Red Thread Disease is a fungal infection found on lawns and other turfed areas. It is caused by the corticioid fungus

Corticioid fungi

The corticioid fungi are a group of fungi in the Basidiomycota typically having effused, smooth basidiocarps that are formed on the undersides of dead attached or fallen branches. They are sometimes colloquially called crust fungi or patch fungi...

 Laetisaria fuciformis and has two separate stages. The stage that gives the infection its name is characterised by very thin, red, needle-like strands extending from the grass blade. The other stage is visible as small, pink, cotton wool-like mycelium

Mycelium

thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...

, found where the blades meet. It is common when both warmth and humidity are high.

Identification

The first signs of infection are small irregular patches of brown/yellowing grass. Upon closer inspection, either the tiny red needles or the pink fluffy mycelium will be visible. As the infection spreads, the small patches will join to form large brown areas.

Treatment

Feeding the lawn with a nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 based fertiliser will help prevent attacks. The most cost-effective nitrogen fertiliser is urea

Urea

Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

 (48% active nitrogen) and is available from most farm/feed supply stores. Application rate of 50 to 100 pounds per acre (12 to 25 kg / hectare). Cost of urea in 2011 at farm/feed stores in the United States is approximately 20 US dollars per 50 lb (approx. 25 kilogram) bag.

Red Thread can be treated using a fungicide that contains benomyl

Benomyl

Benomyl is a fungicide which was introduced in 1968 by DuPont. It is a systemic benzimidazole fungicide that is selectively toxic to microorganisms and to invertebrates, especially earthworms. Benomyl binds to microtubules, interfering with cell functions such as meiosis and intracellular...

 or carbendazim

Carbendazim

Carbendazim is a widely used broad-spectrum benzimidazole fungicide. A 4.7% solution of carbendazim hydrochloride is sold as Eertavas, an effective treatment for Dutch elm disease....

. The infection will rarely kill the grass, usually only affecting the blades and not the roots, and the lawn should recover in time.

External Links (with pictures)

http://www.lawnandmower.com/red-thread-disease.aspx

http://www.grassclippings.co.uk/RedThread.pdf

http://www.rolawndirect.co.uk/turf_pest_and_disease_control-red_thread_disease.html