Grey Leaf Spot
Causal Agent
Pyricularia grisea
What is grey leaf spot?
Grey leaf spot is a turfgrass disease that often first appears as as tiny, brown leaf and stem lesions, which enlarge rapidly into round to oblong spots. However, symptoms of Grey Leaf Spot will vary depending on the grass cultivar. Grey Leaf Spot disease is often more severe in newly established planting with high nitrogen levels.
What are the symptoms of grey leaf spot?
The symptoms of Grey Leaf Spot will vary depending on the grass cultivar. However, some general symptoms include:
-
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.
Grey Leaf Spot INFO SHEETWhat turfgrasses are particularly susceptible to grey leaf spot?
All turf species, especially Buffalo grass, Ryegrass and Kikuyu are susceptible to grey leaf spot.
When does grey leaf spot occur?
The general conditions favouring grey leaf spot are:
-
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.
What can I do to manage and control grey leaf spot?
Management practices that can help control or reduce instances of grey leaf spot include:
-
Avoid medium to high nitrogen levels during midsummer.
-
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 vertical cutting.
-
Prevent compaction of the soil.
-
When possible, plant turfgrass that is resistant to Grey Leaf Spot.
-
Avoid using herbicides or plant growth regulators when the disease is active.
