Take All Root Rot

Springtime weather brings beautiful wildflowers, lovely weather for picnics, and lots of fungus among us.  I wish I was talking about tasty mushrooms that we can sauté with a good steak, but the fungus that is popping up in many lawns this spring is Take All Root Rot.

Take All Root Rot, gaeumannomyces graminis var. garminis, is a fungual disease that causes weak, dead patches in turfgrass.  St. Augustine grass is most affected by take-all root rot, but it can also affect bermudagrass and Zoysia grass.

The symptoms of take-all root rot usually appear in spring and early summer

with yellowish grass that eventually turns brown and wilts.  The turfgrass thins and leaves brown patches that range in size from one foot to more than 20 feet in diameter.  As you can imagine from the name of this fungus, the roots of infected grass turn black and rot.

Take-all root rot lives in the thatch layer of turfgrass, the layer of roots, stolons, and decaying plant matter that lives at the soil surface.  The fungus is always present but takes advantage of turfgrass that is under stress from environmental conditions like too much shade, water, or extreme temperatures.

Our lawns have certainly been through a stressful few years.  We have been in drought for more than a year, and the summer of 2022 was very hot and dry.  The hard freeze in late December 2022 with temperatures down to 12 degrees Fahrenheit was an additional stress, followed by a cool spring.  These environmental stresses make it hard for turfgrass to resist a fungus like Take All Root Rot.

Sometimes our lawn care programs can contribute to conditions that will encourage Take All Root Rot.  Too much irrigation, over-fertilization, compaction, and improper mowing can all weaken the grass and create conditions for the fungus to spread.

You can prevent Take All Root Rot in your lawn by following some best practices for lawn care.  Water only when the grass needs supplemental irrigation, and water deeply to encourage deep rooting.  Deep, infrequent watering is better for your lawn than frequent, shallow watering.

Aerating your lawn with a hollow-tine aerator will relieve compaction, increase oxyen availability to the roots, and improve water infiltration.  Conduct a soil test to determine how much fertilizer your lawn needs.  Too much fertilizer will contribute to fungal growth, so only apply what is required.  Grass clippings and an application of compost might be all the fertilizer your lawn needs.

If you think you might have Take All Root Rot, you can submit a sample to the Texas A&M Plant Disease Diagnostic Lab.  The submission forms and a tutorial video about how to collect a grass sample may be found at plantclinic.tamu.edu/.  If take-all root rot has infested a lawn, a fungicide should be applied in the spring and fall.  Water the lawn thoroughly after fungicide application to ensure it moves into the root zone.

For more information about trees or other lawn and garden topics, contact County Extension Horticulturist Kate Whitney-Hajda at the Williamson County AgriLife Extension Office at 512-943-3300.

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