The development of a crop, and therefore its health, is always the result of interplay between biological and environmental factors, as influenced by human agency. In other words, crop health is a highly complex affair. This book is concerned with only one group of agents affecting crop health, the pathogens, and not with animal pests or direct effects of physiological or weather factors. Even within this one group, however, the interaction of causal agents with environmental and biotic factors is highly complex. No less complex is the effect of cultural practices on the crop and its health. There is probably no major practice that does not affect diverse facets of crop growth, which in turn affects crop/pathogen relationships. Thus tillage se­ quentially affects depth and rate of root development, hence nutrient uptake, hence general plant size and habit as well as crop climate and crop susceptibility. Irri­ gation affects all these parameters, and facilitates crop growth under diverse macro­ climatic conditions, with all the ensuing implications for disease development. In this book an attempt is made to superimpose one set of complexities, the cul­ tural practices, on another such set, crop health. This may seem overambitious, not to say foolhardy, unless we remember that it has been done by farmers, consciously or unconsciously, ever since the beginnings of agriculture. We are here chiefly try­ ing to rationalize traditional practices, review modern research on the development of further practices, and assess the place of the latter in integrated disease control.

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1 Climate, Cropping and Crop Disease.- 1.1 Agro-Ecosystems, the Cultural Practices They Have Generated, and the General Impact of Such Practices on Crop Disease.- 1.1.1 Humid Agroclimates.- 1.1.1.1 The Humid Cool Temperate Agroclimates.- 1.1.1.2 The Warm Humid Temperate Agroclimates.- 1.1.1.3 The Wet Tropics.- 1.1.2 Dry Agroclimates.- 1.1.2.1 The Cool Dry Temperate Agroclimates.- 1.1.2.2 The Warm Dry Temperate Agroclimates.- 1.1.2.3 The Semi-Arid Tropical Agroclimate.- 1.1.3 Agroclimates and Crop Disease - Outlook for the Future.- 1.2 Microclimate and Crop Climate.- 1.2.1 The Microclimate as Affected by Topography and Soil.- 1.2.1.1 Topography.- 1.2.1.2 Soil.- 1.2.2 Crop Factors Interacting with Microclimate, and the Resultant Crop Climate.- 1.2.2.1 Density of Plant Cover (Canopy).- 1.2.2.2 Shade.- 1.2.3 When, Where and How Much Can Cultural Practices Influence the Crop Climate?.- 1.3 The Collective Approach to Disease Control: Epidemiological Considerations and the Role of Cultural Practices in Regional Management of Inoculum.- 1.3.1 The Cardinal Role of Inoculum and its Control for the Farming Community as a Whole.- 1.3.2 Various Crops Susceptible to the Same Pathogen - Which Crop is More Valuable to the Farming Community?.- 1.3.3 Crop Varieties Differing in Susceptibility - Dangers and Opportunities.- 1.3.4 Restricting Seasons, Locations and Growing Practices for Susceptible Crops.- 1.3.5 Minimizing Multiplication and Spread of Air- and Vector-Borne Inoculum.- 1.4 Soil, Soil Microbiota, and Soil-Borne Disease.- 1.4.1 Soil and the Growth of Underground Organs of the Crop.- 1.4.1.1 Texture and Depth.- 1.4.1.2 Soil Reaction.- 1.4.1.3 Soil Water.- 1.4.2 Soil Microbiota and Their Interaction with Soil-Borne Pathogens.- 1.4.2.1 Soil Microbiota Restricting Pathogen Development.- 1.4.2.2 Soil Microbiota Transmitting Plant Pathogens or Associated with Their Development.- 1.4.2.3 Plant Symbionts and Plant Pathogens.- 1.4.3 Suppressive or Resistant Soils.- 1.5 Stress, Strain and Predisposition.- 1.5.1 Types of Stress-Induced Strain.- 1.5.2 Temperature Strain.- 1.5.2.1 High-Temperature Strain.- 1.5.2.2 Low-Temperature Strain.- 1.5.3 Water Strain.- 1.5.3.1 Water Deficit Strain.- 1.5.3.2 Excess Water Strain.- 1.5.4 Other Strains.- 1.5.5 Combinations of Stresses and Strains.- 1.5.6 Charcoal Rot (Macrophomina phaseolina): Prototype of a Disease on Crops Under Stress.