Red Thread


Red Thread

by ians147 (All rights reserved)
1 of 2
A close up of some red thread growing in some grass
by ians147 (All rights reserved)
1 of 2
Red thread is a fungal disease that attacks various species of fine lawn grasses, such as the fescues. It appears as red and pink thread-like structures in patches of grass, up to 8 cm in diameter. Though red thread spoils the appearance of grass, it rarely kills it. Red thread is a common cause of patches of dead grass on lawns during wet summers and in autumn. It is caused by the fungus Laetisaria fuciformis. Red thread will rarely kill the grass completely, and the patches will recover with appropriate remedial action. The disease can develop at any time of year, but is most common in late summer and autumn.


Red Thread can be identified as thin, red, thread-like structures growing amongst normal grass, which tends to appear dead due to the infection. Pale pinkish, gelatinous strands are entangled with individual leaf blades. These later develop into red-pink fluffy growths. The grass is weakened (not killed), with a spoiled appearance.

Growth factors

Light or poor soils are most susceptible especially after long periods of heavy rain. Soil with low nitrogen.


Yellowing patches of grass
Pink and red thread-like structures intertwined with the blades of grass
Grass can almost appear as bleached
Sometimes it's possible to see tiny clumps of pinkish-white cottony fungus.

Biological treatment

There are no biological treatments for this disease.

Chemical treatment

There are some chemical fungicide treatments that can kill this fungus. Chemicals marketed for the treatment of Snow Mould will treat the fungus.


The stromata (cushion-like masses of fungal tissue) lay dormant in the soil and then infect the leaves of the grass once the conditions are met.


Good lawn health. Not having a soil that is too free-draining. Scarifying lawns will help to remove things like moss growing on the surface, improving aeration. Ensure soil isn't deficient in Nitrogen.

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