Why is my grass red? (6 ways to get rid of red thread)

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If you are wondering why your grass is turning red and is beginning to look patchy, then your lawn is probably suffering from red thread. This article is the ultimate guide on what is red thread, what does it look like and how do you get rid of it. Read on for more information.

What is red thread and what does it look like?

Red thread is a lawn condition caused by a fungus called Laetisaria fuciformis, that attacks the leaf parts of the grass and causes it turn red and slowly die.

It is particularly a problem for fescue and perennial rye grasses, although other grasses can be affected too.

The fungus that causes red thread (Laetisaria fuciformis) is present in all lawns however it stays dormant for the majority of the year.

Red thread is more common during the months of late summer and early fall/autumn as the weather is generally damp and warm. The fungus loves these humid conditions and therefore spreads it spores during this weather period.

So how do you spot that your lawn is suffering from red thread?

First of all you will notice that small yellow and brown patches are appearing on the lawn. These will range in size from between 3 inches and 7 inches in size.

The brown patches might begin to multiply or get larger however they will stop eventually as the weather becomes drier or cooler.

On close inspection, the tips of the grass blades will have a pinkish-red tip. The tip will likely have a feathered appearance and could be tangled to a neighboring grass blade. This will give the grass a matted effect that isn’t pleasant to look at.

Eventually, the grass blades will dry out and die.

Next, lets see how we can get rid of red thread from your lawn.

How do I get rid of red thread?

The short answer to this question is apply a nitrogen rich fertilizer or a special lawn fungicide as soon as you see red thread appearing in your lawn.

Let’s look at why applying a fertilizer will help your lawn recover from this fungal infection.

This is key for two reasons.

  1. Red thread is usually a sign of an under-fed, nutrient hungry lawn. Applying a fertilizer will replenish the lawn with what the grass needs to prevent the spread of the problem.
  2. Red thread doesn’t kill the grass roots, meaning that the plant will be able to replace the damaged grass blades with lush green grass shoots. The nitrogen will stimulate this new growth quickly.

It’s also possible to apply a lawn fungicide to kill the fungus that is causing the damage to the grass. Gardeners from the U.S. could use a fungicide such as BioAdvanced Fungus Control for Lawns.

Gardeners from the U.K. could use a fungicide like Provanto Lawn Disease Control.

Both of these products should protect your lawn for up to 4 weeks.  Although they can be applied at any point in the year, we would recommend that you only apply these fungicides when the weather is at its most humid during the summer months. This is the period of the year when your lawn is most susceptible to red thread.

As always, closely follow the manufacturers instructions on the packet.

One thing to remember when using fungicides is not to overuse them. This is because the fungus that is naturally present in the lawn may build up a resistance to these products, meaning that if red thread reoccurs, you won’t be able to remove it as easily.

Therefore, ensure that you apply a fungicide no more than once every 2 years.

Rather than using a fungicide, the best solution would be to prevent red thread from affecting your lawn in the first place. With that in mind, let’s look at preventing it in the next section.

How do I prevent red thread in my lawn?

Knowing how to prevent red thread from attacking your lawn requires you to know the root causes of this fungal infection. The basic factors that contribute to red thread is continuous humid weather as well as a stressed lawn.

These are the main causes of a stressed lawn that red threat will take advantage of:

  1. Lawn nutrition.
  2. Blunt mower blades.
  3. Lawn thatch.
  4. Over-watering.
  5. Low light/shade.

Lawn nutrition – soil with low nutrient content will generally result in grass that is of low quality and prone to attack from fungus such as red thread. Ensuring that your grass is well fed with a high-quality fertilizer will help reduce the chances of disease in your lawn. We’ve written an article on good lawn feeding practices.

Blunt mower blades – A blunt mower blade will tear and rip the grass blades instead of cutting neatly through them. This tearing will wound the plant and allow a fungus to attack it given the right weather conditions. Sharpen your mower blades once a year at a hardware store so that the mower slices through the grass cleanly.

Lawn thatch – Thatch in your lawn will prevent air and nutrients from penetrating into the soil effectively. Over time, this will reduce the vigor of your turf. Scarify your lawn once a year, preferably in the early fall/autumn.

Over-watering – This will create a humid environment in your turf that is the ideal growing condition for the spread of fungus’ such as red thread. The golden rule for watering is to water your turf thoroughly but infrequently. Follow this guide on how to ensure that you don’t over-water your grass.

Low light/shade – Try to thin out any shrubs or trees that might cast a shadow over your lawn. Higher light levels will mean stronger grass. It will also allow your turf to dry quickly when wet thus decreasing the chances of the spread of fungus.

Aeration – aerating your lawn will allow air, nutrients and water to seep into the soil to encourage strong root growth. Strong roots will lead to a strong grass blade that won’t be as susceptible to red thread.

Another general tip is to collect your lawn clippings after mowing your lawn at the first appearance of red thread instead of leaving them on the turf.

This won’t prevent red thread from appearing initially but it will prevent the spreading of the disease further.

Will red thread go away?

If your lawn is suffering from red thread, don’t despair as your lawn will recover from this even without applying fertilizers or fungicides.

Red thread will not kill the grass roots which means that the roots will produce new green growth. The brown and pink grass will eventually rot down or be removed by a lawnmower.

It’s likely that turf with a small outbreak of red thread will recover within a few weeks. Larger outbreaks probably won’t recover for a few months or until the beginning of the next growing season.

Laetisaria fuciformis will always be present in the majority of lawns so the best course of action is to prevent it from infecting your grass by removing the conditions that allow it to take hold.