Experimental Techniques in Plant Disease Epidemiology

I General Techniques.- 1. Experiments and Procedures in Epidemiological Field Studies.- 1 Introduction.- 2 Planning and Conduct of Field Experiments.- 2.1 Formulation of the Hypothesis and Selection of Variables.- 2.2 Single-Plot Field Experimentation.- 2.3 Sampling in Single-Plot Experiments.- 2.4 Data Acquisition and Handling.- 2.5 Experimental Error.- 3 Combination of Field and Growth Chamber Experiments in Studying Epidemiological Problems.- 3.1 Examples for the Combination of Field and Growth Chamber Experiments.- 3.1.1 Manipulating the Pathogen.- 3.1.2 Manipulating the Host - The Use of Trap Plants.- 3.1.3 Manipulating the Environment.- 3.2 Conclusions.- 4 References.- 2. Techniques of Controlled-Condition Experiments.- 1 Introduction.- 2 The Controlled Habitat.- 2.1 Light.- 2.2 Temperature.- 2.3 Humidity.- 2.4 Free Leaf Moisture.- 2.5 Relation of the Controlled Habitat to the Field Habitat.- 3 The Choice of Hosts and Pathogens.- 3.1 The Ideal Host.- 3.2 The Ideal Pathogen.- 3.3 Relation of the Reaction of Hosts and Pathogens Under Controlled Conditions to Their Reaction in the Field 23.- 4 Types of Controlled-Condition Experiments.- 4.1 Monocyclic Experiments: Inoculation, Infection and Colonization, Sporulation.- 4.1.1 Inoculation.- 4.1.2 Infection and Colonization.- 4.1.3 Sporulation.- 4.2 Polycyclic Experiments.- 4.3 Auxiliary Experiments.- 4.4 Relation of Results Obtained Under Controlled Conditions to Results Obtained in the Field.- 5 Preparation of Data for Simulation.- 6 Epilogue.- 7 References.- II Measurement and Their Analysis.- 3. Measuring Plant Disease.- 1 Introduction.- 2 About Terms.- 3 Sources of Error in Disease Assessment.- 3.1 Individual Errors.- 3.2 Object-Dependent Errors.- 4 Sampling Techniques for Disease Assessment.- 5 Techniques used in Measuring Disease.- 5.1 Actual Measurement of Disease Intensity.- 5.2 Use of Keys, Standard Diagrams and Classes of Disease Intensities.- 5.3 Use of Incidence Values to Estimate Severity Values.- 5.4 Automatic Measurement and Remote Sensing.- 5.5 Measurement of Disease Intensities Through Spore Catches.- 6 Specific Applications of Disease Measurement.- 6.1 Crop Measurement.- 6.2 Assessment of Several Diseases in the Same Sampling Unit.- 6.3 Disease Assessment for Models and Forecasts.- 6.4 Differences Between Disease Assessment on Shoot and Root Diseases.- 6.5 Some Implications in Disease Assessment for Crop Losses.- 6.6 Measuring Disease in Surveys.- 7 References.- 4. The Measurement and Analysis of the Effects of Crop Development on Epidemics.- 2 The Dynamic Interaction of Host and Pathogen.- 2.1 The Pathogen Affects the Host.- 2.1.1 Plant Growth Dynamics and Loss of Photosynthetic Tissue.- 2.1.2 Growth Stimulation Caused by Disease.- 2.2 The Host Affects the Pathogen.- 2.2.1 Host Susceptibility.- 2.2.2 New Tissue.- 2.2.3 Plant-Altered Environment.- 3 Measurement and Analysis of Host Development.- 3.1 Physiological Time.- 3.2 Host Phenology.- 3.3 Measurements for Growth Analysis.- 4 Measuring the Dynamic Interaction.- 4.1 Measuring Time- and Space-Dependent Susceptibility.- 4.2 Measuring Disease in the Presence of Changing Host Tissue.- 4.2.1 Increases in the Amount of Susceptible Tissue.