University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Dissertations and Student Research in Entomology Entomology, Department of 12-2014 The effect of agricultural practices on sugar beet root aphid (Pemphigus betae Doane) and beneficial epigeal arthropods Rudolph J. Pretorius University of Nebraska-Lincoln Follow this and additional works at: http://digitalcommons.unl.edu/entomologydiss Part of the Agricultural Science Commons, Entomology Commons, and the Plant Pathology Commons Pretorius, Rudolph J., "The effect of agricultural practices on sugar beet root aphid (Pemphigus betae Doane) and beneficial epigeal arthropods" (2014). Dissertations and Student Research in Entomology. 35. http://digitalcommons.unl.edu/entomologydiss/35 This Article is brought to you for free and open access by the Entomology, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Dissertations and Student Research in Entomology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. THE EFFECT OF AGRICULTURAL PRACTICES ON SUGAR BEET ROOT APHID (PEMPHIGUS BETAE DOANE) AND BENEFICIAL EPIGEAL ARTHROPODS by Rudolph J. Pretorius A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy Major: Entomology Under the Supervision of Professors J.D. Bradshaw & G.L. Hein Lincoln, Nebraska December, 2014 THE EFFECT OF AGRICULTURAL PRACTICES ON SUGAR BEET ROOT APHID (PEMPHIGUS BETAE DOANE) AND BENEFICIAL EPIGEAL ARTHROPODS Rudolph Johannes Pretorius, Ph.D. University of Nebraska, 2014 Advisers: Jeffrey D. Bradshaw and Gary L. Hein This study investigated the effect of several agricultural practices on the sugar beet root aphid (Pemphigus betae Doane) and beneficial epigeal natural enemies in western Nebraska sugar beet agroecosystems. Eight glyphosate-tolerant sugar beet varieties were evaluated under field conditions for their resistance to root aphids. High levels of aphid resistance were detected for some varieties. In conjunction to this, pitfall sampling was conducted to determine the beneficial epigeal natural enemy complex in the area, which could contribute to the management of both root aphids and glyphosate-resistant weeds. Ground beetles comprised an important and abundant component of this fauna, with 79 species collected throughout this study. The second investigated the impact of a seed-applied insecticide, Poncho Beta (clothianidin and beta-cyfluthrin), and sugar beet plant density (25,000 plants/acre vs. 35,000 plants/acre) on root aphids and beneficial epigeal arthropods. The insecticide significantly reduced root aphid populations, but not to levels which can be considered adequate control. Soil- dwelling beneficial arthropods remained largely unaffected by the seed-applied insecticide, except for a single ground beetle species (Bembidion quadrimaculatum oppositum) which showed higher activity in the untreated plots during one of the two years. Plant density had minimal impact on the aphids and beneficial arthropods. Finally, this study also investigated the impact of tillage (conventional versus reduced tillage) on beneficial epigeal arthropods, and their associated ecosystem services (particularly weed seed consumption and predation of live prey). Overall, the results indicated a strong incentive for adopting reduced tillage practices for sugar beet production, based on increased activity of spiders, centipedes and rove beetles. Although prey consumption remained unaffected by the tillage system used, increased weed seed consumption was observed under the zone tillage system. This study also illustrated the importance of examining important beneficial taxa, such as ground beetles, on the species level rather than on the family level, based on the differing responses to tillage by different species. iv DEDICATION I dedicate this work to my grandparents, Otto and Elize Conradie. Only through your lifelong hard work and unconditional devotion to your children and grandchildren have I been able to reach this milestone. For this I thank you dearly. v ACKNOWLEDGEMENTS I would like to sincerely thank the following for all their respective contributions to my studies, without whom, none of it would have been possible: Henda Pretorius for tons of help and continued support throughout my studies. Thank you for believing in me, your continued encouragement, and for always being on my side through thick and thin. Thanks for never doubting my descisions and being willing to finish your M.Sc. in the United States just to be with me. Thea Pretorius and Phillipa Visser for your continued support, and for enduring the long years without our presence. Thank you for all your prayers and for doing your utmost best to make us feel at home on the other side of the world. Professor J.D. Bradshaw for allowing me to be a student in his program and for all the support and advice. Professor G.L. Hein for all his support and advice on my studies. Professors E.E. Blankenship, R.J. Wright, and N.J. Miller for your willingness to serve on my committee and for the help with my statistical analyses. Professor F. Purrington for readily identifying my ground beetle specimens – a crucial aspect of this study. Thank you for your friendship. Professor J.G. Lundgren for his advice on ground beetle sampling and measurements of ecosystem services. Professor R.G. Wilson for his help and advice pertaining to weed management in sugar beet. vi Rick Patrick and Susan Harvey for all your help, support, kindness, and friendship – you guys really made it all worth it. Gene Kizzire, Phil Mitchell and Jim Siemsen for all your effort in preparing and maintaining my research plots. Tevyn Baldwin, Nathan Faulkner, Jeanna Dale Jenkins, Kyle Koch, Christopher McCullough, Kelli Neiger, Sarah Peterson, Jarron Rasnic, Riley Shea Smith, and Marissa Yonts for all the summer help provided – it is very much appreciated. The Fulbright Program for turning a goal into reality. University of Nebraska-Lincoln, Department of Entomology for accepting me to be a graduate student into the program. Western Sugar for financial support provided. The Central University of Technology, Free State for sabbatical leave granted. Family members Otto Pretorius, Tiaan & Elza Olivier, Otto & Elize Conradie, Marinus Visser, Jerry & Driekie Smit, Hennie, Linda & Lydia Landman, and Paul & Corné Smit for all your support, encouragement, letters, and for believing in me throughout this time. My Heavenly Father for carrying me through something I would never would have thought possible. vii TABLE OF CONTENTS Page CHAPTER 1: INTRODUCTION Sugar beet classification ..................................................................................................... 1 Origin and domestication of cultivated sugar beet.............................................................. 1 Sugar beet uses .................................................................................................................... 2 Sugar beet production ......................................................................................................... 3 Arthropod pests of sugar beet ............................................................................................. 4 Sugar beet and weed competition ....................................................................................... 5 Sustainable sugar beet pest and weed management ............................................................ 9 Research objectives ........................................................................................................... 16 CHAPTER 2: THE SUGAR BEET ROOT APHID, PEMPHIGUS BETAE DOANE (HEMIPTERA: APHIDIDAE): BIOLOGY, ECONOMIC SIGNIFICANCE, AND MANAGEMENT STRATEGIES Introduction ....................................................................................................................... 19 Description of the sugar beet root aphid ........................................................................... 20 Primary and secondary host plants ................................................................................... 20 Sugar beet root aphid life cycle ........................................................................................ 21 Economic significance of the sugar beet root aphid ......................................................... 23 Sugar beet root aphid surveillance .................................................................................... 24 viii Management practices ...................................................................................................... 25 Conclusions ....................................................................................................................... 29 CHAPTER 3: VARIETAL RESISTANCE OF GLYPHOSATE-TOLERANT SUGAR BEET TO THE SUGAR BEET ROOT APHID (HEMIPTERA: APHIDIDAE) AND THE RESPONSE OF EPIGEAL NATURAL ENEMIES Introduction ....................................................................................................................... 35 Materials and methods ...................................................................................................... 38 Results ............................................................................................................................... 43 Discussion and conclusions .............................................................................................