6l,tlr v lUE }TAI{AGET'IE¡I1 OF SPOTTED ÄLFALFA APEID, TEEM2A?HIS lWE1LIr GTONETL) E. MACALATA, IN I'RYT.AI{D LUCERNE PASTT'RE IN SOI'1I AT'STR.AIIA A theeis presented in fuLfiLment of the nequirements fon the Degree of Doetor of P?tiLosophy, EaeuLty of AgricuLturaL Seience, llnioereity of AdeLaide. by P.G. ALLEN I'l.Ag.Sc. Department of Agrlculture, SouÈh Australia March, L984 To I',II]RRAY V. SMITH ( r 942-r 980) A friend and colleague whose research contributed to the knowledge on gxazl-r.g managemenÈ of dryland lucerne pastures grovtn on siliceous sands in the Upper- south-East of South AustralLa. INDEX Page No. SI]MMARY (1) STATB"lENT (v) ACKNO!,ILEDGEMENTS (vi ) SECTION 1: IMRODUCTION I 1.1 Value of Lucerne Pastures in the Upper-South-East of South Australia 2 I.2 Control of SAA 1n the U,S.A. 3 f.2.1 The early use of chemical insecticides 3 L.2.2 Conservation of native predators 5 I.2.3 Introduced parasites 5 L.2.4 Pathogens 6 1.2.5 Resistant cultivars of lucerne 7 1.3 FuÈure Control of SAA in Sout,h Australia I 1.4 References 9 SECTION 2: TITE STITDY AREA . TTIE UPPER-SOUTTI-EAST OF SOUTH AUSTRALIA t2 2.I CllmaÈe T2 2.2 Soil L2 2.3 I'fanagernent of Lucerne-based Pasture L4 2.4 References 16 SECTION 3: TIIE SEASONAL ABUNDANCE AND ESTABLISH},ÍENT OF SAA IN DRYI.,AND LUCERNE IN TIIE UPPER-SOUTII-EAST OF SOUTI{ AUSTRALIA L7 Sumroary L7 3.1 Introduction 18 3.1.f Seasonal abundance of SAA overseas 18 3.I.2 Expected seasonal abundance of SAA in South Australia 19 3.1.3 Design of an experirnent for a 3-year study of SAA abundance in dryland lucerne pasture r9 3.1.4 The spread of SAA in South Australia 20 3.2 l"laterlals and Methods 20 3.2.L The abundance of SAA in Èhe UPper-South-East 20 3.2.2 Initíal migration of SAA inÈo the experimental site 24 Page No. 3.3 Results and Discussion 24 3.3.f The abundance of SAA ln the UPper-South-East 24 3.3.2 Initial migratlon of SAA into Ehe experirnental site 30 3.3.3 Abundance of SAA alates in dryland lucerne pasture 32 3.4 References 33 SECTION 4: INFLUENCE OF SAA ON PERSISTENCE AND PRODUCTION OF DRYLAND LUCERNE IN flIE UPPER-SOUTII-EAST OF SOUTH AUSTRALIA 36 Summary 36 4.1 Introductlon 37 4.2 SAA Danage to Lucerne Plants 38 4.3 Background to the Experiments 40 4.3. f Experlmental site 40 4.3.2 Climate 4T 4.4 Influence of Different Threshold Densitíes of SAA on the ProducÈion and Persístence of Gtazed Dryland Lucerne Pasture 42 4.4.L I'faterials and nethods 43 4,4,2 Results and discussion 47 4,5 Influence of SAA on the Growth and DM of Individual Plants of Lucerne in the field 66 4.5.1 MaÈerials and methods 66 4.5.2 ResulÈs and discusslon 68 4.6 Economic Threshold for SAA in Dryland Lucerne Pasture 72 4.7 References 73 Appendices 77 SECTION 5: INTLUENCE OF CHEMICAI INSECTICIDE, GRAZING AND CULTIVARS OF LUCERNE ON TIIE DENSITY OF SAA IN DRYLAND LUCERNE IN THE UPPER-SOUTII-EAST OF SOUTII AUSTRALIA 85 Suumary 85 5.1 InEroduction 86 P"e:__Ig. 5.2 l"faÈerials and MeÈhods 87 5.2.1 Influence of chemical insectícide and grazing 87 5.2.2 Influence of resisEant cultivars of lucerne 89 5.3 Results and Discussion 90 5.3.1 Influence of chemical lnsectlcide 90 5.3.2 Influence of graztng 93 5.3.3 Influence of resistant cultivars of lucerne 97 5.4 References 100 SECTION 6: INFLUENCE OF PREDATORS A}ID PARASITES ON THE DENSITY OF SAA IN DRYI,AND LUCERNE IN THE UPPER-SOUTH-EAST OF SOUTIT AUSTRALIA 103 Summ¡¡Y 103 6.1 Introduction 104 6.2 ldentification and Abundance of Potential Predators of SAA r05 6.2.1 I'faÈerials and methods r05 6.2.2 Results r06 6.2.3 Discussion r07 6.3 Augmentation of C. r'epand.a' During Summer 108 6.3. I I'faterials and meÈhods 108 6.3.2 Results 110 6.3.3 Discussion r15 6.4 Influence of Predators of SAA ln Spring and Summer rL7 6.4.I MaËerials and roethods r18 6.4.2 ResulEs L22 6.4.3 Dlscussion L27 6.5 Abundance of. Tnioæye conplann'tus ín Dryland Lucerne Pasture L29 6.5. I l"faterlals and methods 129 6.5 .2 Re sult,s 130 6.5.3 Discussion r32 6.6 The Role of Natlve Predators and Introduced ParaslÈes in the Control of SAA 1n Dryland Lucerne Pasture r35 6.6.1 Predators 13s Page No. 6.6.2 Tactics for management of SAA r37J 6.7 References 