How to Treat Lawn Fungus

It comes in many forms: irregular brown patches, unsightly gray splotches, stringy red threads, a dusting of orange-red powder, and more. Regardless of the specifics, however, when a lawn fungus strikes your lawn, you must take prompt action to prevent it from spreading and destroying your grass. Many post-disease treatments double as preventative measures and involve improving the drainage and air flow of your soil. Prevention, in fact, is the best treatment against lawn fungus. You can also apply various fungicides, both chemical and organic, to aid your lawn in its efforts to fight back against the disease.


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    Only water your lawn as much as necessary. The average yard only needs about 1 inch (2.54 centimeters) of water once a week to stay healthy. Most fungi, including brown patch and pythium blight, thrive in moist conditions. Do not keep your lawn too dry, however, since dry soil will lead to weak grass subject to diseases like rust and mildew.
    • Water early in the morning. Your lawn can absorb all the water it needs and dry by the afternoon.
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    Avoid spreading it. Dollar spot and several other fungal diseases spread within minimal effort. Avoid walking over the fungus and clean your yard tools after they touch the infected area.
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    Fertilize your lawn. Grass that does not receive enough nitrogen and potassium can become weak, which makes it easier to catch a fungal disease and harder to fight off. Fertilizer does for sick lawns what vitamin C does for humans during a cold. A good dose of slow-release fertilizer can give your grass what it needs to begin its recovery from various fungi, such as red thread and rust.
    • Note that too many feedings can also weaken your lawn, however. It is best to apply fertilizer as instructed on the label.
    • Try using a low-nitrogen, slow-release fertilizer to prevent fungal diseases like gray snow mold. Even though grass deprived of nitrogen is susceptible to fungi, it is also easy to overdose your grass with nitrogen and weaken it that way.
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    Keep your lawn mowed at a healthy height. Raise your lawn mower blade to the highest setting and never trim away more than 1/3 of the grass height at a time. Your grass needs to stay thick and lush. Short grass is young grass, and young grass is tender and weak against fungi. Taller, older grass is stronger and stands a better chance of fighting back against disease.
    • Make sure you keep the blade sharp and clean. Dull blades do a sloppy job of cutting and may make the grass weaker. Dirty blades could spread lawn disease.
    • Mow your lawn a little shorter than usual before snow comes. Stubble spells death for your lawn during any season, but notably long grass during the winter may breed gray snow mold.
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    Give things time. Many fungal diseases go away on their own with proper lawn maintenance. Gray snow mold usually goes away once temperatures reach above 40 degrees Fahrenheit (4 degrees Celsius), especially if the temperatures climb quickly. Likewise, red thread usually disappears by summer, when the weather heats up and dries out. Even though these diseases are unsightly, they do not always mean immediate death for your lawn.
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    Mulch leaves into your lawn in autumn. A thick coating of leaves could invite gray snow mold and other winter-bred fungi. Instead of allowing the leaves to pile up, remove them completely or use your lawnmower to mulch them into the grass.
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    De-thatch your lawn. Thick build-ups of thatch—a layer of dead grass, leaves, roots, and stems—smother the soil, preventing it from breathing. Soil that lacks proper air circulation is more likely to get a fungal disease, so de-thatching is often used for preventative treatment. De-thatching can also stop the spread of some fungi, like necrotic ring spot, melting out, leaf smut, and summer patch, after it infects your lawn.
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    Top-dress your yard to improve the soil quality. Top-dressing is a layer of nutritional, well-draining growing medium. It often consists of materials like sharp sand to improve drainage, a crumbly soil like loam or topsoil, peat, or compost to provide extra nutrition. Spread the top-dressing over your lawn and rake it into the soil. The top-dressing will improve the soil's ability to drain, thereby fighting fungi.
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    Apply a fungicide to your lawn. Usually, you need to apply a fungal control product once every other week, three times or more. Some fungi respond best to certain chemical treatments, however, while others do not respond to any at all. Before purchasing and applying a fungicide, you should determine what fungus your lawn has and which chemical can take care of it best.[1]
    • Benomyl is potent against a range of fungi, including snow mold, brown patch, and dollar spot.
    • Triadimefon works well against anthracnose and rust.
    • Chlorothalonil does best against brown patch and red thread.
    • Fairy ring has no cure once it establishes itself in your lawn, and fungicides are only effective against necrotic ring spot if accompanied by a de-thatching process.
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    Try an organic fungicide. If you prefer to stay away from chemical fungicides, many natural treatments can be used instead, especially while the fungus is still small. Neem oil, compost tea, and baking soda solutions are some of the most common.


  • Aerate your lawn every year or two. By loosening the soil, you temporarily improve air circulation and drainage, reducing the likelihood of fungi attacking in the process.
  • Periodically perform soil tests to detect nutrient deficiencies that have the potential to invite disease. If you can identify a deficiency before it weakens your grass, you may be able to prevent fungi from developing. Soil tests are also useful in diagnosing fungal diseases.
  • Choose a type of grass that is well suited for your climate and soil. Native grasses have stronger defenses against native fungal spores. Many exotic grasses will be weak against these spores, though.


  • Exercise caution when applying chemical fungicides. Many of these fungicides could be harmful to pets and small children if they accidentally ingest them shortly after application. To be on the safe side, keep kids and animals off your lawn for several days following the application of any lawn chemical.

Things You'll Need

  • Garden hose
  • Fertilizer
  • Lawn mower
  • Rake
  • Fungicide, chemical or organic

Article Info

Categories: Lawn Care