Open Research Online The Open University’s repository of research publications and other research outputs The effect of habitat creation for predatory arthropods on aphid populations in winter wheat Thesis How to cite: Collins, Katherine Lucy (1999). The effect of habitat creation for predatory arthropods on aphid populations in winter wheat. PhD thesis The Open University. For guidance on citations see FAQs. c 1999 Katherine Lucy Collins Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000ff4f Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk ^^uucbcKvv. \Jt3Z<ssrRi£t&E) THE EFFECT OF HABITAT CREATION FOR PREDATORY ARTHROPODS ON APHID POPULATIONS IN WINTER WHEAT KATHERINE LUCY COLLINS BSc. (Hons.) ZOOLOGY A thesis submitted in partial fulfillment of the requirements of The Open University for the degree of Doctor of Philosophy Discipline: Agriculture / Environment MAY 1999 Harper Adams University College SpOEESomg es&blÊsbmDmt: and Food A Merton Research and Educational Trust Leicestershire ProQuest Number: C801604 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest C801604 Published by ProQuest LLC (2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ABSTRACT Data are presented from research conducted to investigate the role of beetle banks in the biological control of cereal aphids. A project designed to compare overwintering predator densities in a newly established beetle bank and two conventional hedgebanks over a five year period, indicated that predator densities were similar to or greater than those in the surrounding hedgebanks by the second year of the beetle banks establishment Predators found overwintering on the beetle bank included many species that are considered to be important predators of cereal aphids. A further overwintering experiment conducted over a four year period, investigated five different grass species sown on beetle banks and a natural regeneration treatment, for their suitability in providing overwintering cover for polyphagous predators. Overall, the highest overwintering predator densities were recorded in grass species with tussocky growth forms and the lowest predator densities were recorded in treatments where the vegetation on the beetle bank had been allowed to naturally regenerate. During the spring and summer, a predator exclusion experiment was conducted to explore the effect of. polyphagous predators emigrating from a beetle bank on cereal aphid populations in an adjacent crop of winter wheat. The results from this experiment indicated that polyphagous predators significantly reduced aphid populations in the crop, though the impact of polyphagous predation appeared to decrease with increasing distance away from the beetle bank. The results from the exclusion experiment, together with the results from a further experiment investigating the effect of the presence or absence of a beetle bank on the distribution of polyphagous predators in crops, also indicated that beetle banks aid the rapid colonisation of cereal fields by polyphagous predators in the early spring, when the potential for aphid control is optimal. Cost-benefit analysis suggested that an aphid population kept below spray threshold levels C by enhanced natural enemy populations emigrating from a beetle bank, could result in a small but potentially useful saving in insecticide costs. The results are discussed in the context of current agricultural policies and in relation to the potential environmental benefits of reducing the .reliance upon chemical methods to control cereal aphids. Further research needs are also identified. ACKNOWLEDGEMENTS I would like to acknowledge the help and support of my supervisors Dr A Wilcox and Dr K Chaney at Harper Adams University College and Dr N Boatman at the Allerton Research and Educational Trust. I would also like to thank Dr J Holland at the Game Conservancy Trust for his advice throughout this research. This work was funded by the Ministry of Agriculture, Fisheries and Food. In addition, I acknowledge Jenny Atkinson and Joanna Wilmott for assisting in the running of field experiments and I acknowledge Mr J Daws for helping to identifying Araneae collected during this investigation. I would also like to thank the farm staff at the Allerton Research and Educational Trust, Parkers Ltd and the Edmonthorpe Estate for accommodating my experiments. Finally, I would like to thank all