In the summer months when humidity is prolonged, temperatures are 65 oF or greater, and air is stagnant, large patches of bronze matted turf begin to make an appearance. We comply with the Federal Trade Commission 1998 Children’s Online Privacy Protection Act (COPPA).Pythium blight is seen on any species of cool-season turf as well as some warm-season grasses like Bermudagrass. The 4-H Name and Emblem have special protections from Congress, protected by code 18 USC 707. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This information is for educational purposes only. Quentin Tyler, Director, MSU Extension, East Lansing, MI 48824. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. MSU is an affirmative-action, equal-opportunity employer, committed to achieving excellence through a diverse workforce and inclusive culture that encourages all people to reach their full potential. One commonly used prediction model requires maximum daily temperatures greater than 86° F (30° C) and a minimum temperature of 68° F (20° C), with at least nine hours of relative humidity above 90 percent. Disease predictor models can be very helpful in determining likelihood of Pythium development. Fungicides should be applied on a preventative bases in areas prone to disease development. Systemic fungicides like propamocarb, mefenoxam, and fosetyl Al, normally have 10-to 14-day residuals when disease pressure is heavy. Contact fungicides such as chloroneb and ethazole, which normally have 5-to 7-day residuals can be effective if applied at appropriate times. ![]() Of all the turfgrasses, the only resistance to Pythium blight appears to be in the improved bermudagrass cultivars.ĭue to the aggressive nature of the pathogen, and the potential for severe turfgrass loss, fungicides are essential tools for Pythium control. High nitrogen levels which cause lush growth are thought to make Pythium blight outbreaks worse, so nitrogen should be kept at low to moderate levels during hot, humid weather. Improving air circulation can also help to manage the disease. Heavy watering can increase the severity of Pythium blight, therefore, light watering, or syringing during midday will help to manage Pythium outbreaks during hot, humid weather, and nighttime watering should be avoided altogether. Good soil drainage is essential for effective management of Pythium blight. Hosts of the disease are Kentucky Bluegrass, Perennial Ryegrass, Tall Fescue, Fine Fescue, Creeping Bentgrass, Annual Bluegrass, and Annual Ryegrass. This can occur during the months of June, July, and August. Foliar symptoms are browning, turning orange, and water-soaked. General symptoms are a circle, streak, spot, wilted, and irregular coloring. ![]() The location of this disease is home lawns and golf courses. Humid periods further favor disease development. When evening temperatures average 68° F or higher, outbreaks will typically first appear in low areas, or poorly drained areas where soil moisture is maintained. As a warm-weather disease of cool season grasses, the disease is most destructive when temperatures are between 85° and 95° F (29.4° - 35° C). ![]() Pythium blight is a good saprophyte, and survives in the thatch and soil as a water mold until proper conditions occur for it to become pathogenic. Infected grass plants collapse quickly, and when conditions are conducive, spots may coalesce and large areas of turf can be lost in a short period of time (overnight). When spots are wet with dew, purplish gray or white cottony fungal mycelia can be seen on the outer margins of the spots. In the morning dew, infected leaf blades appear water soaked and dark and may feel slimy. Pythium first appears as circular reddish brown spots in the turf, ranging in diameter from 1 to 6 in.
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