YATES, W. E. (1964) Problems relating to application of agricultural chemicals and resulting drift residues. Annual Review of Entomology, 9_, 285 - 318.

ALVEY, N., GALWEY, N. and LANE, P. (1982) An introduction to Genstat. 152pp. Academic Press, London.

AMBRUS, A. (1978) The influence of sampling methods and other field techniques on the results of residue analysis. Proceed i ngs 4th International Congress of Pesticides Chemistry - Advances in Pesticide Science. Part 3, 620 - 632.

ANDERSON, C. H. and SCHULTE, W. (1971) Teflon as a surface for deposition of aerosol droplets. Mosquito News, 31, 499 -504.

ANDREWS, M., FLOWER, L. S. , JOHNSTONE, D. R. and TURNER, C. R. (1983) Spray droplet assessment and insecticide drift studies during the large scale aerial application of endosulfan to control Glossina

313 morsitans in Botswana. Tropical Pest Management, 29, 239 - 248.

ANKERSMIT, G. W. (1983) Aphidiids as parasites of the cereal aphids Sitobion avenae and Metopolophium dirhodum. In: Aphid Antagonists. Proceedings of a meeting of the EC Experts Group, Portici, Italy, 23 - 24 November, 1982, 42 - 49 (ed. R.Cavalloro). A. A. Balkema, Rotterdam.

ANON (1983) Fanners Weekly, 5th August, 1983.

ARNOLD, A. C. (1983) Comparative droplet-size spectra for three different­ angled flat fan nozzles. Crop Protection, 2, 193 - 204. i

ARNOLD, A. J. and PYE, B. J. (1981) Electrostatic spraying of crops with the APE 80. Proceedings 1981 British Crop Protection Conference - Pests and Diseases, 2^, 661 - 666.

BACHE, D. H. and SAYER, W. J. D. (1975) Transport of aerial spray I. A model of aerial dispersion. Agricultural Meteorology, 15, 257 - 271.

BACHE, D. H. and UK, S. (1975) Transport of aerial spray II. Transport within a crop canopy. Agricultural Meteorology, 15, 371 - 377.

BAKER, A. N. and DUNNING, R. A. (1975) Some effects of soil type and crop density on the activity and abundance of the epigeic fauna, particularly Carabidae, in sugar-beet fields. Journal of Applied Ecology, 12, 809 - 818.

BALS, E. J. (1977) A new rotary stacked nozzle. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, J3, 523 -526.

BALS, E. J. (1977) Reduction of active ingredient dosage by selecting appropriate droplet size for the target. In: Symposium on Controlled Drop Application. BCPC Monograph No. 22, 101 - 105.

BARAN, M. (1972) The influence of phosphate and potassium fertilizers on the population dynamics of the cereal aphid Sitobion avenae. Biologica, Bratislava 27, 129 - 139.

BARANYOVITS, F. (1973) The increasing problem of aphids in agriculture and horticulture. Outlook on Agriculture, 1_, 102 - 108.

BARTLETT, B. R. (1963) The contact toxicity of sane pesticide residues for hymenopterous parasites and coccinellid predators. Journal of Economic Entomology, 57, 366- 369.

BASEDCW, Th., BORG, A. and SCHERNEY, F. (1976) Effects of insecticides upon the terrestrial predaceous arthropods in cereal fields, especially the ground beetles (Coleoptera, Carabidae). Entomologia experimentals et applicata, 19, 37-51.

314 BASEDOW, Th., BORG, A. and SCHERNEY, F. (1981) Effects of insecticides upon the epigeal arthropods in cereal fields, especially the ground beetles (Col. Carabidae). II. Acta Agricultures Scandinavica, 31, 153 - 164.

BASFORD, W. D. (1978) Controlled drop application - a new approach to spraying. BASF/ Agricultural News, 17, 3 -5.

BINNS, E. S. (1970) Aphicidal activity of benomyl. Report of the Glasshouse Crops Research Institute for 1969, p 113. • i BODE, L. E. and BUTLER, B. J. (1983). New techniques and equipment for ground application of herbicides in the U.S.A. Proceedings 10th International Congress of Plant Protection, 2_, 478 - 485.

BOUSE, L. F. (1976) Select spray nozzles to minimize herbicide drift. Weeds Today, Winter, 1976, 11-13.

BRAZZEL, J. R., WATSON, W. W., HURSH, J. S. and ADAIR, M. H. (1968) The relative efficiency of aerial application of ultra-low volume and emu1sifiable concentrate formulations of insecticides. Journal of Economic Entomology, 61, 408 - 413.

BRIGGS, J. B. (1961) A comparison of pitfall trapping and soil sampling in assessing populations of two species of ground beetles (Col: Carabidae). Report of East Mailing Research Station for I960, 108 - 112.

BRIGGS, J. B. (1965) Biology of sane ground beetles (Col., Carabidae) injurious to strawberries. Bulletin of Entomological Research, 56, 79 - 93.

BRITISH AGROCHEMICALS ASSOCIATION (1985) Annual Report and Handbook 1984 - 85. 36pp.

BROWN, K. (1982) The effects of insecticides on cereal aphids and their predators. Meeting of the U.K. Workers on Polyphagous Predators and Cereal Aphids, 15th October, 1982, Glasshouse Crops Research Institute, Littlehampton.

BROWNE, E., DAIRIKI, J. M. and DOEBLER, R. E. (1978) In: Table of Isotopes p.984 (ed. C.M.Lederer and V.S.Shirley). New York: Wiley and Sons.

BRYAN, K. M. and WRATTEN, S. W. (1984) The responses of polyphagous predators to prey spatial aggregation: aggregation by carabid and staphylinid beetles to their cereal aphid prey. Ecological Entomology, % 251 - 259.

BRYANT, J. E., PARKIN, C. S. and WYATT, J. C. (1984) Partitioning of pesticide spray on and under a cereal canopy. Proceedings 1984 British Crop Protection Conference - Pests and Diseases, 2_, 1007 -

315 1012.

BUTLER, B. J. and BODE, L. E. (1976) Estimating crop damage and drift from sprayincr. Illinois Custom Spray Operators Training School Manual, 148 - 150.

BYASS, J. B. (1969) Equipment and methods for orchard spray application research. III. The measurement of spray deposits on leaves using light from fluorochromes on the surface. Journal of Agricultural Engineering Research, 14, 78 - 88. J BYASS, J. B. and LAKE, J. R. (1977) Spray drift from a tractor-powered field sprayer. Pesticide Science, 8_, 117 - 126.

CARROLL, M. K. and BOURG, J. A. (1979) Methods of ULV droplet Sampling and analysis: effects on the size and spectrum of the droplets collected. Mosquito News, 39, 645 - 655.

CARTER, N. (1983) Modelling the effects of predators on cereal aphid populations. The Game Conservancy Annual Review for 1982, No. 14, Spring 1983, 38 - 42.

CARTER, N., GARDNER, S. , FRASER, A. M. and ADAMS, T. H. L. (1982) The role of natural enemies in cereal aphid populations. Annals of Applied Biology, 101, 190 - 195.

CARTER, N., MCLEAN, I. F. G. , WATT, A. D. and DIXON, A. F. G. (1980) Cereal aphids: a case study and review. Applied Biology, j3, 271 - 347.

CHAMBERS, R. J. , SUNDERLAND, K. D., STACEY, D. L. and WYATT, I. J. (1982) A survey of cereal aphids and their natural enemies in winter wheat in 1980. Annals of Applied Biology, 101, 175 - 178.

CHAMBERS, R. J., SUNDERLAND, K. D., WYATT, I. J. and VICKERMAN, G. P. (1983) The effects of predator exclusion and caging on cereal aphids in winter wheat. Journal of Applied Ecology, 20, 209 - 224.

CHAMBON, J. P. (1982) Recherches sur les biocenoses cerealieres II. Incidence des interventions insecticides sur les ccmposants de 1 'entanofaune. Agronomie, 2, 405 - 416.

CHAN, S. B. (1982) Predators of the green pea aphid. Rastitelna Zashchi ta, 30, 28 - 29.

CHIVERTON, P. (1982) The effects of polyphagous predators on the establishment phase of Bird-cherry oat aphid (Rhopalosiphum padi L. ) infestations in spring barley. Vaxtskyddsrapporter, Jordbruk, 20, 177 - 181.

CHIVERTON, P. A. (1984) Pitfall trap catches of the carabid beetle Pterostichus melanarius, in relation to gut contents and prey

316 densities in insecticide treated and untreated spring barley. Entomologia experimentalis et applicata, 36f 23 - 30.

COAKER, T. H. (1966) The effect of soil insecticides on the predators and parasites of the cabbage root fly (Erioschia brassicae (Bouche)) and on the subsequent damage caused by the pest. Annals of Applied Biology, 54, 397 - 407.

CQAKER, T. H. (1977) Crop pest problems resulting from chemical control. Origins of Pest, Parasite, Disease and Weed Problems (ed. J.M.Cherrett and G.R.Sagar), 313 - 328. Blackwell Scientific.

COFFEE, R. A. (1980) Electrodynamic spraying. In: Spraying Systems for the 1980's, BCPC Monograph No. 24, 95 - 108.

COLE, J. F. H. and WILKINSON, W. (1982) Permethrin, dime.thoate and pirimicarb in cereal crops: Effects of spring applications on arthropods in the cereal ecosystan. Proceedings of AAB meeting, Consequences of Insecticide Use. 22 October, 1982, Natural History Museum, London.

COLE, J. F. H. and WILKINSON, W. (1984a) Selectivity of pirimicarb in cereal crops. Proceedings 1984 British Crop Protection Conference - Pests and Diseases, 311 - 315.

COLE, J. F. H. and WILKINSON, W. (1984b) Permethrin, dimethoate and pirimicarb: Effects of spring applications on arthropods in the cereal ecosystem. Faune et Flore Auxiliaires en Agriculture, Journees d"etudes et d"informations, 4 et 5 Mai 1983, Paris. ACTA (1984), 229 - 237.

CQMBELLACK, J. H. and MATTHEWS, G. A. (1981) Droplet spectra measurements of fan and cone atomisers using a laser diffraction technique. Journal of Aerosol Science, 12, 529 - 540.

COOKE, B. K., HERRINGTON, P. „ J. , JONES, K. G., WESTERN, N. M., WOODLEY, S. E., CHAPPLE, A. C. and HISLOP, E. C. (1985) A comparison of alter­ native spray techniques in cereals. In: Application and Biology, BCPC Monograph No.28, 299 - 309.

