ABSTRACT TAYLOR, MARY CLAIRE GARRISON. Mycophagous Soil Fauna for Biological Control of Soilborne Pathogenic Fungi in Greenhouse and Transplant Crops. (Under the direction of Shuijin Hu and H. David Shew). The objective of this project was to investigate the feasibility of using dairy cow compost as a soil amendment in conjunction with nematodes, collembolans, and mites as an alternative to chemical control for soilborne fungal pathogens and their diseases in greenhouse and transplant crop production systems. Three model systems were used; 1) Tomato attacked by Pythium ultimum, 2) Vinca and Impatiens attacked by Rhizoctonia solani, and 3) Bell pepper attacked by Phytophthora capsici. Five experiments total were conducted using three types of faunal treatments; 1) Nematode Aphelenchus avenae, 2) Collembolan (unidentified), and 3) Mite (unidentified) and three rates of dairy cow compost; 1) 4% by volume, 2) 8% by volume, and 3) 16% by volume. The fungal-feeding nematode Aphelenchus avenae can effectively suppress seedling damping-off caused by Pythium ultimum, Rhizoctonia solani, and Phytophthora capsici to a level equivalent to the standard fungicide treatment. Compost rate affects the disease suppression efficiency of the faunal treatments likely through impacting the mesofauna’s survival and growth in the seedling rhizosphere. Disease suppression capacity resulting from mesofauna may be extended to the field. Mycophagous Soil Fauna for Biological Control of Soilborne Pathogenic Fungi in Greenhouse and Transplant Crops by Mary Claire Garrison Taylor A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Plant Pathology Raleigh, North Carolina 2010 APPROVED BY: _______________________________ ______________________________ Shuijin Hu H. David Shew Committee Co-Chair Committee Co-Chair ________________________________ ______________________________ D. Michael Benson Frank J. Louws DEDICATION To Troy Ashton Taylor ii BIOGRAPHY The author was born in Virginia but spent most of her childhood in North Carolina. She was a class of 2006 Park Scholar at N.C. State and received her B.S. in Microbiology in December 2007. She and her husband met as graduate students in Plant Pathology at N.C. State. iii ACKNOWLEDGMENTS I would like to thank my co-advisors Dr. Shuijin Hu and Dr. H. David Shew, as well as my committee members Dr. D. Michael Benson and Dr. Frank J. Louws for all their time and hard work on my behalf during my time as a graduate student. I would also like to thank the other members of the Soil Ecology lab, Cong Tu, Lei Chen, and Liang Wang for their support. Dr. Barbara Shew hired me in my sophomore year to work as an undergraduate research assistant to work in the “peanut lab” so I have her to thank for introducing me to the world of Plant Pathology. Her graduate student, now Dr. Damon L. Smith, and research technician Joyce Hollowell, taught me more about peanut diseases than I ever really wanted to know! They were both also key in my decision to apply to graduate school in the NCSU Department of Plant Pathology and to them I also owe great thanks. The biggest thank you is of course owed to my parents. I can’t possibly mention everything I have to thank them for, because the magnitude is just too great. I love you Mom and Dad. iv TABLE OF CONTENTS LIST OF TABLES ……………………………………………………………… vii LIST OF FIGURES ……………………………………………………………... viii CHAPTER 1. SOIL BIOLOGICAL INTERACTIONS AND BIOLOGICAL CONTROL OF FUNGAL PATHOGENS IN GREENHOUSE CROP AND FIELD TRANSPLANT PRODUCTION SYSTEMS …………………...... 1 1.1 Greenhouse crop and field transplant production ……………………. 1 1.1.1 The scope of greenhouse and transplant crop production ………..... 1 1.1.2 Soilborne fungi in greenhouse systems ……………………………. 2 1.2 Soilborne fungal pathogens of plants and their biological control…… 3 1.2.1 Soilborne funal pathogens………………………………………….. 3 1.2.2 Biocontrol of soilborne fungal pathogens…………………………... 7 1.3 Soil food web interactions and biocontrol …………………………… 17 1.3.1 Soil mesofauna and soil food web interactions ……………………. 17 1.3.2 Soil mesofauna as biocontrol agents ………………………………. 23 1.4 Integrated biological control of fungal pathogens and diseases in greenhouse and transplant crops: Opportunities and challenges …….. 27 1.4.1 Fungal-feeding animals and soil amendments …………………….. 27 1.4.2 Biological control in greenhouse and transplant crops …………….. 28 1.4.3 Integrated biological control ……………………………………….. 29 1.4.4 The overall goal and specific objectives of this research ………….. 30 References ……………………………………………………………….. 31 CHAPTER 2. BIOLOGICAL CONTROL OF DAMPING-OFF DISEASES OF GREENHOUSE VEGETABLE CROPS AND BEDDING PLANTS …………... 42 2.1 Introduction …………………………………………………………… 42 2.1.1 Host-pathogen systems …………………………………………….. 