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Home » Blog » Red Thread Disease: Understanding and Eliminating Lawn Disease

Posted in: Care & Maintenance, Lawn & Landscaping

Red Thread Revealed: Understanding and Eliminating Lawn Disease

Imagine gazing out at your lawn only to find it marred by unsightly patches of pink or red. Red Thread disease in turf is a common yet perplexing turf disease that can detract from the beauty of your grass.
A deeper knowledge of Red Thread is essential for gardeners and homeowners who treasure their lush, green carpets.
In the following article, we unravel the mystery of Red Thread, from detection and prevention to effective strategies for maintaining a healthy, resilient lawn.

What is Red Thread Disease in My Lawn?

Red Thread disease is a troubling condition afflicting lawns, triggered by the fungal organism Laetisaria fuciformis. This culprit launches an assault on grass blades under specific environmental conditions, often leaving homeowners distraught at the sight of their once-lush turf.

Key Indicators:

  • Appearance: The disease emerges as reddish-brown patches on the lawn, intermingled with pink or red fibers.
  • Structure: The “red threads” are the fungus’s fruiting bodies, and they crystalize into brittle structures outstretching from blade tips.
  • Favored Conditions: Wet weather, insufficient lawn nutrition, and poor air movement are the disease’s best allies.
  • Grass Types at Risk: Perennial ryegrass, fescues, bentgrass.

Managing Red Thread involves fostering a healthy lawn through adequate fertiliser, good soil conditions, and preventing excessive thatch formation.

By ensuring your grass receives the right nutrients and care, you’ll not only keep Red Thread at bay but also maintain a vibrant and healthy lawn.

Is Red Thread something to worry about and can it kill my grass?

Red Thread disease in turf, caused by the fungus Laetisaria fuciformis, is a common sight in lawns, especially during late spring and humid conditions. This lawn disease is named for the red or pink threads that appear on the grass blades, often creating unsightly patches. Although Red Thread can make your lawn look less appealing, the good news is that it rarely kills grass. Instead, it affects the grass superficially, damaging the blades but not invading the grassroots or crowns.

While Red Thread does not typically result in dead grass, it can weaken your lawn’s overall health. A weakened lawn is more susceptible to further stress and possible invasion by other diseases. Therefore, it’s crucial to address the issue to maintain a healthy lawn.

To manage Red Thread disease, one should focus on maintaining optimal lawn health rather than turning to fungicides. Good cultural practices include proper fertilization, regular mowing without cutting too short, and ensuring good air movement. Enhancing the grass plants’ vigor allows them to outgrow the damage, and eventually, the symptoms of Red Thread will fade away, restoring the lush green appearance of your lawn.

It’s clear that while Red Thread can be a concern due to the cosmetic damage it inflicts, with proper lawn care, it’s unlikely to kill your grass.

How do i recognise Red Thread?

Recognizing Red Thread disease in turf, a fungal lawn disease, is straightforward once you know what signs to look for. This malady manifests as pink or tan patches, ranging from one inch to two feet in diameter, amidst your lawn’s green expanse. Within these circles, you’ll notice an intermingling of unaffected grass with symptomatic blades showing signs of decay.

Take a closer look at the afflicted grass blades; they often have protruding pinkish-red threads, a hallmark of the disease caused by Laetisaria fuciformis. These threads are the fungal strands that give Red Thread its name. In wet weather, you might also see pink or reddish cotton-candy-like growths near the grass’s base—another telltale indicator.

Affected grass types, such as red fescue, ryegrass, common bent, and annual meadow grass, display these symptoms, particularly in spring but not limited to it—as outbreaks can also occur in fall and winter. A lawn with Red Thread will have a ragged look due to the mix of healthy and infected blades.