- 1.5.7 Summary of the Effects of Stress and Strain on Diseases Caused by Pathogens.- 1.6 Crop Age, Injury and Disease on Leaf and Fruit, with Special Reference to Disease in the Ageing Crop.- 1.6.1 Germination to Pre-Maturation of the Crop.- 1.6.1.1 Seedling and Early Growth Stage.- 1.6.1.2 Flowering or Full Vegetative Growth Stage.- 1.6.2 Maturation and Senescence.- 1.6.2.1 Physiological Changes.- 1.6.2.2 Changes in Crop Climate.- 1.6.2.3 Injury and Wound Parasites.- 1.6.2.4 The Time Element and the Mounting Inoculum.- 1.6.2.5 Disease in Ageing Tree Crops.- 1.6.2.6 The Ageing Crop as Source of Inoculum for its Neighbours.- 1.6.2.7 Disease Control in the Ageing Crop.- 1.6.2.8 Botrytis cinerea - a Pathogen of Soft and Senescent Tissues.- 1.7 Weeds and Crop Disease.- 1.7.1 Which Pathogens Spread and Survive Through Weeds?.- 1.7.2 Weeds Particularly Apt to Endanger Crop Health.- 1.7.3 Effects of Cultural Practices on Weeds as Related to Disease Control.- 2 Major Cultural Practices and Their Effect on Crop Disease.- 2.1 Cost/Benefit and Risk Assessment and the Complexity of Multiple Choice in Pest Control Decisions on the Farm.- 2.1.1 Cost/Benefit Assessment.- 2.1.2 Risk Assessment.- 2.1.3 The Complexity of Multiple Choice in Pest Control Decisions.- 2.2 Sanitation.- 2.2.1 Aims and Limitations of Sanitation.- 2.2.2 Preventing the Introduction of Inoculum.- 2.2.2.1 Propagating Material.- 2.2.2.2 Irrigation and Drainage Water That Spreads Inoculum.- 2.2.2.3 Inoculum Introduced in Plant Debris, Compost and Manure.- 2.2.2.4 Inoculum Introduced and Spread by Equipment and Man.- 2.2.3 Elimination of Living Plants That Carry Pathogens.- 2.2.3.1 Additional and Alternate Hosts.- 2.2.3.2 Groundkeepers and Volunteers.- 2.2.3.3 Roguing.- 2.2.3.4 Removal of Diseased but Living Parts from Trees.- 2.2.4 Destruction or Inactivation of Inoculum Deriving from Dry Plant Matter and Debris.- 2.2.4.1 Sanitation of Diseased Trees.- 2.2.4.2 Removal of Crop Debris or its Incorporation in the Soil.- 2.2.4.3 Burning or Flaming Crop Residue.- 2.2.4.4 Flooding Fields and Orchards.- 2.2.4.5 Disinfestation of Soil by Heat.- 2.3 Crop Sequence.- 2.3.1 Aims of Crop Sequence Management.- 2.3.2 Economic Considerations.- 2.3.3 Choice of Crop Sequence in Relation to Other Farming Practices.- 2.3.4 The Benefits of Fallowing.- 2.3.5 What Are the Chances of Improving Crop Health by Management of Crop Sequence?.- 2.3.5.1 The "Heritage" of the Preceding Crop.- 2.3.5.2 Survival of Pathogens Outside Crop Debris.- 2.3.5.3 Survival and Multiplication of Inoculum by Aid of Non-Hosts.- 2.3.5.4 Use of Varieties Resistant and Seasons Unfavourable to the Pathogens.- 2.3.6 Monoculture.- 2.3.6.1 Irreversible Disease Pattern.- 2.3.6.2 Reversible Disease Pattern.- 2.3.7 Multiple Cropping.- 2.3.7.1 The Benefits of Multiple Cropping.- 2.3.7.2 Multiple Cropping of Field and Vegetable Crops.- 2.3.7.3 Intercropping in Orchards and Plantations.- 2.3.8 Decoy and Trap Crops.- 2.3.9 Crop Sequence and Crop Disease in the Future.- 2.4 Soil Amendments and Mulches.- 2.4.1 Organic Amendments.- 2.4.1.1 Effects on Soil and Water Relations.- 2.4.1.2 Effects on Pathogens.- 2.4.1.3 Practical Application of Soil Amendments.- 2.4.2 Organic Mulches.- 2.4.2.1 Effects on Soil Temperature and Retention of Precipitation.- 2.4.2.2 Stubble Mulch and Cereal Debris in Relation to Cereal Diseases.- 2.5 Tillage.- 2.5.1 The Aims of Tillage.- 2.5.2 Tillage to Prepare Land for Sowing and Planting.- 2.5.2.1 Depth of Soil Favourable to Root Growth.- 2.5.2.2 Distribution of Inoculum in the Soil Profile and Over the Field.- 2.5.2.3 The Diverse Effects of Non-Tillage.- 2.5.2.4 Tillage Practices as Affecting Cereal Diseases in England.- 2.5.3 Topsoil Management.- 2.5.3.1 Shaping the Topsoil and Earthing-Up (Hilling).- 2.5.3.2 Elimination of Soil Crusts.- 2.5.4 Tillage as a Control Practice.- 2.5.4.1 Destruction of Weeds and Volunteer Plants Between Successive Crops.- 2.5.4.2 Weed Control While the Crop Grows.- 2…