5 Common Diseases Affecting Tennessee Lawns (and how to prevent them)

BY pure turf
May 5, 2022
Lawn Care

Do you find yourself dissatisfied or frustrated with your lawn’s health and appearance? Have you noticed brown patches forming or white fungus growing in your grass? No matter how skilled you are at lawn care, many diseases might infect the grass on your lawn and cause a lot of frustration. Pure Turf is here to help, particularly if you need lawn care in Nashville!

In this article, we cover five kinds of lawn fungi you are likely to encounter in Tennessee and how to manage them. Because prevention is the best strategy, we also address five trusty ways to prevent grass fungus.

5 Common Lawn Diseases (and how to deal with them)

Brown Patch

Brown patch is caused by the fungus, Rhizoctonia solani. Brown patch is likely in several environments. The following three are common:

  • Grass that stays damp when nights are cool and days are hot
  • Grass that is cut too short (exact length varies on the type of grass, but generally grass shouldn’t be shorter than 3 inches)
  • Grass that is over-fertilized with nitrogen-based fertilizers

Identifying brown patch is relatively easy because it looks pretty much how you’d imagine. Here are a few characteristics to look for:

  • Brown Circles: this disease creates roughly circular brown patches. These vary quite a bit size-wise but may have diameters of up to 20 feet in hybrid bermudagrasses. Although the patches are usually brown, they sometimes include purplish hues or very dark green, as if the grass were wet.
  • Brownish Spots on Blades: sometimes the blades of grass don’t turn entirely brown and instead are covered with brown or yellow spots.
  • Smoke Rings: there is often grayish-white growth around the edges of a brown patch. These are especially apparent in the morning before the dew has dried.

Brown patch can be managed via several methods. Increasing air circulation (through trimming and pruning), good drainage, and the use of fungicides and herbicides (Heritage G and Headway G are good options) effectively decrease brown patch. Interestingly, it is best practice to avoid mowing until the brown patch is under control, as mowing can spread the fungus.

Brown patch can be managed by increasing air circulation or providing good drainage

Dollar Spot

Dollar spot sometimes looks like a mini brown patch. It presents small circular spots of dead grass that are about the size of a dollar coin. The infected grass usually looks bleached or tan.

Caused by the fungus Clarireedia jacksonii, this disease affects many kinds of turf grass. It is most active in temperatures ranging from 50 to 90 degrees Fahrenheit. Fascinatingly, both leaves of grass that stay wet and grasses that are experiencing drought stress are equally vulnerable to dollar spot.  Dollar spot is a hardy fungus. It can survive tough conditions!

What are some steps to get rid of troublesome dollar spots? Here are a few techniques you can utilize immediately to manage dollar spot:

  • Proper watering and fertilization
  • Remove excess thatch (dead/dried grass that gets mixed with the living grass)
  • Prune to improve air circulation
  • Remove infecting clippings
  • Wash equipment that has come in contact with the infected grasses

Powdery Mildew

Although powdery mildew attacks a variety of plants, bluegrass is especially susceptible. It generally forms from the fungus Erysiphe graminis and spreads via spores that float through the air. The spores may remain dormant on a plant (even through the winter) until the conditions are right for it to grow. Grass infected with powdery mildew looks like it’s coated with a white powder. From a distance, this can sometimes look like frost.

Powdery mildew

Contributing factors to powdery mildew include:

  • Poor air circulation
  • High Humidity
  • Shade
  • Large amounts of nitrogen fertilization

Increasing sunlight and air movement (by pruning surrounding trees or bushes), appropriate irrigation, and higher mowing heights are all ways to manage powdery mildew. Fungicides are always an option as well.

Red Thread

Caused by the fungus Laetisaria fuciformis, red thread thrives in cool, damp conditions. Red thread most commonly grows on the stems of grass but does kill the entire plant in some severe cases. It turns the grass a pink or red color, hence the name.

