Lawn Diseases

Most lawn diseases are caused by fungi and are harmless. They can occur very quickly and can disappear just as quickly when conditions change. Other diseases can cause damage to the grass and while some can be treated, others will cause damage that will need to be repaired. As most lawn diseases are caused by weather conditions there is little that can be done to prevent them. To help reduce the chance of disease occurring, keep your lawn free of thatch and during the summer apply water only in the early morning. This allows the moisture to dry quickly and not sit on the leaf for long periods.

Some of the more common lawn diseases are listed below.

Crown Rust

Crown rust is a fungal issue that can affect lawns during warmer months, particularly when growth slows. It appears as a fine, powdery coating of yellow or orange spores on the leaves, which can be easily spread by foot to other areas. Crown rust is most common in humid conditions and when nitrogen levels in the soil are low.

Treat Crown Rust by applying fertiliser to the lawn to boost nitrogen levels. No other treatment is usually necessary, as crown rust often disappears on its own once conditions improve.

Dollar Spot

Dollar Spot is a lawn disease that appears as small, straw-coloured spots of varying size. As it progresses, these spots can merge to form larger, irregular patches of damaged grass. Occasionally, a white fungal webbing may be visible on affected leaves. This disease is most common during moist, warm weather and tends to be more severe in lawns that are thatchy or low in nitrogen.

Treat Dollar Spot by applying fertiliser to boost nitrogen levels and help the lawn recover. To prevent future outbreaks, manage thatch levels and maintaining appropriate nitrogen fertilisation.

Fungi

At any time of year when wetter weather occurs, fungi may appear in some lawns. There are many different types of fungi, and they are rarely anything to worry about. Fungi will usually disappear on their own as quickly as they appeared.

Home lawns typically do not require any treatment for fungi.

Fusarium

Fusarium appears as orange-brown circular patches that can develop quickly under favourable conditions, reaching up to 50 cm in diameter. It usually occurs during the winter months and is more common in lawns with a large amount of thatch.

You can help prevent Fusarium from developing by reducing thatch levels in your lawn.

Melting Out

Melting Out disease first appears as small brown spots on grass leaves, known as Leaf Spot, and is typically seen during the summer. As the disease progresses, the spots spread until the entire plant, including the roots, is affected. This results in patches of tan grass with a dark purplish-red border. Lawns with excessive thatch, poor drainage, or over-fertilisation are particularly susceptible.

You can help prevent this disease by managing thatch levels, carefully controlling nitrogen applications, and ensuring all lawn watering is done in the early morning.

Red Thread

Red Thread is a very common lawn disease that can appear at any time of year, although it is more prevalent in moist conditions. It typically occurs when the grass is low in nitrogen. The disease is identifiable by a pink or red tinge over patches or large areas of grass, and on closer inspection, fine threads can often be seen. Affected grass can look unsightly and discoloured.

Treat Red Thread by applying fertiliser to increase nitrogen levels. If this is not effective, Iron Sulphate can be applied during wetter months to strengthen the leaves and help resist the disease.

Slime Mould

Slime Mould appears in lawns during late autumn and early winter, often favouring wet conditions or shaded areas. It can be identified by egg-shaped growths that may appear in a variety of colours.

No treatment is required, as Slime Mould is a temporary condition that will disappear when conditions improve. You can help reduce its occurrence by managing thatch levels in your lawn.