Grass Fungus


There's little more discouraging to a homeowner than seeing what was once a healthy lawn destroyed by a grass fungus. Besides being expensive to repair, a lawn fungus is time consuming, destroying as much as a year's worth of work on a lawn. There are about 10,000 fungi that can cause plant diseases, according to Lawn Several types of lawn fungi can attack grass, so it's important to recognize a particular fungus and know how to eliminate it from a lawn.

Spread of Fungus

Grass fungus is the most common type of lawn disease. The fungi are thread-like organisms that are microscopic and spread by spores as well as by underground filaments. The spores can be spread either by air or water and produce infections when environmental conditions are favorable or whenever a particular host is susceptible.


Rhizoctonia blight, or brown patch, affects warm-season grasses. This fungus involves a purple or gray "smoke ring" that appears in the morning and then fades away later in the day. Leaf spot is detected when brown and purple spots appear on grass blades. Brown patch can be prevented by mowing at the proper height and ensuring that a lawn doesn't stay wet constantly. Fairy ring is a fungus leaving dark green rings and brown mushrooms. The fungus feeds on old thatch and dead vegetation beneath a lawn's surface.


Sometimes lawn fungi are hard to diagnose. Some of the main signs in detecting a fungus include changes in lawn color, abnormal leaf growth and rings that form on grass. The shape and size of dying or dead grass patches and particular spots on leaves are factors that can indicate a fungus. Common symptoms of a lawn fungus are yellow or brown patches, dead grass and mushrooms sprouting in the grass.


Poor soil is often the cause of fungal diseases of grass. The best way to fight this problem is have a lawn aerated in the spring each year. The pH of the soil should be checked to determine if lime should be applied. Over fertilizing can cause a heavy concentration of nitrogen in a lawn, which can result in a lawn fungus. It also helps to maintain a record of lawn treatments, such as watering frequency, mowing heights and types of fertilizers. Fungicides should be used sparingly, as beneficial organisms may be killed as well. The best defense against lawn fungus is the establishment and maintenance of a strong, healthy lawn.


What appears to be a lawn fungus may actually be a dog urine burn. Dog urine can create small areas of dead grass that look like lawn fungus. To determine if a patch of dead grass is due to dog urine, heavily water the area. If the spot becomes green from watering, it was because of dog urine rather than a fungus. Damage from bugs can also resemble a lawn fungus. Being able to pull out a clump of grass in chunks is a common sign of grubs. Closely examine a damaged spot that appears to be a fungus to check for insects crawling around in the dirt.

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About this Author

Venice Kichura has written on a variety of topics for various websites, such as Suite 101 and Associated Content since 2005. She's written articles published in print publications and stories for books such as "God Allows U-Turns." She's a graduate of the University of Texas and has worked in both Florida and Connecticut schools.