Free printable · 3 pages
Take this out to the yard with you.
Get the Houston Lawn Trouble Field Guide — everything on this page, on paper, ready for the next brown spot.
- The 3 tests on one page, big enough to read on your knees
- The fix for each problem, with one-tap links to exactly what it needs
- How to keep it from coming back — water, mowing and feeding
Houston Lawn Help · St. Augustine Grass
Houston lawns take a beating. Heat, humidity, watering that's a little off, bugs, disease — any one of them can turn your St. Augustine grass yellow or brown. The frustrating part: five completely different problems look the same from the driveway. Brown patch, take-all root rot, chinch bugs, sod webworms and gray leaf spot are dead ringers for each other from ten feet away.
They are not fixed the same way. Grab the wrong bag off the shelf and you've wasted your money and stressed a lawn that's already limping. We see it every week across Sugar Land, Missouri City, Katy and the rest of Greater Houston — folks treating a bug problem with a fungicide, or dumping fertilizer on a lawn that's rotting at the roots.
Diagnose first. It's cheaper than guessing. Get down on your knees at the edge of the bad spot — right where the dying grass meets the healthy grass. That's where the answer is. Three tests, about ten minutes, no lab.
First, a two-second gut check: what season is it?
The calendar rules out half the list before you even kneel down.
Chinch bugs hit in the heat. Take-all hits in the wet. Keep that line in your pocket.
The 5 brown-spot problems at a glance
The whole cheat sheet in one place. The tests below land you on the right row.
| Problem | Quick tell | The test | When | Shop the fix |
|---|---|---|---|---|
| Brown / large patch | Circles or horseshoes, yellow outer edge; blade slips out, runner stays | Tug test | Spring & fall | Brown Patch Store → |
| Take-all root rot | Yellow thinning fertilizer won't fix; dark, rotten roots | Tug test | Spring, after wet spells | Take-All Store → |
| Sod webworms | Chewed, ragged blades; tan moths at dusk | Look at the blade | Late summer–fall | Webworm Control → |
| Gray leaf spot | Gray-tan spots with dark borders on whole blades | Look at the blade | July–Sept | Leaf Spot Fungicide → |
| Chinch bugs | Sunny spot by the concrete keeps spreading even though you water | Soap flush | June–Sept | Chinch Bug Store → |
Test 1. The Tug Test
The one that matters most
Walk to the worst spot. Grab a fistful of grass at the edge and pull up gently.
Grab the grass and tug. If the blade slips out and the runner stays behind — that's brown patch. If the whole runner lifts out and the roots are dark and rotten — that's take-all root rot. That one test separates the two problems people mix up the most.
- The blades slip right out and the runner stays in the ground. Feel the base of the blade — soft, dark, slimy. The fungus rots the spot where the blade attaches, so the blade lets go but the runner holds.
→ Brown patch / large patch - The whole runner lifts out with no resistance, and the roots are short, dark and rotten. Look up top too: yellowing that fertilizer never fixes is a classic tell.
→ Take-all root rot - The turf peels back like loose carpet and the roots look chewed off. Dig a few inches — white, C-shaped larvae in the soil are grubs. Confirm before you buy anything.
→ Grubs - The grass holds firm and the roots look white and healthy. Good — it's not a root problem. Move on to Test 2.
→ Keep going
What brown patch looks like
What take-all root rot looks like
Test 2. Look at the Blade
Bites vs. spots
Still down there? Look closely at the actual blades in the bad spot.
- Blades are chewed, ragged and notched — like something took little bites out of the edges, and the patch is thinning. Walk the lawn at dusk: small tan moths flushing up as you go is your confirmation. The caterpillars feed at night.
→ Sod webworms - Blades are whole and intact, but covered in small gray-tan spots — often diamond-shaped — with a darker border. That's a leaf disease, not a bug.
→ Gray leaf spot - Grass chewed down to the dirt in a day or two, with birds all over the lawn. That's not webworms — that's fall armyworms, and they move fast. Treat now, not this weekend.
→ Fall armyworms
Easy way to remember it: bites mean a bug, spots mean a disease.
What sod webworm damage looks like
What gray leaf spot looks like
Test 3. The Soap Test
For hot spots along the concrete
Chinch bugs are the #1 St. Augustine pest in Houston. If the bad patch is in the hottest, sunniest part of the yard — along a driveway, sidewalk or curb — and it keeps creeping bigger even though you're watering, suspect them first.
Quick look first: part the grass at the edge of the dying patch and look down at the soil line. Tiny black bugs with white wing markings, or smaller reddish young ones, are chinch bugs. No luck? Flush them out:
- Mix 1 to 2 tablespoons of regular dish soap into 1 gallon of water.
- Pour it slowly over a 3-foot-by-3-foot area right where the brown grass meets the green.
- Watch for a few minutes. Chinch bugs crawl up to the top of the grass.
