How Do I Treat Grass Mildew & Fungus?


Lawn diseases usually result from pests, poor maintenance or over-watering. Still, even a dense, vigorously growing lawn can be susceptible to mildew and fungus. Most fungal diseases develop after periods of excessive moisture that is combined with warm temperatures. The infected areas of the lawn will generally develop brown, deadened areas, rust colored blades, white or yellow powdery patches, or a combination of the latter. In most cases, lawns with fungal diseases can recover from the illness when treated in a timely fashion.

Step 1

Inspect the grass closely and identify the symptoms. Look to see if discolored blades are wilted, rusted, or browning and dying.

Step 2

Cut back on your current irrigation schedule since most fungal diseases begin with excess moisture. Keep a restrained irrigation schedule until the lawn is treated for disease.

Step 3

Remove any excess debris from the lawn. Rake the lawn thoroughly to comb out any underlying debris. Dethatch the lawn if it has not been dethatched in the past 18 months. Aerate the lawn to improve air circulation and light penetration below the surface.

Step 4

Mow the lawn using newly sharpened and sterilized mowing blades. Keep the lawn between 2.5 and 3 inches during the summer months and between 2 and 2.5 inches during the spring and fall periods. If possible, mow the infected areas last to reduce the potential of spreading the fungus.

Step 5

Remove the mowed debris immediately after completion. Sterilize the mowing blades again to prevent cross contamination of the fungal disease.

Step 6

Purchase a fungicidal spray to treat the lawn. Choose a fungicide that is designed to control the disease, as well as prevent it, such as the Bonide Lawn Fungicide w/Bayleton or Scott's Lawn Fungus Control.

Step 7

Follow the fungicide's directions carefully. Complete the application process on a clear day when temperatures are below 85 degree F and no rain is expected. Do not apply more than the recommended amount. Complete the treatment on a freshly mowed lawn. Repeat the applications as instructed.

Step 8

Irrigate the lawn only when it displays symptoms of drought stress, such as loss of blade resiliency and dullness of color. Water the lawn thoroughly providing 1 to 1.5 inches of water approximately every seven to 10 days. Adjust irrigation levels for rainfall and drought periods.

Things You'll Need

  • Fungicidal spray
  • Water


  • American Lawns: Lawn Diseases
  • Petitti Garden Center: Dethatching Lawn
  • Plant Care: Lawn Fungus Identification and Treatment
  • Bayer Advanced: Controlling Lawn Diseases
  • University of Delaware Cooperative Extension: Fungicide Recommendations for Turfgrass
Keywords: grass fungal diseases, lawn fungus control, treating grass diseases

About this Author

Charmayne Smith is a business professional and freelance writer. She has worked in management for successful organizations since 1994. Smith draws on her business background to write articles, and her work has appeared in a variety of online outlets. She holds a degree in business from Cleveland State University.