What Is Red Thread Disease and how do you treat it?

3 min read

autumn lawn diseases

Red Thread Disease is a common complaint in lawns and it can be very unsightly. Here’s the Turfonline guide to Red Thread Disease

  • Small brown patches in the lawn that steadily get bigger
  • Tiny pinkish red threads attached to affected blades of grass
  • Typically occurs in warm wet weather
  • Can affect any lawn – but worse on underfed lawns
  • Treat by applying lawn feed or Fungal Fighter Plus
  • Avoid a recurrence with careful lawn management

What does Red Thread Disease look like?

Generally, the first clue that your lawn may be suffering from Red Thread Disease is the appearance of small straw-coloured patches in the sward.  These patches usually have an irregular shape and may have a pinkish tinge to them.

Look a bit closer and you’ll see that there are tiny pink-coloured threads attached to each blade of grass. There may also be a pale coloured cobweb like structure at the base of the plant.

This is typical of red thread disease. If your lawn is showing slightly different symptoms, it may be suffering from a different lawn disease. Check our troubleshooting guide 

What causes Red Thread Disease?

Red thread disease is caused by a microscopic fungus called Laetisaria fuciformis

The fungus lies dormant in the soil or the thatch layer until conditions are right for it to grow. This particular fungal infection loves temperatures of between 15 and 25 degrees Celcius and a lovely moist environment. Consequently, it tends to be most active in spring and autumn.

Red thread will affect under nourished lawns much more than healthy grass.  However, as our climate warms gardeners are reporting this disease on some of the UK’s best kept lawns.

How to treat Red Thread Disease

Most outbreaks of the disease will be corrected simply by feeding the lawn. Well fed roots and grass can outgrow the damage done by the disease. That means that the unsightly spots soon disappear.


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But the disease can also be treated with Fungal Fighter Plus . Fungus Fighter Plus is pre-diluted making it easy to apply.  The hand held sprayer makes spot treating easy. Two effective active ingredients give contact and systemic action. Systemic means that the fungicide is absorbed directly into the plant helping to eradicate and prevent the development of the disease. For best results use at the first sign of infestation. The best time to apply is early morning or late evening. Try to avoid spraying in sunlight and when plants are dry at the roots.

In severe or stubborn cases, we recommend contacting a local lawn care professional. Trained professionals usually have access to chemical fungicides which can be used to treat the disease. However, specialist fungicides can be quite costly, so you may prefer to let nature take its course. Most lawns recover in time – they just look a bit odd for a while.

How to avoid Red Thread Disease

The best way to avoid red thread disease is to create conditions that the fungus doesn’t like. Of course you can’t control the temperature, but you can make sure that your grass drains as well as possible.

Firstly, trim trees and bushes to make sure there is plenty of ventilation to help evaporate surface moisture.  Then, scarify and aerate your lawn at least once a year to improve drainage. Scarifying also removes the thatch layer which often harbours fungal spores. Finally, remember to feed your lawn regularly all year round. Use the correct formulation for the season and be sure to follow the manufacturer’s instructions carefully.

Related information

Which are the best spring-summer lawn feeds? 

Buy Fungus Fighter Plus

Why you need winter lawn feed 

Lawn care calendar

Order lawn feed online  

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