Use fungicide treatments as needed along with proper turfgrass culture.Bag and dispose of grass clippings if disease is present. Mow at the proper height and only mow when the grass is dry.Limb up over-hanging trees and prune back nearby shrubs. Improve air circulation and light level on lawn.Avoid medium to high nitrogen fertilizer levels.Avoid using post-emergent weed killers on the lawn while the disease is active.Always irrigate in the early morning, which promotes quick drying of the foliage. This generally means one time per week with one inch of water. When favorable conditions of moisture and high humidity return during the summer, the fungus produces an abundance of spores that are spread by wind, splashing rainfall or irrigation, and the movement of lawn equipment on wet grass. The fungus survives dry summer conditions as fungal mycelium and spores on dead foliage and in the thatch layer. Gray leaf spot is favored when temperatures are between 77 and 86 ☏ during the day and above 65 ☏ at night, and is most severe during rainy, humid periods. Under favorable conditions for disease development, large areas of turf may appear to be scorched, resembling extreme drought stress. Blades of grass will wither and die if leaf spots are numerous. A yellow halo may surround some of the spots, or a general leaf yellowing may occur.ĭuring warm, humid weather, the fungus produces a grayish mycelium (cottony fungal growth) and numerous spores on dying foliage, which gives a grayish appearance to the spots. Augustinegrass, the initial leaf spots are small and brown, but they expand rapidly into large, oval or elongate, tan to gray leaf spots, which are surrounded by purple or brown borders. Augustinegrass ( Stenotaphrum secundatum), but occasionally may also be found infecting tall fescue, bermudagrass, centipedegrass, and ryegrass in home lawns. Gray leaf spot is a fungal disease (caused by Pyricularia grisea) that occurs most commonly on St. Tredway, University of Georgia, Athens, GA Augustinegrass caused by Pyricularia grisea.

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