(,)Ì lGl'1 US WOOLLY APPLE APHID: INTERACTIONS WITHIN AN ORCHARD SYSTEM BY FRANCES FITZGIBBON B. Sc. University of Victoria (Canada) Thesis submitted for the degree of Doctor of.PhilosoPhY ln The University of Adelaide Faculty of Agricultural and Natural Resource Sciences Department of Crop Protection Waite Agricultural Research Institute The University of Adelaide August 1996 TO HAROLD F. MADSEN l92L - L987 TABLE OF CONTENTS Page List of Figures vii List of Tables X Summary xiv Declaration xvi Acknowledgments xvii CHAPTER ONE INTRODUCTION 1 CHAPTER T\ryO A SURVEY OF APPLE GROWERS OF THE ADELAIDE HILLS REGION OF SOUTH AUSTRALIA 2,1, Abstract 6 2.2. Introduction l 2.3. Materials and Methods 8 2.4. Results 10 2.5. Discussion I7 CHAPTER THREE BIOLOGY OF WOOLLY APPLE APHID, Eriosoma lanigerum AND ITS PARASITE' Aphelinus mali 3.1. Abstract 22 3.2. Introduction 23 3.2.1. \ù/oolly apple aphid 23 3.2.2. Aphelinus mali 25 3.3. Materials and Methods 26 3.3.1. Woolly apple aphid 27 3.3.2. Aphelinus mali 27 3.3.2.I. Developmental times 27 3.3.2.2. Sex ratio 28 3.3.2.3. Adult life span 28 3.3.3. Statistical analysis 28 3.4. Results 29 3.4.1. Woolly apple aphid 29 3.4.2. Aphelinus mali 31 3.5. Discussion 33 CHAPTER FOUR INSECTICIDE TOXICITY TO WOOLLY APPLE APHID AND ITS PARASITOID, Aphelinus mali, UNDER LABORATORY CONDITIONS 4.I. Abstract 36 4.2. Introduction 37 4.3. Materials and Methods 40 4.3.1. Aphid colonies 40 4.3.2. Aphelinus mali 42 4.3.2.1. Pre-mummy (larval) stage 42 4.3.2.2. Mummies 42 4.3.2.3. Adult parasitoids 43 4.3.3. Statistical analysis 45 4.4. Results 46 4.4.1. Aphid colonies 46 4.4,2. Aphelinus mali 48 4.4.2:1. Pre-mummY (larval) stage 48 4.4.2.2. Mummies 49 4.4.2.3. Adult parasitoids 55 4.5. Discussion 5l CHAPTER FIVE EFFECTS OF WOOLLY APPLE APHID INFESTATION ON THE GROWTH OF YOUNG APPLE TREES UNDER LABORATORY CONDITIONS AND IN THE FIELD 5.1. Abstract 66 5.2. Introduction 61 5.3. Materials and Methods - Laboratory Experiment 70 5.3.1. Experimental design 70 5.3.2. Plant conditioning and initiation of the experiment 70 5.3.3. Statistical analysis 72 5.4. Results - Laboratory Experiment 13 5.4.I. Experiment 1 14 5.4.2. Experiment 2 76 5.4.3. Experiment 3 19 5.5. Materials and Methods - Field Experiment 83 5.5.1. Experimental design 83 5.5.2. Year One 83 5.5.3. Year Two 86 5.5.4. Statistical analysis 88 5.6. Results - Field Experiment 88 5.6.1. Year One 88 5.6.1.1. Biological overview 88 5.6.1.2. Tree growth 90 5.6.1.3. Leaf growth 9l 5.6.I.4. Aphid numbers 96 5.6.2. Year Two 98 5.6.2.1. Biological overview 98 5.6.2.2. Tree growth 100 5.6.2.3. Leaf and shoot growth 101 5.7. Discussion 103 CHAPTER SIX SEASONAL ACTIVITY OF WOOLLY APPLE APHID ON MATURE TREES 6.1. Abstract rt4 6.2. Introduction 115 6.3. Materials and Methods 118 6.3.I. Colony distribution and number 118 6.3.2. Seasonal movements of aphids r22 6.4. Results r23 6.4.1. Colony distribution and number t23 6.4.2. Seasonal movements t29 6.5. Discussion r33 CHAPTER SEVEN SUMMARY AND CONCLUSIONS T.L SummarY t4r 7.2. Conclusions 148 APPENDIX ONE A SURVEY OF APPLE GROWERS IN THE ADELAIDE HILLS REGION OF SOUTH AUSTRALIA t49 APPBNDIX TWO METHODS FOR GROWING APPLE SEEDLINGS UNDER SEMI.CONTROLLED CONDITIONS 160 APPENDIX THREE METHODS FOR REARING \ryOOLLY APPLE APHID AND Aphelinus malí IN THE LABORATORY A3.1 Introduction r62 A3.2 Materials and Methods 163 A3.3 Discussion r66 APPENDIX FOUR LEAF AREA DETERMINATION OF APPLE LEAVES A4.I. Abstract r67 A4..2. Introduction t67 A4.3. Materials and Methods 168 A4.4. Results and Discussion r69 APPENDIX FIVE ESTIMATION OF THE NUMBER OF INDIVIDUALS \ryITHIN WOOLLY APPLE APHID COLONIES 45.1. Abstract n0 A5.2. Introduction no 45.3. Materials and Methods r7r 45.4. Results and Discussion r72 APPENDIXSIX RELATIONSHIPSBETWEEN WOOLLY APPLE APHID INFESTATION AND TREE GROWTH UNDER LABORATORY CONDITIONS 114 APPENDIXSEVEN RELATIONSHIPSBET\ryEEN WOOLLY APPLE APHID INFESTATION AND TREE GROWTH IN THE FIELD 180 REFERENCES 195 vil LIST OF FIGURES CHAPTER TWO Figure 2.L. Per cent of growers' affirmative response to survey questions. 13 Figure 2.2. Per cent of growers' affirmative response to survey questions. 15 Figure 2.3. Per cent of growers' affirmative response to survey questions' 16 CHAPTER THREE Figure 3.1. Relationship between temperature and developmental rate (l/days to complete development) of WAA. 30 Figure 3.2. Relationship between temperature and developmental rate (l/days to complete development) of A. mali. 32 CHAPTER FOUR Figure 4.L. Aluminium spray cages for adult A. mali' 44 Figure 4.2. Mean per cent reduction (t standard error)of live WAA colonies 24 hours post spray. 