- 4.2.2 Decreases in the Amount of Susceptible Tissue.- 5 Analysis of the Dynamics Interaction.- 5.1 Analysis of Changing Susceptible Host Tissue.- 5.2 Analysis of Changing Asymptotes.- 5.3 Analysis by Simulation.- 6 Considerations and Modifications of Techniques for the Interaction of Perennial Crops.- 6.1 Survival Strategy of Perennials.- 6.2 Size of Perennials.- 6.3 Time-Dependent Susceptibility of Perennials.- 6.4 Sampling and Assessment of Perennials.- 7 Summary and Conclusions.- 8 Acknowledgments.- 9 References.- 5. Quantitative Assessment of Inoculum Production, Dispersal, Deposition, Survival and Infectiousness in Airborne Diseases.- 1 Introduction.- 2 Production, Dispersal and Buildup of Inoculum.- 2.1 Trapping Spores in the Air.- 2.2 Collecting Spores from Leaves.- 3 Survival and Infectiousness.- 3.1 Survival of Overseasoning Inoculum.- 3.2 Survival of Inoculum in the Season.- 3.3 Survival of Spores on Plants Under Controlled Conditions.- 3.4 Survival of Detached Spores Under Controlled Conditions.- 3.5 Techniques for Testing the Effects of Radiation.- 4 Testing Inoculum Potential with Potted Trap Plants.- 5 Epilogue.- 6 References.- 6. Analysis of the Spatial Pattern of Soilborne Pathogens.- 1 Introduction.- 2 Objectives and Requirements for the Analysis of Spatial Pattern of Soilborne Pathogens.- 2.1 Metameters for Measurement of Spatial Pattern.- 2.2 Definable Entities for Inoculum, Infection and Disease.- 2.3 Sampling Units and Sampling Method.- 3 Analysis of Unmapped Data.- 3.1 Goodness-of-Fit to Probability Functions.- 3.2 Indices of Aggregation.- 4 Analysis of Mapped Data.- 4.1 Analysis of Dichotomous Data.- 4.1.1 Transects.- 4.1.2 Transects Across Diffuse Clumps of Disease.- 4.1.3 Disease Mosaics.- 4.1.4 Two-Dimensional Lattice Maps.- 4.2 Analysis of Discrete and Continuous Variables.- 5 References.- 7. Electronic Monitoring and Use of Microprocessors in the Field.- 1 Introduction.- 2 Environmental Data Acquisition Systems.- 2.1 Data Recording.- 2.2 Data Communication.- 3 Monitoring Weather Variables.- 3.1 Temperature.- 3.2 Environmental Water.- 3.2.1 Atmospheric Humidity and Water Potentials.- 3.2.2 Liquid Water on Living Foliage and Fruits.- 3.2.3 Wetness of Dead Tissues.- 3.2.4 Rain.- 3.3 Wind.- 3.4 Irradiance.- 4 Monitoring Soil Variables.- 4.1 Soil Temperature.- 4.2 Soil Water.- 5 Monitoring Sites.- 6 References.- 8. The Analysis of Weather Factors in Epidemiology.- 1 Introduction.- 2 Some Practical Hints for the Monitoring of Weather Factors.- 3 Techniques in Use for the Analysis of Biometeorological Data.- 3.1 Temperature.- 3.1.1 Mean Temperatures and Daily Course of Temperature.- 3.1.2 Frequency of Temperatures.- 3.1.3 Temperature Sums.- 3.1.4 Temperature-Response-Functions.- 3.2 Humidity.- 3.2.1 Relative Humidity.- 3.2.2 Duration of Wetness.- 3.3 Temperature-Humidity Combination.- 3.4 Precipitation.- 3.5 Wind and Turbulence.- 3.6 Light and Radiation.- 4 Estimation of Missing Micrometeorological Data.- 5 Epilogue.- 6 References.- III Special Topics.- 9. The Analysis of Effects of Control Measures on the Development of Epidemics.- 1 Introduction.- 2 Epidemiological Principles of Control.- 3 Analysis of the Effect of Sanitation.- 3.1 The Sanitation Ratio.- 3.2 An Alternative Hypothesis for the Effect of Sanitation.