43 2.1.2 The specific objective……………………………………………….. 45 2.2 Materials and methods …………………………………………........... 45 2.2.1 Preparation of inoculum of nematode Aphelenchus avenae and Pythium ultimum, and germination rates and pathogen inoculum rates……………………………………………………….. 45 2.2.2 The experimental design, treatments, and data collection ………….. 50 2.3 Results ………………….……………………………………………... 56 2.4 Discussion and conclusions………………………..………………….. 70 References ………………………………………………………………… 75 v CHAPTER 3. THE NEMATODE APHELENCHUS AVENAE AND MYCOPHAGOUS COLLEMBOLAN AND MITES AS CONTROL METHODS FOR BELL PEPPER SEEDLING DAMPING-OFF CAUSED BY PHYTOPHTHORA CAPSICI.................................................................................... 80 3.1 Introduction …………………………………………………………… 80 3.1.1 Bell pepper attacked by Phytophthora capsici and disease control…. 81 3.1.2 The specific objective ………………………………………………. 82 3.2 Materials and methods………………………………………………… 82 3.2.1 The preparation of nematode A. avenae, mycophagous collembolan and mites, and pathogen Phytophthora capsici, and determinations of germination rates and pathogen inoculum rates ………………….. 82 3.3 The experimental design, treatments, data collection and analysis …… 85 3.3.1 Experimental design ………………………………………………… 85 3.3.2 Experimental treatments……………………………………………... 86 3.3.3 Data collection …………………………………………..…………... 89 3.3.4 Statistical analysis …………………………………………………... 91 3.4 Results: ……………………………………………………………….. 91 3.4.1 Disease incidence and effects of treatments……………………….… 92 3.4.2 Effects of compost rate ……………………………………………… 94 3.4.3 Disease severity …………………………………………………….. 95 3.4.4 Pathogen activity ……………………………………………………. 96 3.4.5 Nematode populations ………………………………………………. 97 3.5 Discussion and conclusions …………………………………………… 99 References …………………………………………………………………. 103 vi LIST OF TABLES CHAPTER 1. SOIL BIOLOGICAL INTERACTIONS AND BIOLOGICAL CONTROL OF FUNGAL PATHOGENS IN GREENHOUSE CROP AND FIELD TRANSPLANT PRODUCTION SYSTEMS Table 1.1 Microbial diversity in soil ………………………………………. 19 CHAPTER 2. BIOLOGICAL CONTROL OF DAMPING-OFF DISEASES OF GREENHOUSE VEGETABLE CROPS AND BEDDING PLANTS Table 2.1 ANOVA table for both tomato trials……….…………………… 57 Table 2.2 Relative activity of Pythium ultimum in growth chamber microcosms amended with the nematode Aphelenchus avenae, drenched with the fungicide mefenoxam, or left untreated……………….... 62 Table 2.3 ANOVA table for the bedding plants trials…………………….... 64 CHAPTER 3. THE NEMATODE APHELENCHUS AVENAE AND MYCOPHAGOUS COLLEMBOLAN AND MITES AS CONTROL METHODS FOR BELL PEPPER SEEDLING DAMPING-OFF CAUSED BY PHYTOPHTHORA CAPSICI Table 3.1 ANOVA table for pepper seedlings transplanted to infested field soil ……………………………………………. 92 Table 3.2 Average percentage of seedlings with symptoms per week following transplant to infested field soil …………… 93 Table 3.3 Relative activity of Phytophthora capsici for pepper seedlings transplanted to infested field soil in microcosms amended with the nematode Aphelenchus avenae, drenched with the fungicide mefenoxam, mycophagous collembolan, mites, or left untreated …………… 97 vii LIST OF FIGURES CHAPTER 1. SOIL BIOLOGICAL INTERACTIONS AND BIOLOGICAL CONTROL OF FUNGAL PATHOGENS IN GREENHOUSE CROP AND FIELD TRANSPLANT PRODUCTION SYSTEMS Figure 1.1 Close-up picture of the mycelium of the basidiomycete soilborne pathogen Rhizoctonia solani showing the right angular branching and constrictions and cross-walls near junctions and the brown pigmentation that increases with age (EB Nelson, Cornell University) ………..………………... 5 Figure 1.2. Various biological interactions between pathogens and beneficial soilborne pathogens and their disease activities .…. 8 Figure 1.3. Soil mesofauna may play a major role in the suppression of soilborne pathogens and their disease activities .………....... 17 Figure 1.4. Diagram showing interactions between soil mesofauna and soil fungi ………………………………………………….. 24 CHAPTER 2. BIOLOGICAL CONTROL OF DAMPING-OFF DISEASES OF GREENHOUSE VEGETABLE CROPS AND BEDDING PLANTS Figure 2.1 Emergence of tomato seedlings in growth chamber microcosms: a) Trial 1 and b) Trial 2 …………………………. 59 Figure 2.2 Germination rates of tomato seeds as influenced by the rate of compost: a) Trial 1 and b) Trial 2 ………………..... 61 Figure 2.3 Average number of Aphelenchus avenae extracted from microcosms receiving the pathogen + nematode treatment, broken down by compost rate (%) in the second tomato trial ……………………………………………. 63 Figure 2.4 Disease incidence on vinca seedlings in greenhouse pots …….. 65 Figure 2.5 Disease incidence on impatiens seedlings in greenhouse pots ... 66 Figure 2.6 Disease incidence on vinca seedlings in greenhouse pots amended