DAMPING OFF
Causal Agent
Pythium and Rhizoctonia spp.
Susceptible Turfgrass
All turfgrass species at seedling stage.
Symptoms
- Damping-off appears as blighted seedlings. Individual seedlings are stunted with water soaked leaves.
- Seedlings collapse and die, causing circular or irregular patches.
- Patches are water-soaked and dark-coloured early in the morning, they may appear slimy.
- In the morning on dew covered grass white masses of fungal mycelium (cottony blight) may appear.Infected leaves become light brown and shrivelled when dry.
- Dead turf may mat together like paper-mache and can coalesce to form a crust over the surface of the soil.
Plate 1. Pythium damping-off in ryegrass seeded sward.
Plate 2. Post emergence damping-off.
Conditions Favouring Disease
- Damping Off outbreaks favour high temperatures and humidity.
- Warm nights (over 20 C) and hot days (over 30 C) and high humidity (over 90%) combined with wet weather.
- More than 10 hours a day of foliar wetness for several consecutive days.
- Dense seeding preventing moisture escape from the soil. Highly fertilised turf (excess nitrogen) is more susceptible.
General Comments
- There are many species of Pythium known to cause damage to turfgrass and symptoms are equally diverse.
Distribution
Found in all states of Australia.