Lawn Disease Control
Brown patch (Rhizoctonia)
Lawn disease control: Brown Patch
Brown patch is a lawn disease caused by the fungus Rhizoctonia species. It is most common in mid- to late summer, particularly during extended periods of high humidity and warm temperatures. This is a foliar disease and does not affect the crown or roots of the turf plant.
Symptoms of brown patch vary depending on lawn maintenance practices such as mowing height, fertilisation, and watering. Brown to black sclerotia, often accompanied by a musky odour, may be visible on dew-covered turf in the early morning. On closer inspection of the grass leaf blades, small tan to brown, irregularly shaped lesions may also be observed.
Dollar Spot (Sclerotinia homoeocarpa)
Lawn disease control: Dollar Spot
Dollar spot is caused by the fungal pathogen Sclerotinia homoeocarpa. The pathogen affects leaf tissue but does not impact the roots or crowns of the grass. Symptoms typically result in reduced lawn quality and overall appearance. The disease is most active under conditions of high humidity, with warm daytime temperatures and cool nights during spring, early summer, and autumn. Infection occurs through the production of mycelium, which can be spread mechanically from one area to another.
On fine-textured, closely mown lawn, the disease appears as small, round, brown to straw-coloured spots that are slightly sunken and approximately the size of a R5 coin. Dollar spot is distinguished from other turf diseases by the presence of light tan lesions with reddish-brown margins on the leaf blades of living plants near the perimeter of the affected area.
Fairy Ring
Lawn disease control: Fairy Ring
A fairy ring is a naturally occurring ring or arc of mushrooms. These rings can exceed 10 metres in diameter and become stable over time as the fungus expands in search of nutrients below the soil surface. Fungal mycelium is present beneath the ring or arc and may result in a necrotic zone (dead grass) or a ring of dark green, vigorously growing lawn.
Fungi can deplete the soil of readily available nutrients, particularly nitrogen, causing plants within the affected area to become stressed and discoloured. Some fungi also produce compounds that act similarly to plant hormones, stimulating rapid, luxuriant growth in surrounding turf.
Pythium Blight
Lawn disease control: Pythium Blight
Reddish- to brown-coloured spots, ranging from 2.5cm to 15cm in diameter, may develop on affected grass. In the presence of morning dew, infected leaf blades appear water-soaked and dark. As the grass dries, the blades shrivel and turn reddish-brown. Mycelium is visible when the blades are wet, and infected grass plants tend to collapse rapidly.
Pythium blight is a strong saprophyte and is commonly present in the soil or thatch layer of the lawn. As a warm-season disease, it thrives in waterlogged conditions. Damage is often confined to the affected area, as the motile spores require free surface water to spread over longer distances. In addition, the capillary spaces between soil particles act as a natural filter, trapping many of the spores.
Rust
Lawn disease control: Rust
Rust is a plant disease caused by pathogenic fungi that are highly specialised parasites. Unlike many other plant pathogens, rust commonly affects healthy, vigorously growing plants, with infection typically limited to specific plant parts such as the leaf blades of grass. Severely infected plants may appear stunted or discoloured.
All rust fungi are obligate parasites, meaning they require a living host to complete their life cycle. While they generally do not kill the host plant, they can significantly reduce growth and overall vigour. The fungi produce asexual spores that are dispersed by wind, water, or insects, facilitating the spread of infection.