CORE Metadata, citation and similar papers at core.ac.uk Provided by Spiral - Imperial College Digital Repository DEPARTMENT OF LIFE SCIENCES Impact, host range and chemical ecology of the lily beetle, Lilioceris lilii by Andrew Salisbury A thesis submitted for the degree of Doctor of Philosophy of Imperial College London 2008 1 . Declaration DECLARATION I hereby declare that I have composed this thesis. The work of this thesis is a record of my own work; any collaborative work has been specifically acknowledged. Andrew Salisbury 2008 2 . Abstract ABSTRACT The lily beetle (Lilioceris lilii, Coleoptera: Chrysomelidae) has a univoltine life cycle and a limited host range (Lilium, Fritillaria and Cardiocrinum). A survey of 237 professional growers indicates that L. lilii is a problem for many in the UK lily industry. A three-year field trial using six different Lilium indicated that the species Lilium regale is more resistant to L. lilii than the hybrids L. ‘Tiber’, L. ‘Brindisi’, L. ‘Conca d’Or’, L. ‘Eliganzer’ and L. ‘Golden Joy’. Phenology observations between the trial and an established population of the beetle have provided base-line data to which further observations can be compared. Future host susceptibility trials should use a standard lily such as L. regale against which others can be compared. Behavioural bioassays using a linear-track olfactometer demonstrated that the responses of L. lilii to hosts and conspecifics are at least in part odour-mediated. Significantly more diapaused females moved into airstreams containing the odour of intact hosts over clean air, to that of hosts and beetles combined over that of undamaged or manually-damaged plants, and into airstreams from intact plants over larval-infested plants. Pre-diapause males moved into the airstreams of intact hosts in preference to L. lilii-infested plants. Using air entrainment, gas chromatography (GC) and coupled gas chromatography-mass spectrometry (GC-MS), headspace volatiles from beetle- infested host plants have been collected and identified. From these compounds, methyl salicylate, nonanal, cis-jasmone, linalool, 6-methyl-5-hepten-2-one and β-pinene elicited electrophysiological responses from L. lilii using electroantennography (EAG) and coupled GC-EAG. Bioassays indicate that diapaused female beetles move into the airstream of clean air in preference to cis-jasmone. Investigations from all areas of the project have progressed our understanding of the ecology of L. lilii but further studies are needed before more effective control strategies can be developed. 3 . Contents CONTENTS Page DECLARATION 2 ABSTRACT 3 TABLE OF CONTENTS 4 LIST OF FIGURES 8 LIST OF TABLES 12 ABBREVIATIONS 14 GLOSSARY 15 ACKNOWLEDGEMENTS 16 CHAPTER 1. INTRODUCTION: THE BIOLOGY OF THE LILY 17 BEETLE, Lilioceris lilii (Scopoli) (COLEOPTERA: CHRYSOMELIDAE) 1.1. DESCRIPTION 17 1.2. LIFE CYCLE 19 1.3. HOST RANGE 20 1.4. WORLDWIDE DISTRIBUTION 26 1.5. DISTRIBUTION IN THE UK 27 1.6. GENERALIST PREDATORS 27 1.7. PARASITOIDS 28 1.8. DEFENCE 31 1.9. PEST STATUS 32 1.10. MANAGEMENT IN THE UK 33 1.11. BIOLOGICAL CONTROL 33 1.12. CONCLUSIONS 35 1.13. PROJECT OBJECTIVES AND AIM 35 CHAPTER 2. THE LILY BEETLE- A RISK TO UK HORTICULTURE? 36 2.1. INTRODUCTION 36 2.2. RISK ASSESSMENT SURVEY PART 1: EFFECT OF THE LILY 37 BEETLE IN AMATEUR GARDENS 2.2.1. Introduction and methods 37 2.2.2. Results and discussion 37 2.3. RISK ASSESSMENT SURVEY PART 2: PROVIDERS OF LILIES 38 2.3.1. Introduction and methods 38 2.3.2. Results and discussion 38 4 . Contents 2.4. RISK ASSESSMENT SURVEY PART 3: PROFESSIONAL USERS 46 OF LILIES 2.4.1. Introduction and methods 46 2.4.2. Results and Discussion 46 2.5. CONCLUSIONS 51 2.6. RECOMMENDATIONS 51 CHAPTER 3. DO LILIES VARY IN SUSCEPTIBILITY TO THE LILY 53 BEETLE? 3.1. INTRODUCTION 53 3.2. MATERIALS AND METHODS 54 3.2.1. Field trial 54 3.2.2. Observations in the Wild Garden 57 3.2.3. Data analysis 57 3.3. RESULTS 59 3.3.1. Do different lilies vary in susceptibility? 59 3.3.2. Phenology and other observations 61 3.4. DISCUSSION 67 3.4.1. Do different lilies vary in susceptibility? 