Red Thread Grass | Dealing with Red Thread Lawn Disease

Keith Hardy - Bio Photo
Keith Hardy
Senior Editor

Keith has been involved in the gardening and landscaping industry for the past 21 years. From a jobbing gardener to running his own landscaping services....

The fungal illness known as red thread disease can occur on lawns and other grassed surfaces. The disease it is triggered by the pathogen Laetisaria fuciformis, and has two distinct stages. The first stage is distinguished by the presence of very thin, red, needle-like strands that protrude from the grass blade. These needle-like strands are called stromata and are able to survive in the soil for up to two years before dying. As soon as they germinate, the stromata attack the grass leaf blades by infecting their stomata.

In the second type stage little, pink cotton wool-like mycelium appears in infected areas which is caused where the glass blades come into contact with each other usually. This can particularly occur in high temperatures and humidity.

How to spot Red Thread lawn disease?

Red Thread Grass | Dealing with Red Thread Lawn Disease

The earliest indicators of infection in your lawn are little uneven patches of brown or yellow grass that appear randomly over the field. If you look closely, you will be able to see either the small red needles or the second type stage where the pink downy mycelium is visible. Infection grows from tiny patches to huge brown regions, which eventually combine to create vast brown swaths.

Environmental Conditions that are Advantageous to Red Thread

Red Thread lawn disease thrives best when temperatures are between 59 and 77 degrees Fahrenheit and when it is rainy. Under these conditions, the laetisaria fuciformis that causes red thread disease becomes active and can easily spread.

It is therefore during the spring and fall (autumn), when rainfall is heavier and temperatures are a little lower, that provide the most ideal conditions for Red Thread. The rate of development of the fungus reduces dramatically when temperatures are beyond 77°F, and it is unable to grow above around 85°F.

The disease attacks those regions of a lawn that are deficient in nutrients or that develop slowly are those that are more prone to red thread disease.

The sclerotia, thread-like red webbing structures that support the fungus, are the source of the fungus’ growth and there can spread easily through the air.  It is possible for sclerotia to persist for months or years under grass blades if there is strong thatch, or in the soil. The pathogen can be transmitted in various ways but the most common are contact with polluted water, wind, and gardening equipment. 

Because this fungus may persist for extended periods of time, it is critical to look to deal with any affected regions quickly in order to prevent the fungus from spreading further.

Grass Susceptible to Red Thread

Red thread is most often seen in cool-season grasses, which are more sensitive to the disease. Kentucky bluegrass, Red fescue,  bentgrass, and ryegrass, are some of the most common kinds that are susceptible to Red Thread . Compared to cold season turf, warm-season turf grasses tend to be far more resistant to red thread. If you have had a problem with Red Thread then it is good practice to overseed with more resilient grass species. 

What damage can Red Thread do to your lawn?

Despite the fact that the grass in the afflicted regions seems to be lifeless, red thread does not kill the grass since the pink growths on the grass do not infect the plant’s crown or roots, the fungus does not cause the grass to die as a result of its presence. The infected grass is disseminated by the fungus that resides inside it, which spreads via the thatch and soil.

Because of this mowing and other mechanical lawn care processes can easily transfer the fungus to other areas of the grass. It is therefore important to properly clean your equipment after use. If you employ a lawn care company then you should make sure they do the same.

How To Treat Red Thread Lawn Disease

In order to mitigate the impacts of Red Thread, it is advisable to maintain sufficient nitrogen in the soil of the lawn. Indeed it is possible to actually “grow out” the Red Thread infected zone by undertaking an aggressive fertilization program. The fertilizer will aid in the growth of the grass, and then the unhealthy areas of the plant may be mowed away to allow for the growth of younger, healthier blades.

Excessive watering should be avoided during chilly, wet weather since it may cause the grass to stay moist for an extended amount of time. Another two key natural techniques are core aeration and overseeding with enhanced species of grass that are more resistant to Red Thread.

However, once red threads are clearly visible, it can be too late to use a preventive disease control application to stop its spread and you may have to look at other methods of eradication.

Nonchemical control

As discussed above, when red thread forms, applying nitrogen to the afflicted region will often be enough to keep it under control. Nitrogen should be applied in the form of sulfate of ammonia. This should be at a rate of around 12oz per square yard of lawn. It is usually recommended that you do not apply after the end of August to prevent the creation of soft growth that is susceptible to snow mold.

Improved lawn aeration and drainage of the grass may help lessen the possibility of red thread infesting your lawn. Scarifying the grass using a lawn rake or an electric scarifier can take away thatch and moss while also increasing the aeration of the turf.

It is possible to improve poor drainage and compacted regions by the use of forking or by the use of either solid-tine or hollow-tine dedicated aerator. Make certain that the soil does not have a nitrogen deficiency. Disposing of grass clippings (rather than composting them) will limit the quantity of fungus present and the likelihood of re-infection of the lawn.

Chemical control

Where fungicide treatments are needed Trifloxystrobin is the main chemical fungicide readily available to home gardeners for the treatment of red thread in their lawns. This fungicide may be applied anytime throughout the year, with the exception of when the grass is frozen or when there are drought conditions. Because there is a possibility of resistance developing in the fungal population, the fungicide should not be used more than twice a year and should be used in combination with other non-chemical control measures whenever possible.

The use of professional fungicides is offered by certain lawn management firms; nevertheless, there is tight regulation governing the use of professional treatments on residential lawns. Because of this, you will need to ensure that the organization is functioning within the boundaries of the law.

How to prevent red thread disease?

The most effective method of preventing red thread disease is to establish conditions under which the fungus will find it difficult to thrive.

Because it is not feasible to completely eradicate the pathogen or regulate the weather, the most efficient method of eradicating Red Thread is to target the areas that are most sensitive to the infection.

As we have discussed fertilizing lawns in the spring and summer months will aid in the supply of nitrogen to the grass. As the nitrogen is absorbed by the soil and watered in, the majority of lawns will be able to grow out Red Thread. Having said that, there are occasions in which Red Thread may become a chronic issue or develop beyond typical levels, necessitating the use of a fungicide to control the infestation. This isn’t often, but it does happen from time to time.

Allowing good airflow is important for the health of your lawn. Trim trees and shrubs to ensure that there is enough airflow to aid in the evaporation of surface moisture. If you want to increase drainage, aerate and scarify your grass at least once a year. Scarifying also eliminates the thatch layer, which is a common source of fungus spores in the garden.

Make a point of feeding your grass on a regular basis throughout the year! Make sure to use the proper formulation for the season and to carefully follow the manufacturer’s directions at all times.

Keith Hardy - Bio Photo
Keith HardySenior Editor

Keith has been involved in the gardening and landscaping industry for the past 21 years. From a jobbing gardener to running his own landscaping services. He is now dedicated to bringing you the latest in gardening news. Read more

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