Dollar Spot disease appears as small (dollar size) spots of pale, bleached turf. The spots may be slightly sunken, causing an uneven surface, and can merge to form large areas of affected turf. Light tan coloured lesions on the leaves, bordered by a reddish-brown band are characteristic of Dollar Spot.
White cobweb-like mycelium or mould may also be seen on affected areas. The mould usually appears in the mornings when the grass is still covered in dew and disappears as the leaves dry.
In the UK, Dollar Spot most commonly affects close mown turf with a high fescue content. It can also affect bentgrass and annual meadow grass.
What causes Dollar Spot to develop?
Dollar Spot is caused by the fungus Sclerotinia homeocarpa, a naturally occurring turf fungi. When climatic conditions are suitable the spores can become active and result in the development of the disease.
Dollar Spot usually occurs in summer and autumn and is most active during periods of high humidity, warm days and cool nights. Moisture from dew, light rain or irrigation, shade during the morning and lack of air movement (which means the turf stays moist for longer) encourage development of the disease. Low fertility and excessively low mowing heights can also increase the occurrence and severity of the disease.
Treatment of Dollar Spot disease
Fungicide treatments are available to control Dollar Spot, however following an appropriate maintenance regime will reduce the occurrence and severity of the disease:
Prune and thin vegetation surrounding the turfed area to reduce shade and improve air movement in the morning, allowing the foliage to dry quicker.
If watering is required, this should be done less frequently, ensuring water percolates through to the soil, rather than light, frequent watering.
Remove dew first thing in the morning by switching/brushing the turf or dragging a hose across the surface, allowing it to dry quicker.
Follow an appropriate feeding regime.
Mow the turf at recommended heights, increasing the cutting height if necessary to promote grass growth and aid recovery.
Reduce excess thatch.
Aerate compacted areas.
Where else can advice be obtained on Dollar Spot?
Further advice on Dollar Spot can be obtained from the Sports Turf Research Institute, the UK's leading independent turf research organisation. Their contact details are STRI, St Ives Estate, Bingley, West Yorkshire, BD16 1AU. Tel: 01274 565131 www.stri.co.uk.