What is red thread disease?

What is red thread disease?

Red thread disease is caused by a fungal pathogen called Laetisaria fuciformis (formerly known as Corticium fuciforme). It infects and kills leaves of grass but it does not usually kill the plant. Unfortunately, it affects some most of the common lawn species that we see including creeping fescues and perennial ryegrass.

Red Thread

Photo taken by Twitter user @_LawnKing_

Red thread disease shows up as brown patches on a lawn if you look closely you will see fluffy white/pink blobs and the pink thread-like structures that give the disease its name.

It is common for lawns to get red thread disease in warm, humid weather when temperatures are between 15 and 24 degrees Celcius, usually the autumn but sometimes in the spring too.

How do I treat red thread disease?

Red thread disease is nothing to panic about since it rarely kills the plants. Most lawns will bounce back from red thread rather quickly, especially with an application of fertiliser or biostimulant. A fungicide may be used but this can do more damage than good in the long run as you may be upsetting the natural balance of beneficial fungi in the lawn soil.

Most professional lawn care companies find that an application of fertiliser with nitrogen will cause the grass to grow so that the red thread can grow out. This is usually enough to prevent it returning again that season. SmartLawn AutumnGreen [10-5-10 +2%MgO 50% V90] is ideal for this.

How do I avoid red thread disease in the future?

The spores of the fungi can survive for up to 2 years in our climate and are spread by wind, water and by the movement of animals and people. It’s said to prefer soil with a pH of 3.5-7.5 meaning that alkali soils would fair better, but according to our customers, that doesn’t seem to make a difference in practice!

Red Thread

Photo taken by Twitter user @lancslawn

Ensuring good airflow to the lawn will help prevent the damp conditions that favour all fungal diseases. Pruning overgrown shrubs and trees will also help provide more light to the lawn making it stronger and better able to resist disease.

Aeration and scarification are highly advised (I feel like I say this a lot). Aeration will help with drainage and soil health and scarification will remove thatch preventing the moist conditions that favour all fungal diseases.

Lastly, keep the lawn well-fed at times when red thread disease is expected to occur. If you are using AutumnGreen for your autumn (or spring) treatments then you can simply increase the application rate to 40g/sqm to provide more nutrients to the lawn and keep red thread away. If the lawn is looking worse for wear in general then a pep-up treatment such as ONYX Liquid or Seaweed Extract will help it return to health before the winter or summer.

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