Take-All Root Rot in St. Augustine Grass: Signs, Causes and Recovery
- Take-all root rot is caused by the soilborne fungus Gaeumannomyces graminis var. graminis, often shortened to Ggg.
- LSU AgCenter says the fungus is often present in roots without causing much disease, and symptoms show up after the root system is already badly damaged.
- Symptoms start as yellowing and thinning, then brown irregular patches, with short, dark, brittle roots.
- Stress brings it out: compaction, poor drainage, drought, too much water, mowing too low, thatch, poor fertility, shade and herbicide overuse.
- Management focuses on relieving those stresses, keeping soil pH between 5.5 and 6.0 and avoiding lime on affected lawns.
The lawn thinned out over a few weeks. You fertilized, watered more, maybe put down a weed-and-feed, and it kept getting worse. When you pulled at the yellow runners, they came up with barely any roots attached.
That combination points to take-all root rot, a soilborne disease of St. Augustine that does its damage underground before you see anything above it.
At TurnKey Lawn Care, disease diagnosis is part of the seasonal lawn care we provide across the metro. If you’re watching a patch thin out and nothing seems to help, request a free estimate and we’ll dig up a small section and look at the roots with you.
This guide explains what take-all root rot is, how to tell it from look-alikes, which stresses bring it out, and the soil and care changes that give the lawn its best chance to recover.
What take-all root rot is
The LSU AgCenter home lawn series describes take-all root rot as a disease caused by the soilborne fungus Gaeumannomyces graminis var. graminis. You’ll also see it called take-all patch. The unsettling part is how quietly it works. According to an LSU AgCenter article on take-all patch, the fungus is frequently found in turfgrass roots without causing significant disease. The same article warns that aboveground symptoms appear after the root system has already been severely compromised. In practice, the lawn often looks fine for a long time and then declines once something stresses it. By the time you notice the yellowing, the roots underneath have been failing for a while.
Signs to look for
LSU describes the initial symptoms as an overall yellowing and thinning of the turf, sometimes with a drought-stressed look, which later turns into brown, irregular patches. Those early signs are easy to mistake for thirst or a missed feeding. The roots are where the diagnosis gets clearer. Dig up a small section at the edge of a thinning area and look at what comes up:
- Roots that are short, dark and somewhat brittle, where healthy St. Augustine roots are longer and lighter
- Runners that pull out of the lawn easily, because there’s little root holding them down
- Fine black strands on the runners and the base of the leaf sheaths, which LSU says a good hand lens may reveal
- Yellowing that spreads slowly over weeks instead of appearing overnight
LSU notes that affected stolons can be easily removed from the lawn. If you can lift the grass like a loose mat and the roots look dark and stubby, take-all belongs on the list.
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Take-all compared with look-alikes
Several problems yellow and thin a St. Augustine lawn. Our page on why a lawn gets brown patches covers the full range, and this table compares the ones people confuse most.
| Clue | Take-all root rot | Large patch | Chinch bugs |
|---|---|---|---|
| How it starts | General yellowing and thinning | Circular or irregular yellow-edged patch | Yellow patch in full sun near pavement |
| What fails first | Roots, which turn short, dark and brittle | Leaf sheaths rot at the base | Stems and runners drained of sap |
| Tug test | Runners lift out with few roots | Leaves pull off the runner | Blades dry, runners anchored |
| Quick check | Dig and look at the roots | Pull a leaf at the yellow edge | Soapy-water flush at the edge |
A lawn can have more than one of these at once. Our guide to lawn disease prevention in humid Louisiana covers how they overlap through the year.
The stresses that bring it out
LSU says the appearance of symptoms generally coincides with periods of several abiotic, or physical, stresses. The list it gives is long, and almost every item on it is something that can be changed.
Soil compaction and poor drainage
Heavy, compacted soil and low spots that hold water both limit root growth. LSU lists them first. Much of the metro sits on heavy ground that drains slowly, which is one reason regular aeration matters here.
Water, too little and too much
LSU names both drought and excessive irrigation as triggers. A lawn that swings between bone dry and waterlogged puts its roots under constant strain.
Mowing height and thatch
Improper mowing height and excessive thatch buildup are both on the list. Scalped grass has less leaf to feed its roots, and thick thatch holds moisture where the fungus is active.
Fertility, shade and herbicides
LSU also includes improper fertilization, excessive shade and the overuse of herbicides. Repeated weed-and-feed applications on an already struggling lawn are one example.
