Effects of Fungicide Chemistry and Application Timing on Fusarium Head Blight and Deoxynivalenol in Soft Red Winter Wheat THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Daisy L. D’Angelo, B.A. Graduate Program in Plant Pathology The Ohio State University 2013 Master's Examination: Dr. Pierce A. Paul, Advisor Dr. Larry V. Madden Dr. Mike A. Ellis Copyright by Daisy L. D’Angelo 2013 Abstract Demethylation Inhibitors (DMI) and Quinone Outside Inhibitors fungicides are important components of wheat disease management programs. However, only members of former group are usually recommended for the control of Fusarium head blight (FHB) and deoxynivalenol (DON). Since wet, humid conditions during anthesis and early grain fill are highly conducive to FHB development, DMI fungicides are commonly recommended for FHB management when anthesis coincides with wet weather. However, there are several practical limitations to applying a fungicide at anthesis. Research is needed to determine whether applications made after anthesis will provide adequate control of this disease and its associated toxins in soft red winter wheat under field conditions in the U.S. Midwest. In the case of the QoI, these are not usually recommended to FHB and DON management because some members of this group have been reported to increase instead of decrease DON in harvested grain. However, it is unclear whether all QoIs affect DON in the same manner and whether DON response to QoIs vary with application timing. The objectives of this study were to: 1) determine the effect of post- anthesis applications of 19% tebuconazole + 19% prothioconazole and 8.6% metconazole on FHB and DON in soft red winter wheat (SRWW) under different naturally infected and artificially inoculated field conditions, 2) determine whether the magnitude of FHB and DON responses to post-anthesis fungicide applications varied with active ingredient, ii cultivar, and baseline disease and toxin levels, and 3) estimate the efficacy (based on mean percent control of FHB index and DON) of post-anthesis treatments relative to untreated and anthesis reference treatments.; 4) determine the effects of two QoI active ingredients (22.9% azoxystrobin and 23.6% pyraclostrobin), relative to untreated checks and DMI (19% tebuconazole + 19% prothioconazole) reference treatments, on DON contamination of wheat grain and spikes; 5) determine whether the effect of QoIs on FHB index and DON was influenced by application timing; and 6) determine whether the relationships among index, DON, and Fusarium damaged kernels varied with active ingredient and application timing. iii Dedicated to My Husband, Craig E. D’Angelo iv Acknowledgments I would like to thank my advisor, Dr. Pierce A. Paul, for his unending support and guidance throughout my time at OSU. His encouragement and instruction have added great input to this thesis. My student advisory committee members, Dr. Laurence V. Madden, for his help with thesis revisions; and Dr. Michael A. Ellis, for his instruction on fungicide chemistry and management, and help with reviewing this thesis. My lab mates Kelsey Andersen and Jorge David, post docs Jessica Engle and Katelyn Willyerd, and lab technician Kristin Davies for their help conducting experiments and collecting data. Bob James, for his help and support maintaining greenhouse experiments, and the farm crews at Snyder and the OARDC research stations for planting and setting up all field experiments. My Husband and family, without their encouragement and support I would have never decided to return to school and pursue a graduate degree. v Vita June 2002 .......................................................Reynoldsburg High School December 2006 ..............................................B.A. Biology, Capital University 2011 to present ..............................................Graduate Research Associate, Department of Plant Pathology, The Ohio State University Fields of Study Major Field: Plant Pathology vi Table of Contents Abstract ............................................................................................................................... ii Dedication………………………………………………………………………………...iv Acknowledgments............................................................................................................... v Vita .................................................................................................................................... vii List of Tables ..................................................................................................................... ix List of Figures .................................................................................................................... xi Chapter 1: Fusarium Head Blight of Wheat and Deoxynivalenol: A Review ................... 