dark purple to black coloured spots on the leaf blade. As spots enlarge, the centres often turn light tan. At temperatures exceeding 30°C, distinct spots are Bipolaris sorokiniana often absent and the entire Leaf spot (syn. Hot, humid conditions. Helminthosporium leaf blade appears dry and sativum) straw coloured. A warm weather disease affecting leaf sheaths, crowns and roots. Severe thinning of turfgrass stand can occur in a short time. Circular reddish brown spots, 2-15 cm in diameter. Warm weather disease, most Pythium blight, Infected leaves appear wet, destructive between 30-35ºC. Grease spot, Pythium spp. dark and active mycelium Survives well in water and Cottony blight can be seen in the morning. poorly drained soils. Leaves then shrivel and turn reddish brown. Dark leaves in small areas Temperatures greater than and is more obvious in 20ºC with dry nutrient deficient Red thread Corticium fuciforme longer grass. Red-pink i.e. nitrogen. Occurs on mycelium is seen on leaves. water soaked turf. A leaf disease. Yellowish shaped area that is 68 cm in diameter. There is visible regrowth in Warm humid weather, dry soils the centre. The spores Rolf's Disease Sclerotium rolfsii with excessive thatch. (sclerotia) may be present, Generally the turf is unhealthy. they are 2 mm in diameter and orange-black or brown in colour. Bluish-grey or They are unsightly as Moderate temperature with Physarium spp. they mass on the leaf Slime moulds excessively wet soils with poor Mycilago spp. surface. They spread up to drainage. 25 cm across. This is a saprophytic disease.
Leaf spot Bipolaris sorokiniana (syn. Helminthosporium sativum) Hot, humid conditions. dark purple to black coloured spots on the leaf blade. As spots enlarge, the centres often turn light tan. At temperatures exceeding 30°C, distinct spots are often absent and the entire leaf blade appears dry and straw coloured. A warm weather disease affecting leaf sheaths, crowns and roots. Severe thinning of turfgrass stand can occur in a short time. Pythium blight, Grease spot, Cottony blight Pythium spp. Warm weather disease, most destructive between 30-35ºC. Survives well in water and poorly drained soils. Circular reddish brown spots, 2-15 cm in diameter. Infected leaves appear wet, dark and active mycelium can be seen in the morning. Leaves then shrivel and turn reddish brown. Red thread Corticium fuciforme Temperatures greater than 20ºC with dry nutrient deficient i.e. nitrogen. Occurs on water soaked turf. Dark leaves in small areas and is more obvious in longer grass. Red-pink mycelium is seen on leaves. A leaf disease. Rolf's Disease Sclerotium rolfsii Warm humid weather, dry soils with excessive thatch. Generally the turf is unhealthy. Yellowish shaped area that is 68 cm in diameter. There is visible regrowth in the centre. The spores (sclerotia) may be present, they are 2 mm in diameter and orange-black or brown in colour. Slime moulds Physarium spp. Mycilago spp. Moderate temperature with excessively wet soils with poor drainage. Bluish-grey or They are unsightly as they mass on the leaf surface. They spread up to 25 cm across. This is a saprophytic disease.
The%20Biology%20of%20Ryegrass%20and%20Tall%20fescue%202017.docx