CCWAN, W. D. (1983) Spray drift control and droplet performance within the spray sheet. Aspects of Applied Biology, 3: Crop sensitivity to herbicides, 175 - 180.

CRITCHLEY, B. R. (1972a) A laboratory study of the effects of some soil- applied organophosphorous pesticides on Carabidae (Coleoptera). Bulletin of Entomological Research, 62, 229 - 242.

CRITCHLEY, B. R. (1972b) Field investigations on the effects of an organophosphorous pesticide, thionazin, on predaceous Carabidae (Coleoptera). Bulletin of Entomological Research, 62, 327 - 342.

317 CROFT,B.A. and BRCWN,A.W.A. (1975) Responses of arthropod natural enemies to insecticides. Annual Review of Entomology, 20, 285 - 335.

DAMS, R. (1981) Selection of short-lived isotopes for activation analysis with respect to sensitivity. Journal of Radioanalytical Chemistry, 61, 13 - 36.

DAUM, R. J., BURT, E. C. and SMITH, D. (1968) Capturing spray droplets with thixotropic solutions. Journal of Economic Entomoloqy, 61, 1120 - 1121. i DEAN, G. J. (1973) Aphid colonization of spring cereals. Annals' of- Applied Biology, 75, 183 - 193.

DEAN, G. J. (1974a) The overwintering and abundance of cereal aphids. Annals of Applied Biology, 76, 1-7.

DEAN, G. J. (1974b) The four dimensions of cereal aphids. Annals of Applied Biology, 77, 74 - 78.

DEAN, G. J. (1974c) Effect of temperature on the cereal aphids Metopolo- phium dirhodum (Wlk.), Rhopalosiphum padi (L.) and Macrosiphum avenae (F. ) (Hem., Aphididae).Bulletin of Entamolocrical Research, 63, 401 - 409.

DEAN, G. J. (1974d) Effects of parasites and predators on the cereal aphids Metopolophium dirhodum (Wlk. ) and Macrosi phum avenae (F.) (Hem., Aphididae). Bulletin of Entomological Research, 63, 411 - 422.

DEAN, G. J. (1975) The natural enemies of cereal aphids. Annals of Applied Biology, 80, 130 - 132.

DEAN, G. J. (1982) Phenology of aphidophagous predators. Annals of Applied Biology, 101, 182 - 184.

DEAN, G. J. and LUURING, B. B. (1970) Distribution of aphids on cereal crops. Annals of Applied Biology, 66, 485 - 496.

DEAN, G. J. and WILDING, N. (1971) Entomophthora infecting the cereal aphids Metopolophium di rhodum and Sitobion avenae. Journal of Invertebrate Pathology, 18, 169 - 176.

DEAN, G. J. and WILDING, N. (1973) Infection of cereal aphids by the fungus Entomophthora. Annals of Applied Biology, 74, 133 - 138.

DE CLERCQ, R and PIETRASZKO,R . (1983) Epigeal arthropods in relation to predation of cereal aphids. In: Aphid Antagonists. Proceedings of a meeting of the EC Experts Group, Portici, Italy, 23 - 24 November, 1982, 88 - 92 (ed. R. Cavalloro) A.A. Balkema, Rotterdam.

DEMPSTER, J. P. (1968) The sublethal effect of EOT on the rate of feeding

318 by the ground beetle Harpalus rufipes. Entomologia experimentalis et applicata, 11, 51-54.

DEN BOER, P. J. (1970) On the significance of dispersal power for populations of carabid beetles (Coleoptera, Carabidae) Oecologia (Berlin) 4, 1 - 28.

DEWAR, A. M. and CARTER, N. (1984) Decision trees to assess the risk of cereal aphid (Hemiptera: Aphididae) outbreaks in summer in England. Bulletin of Entomological Research, 74, 387 - 398.

DEWAR, A. M., DEAN, G. J. and CANNON, R. (1982) Assessment of Methods for estimating the numbers of aphids (Hemiptera: Aphididae) in cereals. Bulletin of Entomological Research, 72, 675 - 685.

DOBSON, C. M., MINSKI, M. J. and MATTHEWS, G. A. (1983) Neutron activation analysis using dysprosium as a tracer to measure spray drift. Crop Protection, 2, 345 - 352.

DORMAN,R.G. (1952) The atomization of liquid in a flat spray. British Journal of Applied Physics, 3^, 189 - 192.

DUMBAULD, R. K., RAFFERTY, J. E. and CRAMER, H. E. (1976) Dispersion deposition from aerial spray releases. Third Symposium on Atmospheric Turbulence, Diffusion and Air Quality, October 19 - 22 1976, Rayleigh,N.C.: American Meteorological Society, Boston, Mass.

DUNN, P. and WALLS, J. M. (1978) An introduction to in-line holography and its applications. In: Controlled Drop Application, BCPC Monograph No. 22, 23 - 34.

DUNNING, R. A., BAKER, A. N. and WINDLEY, R. F. (1975) Carabids in sugar beet crops and their possible role as aphid predators. Annals of Applied Biology, 80, 125 - 128.

DUNNING, R. A., COOPER, J. M., WARDMAN, J. M.. - and WINDER, G. H. (1982) Susceptibility of the carabid Pterostichus melanarius (Illiger) to aphicide sprays applied to the sugar beet crop. Tests of Agrochemicals and Cultivars No.3 (Annals of Applied Biology, 100, Supplement), 32 - 33.

DUNNING, R. A. and WINDER, G. H. (1975) Resistance to aphicides. Annual Report of Rothamsted Experimental Station for 1974, 55 - 56.

EDWARDS, C. A. (1975) Effects of direct drilling on soil fauna. Outlook on Agriculture, 8^ 243 - 244.

EDWARDS, C. A. and GEORGE, K. (1977) Carabids and cereal aphids. Annual Report of Rothamsted Experimental Station for 1976, Part 1, pi3.

EDWARDS, C. A. and GEORGE, K. S. (1981) Carabid beetles as predators of cereal aphids. Proceedings 1981 British Crop Protection Conference -

319 Pests and Diseases, 1, 191 - 199.

EDWARDS, C. A., PARSONS, N., GEORGE, K. S. and HEILBROON, T. D. (1978) Carabids as predators of cereal aphids. Annual Report of Rothamsted Experimental Station for 1977, Part 1, pi01.

EDWARDS, C. A., SUNDERLAND, K. D.and GEORGE, K. S. (1979) Studies on polyphagous predators of cereal aphids. Journal of Applied Ecology, 16, 811 - 823.

EDWARDS, C. A. and THOMPSON, A. R. (1975) Some effects of insecticides on predatory beetles. Annals of Applied Biology, 80, 132 - 135.

EDWARDS, C. A. , THORNHILL, W. A., JONES, B. A., BATER, J. E. and LOFTY, J. R. (1984) The influence of pesticides on polyphagous predators of pests. Proceedings 1984 British Crop Protection Conference - Pests and Diseases, 1_, 317 - 323.

EDWARDS, P. J. and WILKINSON, W. (1983) A laboratory toxicity test for carabid beetles. Proceedings 10th International Congress of Plant Protection, 2, 719.

EKBLAD, R. B. (1978) Collection efficiencies of sampling surfaces. In: Methods for Sampling and Assessing Deposits of Insecticidal Sprays Released over Forests, 10 - 13 (ed. J.W.Barry, R.B.Ekblad, G.P.Markin and G.C.Trostle). U.S.Department of Agriculture Technical Bulletin No. 1596. Washington: USDA.

ELLIOTT, J. G. and WILSON, B. J. (1983) The influence of weather on the efficiency and safety of pesticide application. The drift of herbicides. BCPC Occasional Publication, No.3, 135pp.

ELLIOTT, W. M. (1970) The action of seme systemic aphicides on the nymphs of Anthocoris nemorum (L.) and A. confusus (Reut.). Annals of Applied Biology, 66, 313 - 321.

ENDACOTT, C. (1983) Non-target organism mortality - a comparison of spraying techniques. Proceedings 10th International Congress of Plant Protection, 2, p.502.

ERICSON, D. (1978) Distribution, activity and density of some Carabidae (Coleoptera) in winter wheat fields. Pedobiologia, Bd. 18, 202 - 217.

EUROPEAN AND MEDITERRANEAN PLANT PROTECTION ORGANISATION (1982) Guidelines for reduced volume pesticide application. 48pp. Paris.

FEENEY, A. M. (1983) The occurrence and effect of pesticides on aphid predators in Ireland, 1979 - 1982. In: Aphid Antagonists Proceedings of a meeting of the EC Experts Group, Portici, Italy, 23 - 24 November, 1982, 123 - 128 (ed. R.Cavalloro). A.A. Balkema, Rotterdam.

320 FLETCHER, K. E. and BARDNER, R. (1969) Cereal aphids on wheat. Annual Report of Rothamsted Experimental Station for 1968, Part 1, 200 - 201.

FRANZ, J. M., BOGENSCHUTZ, H., HASSAN, S. A., HUANG, P., NATON, E., SUPER, H. and VIGGIANI, G. (1980) Results of a joint pesticide test programme by the working group: Pesticides and beneficial arthropods. Entomophaga, 25, 231 - 236.

FRASER, R. P. (1958) The fluid kinetics of application of pesticidal chemicals. In: Advanced Pest Control Research II. 1 - j 106 (ed. R.L.Metcalfe). Interscience, New York.

FROST, A. R. (1978) Rotary atomisation. In: Control1ed Drop Application, BCPC Monograph No. 22, 7 - 21.

GEORGE, K. S. (1974) Damage assessment aspects of cereal aphid attacks in autumn and sprincr-sown cereals. Annals of Applied Biology, 77, 67 -74.

GEORGE, K. S. (1975) The establishment of economic damage thresholds with particular reference to cereal aphids. Proceedings 1975 British Crop Protection Conference - Pests and Diseases, 1_, 79 - 85.

GEORGE, K. S. and GAIR, R. (1979) Crop loss assessment on winter wheat attacked by the grain aphid Sitobion avenae (F.), 1974 - 1977. Plant Pathology, 28, 143 - 149.

GEORGE, K. S. and PLUMB, R. T. (1982) Cereal aphids. Ministry of Agriculture, Fisheries and Food Advisory Leaflet No.586, 8pp.