1 Chapter 2: Efficacy of Post-Anthesis Fungicide Application against Fusarium Head Blight and Deoxynivalenol in Soft Red Winter Wheat .................................................... 14 2.1. Introduction………………………………………………………………….14 2.2. Methodology………………………………………………………………...19 2.3. Results……………………………………………………………………….25 2.4. Discussion…………………………………………………………………...30 Chapter 3: Influence of Fungicide Chemistry and Timing on Deoxynivalenol Contamination of Wheat Grain by Fusarium graminearum……………………………..46 3.1. Introduction………………………………………………………………….46 3.2. Methodology………………………………………………………………...51 vii 3.3. Results……………………………………………………………………….57 3.4. Discussion…………………………………………………………………...62 References ......................................................................................................................... 78 viii List of Tables Table 2.1 Summary of inoculation and treatment application protocols for experiments conducted to evaluate the effects of post-anthesis fungicide treatments on Fusarium head blight of wheat .................................................................................................................. 36 Table 2.2 Summary statistics from linear mixed model analyses of data from field experiments conducted in multiple location-years to evaluate the effects of post-anthesis fungicide treatments on Fusarium head blight index, incidence, Fusarium damaged kernels, and deoxynivalenol in soft red winter wheat as influenced by wheat cultivar, fungicide active ingredient, and inoculum density………………………………………37 Table 2.3 Summary statistics from linear mixed model analyses of post-anthesis treatments effects on Fusarium head blight index and deoxynivalenol content of harvested grain………………………………………………………………………….39 Table 2.4 Log of the response ratio, percent control and corresponding statistics for the effect of fungicide treatments on Fusarium head blight index and deoxynivalenol in soft red winter wheat………………………………………………………………………….41 Table 3.1 Pairwise comparisons of untreated check and DMI reference treatments with QoI treatments from linear mixed model analyses of fungicide effects on Fusarium head blight index, Fusarium damaged kernels, and deoxynivalenol from wheat plots spray- ix inoculated at anthesis with a spore suspension of Fusarium graminearum under field conditions .......................................................................................................................... 68 Table 3.2 Pairwise comparisions of untreated check and DMI reference treatments with QoI treatments from linear mixed model analyses of fungicide effects on Fusarium head blight index and deoxynivalenol for wheat spikes inoculated at anthesis with a spore suspension of Fusarium graminearum under controlled conditions……………………..70 Table 3.3 Regression coefficients from linear mixed model analyses of the relationship between Fusarium head blight index or Fusarium damaged kernels as continuous covariates and log-transformed deoxynivalenol content of harvested wheat grain as fungicide treatments……………………………………………………………………..72 x List of Figures Figure 2.1Fusaruim head blight index for different treatments applied to soft red winter wheat in field experiments conducted at the Ohio Agricultural Research and Development Center (OARDC) Snyder Farm near Wooster, Ohio in 2011 (A), 2012 (B), and 2013 (C); at the OARDC Western Agricultural Research Station near South Charleston, Ohio in 2011 (D), and 2013 (E); and at the Illinois Council for Food and Agriculture Research facility in 2012 (F) and 2013 (G) ................................................... 42 Figure 2.2 Deoxynivalenol content of harvested grain for different treatments applied to soft red winter wheat in field experiments conducted at the Ohio Agricultural Research and Development Center (OARDC) Snyder Farm near Wooster, Ohio in 2011 (A), and 2013 (B), at OARDC Western Agricultural Research Station near South Charleston, Ohio in 2011 (C), and 2013 (D), and at the Illinois Council for Food and Agricultural Research facility in 2013 (E) ............................................................................................................ 44 Figure 3.1Mean Fusarium head blight index (A, C, and E) and deoxynivalenol content of wheat grain (B) and whole spikes (D and F) .................................................................... 74 Figure 3.2 Relationship between Fusaruim damaged kernels and log-transformed deoxynivalenol content of wheat grain (A) and between Fusaruim head blight index and log- transformed DON content of wheat spikes (B and C) ..............................................