Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2021 Estimation of soybean radiation use efficiency with the help of UAV imagery to evaluate the impact of frogeye leaf spot on yield and the effect of fungicides. Xavier Alaric Phillips Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Recommended Citation Phillips, Xavier Alaric, "Estimation of soybean radiation use efficiency with the help ofA U V imagery to evaluate the impact of frogeye leaf spot on yield and the effect of fungicides." (2021). Graduate Theses and Dissertations. 18586. https://lib.dr.iastate.edu/etd/18586 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Estimation of soybean radiation use efficiency with the help of UAV imagery to evaluate the impact of frogeye leaf spot on yield and the effect of fungicides. by Xavier Phillips A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Plant Pathology Program of Study Committee: Daren Mueller, Major Professor Alison Robertson Leonor Leandro Matthew Darr Mark Licht The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2021 Copyright © Xavier Phillips, 2021. All rights reserved. ii TABLE OF CONTENTS Page NOMENCLATURE ...................................................................................................................... iv ACKNOWLEDGMENTS ...............................................................................................................v ABSTRACT ................................................................................................................................... vi CHAPTER 1. GENERAL INTRODUCTION ................................................................................1 Dissertation Format ................................................................................................................... 1 General Introduction .................................................................................................................. 1 Literature Review ...................................................................................................................... 2 Soybeans ............................................................................................................................... 2 Diseases of Soybean ............................................................................................................. 3 Frogeye Leaf Spot ................................................................................................................ 3 Fungicide Use ....................................................................................................................... 6 Disease Severity Assessment and Relation to Yield Loss ................................................... 8 Area Under Disease Progress Curve .................................................................................... 9 Radiation Use Efficiency (RUE) .......................................................................................... 9 Components of RUEgreen .................................................................................................... 10 RUE of Soybeans ............................................................................................................... 14 UAVs in Agriculture .......................................................................................................... 15 Passive and Active Sensors ................................................................................................ 16 Radiometric Calibration ..................................................................................................... 18 Indices ................................................................................................................................ 19 Literature Cited ........................................................................................................................ 20 CHAPTER 2. ESTIMATING SOYBEAN RADIATION USE EFFICIENCY USING A UAV IN IOWA ......................................................................................................................................33 Abstract .................................................................................................................................... 33 Introduction ............................................................................................................................. 34 Materials and Methods ............................................................................................................ 36 Results ..................................................................................................................................... 41 Discussion ................................................................................................................................ 43 Conclusion ............................................................................................................................... 46 Tables and Figures ................................................................................................................... 47 Literature Cited ........................................................................................................................ 57 Appendix. Tables ..................................................................................................................... 62 CHAPTER 3. A COMPARISON BETWEEN DISEASE SEVERITY OF FROGEYE LEAF SPOT AND RADIATION USE EFFICIENCY OF SOYBEAN ACROSS FUNGICIDE TREATMENTS .............................................................................................................................64 Abstract .................................................................................................................................... 64 Introduction ............................................................................................................................. 65 Materials and Methods ............................................................................................................ 69 iii Results ..................................................................................................................................... 76 Discussion ................................................................................................................................ 79 Conclusion ............................................................................................................................... 84 Tables and Figures ................................................................................................................... 85 Literature Cited ........................................................................................................................ 96 Appendix. Tables and Figures ............................................................................................... 103 CHAPTER 4. GENERAL CONCLUSION .................................................................................110 iv NOMENCLATURE GLAI Green Leaf Area Index GLAIDx GLAI With Disease Severity Removed LAI Leaf Area Index NDVI Normalized Difference Vegetation Index RUE Radiation Use Efficiency SPAD Soil Plant Analysis Development TLAI Total Leaf Area Index UAV Unmanned Aerial Vehicle v ACKNOWLEDGMENTS I cannot express how grateful I am to have had this opportunity here at Iowa State University. The amazing Mueller Lab and IPM group that I found myself in, is composed of the most kind and helpful people that I have ever met. I thank all of you for making me feel welcome and for the invaluable help you provided me. I also thank my committee members Dr. Alison Robertson, Dr. Leonor Leandro, Dr. Mark Licht, and Dr. Matt Darr for their support and guidance. I thank you for accepting the commitment of being on my committee. I am thankful to have had Dr. Daren Mueller as my advisor throughout my graduate studies. Your confidence helped me foster my own self-efficacy. I appreciate the continued support and mentorship you provided over all of the challenging adventures I encountered. Special thanks to my parents for their support. I appreciate your trips to visit us and for understanding when we were unable to get back. Finally, I thank my wife and children for taking care of me. Your smiles, laughter, and love get me through each day. vi ABSTRACT Radiation use efficiency (RUE) is a parameter that is directly associated to yield, but difficult to estimate and unreasonable to estimate on a small plot research scale using traditional techniques. It has the potential to be used for evaluation of in-season management techniques and disease impact. During 2018 and 2019, field experiments located in north central and south western Iowa were used to investigate the estimation of RUE of soybean (Glycine max