Dollar Spot

Dollar spot is caused by fungal pathogens in the genus Clarireedia (previously classified under Sclerotinia and later Sclerotinia homoeocarpa). It affects most turfgrass species grown in Australia, including couch, kikuyu, bentgrass, ryegrass and fescue, and is one of the more common turf diseases on golf courses, bowling greens and sports fields.

On the leaf, the fungus produces small lesions that are straw-coloured to bleached white with a reddish-brown to tan border, often described as hourglass-shaped when viewed across a narrow-leafed grass blade. Under humid conditions, particularly early morning, a fine cobweb-like white mycelium can sometimes be seen on affected patches before dew dries off. The fungus survives between infections as dormant mycelium or stromata (small dark resting structures) in thatch and infected leaf tissue, requiring no soil-borne spore stage for typical spread.

Disease development is favoured by warm days and cool nights that produce prolonged leaf wetness or heavy dew, typically in spring and autumn, though it can occur in summer in humid or poorly drained areas. Low nitrogen fertility, drought stress, compacted soil and excessive thatch all increase susceptibility, as does mowing when foliage is wet, which spreads spores and mycelium between patches.

Management relies on cultural practices that reduce leaf wetness duration and improve turf vigour: removing dew and guttation moisture early in the day, avoiding drought stress, maintaining balanced nitrogen fertility, reducing thatch through regular dethatching or aeration, and improving air movement and light penetration in shaded or enclosed areas. Mowing equipment should be cleaned between infected and healthy areas to limit spread.