Does your grass have a red thread infection?

By | 15/05/2012
A lawn infected with Red Thread fungal disease
A patch of red thread infection
A patch of red thread fungus on a lawn

In the England, we are currently experiencing a prolonged period of warm, wet weather. Such conditions are perfect for the spread of fungal infections throughout lawn turf, as damp grass traps spores and creates the ideal environment for their growth.

The most common, especially at the moment, is the fungus commonly called “red thread” (laetisaria fuciformis), and I am seeing it in a great many lawns in the area.

Once you know what you are looking for, it can be very easily spotted, but, more often than not, many lawn owners just accept the fact that their lawn “looks a bit off-colour” and don’t get down to have a look at what is really causing the problem.

A red thread infection is easy to spot

Red thread can be easily spotted using the following process. Firstly stand back and have a look at the overall lawn. If you can see faint, circular, straw-coloured patches rather randomly dotted around the lawn, or an overall red/pink hue to these areas, then the best thing to do is get down on your hands and knees and have a much closer look at the grass.

Within the circles, if a red thread infection is present, then you will see very fine, needle-like, pink structures growing out of the dead grass leaves, sometimes binding the leaves together. If the infection is more developed, you may also see curious, small, furry, cotton-like structures at the ends of the red needles, which are very easy to spot. Red thread often occurs at the same time as pink patch fungus.

The needles of the fungus are the Stromata part of the fungus, and the cotton-like structures are the Mycelium parts. Like most fungus, red thread spreads through the release of spores into the wind. This carries it to the next lawn. It requires the grass to be constantly moist for it to take hold, which means that it is only seen during periods of wet, humid weather.

Red thread can affect any lawn!

Red thread Close up
A close up photo of a red thread infection

It used to be thought that red thread only attacked weak, poorly-maintained grass, but as long as the conditions are correct, it can attack the majority of turf grass species, no matter how well managed they are. Golf courses are particularly prone to red thread attacks and they are some of the most carefully managed grass in the country!

A red thread infection will not kill the grass that it has attacked, as it only infects the leaves and does not damage the roots, meaning that, left alone, the grass will recover over time. However, it will be severely weakened, and, as the fungus will have released its spores, it will be more likely to be infected in subsequent years.

Some sources say that red thread can be controlled by the application of a high-nitrogen feed, such as urea, which strengthens the grass sufficiently to fight the infection itself. However, if trying to do this, great care must be taken to not over-feed, and “burn” the grass. Also, the feed must be taken in by the leaf to be effective, and as red thread is usually prevalent during damp periods, the rain will wash the feed down to the roots and through the soil, hence reducing its take-up by the grass plant.

Fungicide treatments for a red thread infection

A much more effective treatment is a fungicide treatment, which is a preventative and curative systemic fungicide, that is not available in garden centres to the domestic market, but is legal for domestic application by licensed technicians. It will protect your lawn from red thread attack for up to twelve weeks and is extremely effective. I am often surprised myself by how much discolouration to a lawn a fungal attack can cause, and the transformation in the colour of a lawn just a few weeks after the treatment can be stunning.

If you suspect you have a red thread infection in your lawn, or would like professional advice on the treatment of red thread, then please get in touch and I will be happy to advise.

Kris Lord

2 thoughts on “Does your grass have a red thread infection?

  1. Stuart Boelte

    I have been fighting both read thread and rust for years and am wits end. I have tried numerous fungasides before as well as the nitrogen approach all to no avail. I irrigate and (mow height) appropriately. What do you recommend?


    1. Kris Lord Post author

      Hi Stuart,
      Once fungi spores have found their way into a lawn, if they are allowed to reproduce each year then you will continue to have problems. If the problem is persistent, then I recommend applying a professional preventative fungicide early on in the season to break the cycle, and then control it throughout the year. This will hopefully reduce future attacks.
      Contact your local lawn care professional for advice, as I’m afraid such fungicides will not be available to amateur users.


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