67 3.4.2. Phenology and other observations 70 CHAPTER 4. ODOUR-MEDIATED BEHAVIOUR OF THE LILY 72 BEETLE (Lilioceris lilii) 4.1. INTRODUCTION 72 4.1.1. Chemical-mediated behaviour of the Chrysomelidae 72 4.1.1.1. Host location and acceptance 73 4.1.1.2. Conspecific location 75 4.1.1.3. Application of Chrysomelid semiochemistry 77 4.1.1.4 Conclusions 79 4.2. MATERIALS AND METHODS 80 4.2.1. Plant material 80 4.2.2. Insects 80 4.2.3. Linear-track olfactometer tests 81 4.3. RESULTS 85 4.3.1. Insects 85 4.3.2. Linear-track olfactometer tests 86 5 . Contents 4.4. DISCUSSION 97 4.4.1. Insects 97 4.4.2. Odour-mediated behaviour 97 CHAPTER 5. RESPONSE OF LILIOCERIS LILII TO VOLATILES 102 FROM A HOST PLANT 5.1. INTRODUCTION 102 5.2. MATERIALS AND METHODS 103 5.2.1. Collection of plant volatiles (volatile entrainment) 103 5.2.2. Collection of volatiles from adult beetles (Vacuum 105 distillation) 5.2.3. Chromatography and electrophysiology (identification of 106 potentially behaviourally-active volatiles) 5.2.4. Behavioural bioassays 111 5.3. RESULTS 111 5.3.1. Identification of potentially behaviourally-active volatiles 111 from beetle damaged plants. 5.3.2. Behavioural bioassays (confirmation of potential 118 behavioural activity of identified compounds) 5.3.3. Analysis of vacuum distillate from adult beetles 120 5.4. DISCUSSION 5.4.1. Identification of potentially biologically-active compounds 120 from headspace volatiles collected from an infested Lilium regale plant 5.4.2. Assessment of behavioural activity (behavioural bioassay) 122 5.4.3. Analysis of vacuum distillate from adult beetles 123 5.4.4. Conclusions 123 CHAPTER 6. GENERAL DISCUSSION 125 6.1. INTRODUCTION 125 6.2. OBJECTIVE 1: TO INVESTIGATE THE BIOLOGY AND ECOLOGY 125 OF L. LILII 6.3. OBJECTIVE 2: TO INVESTIGATE THE CHEMICAL ECOLOGY OF 126 THE BEETLE 6.4. OBJECTIVE 3: IN CONJUNCTION WITH SURVEY-BASED DATA, 129 TO ASSESS THE RISK TO THE LILY INDUSTRY RELATING TO POT PLANTS, CUT FLOWERS AND OUTDOOR BULB PRODUCTION 6 . Contents 6.5. AIM: BASED ON OUR UNDERSTANDING OF THE BIOLOGY, 130 ECOLOGY AND CHEMICAL ECOLOGY DEVELOP INTEGRATED PEST MANAGEMENT STRATEGIES FOR CONTROL OF L. LILII . 6.6. CONCLUSION 130 REFERENCES 132 APPENDIX 151 A.1. Lily beetle fact sheet, sent with surveys 151 A.2. Survey form sent to lily providers 152 A.3. Survey form sent to gardens open to the public 155 7 . List of Figures LIST OF FIGURES Page 1.1. Lilioceris lilii adult. 17 1.2. Lilioceris lilii eggs on a Lilium leaf. 18 1.3. Lilioceris lilii larvae on Lilium regale. 19 1.4. Worldwide distribution of Lilioceris lilii. 25 1.5. Post 1939 10 km dot distribution map of Lilioceris lilii from records 28 held by the RHS (at October 2007). Produced using DMAP©. 1.6. Lemophagus errabundus female. 29 1.7. Larva of Lemophagus errabundus. 29 1.8. Tetrastichus setifer female. 30 1.9. Tetrastichus setifer larva. 30 1.10. Mesochorus lilioceriphilus female. 30 1.11. Distribution of Lilioceris lilii parasitoids in England (at October 2007). 30 Produced using DMAP©. 1.12. Lilioceris lilii enquiries as a proportion of all pest enquiries received by 33 the RHS (1967 to 2006). 2.1. Replies from 148 enquirers who were asked “If you continue to have 37 a lily beetle problem would you stop growing lilies in the future?“ 2.2. Perceived impact of lily beetle on lily sales. 40 2.3. Where lily providers source new stock. 41 2.4. Providers’ growing regimes for lilies in the UK. 41 2.5. Provider size by number of plants sold. 43 2.6. Sales trend over the past five years, by number of responses. 43 2.7. Lily provider pest problems, by proportion of lilies sold. 44 2.8. Pesticides used by proportion of plants sold (of 6 700 225). 45 2.9. Number of lilies grown by gardens in the survey. 47 2.10. Likely effect on lily growing if lily beetle becomes established in 48 gardens open to the public. 2.11. Where gardens source lilies and the effect lily beetle may have on 49 plant purchases. 2.12. Pests experienced on lilies in gardens open to the public. 50 3.1. The 6 x 6 Latin square design, used in the field trial. 55 3.2. Plot 1 of the field trial (July 2005). 56 8 . List of Figures 3.3. Plot 2 and spare lilies (under fine netting) of the field trial (July 2005). 56 3.4. Lilioceris lilii damage index for the field trial. 59 3.5. Mean number of adult Lilioceris lilii per scoring visit in the field trial. 60 3.6. Mean number of Lilioceris lilii larvae per scoring visit in the field trial. 61 3.7. The mean Lilioceris lilii damage score on Lilium in the Wild Garden 62 and Field Trial at Wisley, over three years. 3.8. The occurrence (mean number) of adult Lilioceris lilii observed in the 63 Wild Garden and Field Trial, Wisley, over three years. 3.9. The occurrence (mean number) of Lilioceris lilii eggs observed in the 64 Wild Garden and Field Trial at Wisley, over three years. 3.10. Frequency of Lilioceris lilii egg batch size observed at Wisley. 65 3.11. The occurrence (mean number) of Lilioceris lilii larvae observed in the 66 Wild Garden and Field Trial at Wisley, over three years.