Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2005
Publication Date: May 15, 2005
Citation: Pratt, R.G. 2005. Fungicide-based estimates of yield losses caused by fungal diseases in bermudagrass on swine waste application sites. Mississippi Water Resources Research Conference Proceedings. p.73. Interpretive Summary: Production of large numbers of swine, poultry, and other animals in confinement requires the disposal of large quantities of waste materials without causing environmental pollution. High levels of phosphorus (P) in animal wastes must be disposed without movement into surface waters to cause eutrophic pollution which destroys water quality. To prevent this problem, animal wastes in the southeastern USA are applied to forages which capture P and incorporate it into their tissues during growth. Effectiveness of this process requires production of high yields by the forages to which animal wastes are applied. Factors such as diseases that reduce forage yields will also reduce effectiveness of pollution control. In this study, samples of bermudagrass sod were collected on swine waste application sites and grown in the greenhouse with and without fungicide treatments to suppress disease development. Differences in yield between untreated and fungicide-treated samples represented estimates of losses caused by fungal diseases. In experiments with diseased-appearing sod collected from three farms, yield loss estimates obtained with the most effective fungicide were 0-57%, with a mean of 37%. In healthy-appearing sod, loss estimates were 0-35% with a mean of 16%. These results indicate that fungal diseases in bermudagrass sod may cause major reductions in forage yield on swine waste application sites. Management practices that reduce or compensate for disease losses are needed to promote high forage yields and maximize P capture on these sites.
Technical Abstract: Plant pathogenic fungi may cause severe disease symptoms in foliage, sod, and roots of forage bermudagrass grown for nutrient conservation on sites where wastes from commercial animal production are disposed. To estimate forage yield losses caused by fungal pathogens in sod, samples of diseased- and healthy-appearing bermudagrass sod from three swine waste application sites were grown in the greenhouse with and without weekly fungicide drench treatments. Loss estimates were based upon dry-matter yield increases observed in fungicide-treated samples, where disease development was suppressed, in comparison to untreated samples where disease development was uninhibited. Mancozeb usually produced the greatest yield increases of three fungicides tested. In eight experiments with diseased-appearing sod, first-harvest losses in potential forage yield estimated with mancozeb were 0-57% (mean 37%). In five experiments with healthy-appearing sod, similar loss estimates were 0-35% (mean 16%). Results indicate that fungal diseases in sod and roots may cause major yield losses in forage bermudagrass grown for nutrient conservation on swine waste application sites.