Dollar Spot (Sclerotinia homeocarpa)

What Is It?

Dollar Spot is a fungal disease which derives its name from the dead straw-coloured spots about the size of an old silver dollar. This disease may be found from early summer through until autumn, usually when soil moisture is low.

Have I Got It?

The visual effect of Dollar Spot depends largely on mowing height. When a practice of close mowing is carried out the straw-coloured spots are quite distinctly outlined in early stages of the disease. When the turf is not cut closely the bleached spots are irregular in shape. Sometimes in the morning when dew is still on the grass, a white cobweb growth of fungus can be seen over the spot.

On individual blades of grass the damaged leaf tissue is first water soaked and dark. As they become drier the affected area becomes lighter giving a straw-coloured appearance.

If I Have Got It How Do I Try To Control It?

Fortunately fungicides are effective against Dollar Spot . Whilst there is no label recommendation in the UK for Myclobutanil it is widely used in the USA where the disease is much more prevalent. Commercial experience has also shown it to be successful in the UK.

Other fungicides which may be used and have UK label recommendations are Mascot Fusion and Mascot Eland . The period of greatest effect is in the summer months when the disease is most active.

The fungal organism can survive conditions which are unfavourable to the fungus as dormant mycelium in infected plants. When daytime temperatures are between 16°C and 27°C the disease may resume growth from infected leaves nearby.

How Do I Try To Prevent Re-Occurrence?

Try to keep adequate nutritional levels, remembering too much is just as dangerous as too little. Moisture in the rootzone should be maintained at suitable levels to assure healthy turf.

As always ensure turf is mechanically aerated to produce good root growth. Always exercise control method of fungicide at the earliest signs of disease; on bowling greens, cricket squares, lawn tennis courts and golf greens where bent grass is most likely found, frequent applications of liquid fertilizer is advantageous. This will ensure the turf does not have highs and lows of nutrition, producing a better playing surface throughout the season.