Watering a chinch bug problem does not fix it. Almost every "mystery brown patch" call we get in July and August is either chinch bugs or a watering habit. Check before you crank up the sprinklers.
What chinch bug damage looks like
Found it? Here's how to fix it.
One problem, one fix. Treat what you found — not everything at once. And remember: a lawn can have more than one of these at the same time. If two tests lit up, treat both.
Brown patch / large patch Fungus
Spring & fall · humid weeks
- Fix the water first. Brown patch is almost always tied to overwatering, evening watering, or too much nitrogen going into fall.
- Water only between 4 and 9 AM, deep and not daily, so the blades dry out during the day.
- No heavy nitrogen in fall. Push tender growth now and you hand the fungus a buffet.
- Then treat with a lawn fungicide labeled for brown or large patch, early, at the label rate.
Take-all root rot Fungus
Spring · after wet periods
- Top-dress with sphagnum peat moss in spring — roughly one bale per 1,000 sq ft.
- Cut back on nitrogen and fix your drainage. Soggy ground feeds this one.
- Raise your mowing height to 3–4 inches to bank every bit of root you have.
- Fungicides for take-all are preventive only. They protect healthy grass; they won't bring back dead roots. This is the one most worth getting diagnosed properly before you spend money.
Chinch bugs Insect
June–September · hottest, sunniest spots
- Treat the damaged patch and a band of healthy-looking grass around it — the bugs are at the edge, not in the dead middle.
- Recheck with the soap test in a week or two. Repeat only if the label allows.
- Once they're handled, water deeply to help the lawn fill back in.
Sod webworms Insect
Late summer–fall
- Treat with SUMMIT Caterpillar & Webworm Control — it hooks right to the hose.
- Spray late in the afternoon or evening. The caterpillars feed at night.
- Good news: webworms eat blades, not roots. A healthy, watered lawn usually grows right back.
- Grass stripped to bare dirt in a couple of days? That's armyworms — use Ortho BugClear for Lawns & Landscapes instead.
Gray leaf spot Fungus
July–September · heat + humidity
- Back off the fertilizer. Heavy nitrogen in summer heat is what drives this disease.
- Water early in the morning only, so the blades aren't wet overnight.
- Treat with Scotts DiseaseEx Lawn Fungicide at the label rate.
Grubs Insect
Summer–fall · turf lifts like carpet
- Dig and confirm first. A few grubs are normal; a handful in one square foot is a problem.
- Treat with a grub control labeled for your grass, then water it in per the label.
Fix the water before you buy the fungicide. Nearly every fungus call in Houston traces back to water — too much of it, or applied too late in the day. A fungicide on top of a watering problem is money you spend twice.
The label is the law. Rates and timing on the bag in your hands beat anything printed here.
Not brown — just yellow?
Yellow even though you fed it? That's iron, not nitrogen.
Houston's soil is alkaline, and high pH locks up iron. The lawn goes yellow between the veins while the blade stays green along them. It's the single most common photo we get in August — and it's not one of the five above.
Yellowing that iron and fertilizer never fix, with roots that pull up easily? Go back to Test 1 — that's take-all root rot.
Get the Liquid Iron → Fertilizer Store →How to stop brown spots from coming back
Most of these problems get a foothold because the lawn was already stressed. Fix the stress and you fix most of the trouble before it starts.
- Water deep, not daily. About 1 inch a week, rain included. Daily sprinkling trains roots to live in the top inch of soil — then July kills them. Put a tuna can on the lawn and time how long your sprinklers take to fill it: that's your run time.
Deep & infrequent - Water between 4 and 9 AM. Wet blades overnight grow fungus.
Mornings only - Mow St. Augustine at 3–4 inches with a sharp blade, and never take more than a third of the blade at once. Torn tips brown out and invite disease.
Mow high, mow sharp - Feed smart. Slow-release, at the right time — and never on dry, stressed grass. Ease off nitrogen in peak heat and going into fall. More is not better.
Feed smart - Fix drainage and thatch. Soggy low spots and a thick, spongy thatch layer both feed disease.
Dry it out - Scout the edges in July and August. Ten seconds on your knees at the edge of a dry-looking patch beats a season of guessing.
Look first
The whole watering picture lives in our Houston Summer Watering Guide, and the sprinklers, hose timers and rain gauges we trust are in Water Smarter with Garden Guy. For the full year — feeding, pre-emergent and timing — grab the free Texas Two-Step Lawn Method guide.
Brown spots in your lawn: quick answers
Why does my St. Augustine grass have brown or yellow spots?
Houston piles on heat, humidity and watering stress, and that opens the door to several problems. In summer the usual suspects are chinch bugs and gray leaf spot; in late summer and fall, sod webworms; in spring and fall, brown patch; and in spring after wet spells, take-all root rot. Three quick at-home tests tell them apart.
How can I tell if my brown spots are a fungus or bugs?
