Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/13/2000
Publication Date: N/A
Interpretive Summary: The concentrated production of large numbers of swine, poultry and cattle in confined facilities is a common practice in modern American agriculture. This practice requires disposal of large quantities of animal waste materials without polluting the environment. The principal polluting substances in animal wastes are nitrogen and phosphorus, and their principal negative effects are induction of high nitrate levels in ground water, and ecological deterioration of surface waters. In the southeastern USA, animal wastes are applied to forage crops as fertilizers. Excess nitrogen and phosphorus are absorbed by forage crops during growth and removed from application sites during harvest of hay. Therefore, any external factors that prevent satisfactory growth of the forages may interfere with this process. In recent years, plant diseases have been observed to kill leaves and stems, reduce plant vigor, and causing stunting gand dying out of forages on waste application sites. This paper reviews observations and studies of diseases and pathogens on bermudagrass and other forages on swine and poultry waste disposal sites in Mississippi. It describes symptoms of diseases, the identity and frequency of pathogens, and their disease-causing capabilities. It also describes approaches to future control of diseases through research on management practices and alternatives, and by breeding plants to develop new disease-resistant varieties.
Technical Abstract: Biological or physical factors that reduce productivity and survival of forage crops on animal waste disposal sites may interfere with hay production, removal of excess nutrients, and prevention of environmental pollution. Observations in recent years indicate that plant diseases may limit the productivity and survival of forage crops on such sites. Symptom of diseases have been observed on bermudagrass and other forages on both swine and poultry sites in Mississippi. These have been attributed largely to fungal pathogens of the genera Exserohilum, Bipolaris, Curvularia, and Drechslera. Eight species of these genera have been isolate from diseased bermudagrass and other forages, and their frequency of occurrence at different sites and sampling times has been evaluated. The virulence, or disease-causing capability, of most of these pathogens also has been determined under standardized conditions. A broad spectrum of virulence has been demonstrated for seven species. Generally the most virulent species were most common on sites with the greatest disease damage while less virulent species were often more common on sites with less severe disease. Control of these plant diseases and removal of the limitations that they pose to environmental pollution control, might be accomplished by development of cultural control practices or by breeding for disease resistance.