GOHLICH, H. (1983) Assessment of spray drift in sloping vineyards. Crop Protection, 2, 37 - 49.

GRAHAM-BRYCE, I. J. and MATTHEWS, G. A. (1981) Controlled Droplet Application of Agricultural Chemicals. Ministry of Agriculture, Fisheries and Food Advisory Leaflet No. 792, 12pp.

GREENSLADE, P. J. M. (1964a) The distribution, dispersal and size of a population of Nebria brevicollis (F.), with comparative studies on three other Carabidae. Journal of Applied Ecology, 33, 311 - 333.

GREENSLADE, P. J. M. (1964b) Pitfall trapping as a method for studying populations of Carabidae (Coleoptera). Journal of Animal Ecology, 33, 301 - 310.

GRIFFITHS, E. (1982) The carabid Agonum dorsale as a predator in cereals. Annals of Applied Biology, 101, 152 - 154.

GROVER, R., MAYBANK, J. and YOSHIDA, K. (1972) Droplet and vapour drift from butyl ester and dimethylamine salt of 2,4-D. Weed Science, 20, 320 - 324.

321 GROVER, R., MAYBANK, J. and YQSHIDA, K. (1978) Reducing droplet spray drift. 1978 Annual Meeting of Canadian Society of Agricultural Engineering, July 3-6, University of Regina, Saskatchewan.

GROVER, R., MAYBANK, J., YOSHIDA, K. and PLIMMER, J. R. (1973) Droplet and volatility drift hazards from pesticide application. Air Pollution Control Association Paper No.73 - 106. 29pp.

HAIGH, J. (1978) The Lockinge Ulvamast Mark 2. Lockinge Farm Enterprises Ltd., Ardington, Wantage. v j

HANCOCK, M. (1983) Cereal aphids: To spray or not to spray. The Game Conservancy Annual Review for 1982, Nb. 14, Spring 1983, p.43.

HARTLEY, G .S. and GRAHAM-BRYCE, I. J. (1980) Physical Principles of Pesticide Behaviour. The Dynamics of Applied Pesticides in the Local Environment in relation to a Biological Response. Vol I., 518pp. Academic Press Inc. London Ltd.

HASSAN, S. A., BIGLER, F., BOGENSCHUTZ, H.,BRCWN, J. U., FIRTH, S. I., HUANG, P., LEDIEU, M. S. , NATON, E. , OOMEN, P. A., OVERMEER, W. P. J., RIECKMANN, W., SAMS0E-PETER SEN, L., VIGGIANI, G. and VAN ZON, A. Q. (1983) Results of the second joint pesticide testing programme by the IOBC/WPRS - Working Group "Pesticides and Beneficial Arthropods". Zeitschrift fur angewandte Entomologie, 95, 151 - 158.

HEIJNE, C. G. (1978) A study of the effect of disc speed and flow rate on the performance of the Micron "Battleship". Proceedings 1978 British Crop Protection Conference - Weeds, 2, 673 - 679.

HEIJNE, C. G. (1979) A study of the effects of rotational speed and flow rate on the performance of a spinning cup for application of pesticides. DIC Thesis, University of London, 61pp.

HEIJNE, C. G. (1981) Development of a spinning cup for controlled droplet application of pesticides. PhD. Thesis, University of London, 190pp.

HELLPAP, C. (1982) Investigations of the effect of different insecticides on predators of cereal aphids under field conditions. Anzeiger fur Schadlingskunde Pflanzenschutz Umweltschutz, 55, 129 - 131.

HENDERSON, I. F. and PERRY, J. N. (1978) Seme factors affecting the build-up of cereal aphid infestations in winter wheat. Annals of Applied Biology, 89, 177 - 183.

HIGGINS, A. H. (1967) Spread factor for technical malathion spray. Journal of Economic Entomology, 60, 280 - 281.

HIMEL, C. M. (1969). The optimum size for insecticide spray droplets. Journal of Economic Entomology, 62, 919 - 925.

322 HIMEL, C. M. ( 1973) The fluorescent particle spray droplet tracer method. Journal of Economic Entomology, 66, 912 - 916.

HIMEL, C. M. (1974) Analytical methodology in ULV. In: Pesticide Application By ULV Methods, BCPC Monograph No. 11, 112 - 119.

HIMEL, C. M. and UK, S. (1975) The biological optimum spray droplet size. Proceedings 5th International Agricultural Aviation Congress, Warwi ck.

HINZ, B., DAEBELER, F. and GIESSMANN, H. J.(1973) Studies on the effect of chlorcholine chloride (CCC) on development and propagation of the cereal aphid Macrosiphum (Sitobion) avenae (F.) on Wheat plants. Archiv fur Phytopathologie und Pflanzenschutz, % 21 - 27.

HISLOP, E. C., COOKE, B. K. and HARMAN, J. M. P. (1983) Deposition and biological efficacy of a fungicide applied in charged and uncharged sprays in cereal crops. Crop Protection, 2, 305 - 316.

HOLLIDAY, N. J. (1977) Sex determination in living adult ground beetles (Coleoptera: Carabidae). Canadian Entomologist, 109, 397 - 398.

HOLT, J., GRIFFITHS, E. and WRATTEN, S. D. (1984) The influence of wheat growth stage on yield reductions caused by the rose-grain aphid, Metopolophium dirhodum. Annals of Applied Biology, 105, 7 - 14.

HORELLOU, A. and EVANS, D. D. (1979) Control of barley yellow dwarf virus with permethrin on winter barley in France. Proceedings 1979 British Crop Protection Conference - Pests and Diseases, _1, 9 - 15.

HURKA, K. (1975) Laboratory studies on the life cycle of Pterostichus melanarius (IIlig.)(Coleoptera: Carabidae). Vestnik Ceskoslovenske Spolecnosti Zoologicke, 39, 265 - 274.

I.C.I. (1978) Plant Protection Division Technical Data. Sheet PP383 Pyrethroid Insecticide.

INGLESFIELD, C. (1984) Field evaluation of the effects of a new pyrethroid insecticide, WL85871, on the beneficial arthropod fauna of oilseed rape and wheat. Proceedings 1984 British Crop Protection Conference - Pests and Diseases, 1_, 325 - 330.

JARMAN, R. T. (1956) Stains produced by drops on filter papers. Journal of the Royal Meteorological Society, 82. p.352.

JOHNSTONE, D. R. (1974) Physical and chemical requirements for ultra-low volume application. In: Pesticide Application by ULV Methods, BCPC Monograph No. 11, 73 - 79.

JOHNSTONE, D. R. (1977a) A twin tracer technique permitting the simul­ taneous evaluation of the field performance of two spraying machines

323 or spraying techniques. Journal of Agricultural Engineering Research, 22, 439 - 443.

JOHNSTONE, D. R. (1977b) A technique for estimating the total insecticide spray collection by individual cotton plants and a canparison of recovery of sprays of dyed water and two ULV formulations of triazophos. Coton et fibres tropicales, 32, 67 - 71.

JOHNSTONE, D. R. (1978) The influence of physical and meteorological factors on the deposition and drift of spray droplets of controlled size. In: Controlled Drop Application, BCPC Monocrraph No.22, 43 - 57* ** JOHNSTONE, D. R., COOPER, J. F. , GLEDHILL, J. A. and JOWAH, P. (1982) Preliminary trials to examine the drift of charged spray droplets. Proceedings 1982 British Crop Protection Conference - Weeds, J3, 1025 - 1032.

JOHNSTONE, D. R., HUNTINGTON, K. A. and COUTTS, H. E. (1974) Penetration of spray droplets applied by helicopter into a riverine forest habitat of tse-tse flies in Vfest Africa. Agricultural Aviation, 16, 71 - 82.

JOHNSTONE, D.R., HUNTINGTON, K. A. and KING, W. J. (1974) Micro- meteorological and operational factors affecting ultra-low-volume spray application of insecticides onto cotton and other crops. Agricultural Meteorology, 13, 39 - 57.

JOHNSTONE, D. R., RENDELL, C.H. and SUTHERLAND, J. A. (1977a) Note on the movement of insecticide droplets through and out of a crop canopy after emission below crop canopy. Journal of Aerosol Science, 8^, 387 - 394.

JOHNSTONE, D. R. , RENDELL, C. H. and SUTHERLAND, J. A. (1977b) The short-term fate of droplets of coarse aerosol size in ultra-low volume insecticide application on to a tropical crop. Journal of Aerosol Science, 8^, 395 - 407.

JONES, M. G. (1972) Cereal aphids, their parasites and predators caught in cacres over oat and winter wheat crops. Annals of Applied Biology, 72, 13 - 25.

JONES, M. G. (1976) The arthropod fauna of a winter wheat field. Journal of Applied Ecology, 13, 61 - 85.

JONES, M. G. (1979) Abundance of aphids on cereals from before 1973 to 1977. Journal of Applied Ecology, 16, 1 -22.

JONES, M. G. and DEAN, G. J. (1975) Observations on cereal aphids and their natural enemies in 1972. Entomolocri st's Monthly Magazine, . 11, 69 - 78.

324 JOOSE, E. N. G. and KAPTEIJN, J. M. (1968) Activity - stimulating phenanena caused by field disturbance in the use of pitfall traps. Oecologia (Berlin), 1^, 385- 392.

KING, W. J. and JOHNSTONE, D. R. (1973) Papers for sampling spray deposits of ultra-low volume carrier solvents. Centre for Overseas Pest Research, Miscellaneous Report No. 9, 7pp.

KOLBE, W. (1969) Studies on the occurrence of different aphid species as the cause of cereal yield and quality losses. Pflanzenschutz - Nachrichten Bayer, 22, 171 - 204. , i KOLBE, W. (1973) Studies on the occurrence of cereal aphids and the effect of feeding damage on yields in relation to infestation density level and control. Pflanzenschutz - Nachrichten Bayer, 26, 396 - 410.

KOLBE, W. and LINKE, W. (1974) Studies of cereal aphids: their occurrence, effect on yield in relation to density levels and their control. Annals of Applied Biology, 77, 85 - 87.

KGMSON, A. (1977) The assessment of spray coverage by different droplet sizes on bean plants using a fluorescent tracer. Thailand Journal of Agricultural Science, 10, 59 - 71.

LAKE, J. R., FROST, A. R. and LOCKWOOD, A. (1978) Drift from an Ulvamast sprayer. Proceedings 1978 Britsh Crop Protection Conference - Weeds, 2, 681 - 686.

