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How to Kill Grass Fungus

By Kelly Shetsky ; Updated September 21, 2017

Hundreds of diseases can affect grass. The most common are Brown Patch and Dollar Spot. Both cause spots to appear on your lawn, ruining the appearance of the grass. Warm, moist conditions create a perfect breeding ground for grass fungus. It can also develop if air is restricted from reaching grass. Kill grass fungus with fungicides.

Measure the pH of your soil with a test kit obtained from a nursery or garden center. Soil needs to be balanced (with a pH between 6.5 and 7.0) before killing grass fungus. Measure your grass twice per season.

Raise the soil pH if it is below 6.5. Apply liquid lime with a sprayer weekly until the soil's pH is high enough for fungicide applications.

Determine the square footage of your property, which is necessary when formulating how much fungicide to use. Multiply the length by the width.

Apply a quick-release liquid fertilizer to the unhealthy grass. Follow the dosage instructions on the label. The lawn will absorb it and become stronger, less likely to fall victim to fungus again. The food also helps kill the disease.

Spray a liquid fungicide over the affected grass. Choose one that has the active ingredient Chloronthalonil. It kills fungus upon contact. The fungicide will also seep into the soil and continue working for up to two weeks.

Re-apply the fungicide seven days later. Treat every two weeks until the weather changes to avoid any more fungus outbreaks this season.


Things You Will Need

  • pH test kit
  • Liquid lime
  • Sprayer
  • Liquid fungicide


  • Use a granular fungicide if you prefer. Spread it over the affected grass with a spreader right before fungus outbreaks usually occur. The granules will release over the course of two to four weeks.
  • Recycling grass clippings will increase the likelihood of grass fungus. Bag clippings instead during fungus outbreaks.


  • Avoid watering your grass in the early evening because it'll stay moist all night, inviting the development of fungus spores.

About the Author


Based in New York State, Kelly Shetsky started writing in 1999. She is a broadcast journalist-turned Director of Marketing and Public Relations and has experience researching, writing, producing and reporting. She writes for several websites, specializing in gardening, medical, health and fitness, entertainment and travel. Shetsky has a Bachelor of Arts in communications from Marist College.