Why are there brown circles in my grass?



You might have Large Patch or Brown Patch disease, both caused by the fungus, Rhizoctonia solani.

In warm-season grasses, it goes by the name of "Large Patch," while in cool-season lawns, it’s called "Brown Patch." Damage from Large Patch is commonly seen in the spring and fall and damage from Brown Patch is commonly seen during the late spring and summer. During the fall, we are beginning to see this in Zoysia, Centipede, and St. Augustine grasses since this fungus thrives in lower temperatures and moist environments.


Look for circles or spots of discoloration in your grass.


This fungus normally lives in our soil, but it begins to cause problems when the environmental conditions are favorable and its growth gets out of hand. It cannot be fully eradicated since it survives in our soil and thatch. Treatments help manage its growth and damage to our lawns, but when lawns have a history of this disease, they do best when they have a fall and spring fungicide treatment.


For a homeowner, the best way to treat this particular fungus is to apply a fungicide labeled for Large Patch. *

* The best products contain the active ingredients, Azoxystrobin and Propiconazole, but they do not sell a combination product with these to homeowners. To be able to treat this at home with products purchased from big box stores, combine Disease X by Scotts with BioAdvance Fungus Control. Disease X has a 0.31% active ingredient of Azoxystrobin and BioAdvance has a 0.51% active ingredient of Propiconazole. This combination is fairly effective at preventing an outbreak, but not at curing an active disease. For comparison, the product that we use is 22.9% active ingredients of Azoxystrobin and 41.8% Propiconizole.



Ways to prevent diseases like Large Patch from getting out of hand in your lawn:
  • Don’t apply high nitrogen fertilizer during the fall.

  • Remove excess thatch (built up grass clippings) from your lawn.

  • Water in the early morning hours, before the dew has evaporated. Do not water in the evenings.

  • Water deep and infrequent, for example, ½” of irrigation 2 times a week.

  • Mow regularly to minimize grass clippings sitting on your grass.


If you have further questions on Large Patch in the Athens or Northeast Georgia areas, contact us.


Further reading:

https://hgic.clemson.edu/factsheet/brown-patch-large-patch-diseases-of-lawns/

https://extension.uga.edu/publications/detail.html?number=C1088&title=Identification%20and%20Control%20of%20Rhizoctonia%20Large%20Patch%20in%20Georgia



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