139 Appendices r46 SECTION 7: LETHAL INFLUENCE OF IIIGH TEI"ÍPERATI]RE ON SAA IN DRYI"AND LUCERNE IN TIIE UPPER-SOUTIT-EAST OF SOUTII AUSTRALIA 149 Sumrnary r49 7.I InÈroduction 150 7.2 Influence of Daily Maxlmum Temperature on Ëhe Density of Field SAA 151 7.2.L Materials and nethods t5l 7 .2.2 Results r52 7.2.3 Discussion 157 7.3 Lethal Effect of ltigh Temperature of SAA in Fíeld Crops r58 7.4 lllgh Teroperature and the Low Numbers of SAA in the Upper-South-East in I980/81, and l98L/82 159 7.5 References 162 Appendices 164 SECTION 8: INFLUENCE OF FOOD QUALITY ON TIIE ABUNDANCE OF SAA DURING SPRING IN DRYI"AND LUCERNE IN TTIE UPPER-SOUTII-EAST OF SOIJTII AUSTRALIA 168 Sumnary 168 8. I Introductíon r69 8.2 Materials and Methods L7L 8.3 Results 173 8.3.1 Rate of increase of SAA 173 8.3.2 Propertles of the plants 175 8.4 Discussion 177 8.5 References 179 Appendices 181 SECTION 9: LIFE TABLES AND RATES OF INCREASE OF SAA ON DRYLAND LUCERNE IN TIIE UPPER-SOUTII-EAST OF SOUTH AUSTRALIA 183 Sunmary 183 9.1 Introduction 185 9.2 l"faterials and Methods 186 Page No. 9.2.L Types of cages 187 9.2.2 SAA for cage treatments 19r 9.2.3 Age of lucerne regrowÈh 19l 9.2.4 TemperaÈure r9r 9.2.5 Tine of nowing Ehe pastures and start of each experiment 192 9.2.6 Tf¡ne and methods of sampling aphids 192 9.3 Results 194 9.3.1 Fecundity and survlval of SAA in leaf cages 194 9.3.2 Growth sÈatistics for SAA at Culburra 199 9.4 DLscussLon 209 9.4.1 Relatlonship between rates of increase of SAA and some envíronmental factors at Culburra 209 9.4.2 Comparison of growth staÈisÈics of SAA at Culburra and Ín other studies 213 9.4.3 RaÈes of increase and the population dynanies of. SAA in dryland lucerne pasture 216 9.5 References 2t7 Appendices 22r SECTION IO: TIIE LOI^IER TEI"ÍPERATURE TITRESIIOLD FOR DEVELOPI"IENT AND RATES OF DEVELOP}4ENT OF NT"IPITAL SAA IN SOUTH AUSTRALIA 225 Summary 225 10.1 Introduction 226 10.2 The Rate of Development and the Threshold for Developnent of Nymphs of SAA at Low Temperatures 227 10.2.1 Materlals and methods 227 10.2.2 Results 230 f0.2.3 Discussion 232 10.3 Rate of Developnent and Survlval of Nyrnphs of SAA in the Field 236 10.3.1 Materials and methods 236 10.3.2 Results and discusslon 240 Page No. 10.4 References 246 Appendices 249 SECTION 1I: A CONTROL PROGRA}.{ FOR SAA IN DRYLAI.ID LUCERNE AND ITS II'ÍPLEMENTATION IN TIIE UPPER-SOUTII-EAST OF SOUTII AUSTRAIIA 250 Summary 250 I l. I Introduction 25r 11.1.1 Pest control 251 ll.2 Data on the Ecology and Control of SAA in Dryland Lucerne Pasture 252 LI.2.I The management of lucerne pasture 253 LL.2.2 Seasonal abundance and fmpact of SAA on lucerne Pasture 254 1L.2.3 Tactics for the control of SAA in lucerne Pasture 255 11.3 A Control Progran for SAA ln l¡¡cerne Pasture 256 11.3.1 Problems with the conÈrol program 259 11.4 Inplemtation of the Control Program in the Upper- SouÈh-EasË 260 11.5 References 263 (i) ST]MMARY I The spotted alfalfa aphid (SAA), Theríoaphis trifoLii (Monell) f. rnøeuLata, qras accldentally introduced inËo Australia and first recorded in South Aust,ralia in ì4ay L977. The known destructive capacity of SAA in s.usceptible lucerne crops in North America stimulated the need for research on the feasibility of the shorÈ-tern control of SAA in highly suscept,ible, low-productívity lucerne (cv. Ilunter River) pastures grordn under dryland (rain-fed) conditions on infertlle, silíceous sands in the Upper-South-East of South Aust,ralia. This research is the subject of this thesis. 2 The profitability of production from the lucerne-based pastures is low and Che cost,s of any control program_for SArl\ need to be ninimal for acceptance of the program by landowners. Experiments were conducted in the field to determine an economíc threshold for SAA in dryland lucerne pastures, Èo test the feasibility of a number of control tactics for inclusion in a control strategy and to study certain aspects of the ecology of SAA which were consldered useful to explain the populatÍon dynanícs of SAA in lucerne pastures. 3 The optinum herbage product,ion from lucerne pastures is achieved with rotationaL grazíng by livestock.