Lawn Fungus Identification & Remedies

Updated April 17, 2017

Many homeowners work long and hard to establish a healthy green lawn only to have their efforts compromised by lawn fungus. Determining what causes lawn disease is not easy because not all brown patches and spots in the yard are caused by fungus. Because it is very difficult to eradicate once it becomes established and its causes are varied, prevention is very important in controlling the disease.

Weather-Related Disease

Some fungus problems are caused by poor soil conditions while others are caused by weather conditions. Each type needs a different course of action. Some diseases caused by long, cool wet periods include leaf spot, powdery mildew, red thread lawn, rust and snow mould. The best method for prevention is application of a granular lawn fungicide treatment in late April and again in late May.

Soil-Related Diseases

Soil-related diseases include pythium and fusarium blight, often referred to as patch diseases. A fast treatment is to have the lawn aerated in spring and fall every year and check the pH balance to see if a lime application is needed. The lawn should not be over-fertilised with heavy nitrogen when these lawn fungi are present.

Other Types of Fungus

There are numerous types of lawn fungus including fairy rings, rust attacks, powdery mildew and grease spot. However, dollar spot and brown patch are the most common. Both tend to thrive in warm, humid environments. Dollar spot tends to grow on grass which is low in nitrogen or not fertilised properly while brown patch tends to grow in grass which is high in nitrogen or over-fertilised.

Fungicide Classifications

There are three basic lawn fungicide classifications: contact, systemic and penetrant. Contact fungicides remain on the top of grass blades, killing any spores that may be present. This process degrades with sunlight and rain and is considered minimally effective. Systemics are dissolved into the soil and taken up into grass plants through the roots. This treatment is longer lasting and more effective in preventing lawn disease. Penetrants are similar to the systemic process but are a more preventive-type treatment.


Properly watering your lawn is an important component in preventing lawn fungus. Deeply water the lawn a few times per week, preferably on days when it is going to be sunny and warm. To help avoid fungus growth, try to remove any excess snow from the lawn which will not quickly melt. Always catch grass clippings when mowing the yard, particularly when a disease is present. Rotate fungicide products so the lawn does not grow resistant to any one product. Mulching and monitoring the lawn's nitrogen level will also help prevent future fungus growth.

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About the Author

Pat Krueger works full-time in the corporate world, manages a home and family, and recently received a Bachelor of Science in business administration from the University of Phoenix. Her freelance writing can be found on and