The biology, behaviour and survival of pupating false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a citrus pest in South Africa A thesis submitted in fulfilment of the requirements for the degree of MASTER OF SCIENCE of RHODES UNIVERSITY by Claire Natalie Love February 2015 i ABSTRACT Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter. ii Acknowledgements This research would not have been possible without the support of a number of people and institutions. To everyone who has assisted with this work, both directly and indirectly, thank you so very much. I could not have asked for more supportive and helpful supervisors than Martin Hill and Sean Moore. Your time, advice, insights and knowledge have been such a benefit to me and this body of work and I am extremely grateful to you both. My heartfelt thanks to both Martin Hill and Sean Moore for your assistance with regards to securing funding and for giving me exposure to the citrus industry, having your support with both of these has truly made all the difference. Thank you to the citrus growers in the Sundays River Valley and Kat River Valley who were so willing to assist and allow for soil collection from their orchards. Your assistance with this made this work possible. Field assistance was very kindly provided by the CRI staff, including Wayne Kirkman and Zongezile Zondi, as well as Kennedy Zimba, Candice Coombes, Veronique Chartier-Fitzgerald, Tamryn Marsberg, Mathew Goddard and Danielle Wiblin from Rhodes University. FCM was kindly supplied by Craig Chambers and the staff of River Bioscience, as well as Mellissa Peyper from Rhodes University. Laboratory equipment was always available for use thanks to the efforts of Tanya Pretorius, Mellissa Peyper and Candice Marshall. I am especially grateful to Terry Butterworth for advising and assisting in this capacity. The support staff at Rhodes University Zoology and Entomology Department is gratefully acknowledged, without whom we would not be able to do our research. I am very grateful to the Rhodes University Geography Department, Gillian McGregor for soils advice and loaning me relevant materials, as well as Glynn Armstrong and Abe Ngoepe for assistance and equipment use. A big thank you must be extended towards Tim Vink and Ryan Wasserman for their time and efforts with the VirtualDubMod and the ImageJ/Fiji software. Your willingness to help made this a much simpler task. iii Statistical assistance was very kindly provided by Julie Coetzee, Philip Weyl and Candice Coombes during various phases of this work. I am so very grateful to the other students who joined me on this postgraduate journey: Diane Smith, Megan Murison, Shana Mian, Dan Danckwerts, Megan Riddin, Jaryd Ridgeway, Izak Pretorious, Dan van der Vyver, Samantha Page, as well as Candice Coombes, Tamryn Marsberg, Tara O’Neill, the Rhodes postgraduate students and the other half of the Claire duo, Claire Faddel. The friendship, support, encouragement, academic discussions and comic relief when needed provided by you all has seen me through both good and challenging times. A special word of thanks to Candice Coombes for being so willing to help with all aspects of this work, from providing expertise to proofreading, your help has been so greatly appreciated. Funding is a vital component of any postgraduate research and this work would not have been possible without the financial support of the National Research Foundation (NRF), the Ernst & Ethel Erikson Trust, Citrus Research International (CRI) and Rhodes University. The support provided by the postgraduate and undergraduate funding office staff members has allowed me to be in a position to pursue my postgraduate studies and for that I am very grateful. I would also like to acknowledge Jeanne van der Merwe for handling the financial matters over the duration of this work. As I move onto the next phase this journey, I must thank all the staff of CRI and River Bioscience, as well as the students at CRI, Sean Thackeray and Sonnica Albertyn for being so welcoming and for giving me new insights into this work. In conclusion, thank you to my parents, sisters, aunts, other family and friends for your support and interest from the early stages of my academic career to those who still continue to encourage me in these latter years. A tribute must be given to my grandfather, Reginald Sweet, a scholar and a true gentleman for having been such a wonderful influence on me in my younger years, both academically and personally. In particular thanks must be given to my mother, Bridget Love for your love and endless support. You have encouraged me since day one and none of this would have been possible without you. iv Table of Contents Abstract………………………………………….…………………………………………….ii Acknowledgments………………………………………….…………………………………iii Table of Contents……………………………………………………………………………...v List of Tables………………………………………………………………………………....ix List of Figures………………………………………………………………………………....x List of Abbreviations………………………………………………………………………xxiii 1. CHAPTER 1 – General Introduction 1.1 SOUTH AFRICAN CITRUS ....................................................................................... 1 1.1.1 The Taxonomy of the Citrus Genus ........................................................................ 1 1.1.2 The South African Citrus Industry .......................................................................... 2 1.1.3 Citrus Export: Sanitary and Phytosanitary regulations (SPS) ................................. 6 1.1.4 Citrus Pests of South Africa ................................................................................... 7 1.2 FALSE CODLING MOTH ........................................................................................ 10 1.2.1 Taxonomic Classification ...................................................................................... 10 1.2.2 Distribution and Host Range ................................................................................. 11 1.2.3 Description of Life Stages ..................................................................................... 12 1.2.4 General Life History of FCM ................................................................................ 13 1.2.5 The Pre-pupal and Pupal Life Stages of Lepidoptera ............................................ 14 1.2.6 Pupation in False Codling Moth ............................................................................ 15 1.2.7 The Economic Importance of False Codling Moth ............................................... 16 1.2.8 Control of False Codling Moth .............................................................................. 16 1.2.8.1 Pre-harvest Control ...........................................................................................