THE EFFECTS OF METHIOZOLIN RATES AND NITROGEN FERTILITY STRATEGIES FOR ANNUAL BLUEGRASS CONTROL AND CREEPING BENTGRASS SAFETY ON GOLF GREENS THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Chen Fang, B.S. Graduate Program in Horticulture and Crop Science The Ohio State University 2015 Master's Examination Committee: Dr. David S. Gardner, Advisor Dr. John R. Street, Co-advisor Dr. T. Karl Danneberger Dr. David J. Barker Copyrighted by Chen Fang 2015 Abstract Annual bluegrass (Poa annua L.) is considered the most problematic weed on golf greens because of its fecund characteristic, low heat and disease tolerance in the summer, massive seed head reproduction, and bright green color. Methiozolin was initially an herbicide for weed control in crop fields and now is being developed for annual bluegrass control on golf greens. It has shown effectiveness and safety on multiple grass species, including creeping bentgrass (Agrostis stolonifera), kentucky bluegrass (Poa pratensis), and bermudagrass (Cynodon dactylon). As a systemic herbicide, methiozolin is mainly taken up by root absorption and shows limited acropetal movement in the plant. It is recommended that methiozolin be watered in immediately after application. Nitrogen, as one of the essential elements of plants, plays an important role in the lateral growth and chlorophyll formation of creeping bentgrass, which can greatly influence the recovery rate, color, and other quality characteristics of the turfgrass surface. Digital Image Analysis (DIA) is a new method for turfgrass surface quality evaluation. DIA has shown efficiency in data analysis with an equal accuracy as the normalized difference vegetation index (NDVI) and better consistency than visual evaluation method (NTEP). Two experiments were conducted on the Ohio State University Golf Club practice green and one on a USGA green at the Ohio Turfgrass Foundation Research and Education Facility. The first project on the OSU Golf Club putting green was designed to study the interaction of methiozolin, nitrogen rate and fertilizing frequency on creeping ii bentgrass recovery and annual bluegrass suppression/control in the spring with fall only methiozolin treatments and fall/spring methiozolin treatments. The second project consisted of three methiozolin rates and four rates to determine the best combination of spring methiozolin rate and spring nitrogen application strategies that shows best control over annual bluegrass while benefiting creeping bentgrass recovery and safety. The third project at the OSU Research and Education Facility was to study the effects of five nitrogen rates on the lateral growth/recovery and quality of creeping bentgrass with/without methiozolin treatments. The first project found that there was no significant interaction between methiozolin, nitrogen rates and fertilizing frequency in the spring. Spring methiozolin applications had a negative effect on creeping bentgrass color and recovering rate, but also a subsequent control on annual bluegrass after methiozolin fall treatments. Among all nitrogen strategies, the 24.4 kg N ha-1 every two weeks and the 12.2 kg N ha-1 every week were the best for creeping bentgrass green-up and recovery in the spring of 2014. The second experiment project found that methiozolin rates higher than the protocol rate (0.53 kg a.i. ha-1) had significant negative effects on annual bluegrass color and significantly more decrease on annual bluegrass population. Both creeping bentgrass and annual bluegrass color increased significantly with higher nitrogen rates and 24.4 kg N ha-1 had significantly more decrease on annual bluegrass population, which means higher nitrogen rates benefits creeping bentgrass more than annual bluegrass under methiozolin iii treatments. The third study found that there was no significant negative effects of methiozolin on creeping bentgrass color or lateral growth. According to the regression, there was a quadratic relation between creeping bentgrass color and time. The lateral growth rate of creeping bentgrass was constant through time and was only influenced by the nitrogen rate. iv Dedicated to my boss, Dr. Street v Acknowledgments I would like to express my special appreciation and thanks to my advisor, Dr. John Street, you have been a tremendous mentor for me. I would like to thank you for encouraging my research and for allowing me to grow as a research scientist. Your advice on both research as well as on my career have been priceless. I would also like to thank my co-advisor Dr. David Gardner and also Dr. Karl Danneberger for serving as my committee members and offering advice constantly without any hesitation. I would especially like to thank the Moghu Research Center