Grey Leaf Spot
Pyricularia grisea
Disease of Foliage
Susceptible Turf
All turf species, especially Ryegrass and Kikuyu
Symptoms
- 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 mycelium during periods of warm, humid weather.
- If 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 turf grasses are stressed by various factors, including drought, soil compaction and excessive nitrogen.
Management Tips
- Avoid high nitrogen levels during mid-summer.
- Irrigate turf deeply and as infrequently as possible to avoid water stress.
- Allow water to remain on leaves for only a short period of time.
- Reduce thatch by verti-cutting.
- Prevent soil compaction.
- Avoid using herbicides or plant growth regulators when the disease is active.
General Comments
Grey Leaf Spot is more severe in newly established planting with high nitrogen levels.