- 3.3 Methods to Test the Effect of Sanitation.- 3.4 Other Considerations of Sanitation on the Epidemic.- 4 Analysis of Effects of Control Measures on Epidemic Rate.- 4.1 Methods.- 4.2 Analysis of Disease Progress.- 4.3 Disease Progress After a Single Application of a Fungicide.- 4.3.1 The Theoretical Disease-Progress Curve.- 4.3.2 The Actual Disease-Progress Curve..- 4.3.3 Prediction of the Increase in Disease.- 5 Epilogue.- 6 References.- 10. How to Conduct and Measure Fungicide Resistance.- 1 Introduction.- 2 Measurement of Resistance.- 2.1 Principles.- 2.2 Use of Artificial Media.- 2.3 Use of Living Plant Material.- 3 Estimation of Resistance Risk.- 3.1 Emergence of Resistance on Agar Medium.- 3.2 Fitness and Buildup of Resistance in the Field.- 3.3 Use of Models.- 4 Detection and Monitoring of Resistance in the Field.- 4.1 Sampling.- 4.2 Handling and Processing of Samples.- 4.3 Recording and Interpretation of Results.- 5 Epilogue.- 6 References.- 11. Analysis of Virulence in Pathogen Populations.- 1 Introduction.- 2 Methods of Virulence Analysis.- 2.1 Sampling the Population.- 2.1.1 Sampling Techniques.- 2.1.2 Sample Size.- 2.1.3 Frequency and Timing of Sampling.- 2.2 Testing the Sample.- 2.2.1 Design of Virulence Tests.- 2.2.2 Reading Infection Types or Counting Colonies.- 2.2.3 Measuring Agressiveness.- 2.3 Analyzing the Data.- 2.3.1 Virulence Frequencies and Associations.- 2.3.2 Race Designation.- 2.3.3 Measuring Virulence and Race Dynamics.- 2.3.4 Measuring Pathogen Diversity.- 3 References.- 12. Analysis of Epidemiological Components in Yield Loss Assessment.- 1 Introduction.- 2 Components Analysis in Yield Loss Assessment.- 2.1 Analysis of the Disease Progress Curve (DPC).- 2.2 Relating DPC Components to Empirical Loss Models.- 3 Components Analysis in Crop Loss Assessment.- 3.1 The Problem of Scale and Aggregation.- 3.2 Crop-Pest Loss Models.- 4 Concluding Remarks.- 5 References.- 13. How to Develop Plant Disease Forecasters.- 1 Introduction.- 2 Fundamental Forecasting Systems.- 2.1 Infection.- 2.1.1 Experimental Procedures.- 2.1.2 Data Analysis.- 2.1.3 Other Physical Factors and Nonconstancy.- 2.1.4 Vectors.- 2.1.5 Inoculum Level.- 2.2 Other Disease Cycle Components.- 3 Empirical Forecasting Systems.- 3.1 Single Season Predictions.- 3.1.1 Qualitative Development of Forecasters Based on Weather.- 3.1.2 Qualitative Development of Forecasters Based on Disease Intensity.- 3.1.3 Quantitative Development of Forecasters.- 3.2 Multiple Season Predictions.- 3.2.1 Qualitative Development.- 3.2.2 Quantitative Development.- 3.3 Combining Fundamental and Empirical Forecasting Systems.- 4 Field Testing.- 5 Implementation - Delivery and Operation.- 6 Summary and Conclusions.- 7 References.- 14. Techniques for Studying Aphid-Borne Virus Epidemiology.- 1 Introduction.- 2 Detecting Plant-Pathogenic Viruses in Plant and Vector Hosts.- 2.1 Visual Inspection of Infected Plants.- 2.2 Laboratory Procedures for Detecting Viruses in Plants and Vectors.- 2.3 Indexing for Disease Progress in the Field.- 2.4 Indexing Incoming Infection in the Field.- 3 Sources of Plant-Pathogenic Viruses.- 4 Assaying for Vector Potential.- 4.1 Laboratory Assays.- 4.2 Field Live Assays.- 5 Vector Potential.- 5.1 Vector Abundance and Activity.