and Moghu USA, namely Dr. Suk-jin Koo and Mr. Kyung-min Han. Without your endless support with funding, information, and product, the whole project would not have occurred. A special thanks to my family. Words cannot express how grateful I am to my mother and father for all of the sacrifices that you’ve made for me. I would also like to thank all of my friends who supported me during difficulties, and incented me to strive towards my goal. At the end I would like express appreciation to my beloved one Jing Tseh, who was always my support and provided a home where I could always take a rest when I was struck by life. vi Vita June 1989 .......................................................Born – Xining, China 2013................................................................B.A. Turfgrass Management, Beijing Forestry University, China 2013................................................................B.S. Turfgrass Science, Michigan State University, MI 2013 to present ..............................................Graduate Research and Teaching Associate, Department of Horticulture and Crop Science, Ohio State University, OH Fields of Study Major Field: Horticulture and Crop Science vii Table of Contents Abstract…………………………………………………………………………………....ii Dedication………………………………………………………………………………....v Acknowledgments…………………………………………………………….………….vi Vita………………………………………………………………………………………vii List of Tables……………………………………………………………….…………….xi List of Figures………………………………………………………………….………..xvi Introduction………………………………………………………………………..............1 Chapter 1: Literature Review……………………………………………….………….….4 Annual bluegrass as a problematic weed………...…………………………….….4 Chemical control of annual bluegrass……………………………………………..6 Methiozolin as a newly developed selective herbicide…………………………..10 Nitrogen as an essential plant nutrient…………………….…..………………....14 Chapter 2: Spring Application of Nitrogen and Methiozolin on Annual Bluegrass Control on Golf Greens after Fall Treatments…………………….18 Introduction………………………………………………………………………18 viii Material and methods…………………………………………………………….19 Results…………………………………………………………………….……...25 Creeping bentgrass color/quality……………………………….…….…25 Coverage of voids………………………………………………….…….35 Annual bluegrass population…………………………………….………46 Conclusions………………………………………………...……………….……54 Chapter 3: The Effects of Methiozolin and Nitrogen Rates for Spring Annual Bluegrass Control on Creeping Bentgrass Greens…………………………………………………116 Introduction……………………………………………………………………..116 Material and methods…………………………………………………………,,.117 Results…………………………………………………………………………..123 Creeping bentgrass color/quality…………..….……………………….123 Annual bluegrass color……………………………………………...….131 Annual bluegrass population………………………………………...…141 Conclusions………………………………………………………………..……148 ix Chapter 4: The Effects of Nitrogen Rates and Methiozolin on Creeping Bentgrass Lateral Growth…………………………………………….………….………….………….….195 Introduction……………………………………………………………………..195 Material and methods………………………………………………….......…....196 Results…………………………………………………………………………..201 Creeping bentgrass color/quality………………………………………201 Creeping bentgrass lateral growth……………………………………..206 Regression of the effects of nitrogen rates……………………………...209 Conclusions……………………………………………………………………..213 Discussion………………………………………………………………………………240 References………………………………………………………………………….…...245 Appendix A: Annual Bluegrass Declining after Fall Methiozolin Applications ………253 Appendix B: Light Box Photos…………………………………………………………256 x List of Tables Table Page 2.1. All treatments of spring application of nitrogen and methiozolin on annual bluegrass control on golf greens after fall treatment…………………………………………..56 2.2. Application dates and rates of methiozolin fall treatments to the experimental area on a practice putting green in the field preparation stage in 2013 and 2014………………………………………………………………………………....57 2.3. Application dates and rates of methiozolin and nitrogen treatments on annual bluegrass control on golf greens after fall methiozolin treatments, 2014 and 2015...............………………….……………………………………………………58 2.4. NDVI of creeping bentgrass influenced by methiozolin, nitrogen rates and fertilizing frequency on annual bluegrass control on golf greens after fall treatment, 2014…………...……………………………………………….59 2.5. NDVI of creeping bentgrass influenced by methiozolin, nitrogen rates and fertilizing frequency on annual bluegrass control on golf greens after fall treatment, 2015…………………………………………………………….60 2.6. Green Index of creeping bentgrass influenced by methiozolin, nitrogen rates and fertilizing frequency on annual bluegrass control on golf greens after fall treatment, 2014…………………………………………………………….61 2.7. Green Index of creeping bentgrass influenced by methiozolin,