Grey Leaf Spot

Causal Agent: Pyricularia grisea

Susceptible Turfgrasses: Buffalo grass and Ryegrass.

Symptoms

• Symptoms of Grey Leaf Spot vary depending on the grass cultivar.

• Grey Leaf Spot first appears as tiny, brown leaf and stem lesions, which enlarge rapidly into round to oblong spots.

• The largest spots may extend nearly across the entire leaf and become a bluish-grey in colour.

• Mature lesions are tan to grey with purple to brown borders.

• A halo or general chlorosis may occur around or near spots.

• The spots may be covered with a grey mould during periods of warm, humid weather.

• When the disease is severe, the entire planting may appear scorched as if it were suffering from severe drought.

Conditions Favouring Disease

• Grey Leaf Spot is most severe during warm, humid weather.

• Temperatures between 25°C to 30°C.

• When turfgrasses are stressed by various factors, including drought, soil compaction and excessive nitrogen.

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