Red thread attacks various turf grasses including bentgrass, bluegrass, fescues, and ryegrasses. Lawns that are under-fertilized with nitrogen fertilizers are especially at risk.

Chemical treatments are generally not recommended for red thread. The most effective way to manage red thread is to properly fertilize with a nitrogen fertilizer. However, a professional should do this as over-fertilizing increases the risk of other diseases like powdery mildew, which we addressed previously.

Nitrogen fertilizer for red thread

Fairy Rings

Although fairy rings sound magical and like a good garden omen, they actually signal that an unwanted fungus has infected your lawn. Fairy rings form from various types of fungi that feed on decaying matter like tree stumps or leaves. There are three different kinds of fairy rings:

  1. Circles of brown, wilted grass
  2. Circles of deep green grass
  3. Circles of mushrooms

Fairy rings do not usually kill the grass (except in severe cases) and generally disappear with changes in the environment. However, there are some more active methods to managing fairy rings than simply waiting for them to disappear. These include:

  • Aeration
  • Thoroughly removing organic matter (leaves, stumps, thatch, etc.)
  • Applying nitrogen fertilizer (for type 2 fairy rings)
  • Pulling or raking mushrooms (for type 3 fairy rings)
Common Types of Grass Disease

Helpful Preventatives For Lawn Diseases

We all know that prevention is the best strategy, which is why it is important to maintain great lawn care habits that decrease the risk of lawn diseases! Following are five key preventative strategies.

Proper pruning and trimming

It is important to keep bushes and trees well-trimmed to promote good airflow. This decreases the risk of various lawn fungi including brown patch and powdery mildew. Keeping grass trimmed to an appropriate length (3-4 inches for most grasses) and mowing regularly also lowers the risk of lawn diseases.

Proper Irrigation and Drainage

Numerous grass fungi form in overly damp conditions. This means it’s vital not to overwater your lawn. If your lawn does need irrigation, it is best to irrigate in the morning so the grass has time to dry before nightfall. Along with this, make sure your lawn has good drainage. Good drainage mitigates low spots where grass remains damp or soil stays soggy.

Grass fungi form in damp conditions

Proper Fertilization

Fertilization is as essential as it is tricky. As we mentioned earlier, over-fertilization may lead to some forms of grass fungus, but, unfortunately, under-fertilization can do exactly the same thing!

However, when a lawn is properly fertilized for the type of grass planted there, diseases are much less common. This takes care, knowledge, and precision, but the outcomes are worth the work!

Thatch Reduction

Grass that dies and grass left behind after mowing turns into thatch. While some thatch is good (it’s a natural fertilizer), too much increases the risk for several diseases, like fairy rings and dollar spot. Dethatching can be done by raking with a regular leaf rake or with a dethatching machine.

A Good Lawn Care Company  

You may be feeling overwhelmed with the amount of work and precision required to maintain a beautiful, healthy lawn. This is where a good lawn care company is a life-saver. Not only do they provide professional insight and experience, but they also take care of the work and worry of lawn care.

The team at Pure Turf, LLC would love to be that lawn care company for you! All of our programs include practices that mitigate disease and promote healthy, beautiful lawns.

With our standard lawn care plan, we include practices like:

  • Balanced fertilization
  • Double core aeration
  • Broadleaf weed control

But it doesn’t have to stop there! We offer Premium and Elite lawn care programs that take your yard to the next level with practices like grub control, liquid soil conditioner, and lawn disease prevention.

beautiful lawn


A healthy lawn makes a big difference in having an inviting, beautiful home. If you’ve recognized any of the grass fungi we discussed as ones that may be infecting your lawn, we’d love to help! Reach out today for a free estimate and take the first step toward a lush, green lawn!

We also offer a variety of other lawn care services:

  • Lawn Fertilization and Weed Control
  • Lawn Disease Prevention
  • Fall Aeration and Seeding
  • Soil Health Elite
  • Mosquito Control

Feel free to contact us anytime. We look forward to hearing from you!

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