How to manage take-all root rot
LSU is clear that management starts with cultural practices that relieve the stresses weakening the grass. Fungicides can help as part of that program, but the soil and care changes come first. Work through them in this order:
- Test the soil. LSU recommends keeping soil pH between 5.5 and 6.0, and specifically says not to apply lime to affected lawns.
- Change the fertilizer. Use slow-release, acidifying forms of nitrogen and provide adequate potassium and magnesium, as LSU recommends.
- Water early and deeply. Irrigate as early in the morning as possible, count the rain, and water deeply and as infrequently as the lawn allows without drought stress.
- Relieve compaction. LSU recommends improving internal soil drainage and reducing compaction by aerating regularly.
- Raise the mower. LSU notes that raising mowing height helps the grass recover and increases root growth.
- Deal with thatch and herbicides. Dethatch if the layer is excessive, and avoid herbicides that inhibit root growth while the lawn is recovering.
Fungicides labeled for take-all root rot may be beneficial as part of an integrated program, according to LSU. The product, rate and application frequency have to follow the label exactly, and fungicide alone won’t fix a lawn whose stresses haven’t changed. A soil test is the step people skip most often, and it’s the one that decides whether lime or acidifying fertilizer is right. Our page on soil testing and pH balancing explains how that works in New Orleans soils.
Why lime makes it worse
Lime raises soil pH. LSU’s guidance to keep pH between 5.5 and 6.0 and not to lime affected lawns means a common spring habit can work against you here. Many homeowners lime by routine without a soil test. On a lawn with take-all, that routine can push pH in the wrong direction. Test first, and let the result decide.
What a recovery year looks like
Take-all rarely turns around in a few weeks. It’s more useful to think of recovery as a year of steady corrections, each timed to when St. Augustine can respond.
- Before anything else: send a soil sample for testing so you know the pH and nutrient levels before you add lime, sulfur or fertilizer
- When the grass is actively growing: aerate compacted areas and deal with heavy thatch, since the lawn needs to be growing to recover from both
- Through the hot months: water early and deeply, count the rain, and keep the mower high so the grass carries more leaf to feed its roots
- On a schedule set by the soil test: apply slow-release, acidifying nitrogen with enough potassium and magnesium, rather than a quick green-up product
- Once runners are rooting again: decide whether any bare areas need plugs or sod, and fix the drainage in those spots first
Our page on the best time to aerate a lawn covers aeration timing for warm-season grasses in more detail. It’s one of the most useful single steps for a take-all lawn on heavy soil. If you’d rather hand the whole year to someone, that’s what our seasonal lawn care program is for. You’ll get the soil test, the timing and the follow-through in one plan.
Can the lawn recover
Recovery depends on how much root system is left and how quickly the stresses are relieved. Because symptoms show up after the roots are already badly damaged, recovery is gradual rather than quick. LSU notes that raising the mowing height helps the grass recover and increases root growth. Combined with better watering, lower compaction and the right fertility, that gives surviving runners the best chance to root down again. Areas where the grass has died completely may need replanting once the soil and care problems are corrected. Replanting into the same compacted, over-limed or waterlogged conditions tends to give the same result. Our St. Augustine grass care guide covers the mowing and watering habits that keep roots healthy once the lawn is on its way back.
Frequently asked questions
Can grass recover from root rot?
It can, if enough roots survive and the stresses behind the disease are corrected. LSU AgCenter recommends raising the mowing height, watering deeply and early, relieving compaction and using slow-release acidifying nitrogen, which together give runners the best chance to root again.
Should you fertilize if you have take-all root rot?
Yes, but carefully. LSU AgCenter recommends slow-release, acidifying forms of nitrogen with adequate potassium and magnesium, guided by a soil test, and it advises against liming lawns affected by the disease.
What is the best fungus treatment for St. Augustine grass?
It depends on the disease. For take-all root rot, LSU AgCenter puts cultural changes first and treats fungicides as one part of an integrated program, applied at label rates and intervals. For large patch and gray leaf spot, different timing applies.
Will root rot go away on its own?
It rarely clears up while the stresses that triggered it continue. LSU AgCenter notes the fungus is often present in roots without causing disease, so relieving compaction, correcting watering and fertility and raising the mower is what lets the lawn outgrow it.
How do I know if my lawn has take-all root rot?
Look for yellowing and thinning that spreads over weeks and doesn’t respond to water or fertilizer. Dig a small section at the edge: LSU AgCenter describes diseased roots as short, dark and somewhat brittle, and affected runners lift out of the lawn easily.
Get the roots checked before you replant
Tell us how long the lawn has been thinning and what you’ve tried. We’ll look at the roots, check the soil and give you a free estimate before any work starts, with the price agreed up front.
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