LATTEUR, G. (1976) Les pucerons des cereales: biologie, nuisance, ennemis. Memoires Centrede Recherches Agronomiques et 1 '6 t a t Gembloux, Nc.3, 74pp.

LAWSON, T. J. (1979) Some factors affecting the dispersal of aerial sprays. Royal Aeronautical Society, Agricultural Aviation Group Symposium.

LAWSON, T. J. (1983) The effect of spray application on herbicide drift damage to non-target crops. Aspects of Applied Biology, 3_, Crop sensitivity to herbicides, 165 - 174.

LAWSON, T. J. and UK, S. (1979) The influence of wind turbulence, crop characteristics, and flying height on the dispersal of aerial sprays. Atmospheric Environment, 13, 711 - 715.

LEE, C. W. (1974) Aerial ULV sprays for Cayman Island mosquitoes. In: Pesticide Application by ULV Methods, BCPC Monoaraph No. 11, 190 - 196.

LEE, G., STEVENS, D. J., STOKES, S. and WRATTEN, S.D . (1981) Duration of cereal aphid populations and the effects on wheat yield and bread making quality. Annals of Applied Biology, 98, 169 - 178.

325 LEWIS, T. (1965a) The effects of an artificial windbreak on the aerial distribution of flying insects. Annals of Applied Biology, 55, 503 - 512.

LEWIS, T. (1965b) The effects of shelter on the distribution of insect pests. Scientific Horticulture, 17, 74 - 84.

LEWIS, T. (1969a) The distribution of flying insects near a lew hedgerow. Journal of Applied Ecology, _6, 443 - 452.

LEWIS, T. (1969b) The diversity of the insect fauna in a .hiedgerow and neighbouring fields. Journal of Applied Ecology, 6_, 453 - 458.

LEWIS, T. (1970) Shelter effects and patterns of distribution of insects. Annual Report for Rothamsted Experimental Station 1969, Part 1,. 243 - 245.

LEWIS, T. and DIBLEY, G. C. (1970) Air movement near windbreaks and a hypothesis of the mechanism of the accumulation of airborne insects. Annals of Applied Biology, 66, 477 - 484.

LITTLE, P. (1979) Particle capture by natural surfaces. Agricultural Aviation, 20, 129 - 144.

LLOYD, G. A. and BELT., G. J. (1982) Relative contamination of humans and the environment by spray drift from use of a tractor-mounted drift sprayer (the Ulvamast) and conventonal hydraulic equipment. Proceedings 1982 British Crop Protection Conference - Weeds, 3_, 1045 - 1054.

LLOYD, G. A., BELL, G. J. and HCWGEGO, A. T. (1981) Contamination by fenitrothion of the aircraft pilot, humans at ground level, and non-target areas. In: Aerial application of insecticide against pine beauty moth, 63 - 72. (ed. A.V.Holden and D.Bevan) Forestry Commission, Edinburgh.

LOFGREN, C. S., ANTHONY, D. W. and MOUNT, G. A. (1973) Size of aerosol droplets impinging on mosquitoes as determined with a scanning electron microscope. Journal of Economic Entcmology, 66, 1085 - 1088.

LOUGHRIDGE, A. H. and LUFF, M. L. (1983) Aphid predation by Harpalus rufipes (De Geer) (Coleoptera: Carabidae) in the laboratory and the field. Journal of Applied Ecology, 20, 451 - 462.

LOWE, H. J. B. (1974) Effects of Metopolophium dirhodum on spring wheat in the glasshouse. Plant Pathology, 23, 136 - 140.

LUFF, M. L. (1968) Sane effects of formalin on the numbers of Coleoptera cauaht in pitfall traps. Entcmologist's Monthly Magazine, 104, 115 - 116.

326 LUFF, M. L. (1973) The annual activity pattern and life-cycle of Pterostichus madidus (F.) (Col., Carabidae). Entomologica Scandin- avica, £, 259 - 273.

LUFF, M. L. (1975) Some features influencing the efficiency of pitfall traps. Oecologia (Berlin), 19^, 345 - 357.

LUFF, M. L. (1978) Diel activity patterns of some field Carabidae. Ecological Entomology, 3^, 53 - 62.

LUFF, M. L. and LOUGHRIDGE, A. H. (1980) Laboratory and fieldJassessment of predation on aphids by ground beetles (Carabidae). AAB Workshop on Methods used to assess the role of Predators, 16 - 17th September, 1980, University of Cambridge.

MARSHAM, T. (1798) Further observations on the wheat insect .in a letter to the Pev. Samuel Goodenough. Transactions of the Linnean Society of London, 4_, 224 - 229.

MATTHEWS, G. A. (1975) Determination of droplet size. PANS, 21, 213 - 225.

MATTHEWS, G. A. (1979a) Pesticide Application Methods, Longman, London. 334pp.

MATTHEWS, G. A. (1979b) Pesticide formulation and technology of application in relation to integrated control requirements. In: Proceedings IOBC Conference, Vienna, 151 - 163.

MATTHEWS, G. A. (1981) Unproved systems of pesticide application. Philosophical Transactions of the Royal Society of London, B295, 163 - 173.

MATTHEWS, G. A. (1982) New developments in pesticide application technology. Crop Protection, 1_, 131 - 145.

MAXWELL, R. C. and HARWOOD, R. F. (1960) Increased reproduction of pea aphids on broad beans treated with 2,4-D. Annals of the Entomological Society of America, 53, 199 - 205.

MAY, K. R. (1945) The cascade impactor: an instrument for sampling coarse aerosols. Journal of Scientific Instruments, 22, 187 - 195.

MAY, K. R. (1950) The measurement of airborne droplets by the magnesium oxide method. Journal of Scientific Instruments, 27, 128 - 130.

MAY, K. R. and CLIFFORD, R. (1967) The impaction of aerosol particles on cylinders, spheres, ribbons and discs. Annals of Occupational Hygiene, 10, 83 - 95.

MAYBANK, J. and YOSHIDA, K. (1969) Delineation of herbicide-drift hazards

327 on the Canadian prairies. Transactions of the American Society of Agricultural Engineers, 12, 759 - 763.

MAYBANK, J. and YOSHIDA, K. (1971) Pesticide spray dissemination. 12th Annual Meeting of the Canada Committee on Agricultural Meteorology - Meteorological Aspects of Pollution in relation to Agricultural Pesticides, 13-24 (ed. J.T.Bergsteinsson and W.Baier)

MAYBANK, J., YOSHIDA, K. and GROVER, R. (1974) Droplet size spectra, drift potential, and ground deposition pattern of herbicide sprays. Canadian Journal of Plant Science, 54, 541 - 546. _ j MAYBANK, J., YOSHIDA, K., and GROVER, R. (1978) Spray drift from agricultural pesticide applications. Journal of the Air Pollution Control Association, 28, 1009 - 1014.

MAYBANK, J., YOSHIDA, K., and SHEWCHUK, S. R. (1976) Comparison of swath deposits and drift characteristics of ground-rig and aircraft herbicide spray systems. Report of the 1975 field trials. Saskatchewan Research Council Report, No. P76 - 1, 27pp.

MAYBANK, J., YOSHIDA, K.,WALLACE, K. and PETERS, M. (1980) Field tests of a spinning disc crop sprayer. Saskatchewan Research Council Report, No. P - 881 - 1 - E - 80, 24pp.

McDANIEL, R. and HIMEL, C. M. (1977) Standardization of field trial methods for determination of insecticide spray droplet size. Office of Naval Research Annual Report No. 2, 54pp.

McLEAN, I. F. G. (1980) The ecology of the natural enemies of cereal aphids. PhD. Thesis, University of East Anglia, 231pp.

McLEAN, I., CARTER, N. and WATT, A. (1977) Pests out of control? New Scientist, 76, 74 - 75.

MIDDLETON, M. R. (1967) Assessment of the efficiency of aerial application: use of kaolin-coated targets. Presented at a Symposium on Agricultural Aviation, organised by the Royal Aeronautical Society and the Society of Chemical Industry, London, 15th February, 1967.

MITCHELL, B. (1963) Ecology of two carabid beetles, Bembidion lampros (Herbst) and Trechus quadristriatus (Schrank). II. Studies on populations of adults in the field with special reference to the technique of pitfall trappincr. Journal of Animal Ecology, 32, 377 - 392.

MOLS, P. J. M. (1979) Motivation and walking behaviour of the carabid beetle Pterostichus coerulescens L. at different densities and distributions of the prey. A preliminary report. In: On the evolution of behaviour in carabid beetles, 185 - 198. Miscellaneous papers (18), Wageningen. H.Veenman and B.V.Zonen.

328 MOREBY, S. J. and POTTS, G.R. (1985) Insecticides and the survival of gamebird chicks in 1984. The Game Conservancy Annual Review for 1984, No. 16, Spring 1985, 47 - 49.

MORTON, N. (1977) Wind, leaf orientation and ULV spray coverage on cotton plants. Food and Agriculture Organisation Plant Protection Bulletin, 25, 29 - 37.

MOUNT,G.A. and PIERCE,N.W. (1972) Droplet size of ultra-low volume ground aerosols as determined by three collection methods. Mosquito News, 32, 586 - 589. • J MULLER, G. (1971) Laboruntersuchungen zur Wirkung von Herbiziden auf Carabiden. Archiv fur Phytopathologie und Pflanzenschutz, 1_, 351 - 364. . „

NANNE, H. W. and RADCLIFFE, E. B. (1971) Green peach aphid populations on potatoes enhanced by funcricides. Journal of Economic Entomology, 64, 1569 - 1570.

NATION, H. J. (1980) The performance and stabilty of spray boons. In: Spraying Systems for the 1980's , BCPC Monograph No. 24. 145 - 158 (ed. J.O. Walker).

NATION, H. J. (1982) The dynamic behaviour of spray booms. Journal of Agricultural Engineering Research, 27, 61 - 70.

NEISESS, J. (1978) Dyes for water- and oil-based insecticides. In: Methods for Sampling and Assessing Deposits of Insecticidal Sprays Released over Forests, pl7 (ed. J.W.Barry, R.B.Ekblad, G.P.Markin and G.C.Trostle) U.S. Department of Agriculture Technical Bulletin No. 1596. Washington: USDA.

NGUYEN, N. T. and SYMMONS, P. M. (1984) Aerial spraying of wheat: a conparison of conventional low volume with ultra-low volume spraying. Pesticide Science, 15, 337 - 343.

