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Controlling Red Thread Disease on your Lawn

Red Thread Disease on LawnsRed Thread Disease can appear in the early to late summer, especially seen on lawns of low fertility, especially Nitrogen.


This disease is now thought to be a combination or complex of two fungal species:

  1. a) L.fuciformis – Red Thread – where the red needles are present
    b) L.fuciformis – Pink Patch – where the pink mycelium is present.
Red Thread is a very common turf and lawn disease. It occurs during mid to late summer and autumn and can persist into mild winters, especially if the weather is humid and damp. As with any other lawn disease, early and correct diagnosis is important. It is commonly seen as little red needles emerging from the leaf of the affected grasses or as a pink ‘cotton wool’ on the surface of the lawn. Affected areas can be the size of a golf ball but can coalesce into larger areas. Ill-defined patches of bleached grass. Pink mycelia are often seen visible in morning dew cover. Red needles are present attached to the leaf blades. Needles (stroma) become brittle on drying and serve to spread disease into new areas.

Where has it come from?

Red Thread naturally occurs as a Pathogen within the turf grass seed and ultimately the mature grasses. The grass seed breeders work hard to cultivate species and varieties of grasses that have ‘freedom of Red Thread’ pathogens. Buying certified and quality grass seed with known Species and Cultivars in the mixture is a good start! It can occur mostly in turf and lawn areas of low fertility levels, particularly Nitrogen. As grass growth slows down due to a lack of Nitrogen, the disease becomes more prevalent. If an area of lawn has recently been fertilised and some of the lawn was incorrectly missed and remains unfertilised, you will get more disease in the part that was not fertilised properly. Remedy this small strip or area by fertilising the missed areas.

Will it kill the lawn if left untreated?

Red Thread does not actually kill the grasses, merely making them look a bit straw like and unsightly, especially once the disease has caused the damage and dried up. Grass plants are rarely totally killed.

Grass species involved

Red Thread Disease can affect most turf grass species, but particularly Red Fescue (Festuca rubra) and Perennial rye grass (Lolium perenne) although the majority of cool season grasses as found in the United Kingdom can suffer an outbreak

What are my options on control of the disease?

Improve fertility levels immediately, especially Nitrogen and Potassium. Feeding a lawn little and infrequently is the worst culprit! Adopt a regular planned feeding programme. Summer control can almost always be assisted by the application of Nitrogen. Winter attacks also pose a problem on fine lawns and an adequate nutrient level must be maintained if the lawn has a history of attack.

Choose disease resistant cultivars for initial sowings, repair and over sowing. Maintain a soil pH of 6.5-7.0. Ensure the lawn is mown with a mower with a sharp blade so that the grass leaf is not damaged and weakened. There is little benefit to be gained from an application of a turf fungicide.

Sometimes, even if you are fertilising your lawn on a regular basis, your lawn may still get an attack of Red Thread Disease but not as bad as an unfertilised lawn. The lawn will be telling you that nutrient levels are getting low in the soil's nutrient bank account! React to what the lawn is telling you!

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