Plant Diseases

ContentsPrefaceChapter 1 The Control of Plant Disease Studied as Part of Epidemiology 1.1. The Population of Pathogens 1.2. Epidemics and Biological Warfare 1.3. The Language of Epidemiology. Some Expressions 1.4. A Suggested Order of Reading the Chapters 1.5. The Spread of Disease and Its Bearing on the Technique of Field Experiments Chapter 2 About Interest on Money. Logarithmic Increase Summary 2.1. Interest is Proportional to Initial Capital 2.2. Interest per Cent and Interest per Unit 2.3. Simple Interest 2.4. Discontinuous Compound Interest 2.5. Continuous Compound Interest 2.6. Continuous Compound Interest Seen in Another Way 2.7. Equivalent Rates of Continuous and Discontinuous Compound Interest 2.8. Variable Rates of Continuous Compound Interest 2.9. Consistent Units of Time 2.10. Natural Logarithms 2.11. Logarithmic Increase Exercises Chapter 3 The Logarithmic and the Apparent Infection Rates Summary 3.1. Statement of the General Problem of This Book 3.2. The Intermittent Increase of Disease 3.3. The Percentage and the Proportion of Disease 3.4. Logarithmic Increase of Disease and Increase That Is Not Logarithmic 3.5. The Meaning of Infection Rates 3.6. The Words, "per Unit," Again ExercisesChapter 4 How to Plot the Progress of an Epidemic Summary 4.1. The Increase of Disease with Time 4.2. Two Ways in Which Disease Can Increase with Time."Compound Interest Disease'* and "Simple Interest Disease" 4.3. Increase of Disease by Multiplication. "Compound Interest Disease" 4.4. The Increase of Disease without Multiplication. "Simple Interest Disease" 4.5. The Correction Factor (l — x) 4.6. The Reason for Using Log [1/(1 - x)] When There is No Multiplication Exercises EpilogueChapter 5 The Basic Infection Rate Summary 5.1. The Basic Infection Rate and the Latent Period 5.2. The Incubation Period 5.3. Some Biological Meanings 5.4. The Early Stages of Artificially Induced Epidemics of Stem Rust of Wheat 5.5. The Relation between r and R 5.6. How R Changes as an Epidemic Progresses 5.7. The Relation between r1 and R 5.8. The Products pr1, pr, and pR 5.9. The Limit to the Explosiveness of an Epidemic 5.10. A Discontinuous Infection Model 5.11. Period of Infection is Reduced to a Point Each Year and p is 1 Year Exercises Chapter 6 The Latent Period Summary 59 6.1. Logarithmic Increase of Infection with p and R Constant 6.2. The Variation of n with Time, with p and R Constant 6.3. The Variation of r{ at an Average Value over an Interval of Time 6.4. The Effect of a Prolonged Period of Inoculation on the Variation of r1 6.5. The Effect of Variation of the Latent Period p on the Variation of r1 6.6. A Wider Interpretation of r1 6.7. The Error from Using a Constant Mean Value p in Eq. (5.7) Instead of a Constant Value p 6.8. Increase of Infection beyond the Logarithmic Phase with p and R Constant 6.9. The Estimation of n after the Logarithmic Stage of an Epidemic 6.10. Three Arbitrary Stages in an Epidemic Exercise Chapter 7 Average Values of Infection Rates. Increase of Populations of Lesions and of Foci. Independent Action of Propagules Summary 7.1. The Relative Infection Rate as an Average 7.2. The Logarithmic Infection Rate 7.3. The Growth of an Individual Lesion in Relation to the Growth of a Population of Lesions 7.4. The Growth of Foci 7.5. The Spread of Pathogens in Relation to the Focal Pattern 7.6. The Growth of an Individual Focus in Relation to the Growth of a Population of Foci 7.7. The Mass Increase of Foci 7.8. Massed Foci of Potato Blight. The Epidemic S 7.9. The Independent Action of Propagules. The General Problem 7.10. The Independent Action of Propagules. Puccinia graminis. Phytophthora infestons, and Some Other PathogensChapter 8 Corrected Infection RatesSummary 8.1. Correction of n and r for the Growth of the Host Plants 8.2. Correction for Removals 8.3. Relation between the Corrected Basic Infection Rate Re and r 8.4. Balance in Epidemics 8.5. Relation between Rc and r1 8.6. A Threshold Theorem 8.7. The Threshold Theorem and Control of Disease by Fungicides 8.8. The Threshold in Epidemics of Two Systemic Diseases 8.9. Looking Back Exercises and Examples Chapter 9 Stochastic Methods in Epidemiology Summary 9.1. Transforming Proportions of Disease 9.2. Sampling Errors of Estimates of Infection Rates 9.3. Deterministic and Probability Methods in Epidemiology 