Interrelationships of plant health and the sustainability of agriculture, with special reference to plant diseases

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Abstract
U.S. crops have the potential routinely to produce 15–25% more, and in some cases 100% more, with no more water or fertilizer, but are prevented from doing so by diseases, nematodes, arthropod pests, and weeds. It is not compatible with the goals of a sustainable agriculture to fertilize, cultivate, and water for maximum production, but then allow diseases and pests to limit actual yields to some fraction of what was paid for with the capital investments and agronomic inputs. In eastern Washington and adjacent northern Idaho (The Palouse), wheat generally yields 4,800–6,200 kg/ha in years of normal precipitation (45–55 cm), but yields 6,900–9,000 kg/ha with the same water and fertilizer if the soil is fumigated to eliminate root disease organisms and weeds, and the plants are protected from rusts, pseudocercosporella foot rot, and aphids. Some practical alternatives to soil fumigation (depending on the value of the crop) include crop rotation, tillage, flooding the soil, heating the soil (using clear plastic tarp or by burning residue on the soil surface), and organic amendments that intensify the biological stresses on pathogen propagules in soil. Other disease controls include using pathogen-free planting material, maintaining a diversity of genetic resistance, and adjusting planting date and method of seeding to escape pathogens. Some of the emerging technologies include improved serological and molecular methods for diagnosing pathogens, microorganisms that kill pathogen propagules in soil or protect the plant, simulation models of epidemics to forecast disease outbreaks, and integrated pest management systems. Better experimental a pproaches are needed to identify and determine the priorities of the combinations of biotic and abiotic factors that limit yields, and more attention should be given to holistic plant health care.

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