NORDBY, A. and SKUTERUD, R. (1975) The effects of boon height, working pressure and wind speed on spray drift. Weed Research, 14, 385 - 395.

NYAMBO, B. T. (1980) The use of Malaise traps to study insect activity in crops. MSc Thesis, University of London. 106pp.

OBRTEL, R. (1961) The effects of two insecticides on Aphidis ervi Hil. (Hym. Braconidae). Folia Zool. Praha, 10, 1 -8.

OKA, I. N. and PIMENTEL, D. (1974) Corn susceptibility to corn leaf aphids and common corn smut after herbicide treatment. Environmental Entomology, 3, 911 -915.

OSWALD, J. W. and HOUSTON, B. R. (1951) A new virus disease of cereals

329 transmissible by aphids. Plant Disease Reporter, 35, 471 - 475.

PARKIN, C. S., WYATT, J. C. and WANNER, R. (1980) The measurement of drop spectra in agricultural sprays using a particle measuring systems optical array spectrometer. In: Spraying Systems for the 1980's, BCPC Monograph No. 24, 241 - 249.

PARTIS, G. A. and BAILISS, K. W. (1980) The toxicity of some benzimidazole fungicides to the pea aphid Acrythosiphon pisum. Annals of Applied Biology, 96, 137 - 142.

PENGILLY, R. W. (1977) Problems and limitations in aerosol particle size distribution measurements. Pesticide Science, 8^, 79 - 83.

PIETRASZKO, R. and DE CLERCQ, R. (1981) Carabidae of arable land in Belgium. Parasitica, 37, 45-58.

PLUMB, R. T. (1974) Properties and isolates of barley yellow dwarf virus. Annals of Applied Biology, 77, 89 -91.

PLUMB, R. T. (1978) Aphids and virus control on cereals. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, 3^,903 - 913.

POLLARD, E. (1968a) Hedges. II. The effect of renoval of the bottom flora of a hawthorn hedgerow on the fauna of the hedgerow. Journal of Applied Ecology, 5_, 109 - 123.

POLLARD, E. (1968b) Hedges. III. The effect of removal of the bottom flora of a hawthorn hedgerow on the Carabidae of the hedge bottom. Journal of Applied Ecology, 5^, 125 - 139.

POLLARD, E. (1971) Hedges. VI. Habitat diversity and crop pests: A study of Brevi coryne brassicae and its syrphid predators. Journal of Applied Ecology, £), 751 - 780.

POTTS, G. R. (1970) Recent changes in the farmland fauna with special reference to the decline of the Grey Partridae. Bird Study, 17, 145 - 166.

POTTS, G. R. (1977) Some effects of increasing the monoculture of cereals. In: Origins of Pest, Parasite, Disease and Weed Problems, 183 - 202 (ed. J.M.Cherrett and G.R.Sagar). 413pp. Blackwells.

POTTS, G. R. (1982) A new approach to insects. The Game Conservancy Annual Review for 1981, No. 13, Spring 1982, 55 - 57.

POTTS, G. R. and VICKERMAN, G. P. (1974) Studies on the cereal ecosystem. Advances in Ecological Research, 8_, 108 - 189.

POTTS, G. R. and VICKERMAN, G. P. (1975) Arable ecosystems and the use of agrochemi cals. In: The Ecology of Resource Degradation and

330 Renewal, 17 - 29, (ed. M.J.Chadwick and G.T.Gocdman) .480pp. Blackwell Sci enti fi c, Oxford.

POWELL, W. (1983) Weeds are helpincr to beat the aphids. Fanners Weekly 17/6/83, p59.

POWELL, W., DEAN, G. J. and BARDNER, R.(1985) Effects of pirimicarb, dimethoate and bencmyl on natural enemies of cereal aphids in winter wheat. Annals of Applied Biology, 106, 235 - 242.

POWELL, W., DEAN, G. J., DEWAR, A. and WILDING, N. (1981) Towards integrated control of cereal aphids. Proceedings 1981 Briitish Crop Protection Conference - Pests and Diseases, 201 - 206.

RANDS, M. (1985) The benefits of pesticide-free headlands to wild gamebirds. The Game Conservancy Annual Review for 1984, No. .16, Spring 1985, 32 - 37.

RANDS, M. and SOTHERTON, N. (1985) Pesticides threaten British wildlife. New Scientist, 1463, p.32.

RATHBURN, C. B. (1970) Methods of assessing droplet size of insecticidal sprays and fogs. Mosquito News, 30, 501 - 513.

RAUTAPAA, J. (1972) Effect of herbicides and chlormeguat chloride on host plant selection and population growth of Macrosiphum avenae (F.) (Horn., Aphididae). Annales Agriculturae Fenniae, 11, 135 - 140.

RAUTAPAA, J. and UOTI, L. (1976) Control of Rhopalosiphum padi (L. ) (Horn., Aphididae) on cereals. Annales Aariculturae Fenniae, 15, 101 - 110.

RIPPER, W. E. (1955) Application methods for crop protection chemicals. Annals of Applied Biology, 42, 288 - 324.

ROBERTS, R. (1978) Chemical analysis of spray deposits. In: Methods for Sampling and Assessing Deposits of Insecticidal Sprays Released over Forests, pi04 (ed. J.W.Barry, R.B.Ekblad, G.P.Markin and G.C.Trostle) U.S. Department of Agriculture Technical Bulletin No. 1596. Washington: USDA.

ROTHAMSTED EXPERIMENTAL STATION (1977) Genstat: A General Statistical Programme. Rothamsted Experimental Station.

ROYAL COMMISSION ON ENVIRONMENTAL POLLUTION (1979) Seventh Report, Agriculture and Pollution. 280pp. HMSO, London.

RUSCOE, C. N. E. (1979) The impact of the photostable pyrethroids as agricultural insecticides. Proceedings 1979 British Crop Protection Conference - Pests and Diseases, 3/ 803 - 814.

RUTHERFORD, I. and ORSON, J. (1982) Use of the Lockinge Ulvamast for

331 pesticide application. MAFF Mechanisation: Occasional Note No. 314, November, 1982.

SAGENMULLER, von A. (1977) The effect of systemic fungicides on the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Walk.) (Homoptera: Aphididae) Zeitschrift fur anqewandte Entomologie, 82, 293 - 300.

SCHNEIDER, F. (1969) Bionomics and physiology of aphidophagous Syrphidae. Annual Review of Entomology, 14, 103 - 124.

SHARP, R. B. (1974) Spray deposit measurement by fluorescence.:1 Pesticide Science, 5^, 197 - 209.

SHARP, R. B. (1984) Comparison of drift from charged and. uncharged hydraulic nozzles. Proceedings 1984 British Crop Protection Conference, 3, 1027 - 1031.

SHIRES, S. W. (1980) Soil surface predators in arable land. The effects of farming practices. Span, 23, 62-64.

SHIRES, S. W. (1985) A comparison of the effects of cypermethrin, parathion - methyl and DDT on cereal aphids, predatory beetles, earthworms and litter decomposition in spring wheat. Crop Protection, £, 177 - 193.

SHOUR, M. H. and CRCWDER, L. A. (1980) Effects of pyrethroid insecticides on the common crreen lacewina. Journal of Economic Entomology, 73, 306 - 309.

SINGER, M. C. and SMITH, B. D. (1976) Use of the plant growth regulator chlormequat chloride to control the aphid Hyperomyzus lactucae on blackcurrants. Annals of Applied Biology, 82, 407 - 414.

SKUHRAVY, V. (1970) Zur Anlockungsfahigkeit von Formalin fur Carabiden in Bodenfallen. Beitrage zur Entomologie, 20, 371 - 374.

SMITH, B. D. (1968) Starvincr out plant pests. New Scientist,40, 84 - 85.

SMITH, D. B., HARRIS, F. D. and BUTLER, B. J. (1981) Ancillary equipment and conditions for drift reduction. 1981 Winter Meeting of the American Society of Agricultural Engineers, December 15 - 18, Chicago, Illinois.

SMITH, D. B., HOSTETTER, D. L. , HARRIS, F. D. , VOGT, C. R. and SOMMER, R. W. (1982) Deposition of suspension spray particles. Contribution of Agricultural Research, SEA/US Department of Agriculture in co-operation with the University of Missouri, Agricultural Experiment Station.

SMITH, R. K. (1981) Studies on ecology of cereal aphids and prospects for

332 integrated control. PhD Thesis, University of London, 400pp.

SOTHERTON, N. W. (1982) The value of field boundaries to beneficial insects. The Game Conservancy Annual Review for 1981, No.13, Sprina 1982, 52 - 54.

SOTHERTON, N. W. (1983) Field boundaries and beneficial insects. The Game Conservancy Annual Review for 1982, No. 14, Spring 1983, 35 - 37.

SOTHERTON, N. W. (1984) The distribution and abundance of predatory arthropods overwintering on farmland. Annals of Applied Biolocry, 105, 423 - 429.

SOTHERTON, N. W. (1985a) The distribution and abundance of predatory Coleoptera overwintering in field boundaries. Annals of~ Applied Biology, 106, 17 - 21.

SOUTHERTON, N. W. (1985b) An insecticidal action of some foliar fungicides. The Game Conservancy Annual Review for 1984, No. 16, Spring 1985, 38 - 40.

SOTHERTON, N. W. and MOREBY, S. J. (1984) Contact toxicity of some foliar fungicide sprays to three species of polyphagous predators found in cereal fields. Tests of Agrochemicals and Cultivars No. 5 (Annals of Applied Biology, 104, Supplement) 16 - 17.

SOUTHWOOD, T. R. E.(1978) Ecological Methods with particular reference to the study of insect populations. 2nd edition. 524pp. Chapman and Hall, London and New York.

SPACEMAN, E. A. (1983) Estimating the frequency of occasions suitable for crop spraying using meteoroloaical data. Aspects of Applied Biology, 3, 155 - 163.

SPACEMAN, E. A. and BARRIE, I. (1982) Spraying occasions determined from meteorological, data during the 1980 - 81 season at 15 stations in the UE and comparison with 1971 - 80. 18th Review of Herbicide Usage. - Croydon: BCPC.

SPEIGHT, M. R. and LAWTON, J.H. (1976) The influence of weed cover on the mortality imposed by artificial prey by predatory ground beetles in cereal fields. Oecologica (Berlin) Z3, 211 - 223.

