OPTIMIZING EFFICACY OF BROMUS TECTORUM (CHEATGRASS, DOWNY BROME) BIOLOGICAL CONTORL IN CROPS AND RANGELANDS by Krista Ann Ehlert A dissertation submitted in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Ecology and Environmental Sciences MONTANA STATE UNIVERSITY Bozeman, Montana April 2017 ©COPYRIGHT by Krista Ann Ehlert 2017 All Rights Reserved ii ACKNOWLEDGEMENTS I would like to thank my advisors, Drs. Jane Mangold and Fabian Menalled, for providing their thoughtful feedback and encouragement throughout my project, as well as my committee members, Drs. Zachariah Miller and Alan Dyer. I would like to say thank you for help from the MSU PGC staff, especially Dave Baumbauer. Hilary Parkinson and Noelle Orloff whole-heartedly and selflessly guided me through graduate school and helped with fieldwork. Tremendous thanks goes to those who helped with long and hot field work days, followed by hours of weighing and sorting samples: Torrin Daniels, Hally Berg, Christina Herron-Sweet, Cecilia Welch, Wyatt Holmes, Chris Larson, Ketchum Wilt, Andrew Thorson, Sam Leuthold, Kyla Crisp, Stacy Davis, and Ali Thornton. Drs. Barbara Keith and Linnea Skoglund provided support and access to equipment. I would also like to thank members of the Mangold and Menalled labs: Sean McKenzie, Erin Burns, Nar Ranabhat, Subodh Adhikari, and Tessa Scott. Thanks goes to the USDA-WRIPM program, as well as the Montana Noxious Weed Trust Fund, for providing funding for my project, in addition to scholarships I received from the Montana Weed Control Association, the Western Society of Weed Science, and MSU's College of Agriculture. I would further like to thank my friends for all of their encouragement, those near and far. Lastly, I lastly like to say thank you to my family - my mom and dad, who always seem to have the right thing to say around the right time and my husband, who has shown me that love, chocolate, and carbs can help conquer a dissertation. This truly has been a memorable learning experience, and an (mostly) enjoyable one at that. iii TABLE OF CONTENTS 1. PROJECT BACKGROUND, THEORETICAL FRAMEWORK, PROJECT SIGNIFICANCE, AND OBJECTIVES .........................................................1 Project Background ..........................................................................................................1 Theoretical Framework: Drivers of Invasion and Mediating Ecological Processes ................................................................................3 Propagule Pressure ..........................................................................................................5 Reproduction ............................................................................................................6 Bromus tectorum ..........................................................................................7 Management Strategies ................................................................................8 Dispersal ................................................................................................................10 Bromus tectorum ........................................................................................11 Management Strategies ..............................................................................12 Abiotic Characteristics ..................................................................................................13 Disturbance ............................................................................................................13 Bromus tectorum ........................................................................................14 Management Strategies ..............................................................................15 Biotic Characteristics ....................................................................................................15 Invader Traits .........................................................................................................16 Bromus tectorum ........................................................................................19 Management Strategies ..............................................................................20 Competition............................................................................................................21 Bromus tectorum ........................................................................................22 Management Strategies ..............................................................................24 Natural Enemies .....................................................................................................24 Bromus tectorum ........................................................................................26 Management Strategies ..............................................................................27 Project Significance .......................................................................................................28 Objectives ......................................................................................................................29 Literature Cited ..............................................................................................................31 2. IMPACTS OF PYRENOPHORA SEMENIPERDA ON NON-TARGET, ECONOMICALLY IMPORTANT GRASSY SPECIES: IMPLICATIONS FOR BIOLOGICAL CONTROL OF BROMUS TECTORUM L. (CHEATGRASS, DOWNY BROME) ..........................................................................47 Introduction ....................................................................................................................47 Materials and Methods ..................................................................................................50 Seeds ......................................................................................................................50 iv TABLE OF CONTENTS — CONTINUED Pyrenophora semeniperda Inoculum Preparation .................................................51 Experimental Design ..............................................................................................52 Inoculum Application and Planting .......................................................................52 Statistical Analysis .................................................................................................53 Seed Weight ...............................................................................................53 Time to 50% Emergence ............................................................................54 Plant Density and Biomass ........................................................................54 Results ...........................................................................................................................55 Seed Weight ...........................................................................................................55 Time to 50% Emergence vs. Seed Weight .............................................................55 Density and Biomass ..............................................................................................56 Discussion .....................................................................................................................60 Literature Cited ..............................................................................................................66 3. IMPACT OF NATIVE SPECIES SEEDING, HERBICIDES, AND FUNGICIDES IN PERENNIAL GRASS ESTABLISHMENT IN BROMUS TECOTRUM L. (CHEATGRASS, DOWNY BROME) INFESTED HABITATS ................................................................................................70 Introduction ....................................................................................................................70 Materials and Methods ..................................................................................................73 Site and Study Description .....................................................................................73 Herbicide, Fungicide, and Seeding Treatments .....................................................74 Vegetation Sampling ..............................................................................................75 Abundance of Pyrenophora semeniperda .............................................................76 Statistical Analysis .................................................................................................76 Results ...........................................................................................................................77 Weather ..................................................................................................................77 Pyrenophora semeniperda Prevalence ..................................................................78 Vegetation Density and Biomass ...........................................................................79 Discussion .....................................................................................................................86 Acknowledgements .......................................................................................................92 Literature Cited ..............................................................................................................93 4. ROLE OF TEMPERATURE ON EFFICACY OF PYRENOPHORA SEMENIPERDA AS A BIOLOGICAL CONTROL AGENT OF THREE DISTINCT, LOCALLY-ADAPTED POPULATIONS OF BROMUS TECTORUM L. (CHEATGRASS, DOWNY BROME) ..........................................................................99