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Lawn Rust | Dealing with Grass Rust Fungi

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....

In the same way that many other plants do, lawn grasses may get infected with rust diseases, which cause the leaves to turn yellow and become ugly. Thankfully dealing with grass rust fungi is relatively straightforward. 

Rust is most often seen in the late summer or early autumn (fall) and is common in damp humid weather and times when heavy dew may be present.

It is a foliar disease that particularly affects turfgrasses on a regular basis. A variety of fungi, mainly of the Puccinia or Uromyces genus, are responsible for the disease. Affected regions have the potential to release large quantities of airborne spores.

Lawn Rust Symptoms and Signs to Look For

The first sign of lawn rust is the appearance of small yellow or brown spots on the grass blades. These spots appear in groups of two or three together. As the disease progresses, the spots will grow larger and become darker in color. Eventually, the entire leaf turns yellow and begins to curl at the edges.

lawn rust

What Are the Main Causes of Lawn Rust

The most common cause of lawn rust is the fungus called Puccinia triticina. It’s spread by windborne spores from infected plants to healthy ones. It thrives in wet soil and damp, humid conditions or weather.

How Grass Rust Fungi Spreads

The fungi appear on the grass blades as orange pustules. These pustules generate tiny spores that travel vast distances in the air propelled by breezes and can spread over vast areas. For the spores to then infect the area the surface of the grass blades has to be moist or damp for a number of hours before germination of the spores can occur. The germination process causes the spores to change into tiny structures called urediniospores. When these structures come into contact with another plant, they can infect it.

This entire process takes approximately two weeks, and that is why longer, un-mowed grass may be more susceptible to a serious rust attack since the infection can establish itself and then spread to other grass plants in the surrounding area, resulting in a severe rust attack.

As such lawn rust is consequently most noticeable during either rainy summers and, more specifically, during the fall months, when prolonged dew causes the grass blade to be wet for lengthy periods.

When the colder weather and winter come, the now black pustules release overwinter spores that are well-adapted to survive in freezing temperatures and less benign conditions.

What Damage can the Grass Rust Fungi Cause

What Damage can the Grass Rust Fungi Cause

When it comes to grasses, rust disease seldom creates major difficulties, and the issue is usually an aesthetic one as the fungi generate vast, ugly swaths of diseased grass.

However, it does weaken the grass and weaker grass might become more vulnerable to infection by other diseases, including red thread or fusarium, that can quickly escalate into a significant issue if left untreated.

The Main Grass Types Commonly Affected with Grass Rust Fungi

There are many different grass types that can be affected by lawn rust diseases. The most common grasses include Bermuda, Kentucky bluegrass, fescue, zoysia, centipede, rye, timothy, brome, bentgrass, and others. In general, it tends to be the broader stemmed grasses that are most susceptible to the disease because of the increased surface area of the individual grass blades. 

How to Identify Grass Rust Fungi

How to Identify Grass Rust Fungi

Most lawn rust is caused by two fungal species: Puccinia graminis and Pucciniarecondita. These fungi infect the leaves and stems of the grass, causing them to turn yellowish-green and eventually die. Lawn rust diseases may appear at any time during the growing season, but they tend to be worse in humid and wet weather.

Problems Associated with Rust Fungus

The most common symptoms of lawn rust include yellowing, (caused by the yellow spots on the blades) and wilting of grasses, especially those infected early in the season. If left untreated, lawn rust can cause a significant scaring effect on an infected lawn.

Dealing with Grass Rust Fungi

Lawn rust fungi grow best at temperatures between 60–80 degrees Fahrenheit. To prevent infection, it’s important to keep the soil moist but not soggy. Additionally, it’s important to apply fungicides at least three times during the growing season to kill the fungus before it has a chance to infect new areas of the lawn.

How to Get Rid of Lawn Rust

Lawn rust can be controlled by using fungicides that contain Azoxystrobin or Chlorothalonil. These should be obtainable from good garden centers. Their effect can be quite rapid with visible results in around 48 hours. One thing to bear in mind is that the runoff can contaminate water bodies such as ponds or streams.

In order to avoid chemicals coming into contact with your skin, or worse, your eyes during treatment, it is recommended that you put on the appropriate safety equipment for the work prior to beginning. Safety eye-wear and long-sleeved clothes should provide sufficient protection.

The most effective technique to cure rust on your lawn is to apply a fungicide directly to the places where you see it has occurred. What this will do is halt the progression of the disease and aid help the grass achieve a speedier recovery time.

Getting Rid of Lawn Rust Naturally

There are many different ways to prevent lawn rust from spreading. First, you should remove all weeds from around your yard. Then, apply a nitrogen-based fertilizer every two weeks. Finally, keep your lawn well-watered, although not drenched, so that it doesn’t dry out.

nitrogen rich fertilizer

For lawns that suffer from repeated rust infections, it might be wise to try overseeding your lawn with grass species that are considerably more resistant to infection in the first place.

Preventing Lawn Rust Good Lawn Care

In common with other lawn diseases, the most effective lawn treatment is to eliminate the circumstances that produce rust.

Preventing lawn rust starts with proper maintenance. Mowing your lawn regularly helps prevent the disease because it keeps the topsoil exposed to air, thus reducing the amount of time the spores can survive.

In addition, you should also fertilize your lawn regularly. You should use a fertilizer that has Phosphorus and Potassium in it and you should apply it at least twice during the fall period. This will give your grass enough nutrients to grow well without having to add extra fertilizer later on. Fertilizer should be applied before rain or irrigation so that it gets into the soil.

Summary: Dealing with Grass Rust Fungi

Lawn rust diseases are caused by pathogenic fungi which infect the grass plants. In addition to lawn rust diseases, fungal lawn diseases include brown patch, dollar spot, fairy rings, gray leaf spot, summer patch, snow mold, turf rot, and other lawn diseases.

The best solution for dealing with grass rust fungi is to implement a good lawn care program so that you can limit or eradicate the circumstances in which it can take hold and ensure good grass growth.

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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