STARY, P. (1970) Biology of Aphid Parasites (Hymenoptera: Aphidiidae) with Respect to Integrated Control. 643pp. Dr.W.Junk, N.V. The Hague, Netherlands..

STEPHENS, R. (1984) Additives aimincr for a taraet. Farm Business, March 1984, 61 - 62.

STEVENSON, J. H., SMART, L. E. and WALTERS, J. H. H. (1983) Evaluation of the effects of pesticides on beneficial . species in arable crops.

333 Proceedings 10th International Congress of Plant Protection, 2, p.714. ♦ STEVENSON, J. H. SMART, L. E. and WALTERS, J. H. H. (1984) Short-term effects of insecticides on beneficial species. Annual Report of Rothamsted Experimental Station for 1983, Part 1, p.103.

STONE, L. E. W. (1977) The incidence and economic significance of pests in cereals in England and Wales. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, 3_, 713 - 719.

SUNDARAM, K. M. S. and SLJNDARAM, A. (1982) Influence of formulation on droplet size, deposit concentration, and persistence of fenitrbthion in conifers following a simulated aerial application. Canadian Forestry Service Research Notes, 2, 2 - 5.

SUNDBY, R. A. (1966) A comparative study of the efficiency of three predatory insects Coccinella septempunctata L. (Coleoptera, Coccinellidae), Chrysopa carnea St. (Neuroptera, Chrysopidae), and Syrphus ribesii L. (Diptera, Syrphidae), at two different temperatures. Entomophaga, 11, 395 - 404.

SUNDERLAND, K. D. (1975) The diet of seme predatory arthropods in cereal crops. Journal of Applied Ecology, 12, 507 - 515.

SUNDERLAND, K. D. (1977) Cereal aphids - can predatory insects prevent outbreaks? The Game Conservancy Annual Review for 1976. No. 8, Spring 1977, 50 - 54. i

SUNDERLAND, K. D. and CHAMBERS, R. J. (1983) Invertebrate polyphagous predators as pest control agents: Some criteria and and methods. In: Aphid Antagonists. Proceedings of a Meeting of the EC Experts Group, Portici, Italy, 23 - 24 November, 1982, 100 - 108 (ed. R.Cavalloro) A.A. Balkema, Rotterdam.

SUNDERLAND, K. D. and FRASER, A. M. (1981) Field studies on spiders as predators of cereal aphids. Annual Report of Glasshouse Crops Research Institute for 1980, p.114.

SUNDERLAND, K. D. and VICKERMAN, G. P. (1980) Aphid feeding by some polyphagous predators in relation to aphid density in cereal fields. Journal of Applied Ecology, 17, 389 - 396.

SWITHENBANK, J. BE&, J. M., TAYLOR, D. S. , ABBOT, D. and McCREATH, G. C. (1975) A laser diagnostic technique for the measurement of droplet and particle size distribution. Report HIC 245, Department of Chemical Engineering and Fuel Technology, University of Sheffield.

SWITHENBANK, J. BEER, J. M., TAYLOR, D. S. , ABBOT, D. and McCREATH, G. C. (1977) Experimental diagnostics in gas phase combustion systems. In: Progress in Astronautics and Aeronautics, 53, lOpp, (ed B.T.Zinn).

334 TAKENAGA, T. (1972) Knapsack type LV concentrate (ULV) sprayer. Japan Pesticide Information No. 13, 5 - 10.

TAYLOR, L. R., FRENCH, R. A., COLE, J. B. , GEORGE, K. and GAIR, R. (1971) NAAS field trials. Annual Report of the Rothamsted Experimental Station for 1970, Part 2, 190 - 192.

TAYLOR, L. R. AND PALMER, J. M. P. (1972) Aerial sampling. In: Aphid Technology (ed. H.F.van Emden) Academic Press, London.

TAYLOR, W. (1985) Biological consequences of sprays emitted by horizontal rotary atomizers. In: Application and Biology, BCPC Monocrraph No. 28, 17 - 19.

THIELE, H. U. (1977) Carabid Beetles in their Environment. A Study on Habitat Selection by Adaptations in Physiology and Behaviour. Zoophysiology and Ecology, 10, 369pp. (ed. ... W.S.Hoar, B.Hoelldobler, H.Langer and M.Lindauer) Springer-Verlay, Berlin, Heidelberg and New York.

THOM, A. S. (1975) Momentum, mass and heat exchange of plant communities. In: Vegetation and the Atmosphere, 57 - 109. (ed. J.L.Monteith) Academic Press, London.

THOMPSON, N. and LEY, A. J. (1982) The quantification of spray drop drift. Proceedings 1982 British Crop Protection Conference - Weeds, 3^, 1039 - 1044.

THORNHILL, E. W. (1979) A rotary droplet sampler. PANS, 25, 68 - 70.

THREADGILL, D. E. and SMITH, D. B. (1975) Effects of physical and meteorological parameters on the drift of controlled-size droplets. Transactions of the American Society of Agricultural Engineers, 18, 51 - 56.

TOTTMAN, D. R. and MAKEPEACE, R. J. (1979) An explanation of the decimal code for the growth stages of cereals, with illustrations. Annals of Applied Biology, 93, 221 - 234.

TURNER, C. R. and HUNTINGTON, K. A. (1970) The use of a water sensitive dye for the detection and assessment of small spray droplets. Journal of Agricultural Engineering Research, 15, 385 - 387.

UK, S. (1977) Tracing insecticide spray droplets by sizes on natural surfaces. The state of the art and its value. Pesticide Science 8, 501 - 509.

UK, S. and COURSHEE, R. J. (1982) Distribution and likely effectiveness of spray deposits within a cotton canopy from fine ultra-low volume spray applied by aircraft. Pesticide Science, 13, 529 - 536.

VAN EMDEN, H. F. (1964) Effect of (2-chloroethyl) trimethylammoni urn

335 chloride on the rate of increase of the cabbage aphid (Brevicoryne brassicae (L.)). Nature, London 201, 946 - 948.

VAN EMDEN, H. F. (1965) The role of uncultivated land in the biology of crop pests and beneficial insects. Scientific Horticulture, 27, 121 - 136.

VAN RENSBURG, N. J. (1978) The effect of foliar sprays with broad-spectrum organophosphates on the coccinellid and syrphid predators of grain-sorghum aphids. Journal of the Entomological Society of Southern Africa, 41, 305 - 309. . i VERIJKEN, P. H. (1975) Physiological research on the harmfulness of three aphid species on wheat. Annual Report 1975, Institute of Phytopathological Research, Wageningen, Netherlands.

VICKERMAN, G. P. (1974) Some effects of grass weed control on the arthropod fauna of cereals. Proceedings 1974 British Crop Protection Conference - Weeds, 3_, 929 - 939.

VICKERMAN, G. P. (1977) The effects of foliar fungicides on some insect pests of cereals. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, _1, 121 - 128.

VICKERMAN, G. P. (1978) The arthropod fauna of undersewn grass and cereal fields. Scientific Proceedings of the Royal Dublin Society (A), 6_, 155 -165.

VICKERMAN, G. P. (1981) Fungicides and their effect on insects in cereal crops. The Game Conservancy Annual Review for 1980, No. 12, Sprincr 1981, 50 - 53.

VICKERMAN, G. P. (1982) Distribution and abundance of cereal aphids (Aphidius spp.) on grassland and winter wheat. Annals of Applied Biology, 101, 185 - 190.

VICKERMAN, G. P. and SOTHERTON, N. W. (1983) Effects of seme foliar fungicides on the chrysomelid beetle Gastrophysa polygoni (L.). Pesticide Science, 14, 405 - 411.

VICKERMAN, G. P. and SUNDERLAND, K. D. (1975) Arthropods in cereal crops: nocturnal activity, vertical distribution and aphid predation. Journal of Applied Ecology, 12, 755 - 765.

VICKERMAN, G. P. and SUNDERLAND, K. D. (1977) Some effects of dimethoate on arthropods in winter wheat. Journal of Applied Ecology, 14, 767 - 777.

VICKERMAN, G. P. and WRATTEN, S. D. (1979) The biology and pest status of cereal aphids (Hemiptera: Aphididae) in Europe: A review. Bulletin of Entomological Research, 69, 1 - 32.

336 WAAGE, J. (1980) Structure and efficiency of parasitoid populations in crop lands. AAB Workshop on Methods used to assess the Pole of Predators, 16 - 17th September, 1980, University of Cambridge.

WALTERS, K. F. A. and CARTER, N. (1981) Settling behaviour of cereal aphids and forecasting outbreaks. Proceedings 1981 British Crop Protection Conference - Pests and Diseases, 1^, 207 - 215.

WALTON, W. H. and PREWEIT, W. C. (1949) The production of sprays and mists of uniform drop size by means of spinning disc type sprayers. Proceedings of the Physical Society, 62, 341 - 351.

WARE, G. W., APPLE, E. J., CAHILL, W. P., GERHARDT, P. D. and FROST, K. R. (1969) Pesticide drift II. Mist-blower vs. aerial application of sprays. Journal of Economic Entomology, 62, 844 - 846.

WARE, G. W., BUCK, N. A. and ESTESEN, B. J. (1984) Deposit and drift losses from aerial ultra-low volume and emulsion sprays in Arizona. Journal of Economic Entomology, 77, 298 - 303.

WARE, G. W., CAHILL, W. P. , ESTESEN, B. J. , KRONLAND, W. C. and BUCK, N. A. (1975) Pesticide drift: Deposit efficiency from ground sprays on cotton. Journal of Economic Entomology, 68, 549 - 550.

WAY, M. J. and CAMMELL, M. E. (1979) Optimising cereal yields - the role of pest control. Proceedings 1979 British Crop Protection Conference - Pests and Diseases, 3_, 663 - 672.

WESTERN, N. M. ,HISLOP, E. C.,HERRINGTON, P. J. and WOODLEY, S. A. (1985) Relationships of hydraulic nozzle and spinning disc spray character­ istics to retention and distribution in cereals. In: Application and Biology, BCPC Monograph No. 28, 191 - 199.

WHITTLES, C. J. (1977) Current practice in integrated pest and disease control in the UK. Proceedings 1977 British Crop Protection Conference - Pests and Diseases, 3_, 773 - 783.

WHO (1971) Methods for the determination of droplet sizes of aerosols and sprays. In: Application and dispersal of pesticides, 30 - 34. World Health Organisation Technical Report Series No. 465, 66pp.