Look at a blade: bites and ragged edges mean a bug (sod webworms); a whole blade covered in gray-tan spots means a disease (gray leaf spot). Then tug the grass: if the blade slips out, or the whole runner lifts with rotten roots, it is a fungal disease such as brown patch or take-all root rot.
What kills brown patch in St. Augustine grass?
Fix the water first: water only early in the morning, deep and not daily, and skip heavy nitrogen in fall. Then use a lawn fungicide labeled for brown or large patch, applied early at the label rate.
Will my lawn recover from take-all root rot?
It can, but take-all attacks the roots, so recovery means fixing the stress: top-dress with sphagnum peat moss in spring (about one bale per 1,000 sq ft), cut back nitrogen, fix drainage and mow higher. Fungicides for take-all are preventive only.
Why is my lawn yellow even though I fertilized?
Usually that is iron chlorosis, not hunger. Houston's alkaline soil locks up iron, so the grass yellows between the veins. A chelated liquid iron usually greens it within days; more nitrogen makes it worse.
Should I use a weed and feed to fix brown spots?
No. Weed and feed will not fix disease or insect damage, and the extra nitrogen can make brown patch and gray leaf spot worse. Identify the specific problem first, then treat that.
How often should I water my Houston lawn?
Deep and infrequent: about 1 inch a week, rain included, applied between 4 and 9 AM. Daily sprinkling keeps roots shallow, and watering at night leaves blades wet and invites disease.
Can a lawn have more than one problem at the same time?
Yes, and it is common in Houston. That is why dumping an insecticide, fungicide and fertilizer on all at once is a mistake: you may treat the wrong thing while the real cause keeps spreading.
Still stumped? Let us take a look.
Send wide photos of the whole area, close-ups of the blades and the roots, your grass type, how often you water, and how much sun the spot gets. Todd will help you figure out what you're really looking at.
Ask Garden Guy → Book a Call with Todd →— Todd & Sabrina, Garden Guy · Serving Sugar Land, Missouri City & Greater Houston since 1991
As an Amazon Associate, Garden Guy earns from qualifying purchases, at no extra cost to you. We only list what Todd actually recommends. Always read and follow product labels — the label is the law.
Free printable · 3 pages
Take this out to the yard with you.
Get the Houston Lawn Trouble Field Guide — everything on this page, on paper, ready for the next brown spot.
- The 3 tests on one page, big enough to read on your knees
- The fix for each problem, with one-tap links to exactly what it needs
- How to keep it from coming back — water, mowing and feeding
Brown spots in your lawn: quick answers
Why does my St. Augustine grass have brown or yellow spots in summer?
Houston summers pile on heat, humidity and watering stress, and that opens the door to several problems at once. Take-all root rot, chinch bugs, sod webworms and gray leaf spot are the usual summer suspects. Brown patch is more of a cool-season thing (fall through early spring). The three at-home tests in this post tell them apart.
How can I tell if my brown spots are a fungus or bugs?
Two quick checks. Look at a blade: bites and ragged edges mean a bug (sod webworms); a whole blade with spots means a disease (gray leaf spot). Then tug the grass: if the blade slips out or the whole runner lifts with rotten roots, you’re looking at a fungal disease — brown patch or take-all root rot.
What kills brown patch in St. Augustine grass?
A lawn fungicide labeled for brown or large patch, applied before it spreads — plus cutting back on water and nitrogen, since brown patch loves wet, over-fed turf. Water deep and early in the morning so the grass dries out during the day.
Will my lawn recover from take-all root rot?
It can, but take-all root rot is the stubborn one because it attacks the roots. Recovery means fixing the underlying stress — better drainage, less water, easy on the nitrogen — along with well-timed fungicide. This is the one most worth having diagnosed properly before you spend money.
Should I use a weed and feed to fix brown spots?
No. Weed and feed won’t fix disease or insect damage, and the extra nitrogen can actually make brown patch and gray leaf spot worse. Figure out what you’re dealing with first, then treat that specific problem.
How often should I water my Houston lawn?
Deep and infrequent beats short and daily. You want the water to soak several inches down so roots grow deep, then let the top dry out before the next watering. Early morning is best — watering at night leaves blades wet and invites disease.
Can a lawn have more than one problem at the same time?
Absolutely, and it happens all the time in Houston. That’s exactly why blindly dumping an insecticide, fungicide and fertilizer all at once is a bad idea — you might treat the wrong thing while the real culprit keeps spreading.
Still stumped? Let us take a look.
Send us wide photos of the whole area, close-ups of the blades and the roots, your grass type, how often you water, and how much sun the spot gets. We’ll help you figure out what you’re really looking at.
— Todd & Sabrina, Garden Guy · Serving Sugar Land, Missouri City & Greater Houston since 1991
As an Amazon Associate, Garden Guy earns from qualifying purchases. Always read and follow product labels.