9.4. Multiple Infections with Systemic Disease 9.5. The Overlapping of Local Lesions 9.6. The Influence of Numbers 9.7. Comparisons with Medical Epidemiology Chapter 10 A Guide to the Chapters on Control of Disease 10.1. The General Proposition 10.2. Control Measures That Reduce xo: Sanitation, Vertical Resistance, and Chemical Eradication 10.3. Control Measures That Reduce r: Horizontal Resistance and Protectant Fungicides Chapter 11 Sanitation with Special Reference to Potato Blight Summary 11.1. A Definition of Sanitation 11.2. How the Infection Rate Affects the Benefit from Sanitation 11.3. The Effect of the Sanitation Ratio 11.4. The Effect of Sanitation on Disease after the Logarithmic Phase 11.5. The Use of Eqs. (11.1) and (11.2) when Disease Is in Foci 11.6. Phytophthora infestans from Potato Cull Piles 11.7. Focal Outbreaks and General Epidemics of Potato Blight 11.8. The Change from Focal Outbreaks to General Epidemics 11.9. The Delay of the General Epidemic as a Result of Destroying Cull Piles 11.10. Cull Piles and Blight Forecasts 11.11. The Increase in Yield as a Result of SanitationChapter 12 Sanitation with Special Reference to Wheat Stem Rust Summary 12.1. Potato Blight and Wheat Stem Rust Contrasted and Compared 12.2. Stem Rust and Barberry Eradication 12.3. Focal Outbreaks and General Epidemics of Wheat Stem Rust 12.4. Barberry Eradication and Wheat Stem Rust in Northwestern Europe 12.5. The Relation between Sanitation and the Percentage of Stem Rust in Ripe Fields 12.6. The Reduction by Sanitation of Loss in Yield 12.7. The Relation between Loss of Yield and the Area under Stem Rust Progress Curve 12.8. The Infection Rate in Relation to Benefits Gained from Sanitation 12.9. Potato Blight and Wheat Stem Rust Compared Again Chapter 13 Sanitation and Two Systemic Diseases. Sanitation when Other Things Are Not Equal Summary 13.1. Common Bunt of Wheat and Fuearium Wilt of Tomatoes 13.2. The Relation between the Number of Spores and Infection of Wheat by Bunt 13.3. The Relation between the Number of Spores and Infection of Tomatoes with Fusarium Wilt 13.4. The Effect of Sanitation on Disease of the "Simple Interest" Type 13.5. The Benefit of Reducing Systemic Disease by Sanitation 13.6. Dependability of Sanitation as a Method of Disease Control in Relation to rt 13.7. Sanitation in Relation to the Absolute Amount of Initial Inoculum 13.8. A Comparison between "Simple Interest" and "Compound Interest" Disease in Relation to Sanitation 13.9. Two Kinds of Initial Inoculum Exercise Chapter 14 Vertical and Horizontal Resistance against Potato Blight Summary 14.1. The Relation between Races of Phytophthora infestons and Resistance Genes in the Potato 14.2. The Mutability of Races of Phytophthora infestons 14.3. Vertical and Horizontal Resistance 14.4. The Unimportance of Vertical Resistance in Varieties without R Genes 14.5. The Distribution of Races 14.6. The Effect of Popularity on the Behavior of R-Types toward Blight 14.7. The Place of Vertical and Horizontal Resistance in Epidemiology 14.8. Analysis of Kirste's Findings: the Effect of Vertical Resistance 14.9. Analysis of Kirste's Findings: the Effect of Horizontal Resistance 14.10. Other Evidence for a Difference in Horizontal Resistance 14.11. Some Published Assessments of Blight Resistance 14.12. The Vertifolia Effect 14.13. Blight on Solanum demissum 14.14. Blight on Mixtures of Clones 14.15. What Vertical Resistance Implies 14.16. The Manifestations of Horizontal Resistance 14.17. The Quantitative Determination of Horizontal Resistance when There Is Also Vertical Resistance 14.18. The Deficiency of Horizontal Resistance in Commercial Varieties 14.19. Breeding Potato Varieties for Resistance to Blight Chapter 15 A Note on the History of Stem Rust Epidemics in Spring Wheat in North America Summary 15.1. The Problem in the Spring Wheat Area of North America 15.2. Some Early History 15.3. Waldron's Evidence 15.4. The Evidence of Stakman and Fletcher 15.5. The First Class Epidemics 15.6. Some Conclusions Chapter 16 Plant Disease in Biological Warfare Summary 16.1 Epidemics as Explosives 16.2. Vertically Resistant Crops as a Target 16.3. Wheat Stem Rust as an Example 16.4. Stem Rust Races that Can Overcome Vertical Resistance 16.5. Weather Adverse to Epidemics 16.6. Horizontal Resistance for Defense 16.7. Horizontal