- 5.2 Monitoring Movement and Host-Seeking Activity.- 6 Epilogue.- 7 References.- 15. Techniques in Quantitative Nematology.- 1 Introduction.- 2 Nematode Community characteristics.- 2.1 Spatial and Temporal Population Patterns.- 2.2 Sampling.- 3 Role of Laboratory and Greenhouse Research.- 4 Use of Artificial Infestations in Fields.- 5 Utilizing Natural Field Infestation.- 5.1 Exploitation of Contagious Spatial Patterns.- 5.2 Means of Establishing Ranges of Population Densities.- 5.3 Following an Epidemic over Prolonged Periods.- 6 Modeling Approaches for Nematode-Induced Epidemics.- 6.1 Simple Population Models.- 6.2 Collecting Data to Derive Models.- 6.3 Formulating the Models.- 6.4 Validation.- 7 Epilogue.- 8 References.- 16. Use of Geophytopathological Information.- 1 Introduction: Definitions - Objectives.- 2 Data Collection.- 3 Data Documentation.- 4 Ecological Interrelationships.- 5 Forecasting.- 6 References.- 17. Monitoring and Mapping Long-Distance Spread of Plant Pathogens.- 1 Introduction.- 2 Factors that Facilitate Long-Distance Dispersal and Deposition.- 3 Methodology of Monitoring.- 3.1 Ground Surveys.- 3.2 Monitoring Dispersal from the Air.- 3.2.1 Monitoring the Synoptic Situation.- 3.2.2 Use of Weather Satellites.- 3.2.3 Validation of Disease by LANDSAT.- 3.3 Future Trends in Aerial Reconnaissance.- 4 References.- IV The Synopsis of Experimental Results.- 18. Modeling Epidemics of Root Diseases and Development of Simulators.- 1 Introduction.- 2 Scope, Purpose, and Types of Models in Plant Disease Epidemiology.- 3 Systems Analysis in Plant Pathology.- 4 Simulation Modeling and General System Theory.- 5 Simulation Models for Root Diseases.- 5.1 Primary Infection.- 5.2 Colonization and Inoculum Production.- 5.3 Effects of Colonization on Plant Growth and Yield.- 5.4 Secondary Infection.- 6 Interfacing Epidemiological Models with Crop and Single Plant Growth Models.- 7 References.- 19. Modelling Epidemics of Polycyclic Foliar Diseases and Development of Simulators.- 1 Introduction.- 2 Modelling of Polycyclic Epidemics.- 2.1 Objectives of Modelling Epidemics.- 2.2 Steps in Modelling Epidemics.- 2.2.1 Restriction of Models.- 2.2.2 Approaches to Modelling.- 2.2.2.1 The Analytic Approach.- 2.2.2.2 The Synthetic Approach.- 2.2.3 Experimentation.- 2.2.4 Development of Models.- 2.2.5 Testing of Models.- 2.2.6 Implementation and Application of Models.- 3 Combination of Models.- 3.1 Combination of Crop Growth and Plant Disease Models.- 3.2 Combination of Epidemiological Models.- 4 Concluding Remarks.- 5 References.- 20. The Methodology of Comparative Epidemiology.- 1 Introduction.- 2 Some Basic Aspects of Comparative Epidemiology.- 2.1 The General Framework.- 2.2 Terminology.- 2.3 Published Evidence as Data Base for Comparison.- 3 Comparative Experiments.- 3.1 The Scope.- 3.2 The Criteria.- 3.2.1 Comparison of the Pathosystems and Population Levels.- 3.2.2 Comparison of Epidemics, Their Behaviour and Patterns.- 3.2.3 Comparison of Soilborne Diseases and their Epidemics.- 3.2.4 Comparison at the Community Level.- 4 Tools and Procedures in Comparative Epidemiology.- 4.1 Data Reduction and Curve Approximation.- 4.2 Use of Coefficients and Multivariate Statistical Methods.- 4.3 Use of Computers in Comparison.- 5 Conclusions.- 6 References.