Why the Best Control for Lawn Diseases is Prevention

The majority of lawn diseases are caused by fungi that live in the soil.

There are both good and bad fungi that live in your soil. The good fungi help break down the thatch so water and nutrients can reach the soil and grass roots. The bad fungi, called pathogens, are the fungi that cause disease. The pathogens are usually controlled by the good fungi and micro-organisms that live in your lawn.

Understanding the Factors that Contribute to Lawn Disease

Your first step should be to understand the factors that leave your grass susceptible to lawn diseases.

There are 3 factors. All 3 factors must be present in order for the fungal disease to develop.

  • There must be a pathogen
  • The grass plant must be vulnerable to disease.
  • The right conditions must exist.

Identification – A Difficult Task

Lawn diseases can be very difficult to identify. They can easily be confused with drought and lawn pest damaged grasses. The signs and symptoms for most diseases are very similar. Correct diagnosis can prove to be very difficult.

There are 4 steps you can take in identification:

  • Look for a pattern in the damaged grass (i.e. color of grass, shape of damaged areas and how often damaged areas appear throughout the grass).
  • Look at the grass blades for a change in their color. Also, look for striping and/or a powdery substance on the grass blades.
  • Make note of when you first noticed the lawn damage and what weather conditions existed.
  • If necessary, ask a professional for assistance in the correct diagnosis.

Common Lawn Diseases

Brown Patch - Large circular areas throughout your lawn. The patches have a discoloration that appears to be either brown or gray. The edges of the grass blade appear to be drenched with water. Learn more about brown patch.

Dollar Spot - Small spots of grass die. The spots tend to be a straw color. In the morning, you may notice a cobwebby white fungus on the grass plant. Learn more about dollar spot.

Fairy Rings - Dark green rings of grass outlining areas of lighter colored or dead grass. Lawn mushrooms may be present on the perimeter of the ring. <strong>Don’t eat the mushrooms</strong>, they are poisonous. Learn more about fairy rings.

Fusarium Patch (Pink Snow Mold) - Small white or pink patches on dead grass. Usually develops under snow or near a melting snow bank.

Powdery Mildew - During cool, rainy weather light patches of dusty white to gray grows on the grass blades.

Your Best Defense Against Lawn Diseases is Proper Lawn Maintenance

Fungal diseases are easier to prevent than to cure. Proper lawn maintenance and knowledge will help ward off lawn diseases. Early detection that something is off with your lawn care regiment is important. You can take that information and modify your lawn maintenance practices as necessary.

Grass Type - Make sure the type of grass you have works well in your particular climate. If your grass cannot adapt to the weather conditions that you live in, it becomes weak and prone to disease. Learn more about grass types and what climates are best for each type.

Cutting Grass - Cutting your grass too short weakens the grass plants. Weak grass plants make the grass plant susceptible to disease, lawn weeds and lawn pests. Remember you should only remove 1/3 of the grass blade each time you mow. Always keep your mower blades nice and sharp. To keep disease away from your grass plants, you want a clean crisp cut rather than a cut with ragged ends. Learn more about cutting grass.

Fertilizing - Apply proper amounts of fertilizer for your grass type. Applications should also be made at the suggested times of the year as well. Using controlled release (slow-release) fertilizers is best.

Too much fertilizer can encourage thatch growth in some lawns. The thatch provides a home and food source for the disease causing organisms. Keep your thatch layer less than ½ of an inch thick. Otherwise, the grass will be weakened because it slows (in some cases stops) water and nutrients from reaching the grass roots. Learn more about fertilizing your lawn.

Watering Your Lawn - Wet conditions invite fungus. Watering your lawn during the day is of the utmost importance. This allows the grass to dry up before nightfall. Also, only water your lawn when it is absolutely necessary. Be sure to water deeply, this promotes deep root growth. Learn more about watering your lawn.

Soil Compaction - This is very important. The water and nutrients must be able to reach the grass roots to grow healthy plants. Aerating and adding organic matter is very helpful.

Use of Chemicals - Over use of herbicides, insecticides and fungicides can disrupt the natural composition of your lawn and soil. Both the beneficial and harmful organisms can be destroyed. This can weaken your grass plants leaving them susceptible to lawn diseases.

Lawn Fungicides – Should You Use Them?

Fungal diseases are tough to control with chemicals. Since the fungus moves inside the plant itself, it is very difficult to kill the fungus. You can make a bad situation worse by using a fungicide.

There are 2 types of fungicides:

  • Contact Fungicides - Treat the outside of the plant. This type of fungicide works best when applied before the disease appears (i.e. if you know your grass type is prone to a specific disease).
  • Systemic Fungicides - Treats the fungus from inside the plant. This is the most effective type of fungicide. Read the label carefully, because this type of fungicide usually only treats a specific disease.

There are some precautions that should be taken when applying fungicides.

  • Can cause skin irritation.
  • Read and follow the directions exactly as indicated on the package.
  • Be sure the fungicide you purchase controls the type of disease in your specific grass type.

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Brown Patch

Brown Patc

Dollar Spot

Dollar Spo


Fairy Rings

Fairy Rings


Pink Snow Mold

Pink Snow Mold

Emil Yedowitz Landscaping

Powdery Mildew

Powdery Mildew

Iowa State University