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Pythium Blight

Caused by: Pythium spp.

 

Susceptible Turfgrass
All turfgrass species, especially Annual Bluegrass, Perennial Ryegrass, Bentgrasses, and tall Fescue and Bermudagrass.

 

Symptoms

  • Pythium Blight appears suddenly during hot, humid weather.

  • This disease causes greasy, brown circular spots that are initially about 2 cm to 5 cm in diameter and then rapidly enlarge in size.

  • The spots are water-soaked and dark-coloured early in the morning.

  • They also form fluffy white masses of fungal mycelium (cottony blight) and can coalesce to form large, irregular areas of dead turf.

  • Infected patches may appear brownish-orange in colour.

 

Conditions favouring Disease
Pythium blight favours night temperatures of over 20°C. It occurs in areas that experience more than 10 hours a day of foliar wetness for several consecutive days. It is found in the wettest areas of turf and in areas with poor drainage and air circulation. Lush-growing turf growing under nitrogen fertilisation is particularly
susceptible to the disease.

 

Solutions

Integrated Turf Management

  • Avoid mowing wet turf when the foliar mycelium is evident to minimise spreading the disease.

  • Reduce thatch.

  • Avoid excessive nitrogen application during hot weather.

  • Increase air circulation to speed the drying process of the turf.

  • Minimise the amount of shade.

  • Irrigate turf early in the day. Avoid late-day watering.

  • Improve soil drainage.

  • Irrigate turf deeply and as infrequently as possible.

 

Fungicidal Control

Heritage has label recommendation for Pythium blight control in South Africa.