Dollar Spot

Dollar spot is caused by fungal pathogens in the genus Clarireedia (previously classified under Sclerotinia and later Ophiosphaerella). It affects most turf species grown in Australia, including couch, kikuyu, buffalo, bentgrass and fine fescues, and is one of the most common diseases seen on home lawns and fine turf alike.

On close inspection, the fungus produces fine, cobweb-like white mycelium across affected leaves, most visible in early morning while dew is still present. Individual leaf blades develop small lesions that are tan or straw-coloured with a distinct reddish-brown to purple margin, often hourglass-shaped as they pinch in at the midpoint of the leaf blade. No visible spores are produced above ground; the fungus survives between seasons as dormant mycelium in thatch and dead leaf tissue, spreading via mowing equipment, foot traffic, water movement and infected clippings.

The disease is favoured by warm days (18–28°C), cool nights, high humidity and prolonged leaf wetness from dew, irrigation or poor drainage. It is particularly common in spring and autumn in southern states and can persist year-round in warmer, humid parts of northern Australia. Turf that is nitrogen-deficient, under drought stress, or has excessive thatch build-up is more susceptible.

Management relies on improving turf vigour and reducing the conditions that favour the fungus. This includes maintaining adequate (not excessive) nitrogen fertility, watering deeply but infrequently early in the day to reduce prolonged leaf wetness, improving airflow and light penetration by pruning overhanging vegetation, dethatching where thatch layers are heavy, and mowing at the correct height for the turf species since low, stressed turf is more prone to infection.