Gray leaf spot is a foliar disease that affects perennial ryegrass and tall fescue. Gray leaf spot is caused by the fungus Cercospora zeae-maydis. Gray leaf spot of St. Augustinegrass is a disease caused by a fungus that is common during extended periods of hot, humid weather. ; Disease development is favored by warm temperatures, 80°F or 27 °C; and high humidity, relative humidity of 90% or higher for 12 hours or more. It is more likely to develop in regions which experience high humidity levels and temperatures of 26-32 C. What damage or effects will Gray Leaf Spot have? . In Harvey . Gray leaf spot (GLS), caused by the fungus Cercospora zeae-maydis, has been one of the most prevalent foliar fungal diseases of corn in the state of Ohio ever since it was first reported in parts of Pickaway, Ross, Pike and Scioto counties in 1978. Spots develop a gray center surrounded by a yellow halo. If you’ve seen evidence of Brown Patch and Gray Leaf Spot in your … New hot spots of the disease have been reported in the Mohawk Valley and the Leatherstocking Region. Lawns with severe gray leaf spot have areas that seem to just fade or melt away. The entire plant may be affected. Gray leaf spot is a common disease found in St. Augustinegrass caused by the fungus Pyricularia grisea, but it has also made its way to annual ryegrass, perennial ryegrass and tall fescue recently. Leaves turn yellow, then brown, then drop. Leaf infections can progress into the crown area, resulting in death of individual plants. Gray leaf spot may be showing up due to prolonged leaf wetness, brought about by nighttime watering, frequent rainfall, high humidity or heavy dew plus rapid, lush growth courtesy of recent fertilizations. How to Prevent and Treat Gray Leaf Spot in Houston. We have the fungicides you need to prevent those issues.. Gray leaf spot has already been found on corn this year in Pottawatomie and Harvey counties when the corn was only in the V7- V8 stage of development. The center of the spot may fall out leaving holes. Epidemics of gray leaf spot have been observed in New York State in the Southern Tier and the Hudson River Valley. Most of the time in Australia, Gray Leaf Spot is a minor disease of turf. What does gray leaf spot look like? Gray leaf spot (GLS) is a common fungal disease in the United States caused by the pathogen Cercospora zeae-maydis in corn. Gray Leaf Spot on Corn. Newly sprigged, sodded, or rapidly growing grass is more susceptible than well-established grass. Brown to black specks appear first on older leaves, then newer growth. When does Gray Leaf Spot occur? It is caused by a fungal pathogen (Pyricularia grisea) that readily infects and kills leaf blades. Gray leaf spot is a generally a summer disease. 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