GREY LEAF SPOT

Causal Agent

Pyricularia grisea 

Susceptible Turfgrass

All turfgrass 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 turfgrasses are stressed by various factors, including drought, soil compaction and excessive nitrogen.

General Comments

• Grey Leaf Spot is more severe in newly established planting with high nitrogen levels. 

Distribution

Found in all states of Australia.

Management practices

• 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.

  

Fungicidal control

The following products have label recommendation for Grey Leaf Spot control in Australia:  

Parameter	Daconil Weather Stik	Heritage Maxx
Mode of action	Contact	Systemic
Optimum timing	When first sign of disease	When conditions favour disease development
Dose rate	24 l/ha	6 l/ha
Ideal water volume	350-600 l/ha	350-600 l/ha

Refer to label for full details.

Suggested Programme

 

Contact Syngenta for assistance in creating a custom GreenSure Plan for your course.