WILDING, N. (1969) The effect of humidity on the sporulation of Entomophthora aphidis and thaxteriana. Transactions of the British Mycological Society, 53, 126 - 130.

WILDING, N. (1972) The effect of systemic fungicides on the aphid pathoaen, Cephalosporium aphidicola. Plant Pathology, 21, 137 - 1391

WILKES, L. H. and BRUSSE, J. C. (1963) Activation analysis techniques for pesticide tracers. Transactions of the American Society of Agricultural Engineers, 6, 102 - 103.

337 WILSON, G. P. (1977) Principles and problems of aerial pesticide application. Part II. World of Agricultural Application, 41, 13 - 1.6 .

WOODFORD, E. K. (1964) Weed control in arable crops. Proceedinas 1964 British Crop Protection Conference - Weeds, 3_, 944 - 962.

WRATTEN, S. D. (1975) The nature of the effects of the aphids Sitobion avenae and Metopolophium dirhodum on the growth of wheat. Annals of Applied Biology, 79, 27 - 34. , J WRATTEN, S. D. (1978) Effects of feeding position of the aphids Sitobion avenae and Metopolophi urn dirhodum on wheat yield and quality. Annals of Applied Biology, 90, 11-20.

WRATTEN, S. D., BRYAN, K., COQMBES, D.and SOPP, P. (1984) Evaluation of polyphagous predators of aphids in arable crops. Proceedings 1984 British Crop Protection Conference - Pests and Diseases, J_, 271 - 276.

WRATTEN, S. D., LEE, G. and STEVENS, D. J. (1979) Duration of cereal aphid populations and the effects on wheat yield and quality. Proceedings 1979 British Crop Protection Conference - Pests and Diseases, 1_, 1-8.

WRATTEN, S. D.and REDHEAD, P. C. (1976) Effects of cereal aphids on the growth of wheat. Annals of Applied Biology, 84, 437 - 440.

YARHAM, D. J. (1975) The effect of non-ploughing on cereal diseases. Outlook on Agriculture, 8_, 245 - 247.

YATES, W. E. and AKESSON, N. B. (1973) Reducing pesticide chemical drift. In: Pesticide Formulations, 275 - 341 (ed. W. van Valkenburg) 481pp. Marcel Dekker, New York.

YATES, W. E., AKESSON, N. B. and BAYER, D. E. (1978) Drift of glyphosate sprays applied with aerial and around equipment. Weed Science, 26, 597 - 604.

YATES, W. E., CCWDEN, R. E. and AKESSON, N. B. (1982) Procedure for determining in situ measurements of particle size distribution produced by agricultural aircraft. In: Proceedings of the 2nd International Conference on Liquid Atomisation and Spraying Systems, Wisconsin, USA, 335 - 339.

YEO, D. (1955) Some physical and meteorological aspects of field applications of insecticide. Tropical Pesticides Research Institute Miscellaneous Report No. 135 (TR/1/2/2/66) 21pp.

YOUNG, B. W. (1985) Pesticide application - how can we improve pur understanding and control of the process? In: Application and

338 Biology, BCPC Monograph No. 28, 163 - 171.

YUILL, J. S. and SECFEST, J. P. (1966) The dye-tracer method for measuring aerial spray deposits in forest insect research. Journal of Economic Entomology, 59, 720 - 723.

ZIMMERMANN, G. (1976) Effect of systemic fungicides on aphid-infesting Entomophthoraceae (Zygomycetes) in vitro. Zeitschrift fur Pflanzen- krankheiten und Pflanzenschutz, 83, 261 - 269.

339 APPENDIX 1 Diagram and parts list for the UlvamastMk2 sprayer.

Electrical section 11 LF2020 Atomizer motor pulley 20 LF2105 RV10 Set rollers 1 LF3010 Cable loom complete 12LF2055 Atomizer motor driving 21 LF2106 RV10 End seals ring 2LF3011 Cable battery to 22 LF2107 RV10 Shaft bearing control box i Atomizer 23 LF2108 RV10 Flange ‘O’ ring 3LF3012 Control box |13LF2054 CompleteX16 24 LF3046 RV10 Torque bar 4LF3013 Control switch 114 LF2116 Rear sealed bearing 5LF3014 Atomizer motor 15LF2117 Front cup & cone Hydraulic 6LF3015 Atomizer motor bearing retaining bolts x3 25LF2023 Hydraulic ram 7LF2110 Atomizer motor brush 16LF2118 Discs x16 26 LF2024 Hyd. ram seals set ! 17 LF3017 Rear moulding box 27 LF2122 x f" Hex. unions 8LF3016 Atomizer motor *18LF3018 Front moulding rubber blocks x4 28LF3019 Top hydraulic hose 9LF2018 Solonoid Roller vane pump 29 LF3020 Bottom hydraulic hose 10LF2012 Solonoid seal kit 19 LF2104 RV10 Pump 30LF2125 Bonded seals

340 Diagram and parts list cont'd.,

View with tank removed

Wiring circuit cable loom 1 complete

Pipework and tank 51 LF2141 i"Poly hose Framework etc. (n .i.) = Not illustrated 74LF3034 Frame less jib 31 LF2126 Pressure control 52 LF2144 i” Hose coupling complete 53 LF2145 i" Hose tail 75LF3035 Jib less atomizer bracket 76 LF3036 Atomizer bracket 32 LF2127 Filter screen 54 LF3027 Blue yellow restriction 33 LF2128 Filter screen ‘O’ring 77 LF3037 Atomizer motor 55 LF3028 Yellow yellow restriction mounting plate 34 LF3021 Changeover valve ‘O’ ring 56 LF3029 Red white restriction 78LF3038 Atomizer motor guard 35 LF3022 Pressure control 57 LF2146 f" Hose tail 79LF2168 Atomizer bracket hinge piston ‘O’ ring 58LF2147 | ”Hex. nipple pin 80LF3039 Parallel link rod 36 LF3023 Pressure control 59 LF3030 Elbow piston spring 81 LF2048 Parallel link rod end x2 60 LF2149 i" Tee 37 LF2129 Low pressure gauge & 82LF3040 Jib hinge stud tail 61 LF2150 }" Socket 83LF3041 Jib hinge stud with 38 LF2130 Low pressure gauge 62 LF2155 1” Jubilee clips greaser pipe line 63 LF2156 ¥' Jubilee clips 84 LF3042 Jib hinge assembly bush 39 LF2131 Main tank 64LF2159 x i" Reducer 85 LF2172 Ram attach bolt upper 40LF2132 Main Tank calibration strip 65 LF3031 }" Tail QR couplings 86LF2173 Ram attach bolt lower 41 LF2029 Tank lid 66LF3032 J" Tail 87 LF2059 Nylon cable ties x10 42LF2028 Tank screen 88LF3043 Instruction & parts list (N.l.) 43LF3024 Tank outlet suction Transfers (N.l.) = Not illustrated 89 LF2177 Calibration beaker (N.l.) 44LF3025 Tank outlet return 67 LF2160 Protect from frost (N.l.) 90LF3043 Parts list 45LF2135 Distribution valve 68 LF2161 Main valves (N.l.) Ulvamast RM (N.l.) 46 LF2136 3 way valve x2 69 LF2162 Suck back & spray etc. 91 LF3044 Pickup forks (N.l.) 47 LF2030 Flushing tank 92 LF3045 Pressure control 48LF2138 1" Reinforced PVC 70LF2163 Danger keep clear (N.l.) mounting plate hose 71 LF2164 Ulvamast (N.l.) 93LF3046 Tank straps 49 LF2139 f ' Reinforced PVC 94 LF3047 Tank support frame hose 72 LF3033 Calibration chart (N.l.) 95LF3048 Cat. 1 link pin x2 50 LF3026 Reinforced PVC 73 LF2132 Tank strip 0-55 gals. hose (N.l.) 96 LF3049 Cat. 2 link pin x2

341 A= 0790 A= 1814 A= 1418 A= 1930 A= 2047 A= 1953 A= 1674 A= 1558 A= 1139 A= 0976 A= 1302 A= 1674 A= 1302 A= 0511 A= 0907 C= 1229 C= 1543 C= 1831 C= 1990 C= 0617 C= 1781 C= 1577 C= 1139 C= 0941 C= 0599 C= 0758 C= 0889 +0.27% +0.81% +1.52% +3.43% C= 2043 +0.00% +4.53% C= 1953 +5.83% +7.47% +9.38% C= 1348 +0.02% +2.30% +20.70% +13.48% +11.81% +18.45% N= N= N= N= N- N= N= N= N= N= N= N= N= N= +1.87% +0.26% +5.11% +8.40% N= +3.09% +0.71% +0.42% +1.13% +99.97% +94.51% +75.08% +52.89% +34.96% +22.46% +13.76% R= R= R= R= R= R= R= R= R= .16% .29% R= .22% .70% .93% .43% .03% .42% R= .02% .36% .74% R= .49% R= .19% R= .46% .29% R= +0 + 8 + +0 +0 +3 +0 +2 +1 + 5 + +5 +0 +19 +17 + 22 + +12 00120500 P= E= P= P= P= P= P= P= P= P=. P= P= P= P= P= P= .1 66 22 35 81 44 48 02 46 89 58 49 03 93 +15. + 19. + +63. 16 + 49. + + 80. + +38. + 30. + +24 . +24 +300. +171. 98 +224. +103. +133. + 426. + +697. = = +2 > > > > > > > > > > > > > > W= .0 35 66 81 02 > 49 46 03 16 93 98 ** +19. + 24. + + 80 . 80 + +30. 44 +49 . +49 + 38. + + 63. + ***** +426. 89 +224 .48 +224 + 300 .58 300 + + 697. + +103. +133. +171. = +257 = CHAFER CHAFER GREEN NOZZLE CONE): (HOLLOW Pressure: 38 p.s.i. PE= D= D= D= D= D= D— Replicate 1 D= D= D= D= D= D= D= D= APPENDIX 2 Malvern droplet sizing : specimen print-out (see key on page 6 3 ) D=

342 APPENDIX 3 Ordnance survey map of field site m surrounding area (2.5 inches to 1 mile).

343 APPENDIX 4 The mean daily rainfall and maximum and minimum daily temperatures during MAY 1981. F : frost

T : thunderstorm

— : maximum T °

-- : minimum T °

CO

0

DAY APPENDIX 5 The mean daily relative humidity and hours of sunshine during MAY 1981 .

