Epidemiology and Management of Stem and Bulb Nematode by Lilieth Ives A Thesis Presented to The University of Guelph In partial fulfilment of requirements for the degree of Master of Science in Plant Agriculture Guelph, Ontario, Canada © Lilieth Ives, March, 2019 ABSTRACT EPIDEMIOLOGY AND MANAGEMENT OF STEM AND BULB NEMATODE Lilieth Ives Advisors: University of Guelph, 2019 Professor M.R. McDonald Professor K. Jordan Ditylenchus dipsaci is one of the most destructive pathogens of garlic in Ontario. Ditylenchus dipsaci can cause total yield loss and decreases the availability of seed cloves for successive planting. There are limited options available for management in Canada. The management and host range of D. dipsaci were investigated as was the interaction of D. dipsaci and Fusarium oxysporum f. sp. cepae, the causal agent of basal plate rot of garlic. Several new chemistries, applied as seed treatment, in-furrow drench, and seed fumigant, were evaluated for their effectiveness to control D. dipsaci. Fluopyram was the most effective chemistry for suppressing D. dipsaci, and increasing yield. In greenhouse studies, soybean and wheat effectively reduced the population density of D. dipsaci. Both antagonistic and no effect interactions occurred between D. dipsaci and F. oxysporum f. sp. cepae. There was a greater reduction in shoot dry weight, and an increase in disease incidence compared to either pathogen alone. ii ACKNOWLEDGEMENTS I would like to thank God for giving me the strength and support needed for this work. I am grateful to my chief supervisor, Professor Mary Ruth McDonald for her support and direction. In addition, I would like to thank the other committee members Professor Katerina Jordan and Mr. Michael Celetti for their continued support and guidance. For the invaluable assistance in establishing and maintaining my research plots over the past two summers, as well as all their technical support, I would like to thank Kevin Vander Koi, Laura Riches, Shawn Janse, and the rest of the Muck Crops Research Station staff. I would also like to thank Sue Couling, and the greenhouse staff (Guelph) for their assistance. A special thanks to Zachary Telfer, who was kind enough to provide transportation for me to and from the Muck Crops Research Station. I would like to thank my family, friends and fellow graduate students for their prayers and encouragement. Finally, special thanks to my son Simon and my partner Paschal, who were with me every step of the way. iii TABLE OF CONTENTS ABSTRACT .............................................................................................................................. ii Acknowledgements ................................................................................................................... iii Table of Contents ...................................................................................................................... iv List of Tables .......................................................................................................................... viii List of Figures .............................................................................................................................x List of Symbols, Abbreviations or Nomenclature ...................................................................... xi List of Appendices .................................................................................................................. xiii CHAPTER ONE .........................................................................................................................1 LITERATURE REVIEW ............................................................................................................1 1 Introduction .........................................................................................................................1 1.1 The host: history and origin of garlic ...................................................................... 2 1.1.1 Morphology of garlic ...................................................................................... 3 1.1.2 Production, usage and economic importance of garlic ........................................ 4 1.1.3 Fungal diseases and nematode pests of garlic .................................................... 6 1.2 Stem and bulb nematode – biology and development ................................................ 6 1.2.1 Distribution and economic impact .................................................................... 9 1.2.2 Influence of the environment ......................................................................... 11 1.2.3 Host range ................................................................................................... 13 1.2.4 Host-parasite relationship .............................................................................. 14 1.2.5 Symptoms on garlic ...................................................................................... 14 1.3 Management practices ......................................................................................... 15 1.3.1 Physical control ........................................................................................... 15 1.3.2 Cultural control ............................................................................................ 18 1.3.3 Chemical control .......................................................................................... 21 iv 1.3.4 Biological control ......................................................................................... 24 1.3.5 Genetic control ............................................................................................ 26 1.4 Fusarium oxysporum ........................................................................................... 27 1.4.1 Basal plate rot in garlic ................................................................................. 29 1.4.2 Interaction of plant parasitic nematodes and soil-borne fungal pathogens ........... 30 1.5 Summary ........................................................................................................... 33 1.6 Research objectives and hypothesis ...................................................................... 34 CHAPTER TWO ...................................................................................................................... 36 EVALUATION OF NEW CHEMISTRIES AND APPLICATION TECHNIQUES FOR THE MANAGEMENTOF STEM AND BULB NEMATODE IN GARLIC ...................................... 36 2 Introduction ....................................................................................................................... 36 2.1 Materials and Methods ........................................................................................ 42 2.1.1 Experimental design ..................................................................................... 42 2.1.2 Plant material............................................................................................... 43 2.1.3 Treatments .................................................................................................. 44 2.1.4 Assessments ................................................................................................ 48 2.1.5 Statistical analysis ........................................................................................ 52 2.2 Results............................................................................................................... 53 2.3 Discussion ......................................................................................................... 69 2.4 Conclusion ......................................................................................................... 78 CHAPTER THREE ................................................................................................................... 81 EFFECT OF ROTATION CROPS ON DITYLENCHUS DIPSACI POPULATION DENSITY IN A GREENHOUSE SCREENING STUDY ................................................................................ 81 3 Introduction ....................................................................................................................... 81 3.1 Materials and Methods ........................................................................................ 84 3.1.1 Species identification .................................................................................... 84 v 3.1.2 Host range ................................................................................................... 85 3.1.3 Assessments ................................................................................................ 90 3.1.4 Statistical analysis ........................................................................................ 92 3.2 Results............................................................................................................... 92 3.3 Discussion ....................................................................................................... 100 3.4 Conclusion ....................................................................................................... 109 CHAPTER FOUR ................................................................................................................... 111 BASAL PLATE ROT IN GARLIC: A NEMATODE – FUNGUS DISEASE COMPLEX ...... 111 4 Introduction ..................................................................................................................... 111 4.1 Materials and Methods .....................................................................................