View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by University of Birmingham Research Archive, E-theses Repository The thermal biology and thresholds of Phytoseiulus macropilis Banks (Acari: Phytoseiidae) and Balaustium hernandezi von Heyden (Acari: Erythraeidae) By Megan R. Coombs A thesis submitted to the University of Birmingham For the degree of DOCTOR OF PHILOSOPHY School of Biosciences College of Life and Environmental Sciences University of Birmingham September 2013 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract Phytoseiulus macropilis Banks (Acari: Phytoseiidae) and Balaustium hernandezi von Heyden (Acari: Erythraeidae) have been identified as candidate augmentative biological control agents for the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The two-spotted spider mite is a significant pest of many commercial crops, including those grown in glasshouses. This study investigated the potential of both species to survive a typical northern European winter, and risk of establishment. The thermal thresholds of each species were also assessed to determine the efficacy of the predator in a horticultural system. Through a combination of laboratory and field trials, P. macropilis was shown to present a low risk of establishment in northern Europe. Survival of winter field exposures was limited to three weeks, and the mite did not demonstrate the ability to enter a diapause state. Similarly, the lower thermal activity thresholds allowed movement of the mite at temperatures where T. urticae became immobile, but were not so low as to pose a threat of dispersal in a northern European winter. The predatory ability of P. macropilis on tomato and French bean leaf surfaces was investigated, and found to be similar to the current leading market predator of T. urticae, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae). In contrast, B. hernandezi demonstrated a high tolerance of northern European winter temperatures, surviving in the field for over four months. Balautium hernandezi was able to move at temperatures where T. urticae became immobile, however, there was some movement at sub-zero temperatures suggesting any escapees from the glasshouse would have the ability to move and survive a typical northern European winter. Smooth seas do not make skilful sailors African Proverb Acknowledgments My utmost thanks and gratitude go to my supervisor, Prof. Jeff Bale. Thank you for your patience and support during the more testing moments of the last four years, and for always making time to meet, despite having a rather busy schedule! I would like to thank Biobest and the BBSRC for funding this project, and supporting my travels to conferences in the UK, France and Canada. I particularly wish to thank Dr. Yves Arijs, Biobest, who sent me my starter populations and calmly helped through all my mite- related crises; your help was invaluable. I would also like to extend my gratitude to the Elms Road Laboratory and Winterbourne Gardens for growing and delivering the French bean plants throughout the course of my PhD. Thank you to my amazing colleagues in the Arthropod Ecophysiology lab group at Birmingham: Gwen, Lucy, Stuart, Bobbie, Ji, Paul, Matt, Emily and Nicky. I could not have wished to meet a more wonderful group of people. With Stick Insect Tuesdays, Cake Wednesdays, Eco Flux, Bananagrams, and everything in between, you’ve made the last four years so much fun. I’ll miss working with you every day, but look forward to continuing your friendships! To Rhys, Maria, Sheila, Kay, Lewis and Rob, who have always asked after the mites and my experiments, thank you. I’ve appreciated all your support. There are three people whom deserve my most particular thanks. Firstly my parents, Annie and Phil, for your incredible support in everything I’ve done. I wouldn’t be where I am now without you. I can’t thank you enough. Finally, to Andrew, who now knows more about mites than I’m sure he ever wished to know, thank you. I could not have done it without you by my side. Contents CHAPTER 1 .............................................................................................................................. 1 Introduction ............................................................................................................................... 1 1.1. Pest Control ............................................................................................................ 3 1.1.1. Chemical Control ................................................................................... 3 1.1.2. Integrated pest management .................................................................. 6 1.1.3. Biological Control ................................................................................. 7 1.2. Advantages and disadvantages of biological control ........................................... 11 1.3. Tritrophic Interactions in Biological Control ....................................................... 12 1.4. Selection and legislation ....................................................................................... 14 1.4.1. Identifying candidate biological control agents .................................. 14 1.4.2. Pre-release risk assessment .................................................................. 15 1.4.3. Access and benefit sharing .................................................................. 18 1.4.4. Post-release monitoring ....................................................................... 20 1.5. Physiology of cold hardiness ................................................................................ 21 1.5.1. The supercooling point ........................................................................ 22 1.5.2. Freeze tolerance ................................................................................... 23 1.5.3. Freeze avoidance ................................................................................. 24 1.5.4. Chill tolerance ..................................................................................... 25 1.5.5. Chill susceptibility ............................................................................... 25 1.5.6. Opportunistic survival ......................................................................... 26 1.6. Measurement of thermal biology .......................................................................... 26 1.6.1. Acclimation ......................................................................................... 26 1.6.2. Lethal temperature ............................................................................... 27 1.6.3. Lethal time ........................................................................................... 28 1.6.4. Diapause .............................................................................................. 29 1.6. Thermal activity thresholds .................................................................................. 32 1.6.1. CTmin and chill coma ........................................................................... 32 1.6.2. Recovery .............................................................................................. 33 1.6.3. CTmax and heat coma ........................................................................... 34 1.7. Study species ........................................................................................................ 34 1.7.1. Phytoseiulus macropilis Banks ............................................................ 34 1.7.2. Balaustium hernandezi Von Heyden ................................................... 36 1.8. Objectives ............................................................................................................. 39 CHAPTER 2 ............................................................................................................................ 40 Rearing Methods ..................................................................................................................... 40 2.1. Phytoseiulus macropilis and Phytoseiulus persimilis ........................................... 40 2.2. Balaustium hernandezi ......................................................................................... 41 2.3. Tetranychus urticae .............................................................................................. 41 2.4. Studying individual mites ..................................................................................... 41 CHAPTER 3 ............................................................................................................................ 43 Thermal biology of the spider mite predator Phytoseiulus macropilis ................................... 43 3.1. Abstract ................................................................................................................. 43 3.2. Introduction .........................................................................................................