100 9 80 0) CO Ol C§ a- 60 c 3 a 40 H* *< IT u-CO 20 8 0 d> c !£ cCO 3 (/> 0

DAY APPENDIX 6 The mean daily rainfall and maximum and minimum daily temperatures during JUNE 1981. — : maximum T° -- : minimum T °

a 3 S

CO CD O APPENDIX 7 The mean daily relative humidity and hours of sunshine during JUNE 1981.

DAYS APPENDIX 8 The mean daily rainfall and maximum and minimum daily temperatures during JULY 1981.

— : maximum T ° -- : minimum T °

DAY APPENDIX 9 The mean daily relative humidity and hours of sunshine during JULY 1981. eaie humidity(%) Relative

CO A CO

DAY APPENDIX 10 The mean daily rainfall and maximum and minimum daily temperatures during F: frost MAY 1982 . T : thunderstorm

H: hail maximum T ° 5* minimum T ° 3 ■o

DAY APPENDIX 11 The mean daily relative humidity and hours of sunshine during MAY 1982.

100 eaie uiiy( ) (% humidity Relative 80

60

40 co Ol 20

0

DAY APPENDIX 12 The mean daily rainfall and maximum and minimum daily temperatures during JUNE 1982.

30 eprtr (C) (°C Temperature 20

10

CO 0 cn r\o

DAY APPENDIX 13 The mean daily relative humidity and the hours of sunshine during JUNE 1982.

100 eaie uiiy (%) humidity Relative 80

60

40 co cn co 20

0

DAY APPENDIX 14 The mean daily rainfall and maximum and minimum daily temperatures during JULY 1982. T : thunderstorm - : maximum T ° -■ : minimum T °

5* 3 n 0)-n c-n CD COOl

DAY APPENDIX 15 The mean daily relative humidity and hours of sunshine during JULY 1982.

100 eaie uiiy (%) humidity Relative

80

60

UlCO Ul 40

20

0

DAY APPENDIX 16 The mean daily rainfall and maximum and minimum daily temperatures during the first half of AUGUST 1982 . T : thunderstorm “ : maximum T° : minimum T° 30 iS1 20 3 T3 CD 10 S'3 o cnCO 0 0)

0

DAY APPENDIX 17 The mean relative humidity and hours of sunshine during the first half of AUGUST 1982.

100

60 c 3 a 40 cnCO -nI 20

0

DAY analysis). 5=(1 : TRAP $ $ TRAP : 180(1...8) 4.04B $S=15(1,2,3)32 $0=45(1...4)8 $1440=1...1440 RCARAB=SQRT(CARAB+0.5) Specimen Genstat programme and ANOVA (Carabid numbers 1982:3 factor CARAB SPRAY SPRAY DIST DIST D=1OOM,30M,1OM,OM S=HV,ULV,UT BLK/SPRAY/DIST/TIME/TRAP T=-2,-1,1,3,5,8,10,1 4 T=-2,-1,1,3,5,8,10,1 CARAB ' RCARA3 ' ' SPRAY*DIST*TIME ' ' NOS NOS ' 'BLOC' ' RUN ' RUN ' 'FACT' 'TREAT 'FACT' 'CALC' 'UNITS 'FACT' TIME $T = = $T TIME 'FACT' $BLK 3=5(1,2,3)96 : 'NAME' 'NAME' ' REFE' ' . 'PRINT/P' NOS,BLK,DIST,SPRAY,TIME 'PRINT/P' . 4 8 9 5NAME' 6 • 7 2 3 1 15 'ANOVA 11 13 14 12READ' ' 16 10 COPYRIGHT 1984 LAWES AGRICULTURAL TRUST (ROTHAMSTED EXPERIMENTAL STATION) EXPERIMENTAL (ROTHAMSTED TRUST AGRICULTURAL LAWES 1984 COPYRIGHT GENSTAT V V GENSTAT RELEASE APPENDIX 17

358 VR 1.056 1.597 0.893 0.575 2.571 6.473 3.863 MS 0.21 87 0.21 3.3399 1.3193 0.4070 0.1464 0.2682 5.7202 2.2248 1.1076 0.9844 S S X S S 4.86 1.0491 1.71 1.77 2.20 5.25 6.7910 1.58 5.24 2.95 2.29 0.68 11.82 1.7001 11.03 0.2548 64.85 17.41 .100.00 SS 8.5478 6.8906 3.1839 0.82 0.2274 6.1497 6.6456 8.8992 2.6387 20.3731 45.9026 18.3840 20.3397 42.8079 67.5799 11.4405 388.2148 251.7539 1.053 1151 ( 1) ( 1151 ***** variance

of

1063 1063 1.127 UNIT UNIT ESTIMATED NUMBER NUMBER VALUE analysis DIST.TIME DIST.TIME 21 RESIDUAL RESIDUAL 18 TIME TIME SPRAY.TIME SPRAY.DIST.TIME RESIDUAL 42 14 168 7 RESIDUAL RESIDUAL DIST SPRAY.DIST 4 6 3 SPRAY SPRAY 2 ANOVA cont'd NUMBER OF MISSING VALUES VALUES MISSING ITERATIONS OF OF NUMBER NUMBER MAXIMUM 2 1 GRAND TOTAL TOTAL GRAND 1438 BLK.SPRAY.DIST.TIME STRATUM BLK.SPRAY.DIST.TIME ESTIMATED GRAND MEAN MEAN GRAND ESTIMATED SOURCE OF VARIATION VARIATION OF SOURCE DFCMV) TOTAL TOTAL 27 BLK.SPRAY.DIST.TIME.TRAP STRATUM BLK.SPRAY.DIST.TIME.TRAP TOTAL TOTAL STRATUM BLK.SPRAY.DIST 6 TOTAL NUMBER OF OBSERVATIONS OBSERVATIONS OF NUMBER TOTAL 1440 BLK STRATUM STRATUM BLK 2 ***** ***** OLK.SPRAY STRATUM OLK.SPRAY VARIATE: RCARAB VARIATE: TOTAL TOTAL 252

359 14 14 0.922 0.934 0.971 10 10 1 .036 1 1.056 0.961 8 1.241 1 .244 1 0.967 1 .148 1 0.960 0.880 5 '5 8 .264 1.199 1.122 1 1 0.904 3 o m 1.109 0.989 1.061 1.230 0.823

1 m 1 3 UT 1 0 M 0 1 OM 1 0 1 .080 1 0.954 0.830 .061 1 1 .1 5 U 5 .1 1 1.147 0.971 0.971 0.959 1.034 0.925 0.951 1 .164 1 -1 -1 30M 30M 1 .447 1 1.254 1.049 1 .134 1 1.120 0.987 1.182

***** HV ULV -2 1 OOM 1 1.183 0.981 1.052 0.913 1.053 1.027 1.034 0.994 0.834 1.143 0.932 HV HV UT UT 1.013 ULV ULV DISTOOM 1 TIME -2 DIST TIME SPRAY SPRAY SPRAY TABLES OF MEANS MEANS OF TABLES GRAND MEAN GRAND ***** VARIATE: RCARAB VARIATE: ANOVA ANOVA cont'd

360 ANOVA cont'd

TIME -2 -1 1 3 5 8 10 14 DIST 1 OQM 1.019 1 .085 1.125 1.083 1 .011 1.038 0.958 0.895 30M 1.095 1.117 1.342 1.471 1 .444 1.287 1.089 1.183 10M 0.857 1 .014 1 .007 1 .008 1 .057 1.138 0.828 0.863 0 M 0.951 0.993 0.844 0.874 0.977 1.130 0.969 0.936

TIME -2 -1 1 3 5 6 10 14 SPRAY 01 ST HV . 1 00M 1.132 1.130 1 .446 1.355 1.103 1 .163 1 .093 1.041 0)CO 30M 1 .277 1.259 1.530 1 .705 1.694 1.501 1.253 1.356 10M 0.834 1.021 0.905 1 .026 1.131 1.137 0.776 0.800 OM 0.893 1.069 0^.7 7-6, 0.334 1.128 1.163 1 .023 1.029 ULV 100M 0.962 0.972 0.877 0.938 0.742 0.880 0.893 . 0.811 30M 1.021 0.982 1 .141 1-257 1 .207 1 .185 1.009 1.270 10M 0.834 1 .097 0.903 0.9C3 0.893 0.927 0.707 0.776 OM 0.834 0.897 Q.776 0.707 0.776 0.847 0.9U9 0.877 UT 1 OOM 0.962 1.151 1.052 0.957 1.189 1.071 0.388 0.834 30M 0.987 1.108 1.355 1 .452 1.432 1.175 1 .005 0.933 1 OM 0.903 0.923 1.212 1 .1)9 6 1 .147 1.350 1.001 1.013 OM 1.126 1 .013 0.981 1 .082 1 .026 1 .380 0.974 0.903

15 DIST TIME SPRAY 0.2173 0.2283 0.1843 0.2173 45 DIST TIME 0.1064 LEFT) 60 TIME SPRAY 0.0922 (9994 (9994 15

120 ***** DIST SPRAY 0.1496 0.1292 0.1254 0.1322 5.0 CVX 21.4 15.4 44.4 11.2 OF: ***** TIME 0532 DATA UNITS USED AT LINE AT USED UNITS DATA SE 0.0524 0.1620 0.4677 0.1179 0.2257 360 130 22774 OF 0.0763 0.0763 0.

2 WITH SAME LEVELCS) SAME WITH 4 DF 168 1151 480 SPRAY DIST 0.0963 * CARAd. MAXIMUM CARAd. COMPARING MEANS COMPARING

'CLOSE1 STRATUM STANDARD ERRORS AND COEFFICIENTS OF VARIATION OF COEFFICIENTS AND ERRORS STANDARD STRATUM STANDARD ERRORS OF DIFFERENCES OF MEANS MEANS OF DIFFERENCES OF ERRORS STANDARD

SPRAY SPRAY.DIST DIST SPRAY.TIME 108 108 ******** END OF ******** END {NOT ADJUSTED FOR MISSING VALUES) MISSING FOR ADJUSTED {NOT SED REP EXCEPT WHEN EXCEPT ***** ***** STRATUM BLK BLK.SPRAY BLK.SPRAY.DIST.TIME BLK.SPRAY.DIST.TIME.TRAP ***** BLK.SPRAY.DIST 18 TABLE

362