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Pythium blight — Pythium aphanidermatum
Pythium first appears as circular reddish brown spots in the turf, ranging in diameter from 1 to 6 in. In the morning dew, infected leaf blades appear water soaked and dark and may feel slimy. When spots are wet with dew, purplish gray or white cottony fungal mycelia can be seen on the outer margins of the spots. 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).
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. 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). 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. Humid periods further favor disease development.
Pythium first appears as circular reddish brown spots in the turf, ranging in diameter from 1 to 6 in. In the morning dew, infected leaf blades appear water soaked and dark and may feel slimy. When spots are wet with dew, purplish gray or white cottony fungal mycelia can be seen on the outer margins of the spots. 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).
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. 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). 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. Humid periods further favor disease development.
Also Known As...
- Downy mildew
- Location:
» Home, Golf Course
- General Symptoms:
» Circle, Streak, Spot, Wilted, Irregular
- Foliar Symptoms:
» Brown, Orange,Water-Soaked
- Time of Year:
» Jun, Jul, Aug
- Irrigated:
» Yes, No
- Hosts:
» Kentucky Bluegrass, Perennial Ryegrass, Tall Fescue, Fine Fescue, Creeping Bentgrass, Annual Bluegrass, Annual Ryegrass
Good soil drainage is essential for effective management of Pythium blight. 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. Improving air circulation can also help to manage the disease. 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. Of all the turfgrasses, the only resistance to Pythium blight appears to be in the improved bermudagrass cultivars.
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- Chemical Control of Turfgrass Diseases 2011
University of Kentucky College of Agriculture
Turfgrass hosts include, but are not limited to: annual bluegrass, Kentucky bluegrass, bermudagrass, creeping bentgrass, tall fescue, fine-leaf fescues, perennial ryegrass, and annual ryegrass.