41 Figure 4.3. Life span (mean * standard eror) (days) of adult A- mali adúlts emerging aftèr treatment at the pre-munìmy stage (four days after oviposition). 50 Figure 4.4. Life span (mean * standard error) (days) of adult A. mali adults emerging aftèr treatment at the late post-mummy stage (10 days after egg lay). 54 Figure 4.5. Time to death (mean * standard error) (days) of adult A. mali after 24 hours exposure to pesticides in 'sandwich' cages. 56 CHAPTER FIVE Figure 5.1. Relationship between tree parameters (mean t standard error) and woolly apple aphid densities over time in Experiment 1. 75 Figure 5.2. Relationship between tree parameters (mean * standard error) and woolly apple aphid densities over time in Experiment2' 78 Figure 5.3. Relationship between tree parameters (mean t standard error) and woolly apple aphid densities over time in Experiment 3' 80 vlll Figure 5.4. Number (mean * standard error) of aphids on trees infested with difierent densities of woolly apple aphid in three experiments. 81 Figure 5.5. Relationships between tree parameters_(mean t standard error) anã woolly apple aphid diensities during Year 1 (1989-1990) and Year 2 (1990-1991) in Block A. 92 Figure 5.6. Relationships between tree p¿ìrameters (mean * standard error) and woolly apple aphid densities during Year 1 (1989-1990) and Year 2 (1990-1991) in Block B. 93 Figure 5.7. Relationships between tree parameters (mean * standard error) and woolly apple aphid densities during Year 1 (1989-1990) and Year 2 (1990-1991) in Block C. 94 Figure 5.8. Number (mean t standard error) of colonies and aphids_ on treés infested with different densities of woolly apple aphid in Year 1 (1e89-19e0). 97 Figure 5.9. Percentage of trees that were dormant or dead in three blocks (combined) during Year 2 (1990-1991). 99 CHAPTER SIX Figure 6.1. Tree divided into (A) height strata and (B) directional quadrants. t20 Figure 6.2. Total number (mean t standard error) of WAA colonies on trees through the season. 124 Figure 6.3. Percentage (mean * standard error) of total V/AA colonies counted in the first season (1989). t26 Figure 6.4. Percentage (mean t standard error) of total WAA colonies counted in the second season (1989-1990). r28 Figure 6.5. mean (+ standard error) number of WAA/mm tape caught on sticky tape traps 131 Figure 6.6. Aphids caught on the lower trunk traps expressed as a percentage of the total aphids caught on both the lower and upper traps. t32 APPENDIX ONE Figure 4L.1. Per cent of growers' affirmative response to survey questions r57 Figure A1.2. Per cent of growers' affîrmative response to survey questions 158 Figure 4L.3. Per cent of growers' affirmative response to survey questions 159 lx APPENDIX THREE Figure 43.1. Lantern globe cage used in rearing woolly apple aphid and A. mali under laboratory conditions. 164 APPENDIX SEVEN Figure A7.1. Relationships between tree parameters_ (me^an + standard error) anã woolly apple aphid infèstation during Year 2 (1990-1991) t94 X LIST OF TABLES CHAPTER THREE Table 3.1. The durations (mean * standard error) of the life stages of WAA reared on small apple seedlings at three constant temperatures. 30 Table 3.2. The durations (mean * standard error) of development from egg lay to mummification and from mummification to emergence of A. mali. 31 Table 3.3. Mean (+ standard error) life span (days) of male and female A. mali at three constant temperatures. 32 CHAPTER FOUR Table 4.1. Trade names, common name, class and field rates of 10 pesticides tested against WAA colonies andAphelinus mali. 4I Table 4.2. Per cent emergence, mean time to emergence, sex ratio and mean life span of A. mali ãfter being treated with pesticides at the pre- mummy (larval) stage. 49 Table 4.3. Per cent emergence, mean time to emergence, sex ratio and mean life span of A. mali áfter being treated with pesticides at the post- mummy stage. 51 Table 4.4. Per cent emergence, mean time to emergence, sex ratio and mean life span of A. mali after being treated with pesticides at the post- munìmy stage, Potter's Tower. 53 CHAPTER FIVE Table 5.L. P values of the F statistic comparing the regression lines for tree height, total leaf number, total leaf area of trees infested with different densities of woolly apple aphid in Experiment 1.