With recent warm and humid conditions please keep an eye out for
Red thread (Laetisaria fuciformis).  It is especially prevalent at the moment.
Perennial ryegrass and red fescue are very susceptible to damage from Red Thread.
The above grass species are prevalent in most lawns in the UK and therefore prone to attack when conditions are right.


Grass becomes water soaked and rapidly dies in circular or irregularly shaped small to large patches 2-24 inches (5-60 cm) in diameter.

The straw brown to yellow/brown colour of dead leaves may be the first symptoms observed. The damaged leaves are often interspersed with healthy leaves which give a scorched ragged appearance to the patch.  The patches may be widely scattered or close together and may join to form large areas of infected grass.

When ample moisture is present the pathogen produces colourful red threads hence the name of the disease.

In dry weather these threads turn bright red and become brittle.  In this condition they are easily detached and spread by mowing, people and animals.

Early symptoms on infected grass. (source Dr. Eric B. Nelson, Cornell University)


Maintain adequate fertility.  Applications of nitrogen help reduce the severity of the disease, but excessive rates of nitrogen should be avoided.

It is possible that L. fuciformis is adapting to the surrounding conditions and becoming more aggressive. In this situation, especially if the grass sward is thinning, we have found that an application of a fungicide is required and will keep the disease at bay for up to 6 weeks.

A close-up of the"Red Threads". (source Dr. Eric B. Nelson, Cornell University)

Cultural factors to help

  • If irrigation is practiced, it should be applied deeply and as infrequently and as early in the day as possible. Avoid frequent, light applications of water in late afternoons and evenings, which allow the leaves to remain wet for a prolonged period.
  • M with sharp blades to minimise wounding of leaf tips during periods when the grass is growing slowly.
  • Do not allow thatch levels to accumulate more than 1 inch (2.5 cm)

Have questions?

Want to learn more and find out how ProLawnCare can help your lawn looking healthy over the summer season? Then please get in touch by using the form below, emailing us at or calling 01480 812393.

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