Resistance to Stem Rust 16.8. Quantitative Interpretation of the Evidence 16.9. The Transition Exercise Chapter 17 The Bases of Vertical Resistance Summary 17.1. Introduction 17.2. The Different Response of Horizontal and Vertical Resistance to Diversity of Varieties 17.3. The Dependence of Vertical Resistance on Varietal Diversity 17.4. A Reason Why Vertical Resistance Is Commonly Chosen to Protect Varieties 17.5. Diversity and Novelty 17.6. The Fitness of Simple Races on Simple Varieties 17.7. Evidence for Stabilizing Selection of Simple Races of Puccinia graminie tritici 17.8. Vertical Resistance without Novelty 17.9. Natural Stability in Vertical Resistance Chapter 18 General Resistance against Disease Summary 18.1. General Resistance 18.2. Results of Troutman and Fulton and of Holmes 18.3. The Commonness of Resistance 18.4. The Need to Stress Affinities 18.5. The Search for General Resistance Chapter 19 The Choice of Type of Resistance Summary 240 19.1. The Aims of Plant Breeding 19.2. The Difficulty about Generalizing 19.3. The Usual Preference for Vertical Resistance 19.4. The Case for Vertical Resistance 19.5. The Possibility of Improving Vertical Resistance 19.6. The Choice of Horizontal Resistance when There Has Been a Record of Varietal Change 19.7. The Choice of Horizontal Resistance when rt Is High 19.8. The Choice of Horizontal Resistance when There Is Danger of a Vertifolia Effect 19.9. The Choice of Horizontal Resistance when There Is Danger of Biological Warfare 19.10. The Choice of Horizontal Resistance when Fungicides Are Used Chapter 20 The Quantitative Effect of Horizontal Resistance Summary 20.1. The Components of Horizontal Resistance 20.2. Changing the Basic Infection Rate 20.3. A Return to Tables 16.3 and 16.4 20.4. Relative Insensitivity of the Apparent Infection Rate to Change when the Basic Rate Is High 20.5. The Effect of a Change of the Latent Period on the Apparent Infection Rate 20.6. The Effect of Removals on the Apparent Infection Rate 20.7. The Effect of Resistance 20.8. The General Simplification Chapter 21 Control of Disease by Fungicides Summary 21.1. The Fungicide Square 21.2. Laboratory and Glasshouse Experiments with Phytophthora infestans 21.3. The Performance of Fungicides against Potato Blight in the Field 21.4. Citrus Black Spot and Apple Scab 21.5. The Calculated Effect of Horizontal Resistance or Adverse Climate on the Degree of Fungicidal Activity Needed 21.6. Other Calculated Effects 21.7. Variable Results with Fungicides and the Need for Recording 21.8. The Timing of Application of Protectant Fungicides 21.9. Eradicant Fungicides in Relation to the Infection Rate 21.10. The Fungicide Frontier 21.11. The Forgotten Factor Chapter 22 How Disease Spreads as It Increases Summary 22.1. Increase and Spread of Disease 22.2. The Spread of Wheat Stem Rust 22.3. The Spread of Potato Blight 22.4. Wheat Stem Rust and Potato Blight Contrasted Again 22.5. The Flattening of Gradients 22.6. Increasing Disease and Increasing Scale of Distance of Spread 22.7. The Behavior of Populations of Pathogens and of Individual Propagules; the Disease Triangle Chapter 23 The Cryptic Error in Field Experiments Summary 23.1. Errors of Representation in Results from Plots in a Field Experiment 23.2. An Experiment with Tomato Fruit Diseases 23.3. An Experiment with Leaf Rust of Wheat 23.4. An Experiment with Stem Rust of Wheat and Rye 23.5. The Deposition of Spores 23.6. Some Calculations for Potato Blight 23.7. Large's Observations on Potato Blight 23.8. The Inadequacy of Guard Rows in Conventional Designs 23.9. The Gradient Fallacy 23.10. The Gradient Fallacy Illustrated 23.11. The Cryptic Error 23.12. Where the Onus of Proof Lies 23.13. The Error when Unsprayed Plots Represent Unsprayed Fields 23.14. The Loss of Air-borne Spores from Plots and Fields 23.15. The Movement of Spores between Plots within an Experimental Area 23.16. The Effect of the Size of Plot 23.17. The Effect of Shape of Plot 23.18. Interference between Plots 23.19. Different Types of Experiment 23.20. The Screening and Ranking of Fungicides in the Field 23.21. Quantitative Comparison of Fungicide Treatments 23.22. Experiments with Plots That Differ Greatly in Disease 23.23. Variety Trial 23.24. The Conservative Error Theory 23.25. The Field Side of the Story Appendix ReferencesAuthor Index Subject Index