Pythium Leaf Blight / Damping Off
Causal Agent
Pythium spp.
What is Pythium Leaf Blight?
Pythium leaf blight or 'Damping Off' is a turfgrass disease caused by Pythium spp. This disease can appear suddenly during hot, humid weather and the patches of affected grass can enlarge at a rapid rate. When affected by Pythium Leaf Blight, early morning grass can appear water-soaked and in dark patches. These infected leaves become light tan to brown and shrivelled and matted when dry.
Excessive moisture is required before Pythium spp. can cause extensive damage and the disease may be more severe in alkaline soils than acidic soils.
What are the Symptoms of Pythium Leaf Blight?
Symptoms of Pythium Leaf Blight include:
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Infected patches of grass can enlarge at a rapid rate.
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In the early morning, grass leaves appear water-soaked and dark in patches.
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When rubbed between the fingers, these water-soaked patches feel oily.
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Infected leaves become light tan to brown, shrivelled and matted when dry.
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When humidity remains high, especially at night, the collapsed leaves become matted and covered with a fluffy white mass of fungal mycelium
Leaf Blight / Damping Off INFO SHEETWhat turfgrass are especially susceptible to Pythium Leaf Blight?
Cool and warm season turfgrass species are particularly susceptible to Pythium Leaf Blight.
When does Pythium Leaf Blight Occur?
Conditions that favour pythium leaf blight are:
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Hot days (30-35°C), humid or rainy weather when night temperatures are warm (above 20°C).
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Relative humidity exceeding 90% for at least 14 hours and a minimum temperature not falling below 20°C.
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Lush, dense grass growing under high nitrogen fertility is especially susceptible to attack.
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Turf areas with poor drainage and air circulation.
What can I do to manage or control Pythium Leaf Blight?
Management practices that can help control or reduce instances of Pythium leaf blight include:
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When establishing a new area, provide for good surface and subsurface drainage.
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Avoid over-watering new plantings, and avoid watering late in the day.
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On established turf water early in the day. Water infrequently and deeply.
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Removal of excessive thatch.
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Do not over fertiliser turf with nitrogen.
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Avoid mowing during moist, hot weather.
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Promote good light penetration into the turf canopy.
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Increase air circulation to speed the drying process of the turf.
