Downy Mildew

Causal Agent: Sclerophthora macrospora

Susceptible Turfgrasses: All cool season turfgrass species.

Symptoms

  • Early symptoms are slightly stunted growth and slightly thickened or broadened leaf blades without any discolouration.

  • When the disease is severe, small yellow circular patches 1 to 10cm in diameter appear in the turf.

  • Patches contain a dense cluster of excessively tillered yellow shoots with shortened roots, which are easily pulled from the turf.

  • Infected new seedling turf form individual clusters of dense shoots that are yellow in colour.

  • A white downy growth may occur on leaf surfaces during cool, wet periods.

Conditions Favouring Disease

  • Wet conditions are required for Downy Mildew to develop.

  • The yellow tufting symptom occurs more commonly in temperate climates, with the downy growth occurring only in warmer weather.

  • Typically occurs in wet, poorly drained low areas.

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