my colleagues at Harper Adams and my family, especially Garth, for their support and encouragement throughout this research. PUBLICATIONS Collins K L, Wilcox A, Chaney K and Boatman N D (1996) Relationships between polyphagous predator density and overwintering habitat within arable field margins and beetle banks. Brighton Crop Protection Conference 2:635-640 Collins K L, Wilcox A, Chaney K, Boatman N D and Holland J M (1997) The influence of beetle banks on aphid population predation in winter wheat. Aspects of Applied Biology 50: 341-346 Abstract i Acknowledgements ii Publications iii Contents iv List of plates vii List of figures viii List of tables x CHAPTER 1. Introduction and Literature Review 1 1.1 Introduction 2 1.2 Polyphagous arthropod predators and their potential for 2 use as biological control agents against cereal aphids 1.3 Enhancement of predator communities on farmland via 8 habitat creation 1.4 The development of integrated farming systems 16 1.5 Experimental aims and hypotheses 22 CHAPTER 2. Overwintering predator population densities 24 within beetle banks in Leicestershire 2.1 Introduction 25 2.2 Materials and methods: 2.2.1 Comparison of polyphagous predator species composition 27 and density within a beetle bank and two conventional hedgebanks 2.2.2 Assessment of overwintering habitat preference for different 32 grass species 2.3 Results: 2.3.1 Comparison of polyphagous predator species composition 34 and density within a beetle bank and two conventional hedgebanks 2.3.2 Assessment of overwintering habitat preference for different 47 grass species iv 2.4 Discussion: 2.4.1 Comparison of polyphagous predator species composition 57 and density within a beetle bank and two conventional hedgebanks 2.4.2 Assessment of overwintering habitat preference for different 66 grass species 2.5 Summary 72 CHAPTER 3. The influence of beetle banks on cereal aphid 76 predation in winter wheat 3.1 Introduction 77 3.2 Materials and methods 78 3.3 Results 83 3.4 Discussion 98 3.5 Summary 108 CHAPTER 4. The impact of beetle banks on the dispersal 110 distribution of polyphagous predators in cereal crops 4.1 Introduction 111 4.2 Materials and methods 112 4.3 Results 116 4.4 Discussion 127 CHAPTER 5. General discussion 135 5.1 General discussion 136 REFERENCES ' 144 v APPENDICIES Appendix I Latin names and authorities of all the flora and fauna mentioned in the thesis, including english names where applicable Appendix H Tabulated representation of the linear randomised block design of the treatments sown on the beetle banks (section 2.2.2) Appendix lH Carabid and Araneae species composition in the beetle bank (section 2.3.1) between the winters 1993 & 1997 Appendix IV Vegetation data for the beetle bank and hedgebanks in section 2.3.1 Appendix V Carabid and Araneae species composition in the beetle banks in section 2.3.2 Appendix VI Vegetation data for the beetle banks in section 2.3.2 Appendix VU The influence of beetle banks on cereal aphid predation in winter wheat Appendix VHI The impact of beetle banks on the dispersal and distribution of polyphagous predators in cereal crops LIST OF PLATES Plate Title Page 1 A beetle bank (right hand side of picture) on the Loddington Estate, 11 Leicestershire 2 Creation of an enclosure using a tractor mounted barrier laying 80 machine 3 Invertebrate sampling in an enclosure using a Dietrick suction 80 sampler vii LIST OF FIGURES Figure Title Page 1 Schematic plan of the experimental area containing the beetle bank 28 and hedgebanks 2 Mean percentage ground cover of the vegetation on the beetle bank in 45 the summers of 1993, 1994,1996 & 1997 3 Mean percentage vertical cover of the vegetation on the beetle bank 46 in the winters of 1993, 1995 & 1997, and on the hedgebanks in the winter of 1997 4 Mean percentage ground cover of the vegetation in the Dactylis 56 glomerata, Festuca rubra, Phleum pratense, Arrhenatherum elatius and Cynosurus cristatus plots in the summers 1994, 1995, 1996 and 1997 5 Schematic plan of the experimental area containing the beetle bank 79 and enclosed and control areas positioned in the crop, at four fixed distances away from the beetle bank 6 Mean number of aphids per ear in the enclosures and controls on the 84 marked tillers of wheat 7 Mean number of aphids per tiller in the enclosures and controls on 84 the marked leaves of wheat 8 Mean number of aphids per transect