By identifying these key signs, you can confirm the presence of Red Thread disease in your lawn:

  • Pink or tan patches within the grass
  • Distinguishable red threads on grass blades
  • Decaying grass areas with a ragged appearance
  • Pink/reddish cotton-candy-like growths (under wet conditions)

This fungal affliction thrives in specific environmental conditions such as wet, humid weather, and poor air movement, so be vigilant during such times.

What conditions encourage Red Thread?

Red Thread disease in turf, a widespread lawn ailment, adversely affects many grass varieties. This fungal disease is particularly active under specific environmental conditions, which are conducive to its growth and spread. The following factors can encourage Red Thread in your lawn:

  • Temperature and Humidity: Red Thread disease flourishes when the thermometer registers cool temperatures, between 40 to 75 degrees Fahrenheit. It’s at these cooler temperatures that high humidity can also play a pivotal role in the disease’s development, offering a moist environment where the pathogen can thrive.
  • Moisture: This fungal lawn disease finds its perfect breeding ground in excessively wet weather. Whether from overwatering, poor drainage, or a naturally wet season, too much moisture is practically an open invitation for Red Thread.
  • Lawn Health Factors: Lawns that are not in their peak condition are more susceptible. Specifically, lawns with a hefty thatch layer, those suffering from low nitrogen, or nutrient-poor grass are prime targets.
  • Unfavorable Growth Conditions: Grass that doesn’t get enough sunlight, is under drought stress, or experiences heavy foot traffic can become weak, making it far more vulnerable to a Red Thread invasion.

By ensuring your lawn is well-nourished, free of excessive thatch, and properly drained, you can create an environment that is less inviting to Red Thread and helps keep your grass healthy and vibrant.

Are there grasses that are resistant to Red Thread?

Absolutely, certain grass varieties exhibit a higher resistance to Red Thread disease in turf, a common issue caused by the fungal pathogen Laetisaria fuciformis. Notably, some Barenbrug fescue varieties have been acknowledged for their robust resistance against this lawn disease. Two prominent Barenbrug varieties that stand out for their Red Thread resilience are Barcrown and Barpearl.

When selecting grass varieties with greater resistance to fungal diseases like Red Thread, these specific fescues can be an excellent choice for lawn enthusiasts seeking to maintain a vibrant and healthy lawn. Keeping grass healthy and less susceptible to thread fungus, these varieties can help to minimize the appearance of the characteristic pink or red threads and unsightly brown patches associated with the disease.

Ensuring that your lawn consists of grass varieties with innate resistance is a proactive step towards combating fungal growth and fostering a robust turf. Here’s a snapshot of the aforementioned resistant grass varieties:

By integrating these resistant types of grass into your lawn, you create a resilient foundation that can withstand unfavorable environmental conditions, such as wet and humid weather, that typically promote the growth of fungal lawn diseases.


Red Thread disease in turf is an unsightly condition that often points towards underlying health issues with your turf, such as low nitrogen levels or environmental stress. This fungal lawn disease, caused by the pathogen Laetisaria fuciformis, emerges as small brown patches that grow larger over time, often under wet or humid conditions.

Chemical treatments for this condition are generally discouraged, particularly for residential lawns, and should only be considered in severe cases. Instead, the best line of defense involves cultural practices. An appropriately balanced fertilization regime, specifically tailored to provide adequate nitrogen, can hinder the development of Red Thread and promote a lush, resilient lawn.

Maintaining the health of your turf post-treatment is imperative. Regular and correct mowing, smart fertilizing, and judicious watering are key in sustaining a vigorous lawn appearance and function. If you suspect your lawn is infected, accurate identification is paramount for targeted control. Consulting a turfgrass pathology lab may be beneficial for those who need assistance with fungus identification.

Remember, a proactive approach with proper lawn care techniques can effectively manage Red Thread and keep your grass looking healthy and vibrant.




Apply the proper amount of nitrogen to support growth.


Cut the grass to the correct height and with sharp blades.


Water deeply but infrequently to encourage strong roots.

Chemical Treatment

Use as a last resort for severe infestations.