What is lawn fungus and is it killing my grass?

[fa icon="calendar"] Thu, 04/02/2015 - 9:30 / by Lynn Tootle

Fungal turf diseases are very common throughout the country and can leave your lawn looking brown or burnt and in some cases, permanently kill the grass all together. In the Southeast, the most common of these diseases are Brown Patch, Take All Patch and Gray Leaf Spot.


Certainly grass type and soil quality are important when it comes to having a beautiful lawn, but it’s the ongoing care - watering, mowing, fertilizing, etc that has the most impact. Upwards of 80% of yard issues are caused by homeowners and most of those are related to irrigation, typically over-watering. We all know that plants need water but often fall victim to the thinking that if some is good, more is better. Many of us have also invested our hard earned dollars into irrigation systems and want to see them put to use. Mowing the grass too short can also make the lawn more susceptible to compounding issues. Stressed plants emit pheromones which attract bugs, wet thatch encourages disease and overfeeding can inspire the growth of unwanted plant and fungal species. To learn more about watering and mowing guidelines, check out this Spring Checklist to get your lawn healthy before the heat of summer.


If you have turf, it is at risk of turf disease. Soil microbes are naturally occurring and exist in all soil. These generally work symbiotically with plants but when certain environmental conditions are met, they react and can cause lawn fungus or disease damage. Three things are necessary for turf diseases to become active:

  1. Pathogen - naturally occurring in the soil (soil is mandatory for a lawn)

  2. Host - grass is the host (grass is mandatory for a lawn)

  3. Environment - temperature, wetness, and humidity all play a role; when the right conditions of all three are present at the same time, some diseases thrive (the natural environment is impossible to control but you can take steps such as following proper watering guidelines, removing thatch and improving drainage to counter ground wetness)

Brown Patch & Take All Patch

Symptom Descriptions: My grass was green but now has circular brown patches; the patch started about the size of a coffee cup but is radiating out equidistantly; some of the patches may be overlapping each other; my cousin is convinced aliens made crop circles in my lawn.

Grass Affected: all grass types are susceptible to Brown Patch and Take All Patch

About Brown Patch & Take All Patch: Both diseases are caused by naturally occurring, soil borne fungi, when conditions are warm and wet. The symptoms are nearly identical and are most common when temperatures are 70-90+ degrees fahrenheit and humidity levels reach 70% or greater. Lawns are most susceptible to these diseases when thatch (the area between the dirt and the green part of the grass) is wet for eight hours or more. Low spots or depressions in which water tends to collect are most likely to be affected as well as grass growing in soil which contains clay.

Gray Leaf Spot

Symptoms Descriptions: My grass looks like it is melting; it’s more grey than green and the leaves have small grey or brown spots; the leaves are fizzling out; it looks like we’re suffering from drought even though I’m watering frequently.
gray leaf spot damage

Grasses Affected: this disease is specific to St. Augustine grass

About Gray Leaf Spot: This opportunistic turf disease thrives on stressed grass most often in the peak of summer when temperatures are 85 degrees fahrenheit or greater and the thatch has an excess of eight hours of wetness. PRO-TIP: High traffic areas or grass that is cut with dull blades are most susceptible.



Treatments for most turf diseases include a combination of fungicides and an adaptation to the lawn itself including strategies to rid excess moisture: thatch removal, irrigation improvements, changes to watering protocols, etc. Depending on the type of disease, some treatments should be followed up with applications of fertilizer while other should not. For more detailed information on treatment of these turf diseases and more, download a copy of our free e-book: What’s Happening to My Lawn & What Can I Do?

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Topics: lawn care

Lynn Tootle

Written by Lynn Tootle

K. Lynn Tootle is the General Manager of GroMasters Inc., a division of TideWater Landscape Management Inc. Lynn is a certified arborist and turf grass professional, a past president of the Coastal Landscape and Turf Professional Association and a graduate of the Urban Ag Leadership program. He graduated from Clemson University in 1999 with a BS in Wildlife Biology and a minor in Forest Resources.

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