Pathogen: Rhizoctonia solani
Also called: brown patch (on warm-season grass), Rhizoctonia large patch, zoysia patch
Large Patch
Planted in fall, seen in spring
Large Patch At-a-Glance
Grass Type Affected
Warm-Season Grasses
Recovers on Its Own?
Yes, Slowly
Is Spraying Worth It?
Sometimes Worth It
Disease Type
Fungal
Active Season
Early Spring
Late Spring & Early Summer
Fall
Winter
Damage Potential
Weakens Over Time
Can Be Fatal
Large Patch Quick Answers
What Large Patch Looks Like
From Standing Height
Large patch shows up as roughly round patches of yellow to straw-colored, thinned grass, from about a foot across to well over 20 feet. While it’s active, the outer edge of the patch glows: bright yellow on St. Augustinegrass and zoysiagrass, reddish to orange on centipedegrass. Inside that edge, the grass turns tan and thins until the patch looks slightly sunken. As weather warms, the center often starts greening up first, leaving a ring, and neighboring patches can merge into large irregular areas.
Up Close: Blades, Crowns and Roots
Large patch is a rot of the leaf base, not a leaf-spot disease, so the upper blades show no spots or lesions of their own. The fungus attacks the leaf sheath, the lower part of each leaf that wraps around the runner near the soil. There it causes dark brown, reddish-brown or black, water-soaked lesions that turn soft and slimy as the rot spreads.
Once the sheath rots through, the leaf above loses its water supply. Blades die back from the tip toward the base, turning yellow, orange or red first (depending on the grass) and then brown. The rotted base also lets the leaf slide off the runner with almost no resistance, which is the most reliable diagnostic feature.
In typical cases, the runners and roots stay firm and healthy, which is why most lawns recover. In severe, repeated outbreaks, especially in waterlogged or heavily fertilized lawns, the rot can reach the crowns, and those plants die.
Signs of the Fungus
You usually won’t see the fungus itself. Large patch makes no spore dust, threads or mushrooms on the grass, and the fungal strands that do the damage stay down in the thatch at the base of the leaves, too fine to see without a microscope. What you can see is the damage it causes at the leaf base, which the tug test below brings into view.
Could It Be Something Else?
Common Lookalikes
Take-All Root Rot hits the same St. Augustinegrass and bermudagrass lawns and also shows up as yellow, thinning, irregular patches from 1 foot to more than 20 feet across in spring and early summer. The difference is underground: take-all rots the roots, so whole runners lift off the soil, while large patch rots the leaf bases and leaves the roots alone. The two can also show up in the same lawn.
Spring Dead Spot causes round, straw-colored patches that appear at spring green-up in bermudagrass and zoysiagrass, often in the same spots year after year — just like large patch. Spring dead spot patches stay dead while the lawn around them greens up and have no bright yellow or orange edge, and their roots and runners are dark and rotted.
Chinch bug damage in St. Augustinegrass starts as yellowing patches that turn brown and spread, so it gets blamed on disease. Chinch bugs do their damage in hot, dry summer weather in sunny spots, when large patch is shut down — and the grass doesn’t pull loose at the base.
Field Checks Before You Treat
- Do the tug test. At the yellow or orange outer edge of a patch, grab a few discolored leaves and pull gently. If they slide right off the runner and the base of the leaf is dark brown, water-soaked and slimy, it's large patch. If the leaves hold or snap off higher up, look elsewhere.
- Lift a runner. In the thin center of the patch, slide your fingers under a runner and lift. If it stays anchored and the roots are white to light tan, that fits large patch. If the whole runner lifts off easily and the roots are short, black and rotted, suspect take-all root rot or spring dead spot.
- Look at the edge color. From a standing view, check the border of the patch. A bright yellow edge on St. Augustinegrass or zoysiagrass, or a reddish to orange edge on centipedegrass, points to active large patch. A patch that is uniformly straw-colored with no bright edge points away from it.
- Check the calendar. Large patch is active in fall and spring, when the grass is going into or coming out of dormancy. Patches that first appear in mid-summer heat are more likely chinch bugs, drought or another disease.
- Do a soap flush for chinch bugs. At the edge of a summer patch in St. Augustinegrass, mix 2 tablespoons of dish soap in a gallon of water and pour it over about a square foot of grass. Chinch bugs crawl up within a few minutes: adults are black, about 3/16 inch long, with white wings folded on the back; young ones are smaller and reddish with a white band.
Grasses at Risk
Which Grasses Suffer Most
Centipedegrass and seashore paspalum are the most susceptible and suffer the fastest collapse. St. Augustinegrass and zoysiagrass are close behind, and because so many Southern and transition-zone lawns are planted in them, they account for most chronic cases; large patch is the most important disease of both. Bermudagrass gets it too, but rarely badly: it grows fast enough to outgrow the damage once the weather warms. Buffalograss is also a host.
No warm-season grass is fully resistant. Tall fescue, Kentucky bluegrass and the other cool-season grasses are immune to the large patch strain, which makes switching to them a real option in the transition zone, where they grow well. The exception is overseeded perennial ryegrass: LSU lists the cool-season grasses used for winter overseeding as hosts. To compare cultivars, check disease ratings in the National Turfgrass Evaluation Program (NTEP) trials, which score cultivars from 1 to 9, with 9 the most resistant.
Why It Shows Up
Conditions That Trigger It
Large patch is a disease of the in-between seasons. It strikes when warm-season grass is slowing down for winter or just waking up in spring — growing too slowly to replace damaged leaves — while the weather still suits the fungus. It starts in fall when soil temperature drops to about 70°F, and it is most active when the thatch layer sits between 50°F and 70°F. In air temperatures, it moves fastest when nights run 60–75°F and days stay below 85–90°F. Once summer days stay above about 90°F, it stops.
Moisture is the trigger. The fungus needs free water on the grass: more than 10 hours of continuous leaf wetness lets it spread, and 48 hours or more of rain, heavy dew or damp, cloudy weather sets off the worst outbreaks.
These care and site factors make it worse:
- Nitrogen at the wrong time. Fertilizer in mid-to-late fall or early spring, before full green-up, pushes soft new leaf tissue the fungus can easily invade while the grass can’t outgrow the damage. Fast-release nitrogen is the worst offender.
- Overwatering. Frequent, light or evening watering keeps the leaf bases and thatch wet for hours longer.
- Poor drainage. Low spots and saturated soil make it much more severe; it is markedly worse in zoysiagrass on soggy ground.
- Thick thatch. Thatch over ½ inch holds moisture right around the leaf bases and is where the fungus lives between outbreaks.
- Low mowing. Mowing below the grass’s recommended height stresses it and slows recovery.
- Shade and still air. Trees, shrubs and fences block sun and wind, so the grass stays wet long after rain or watering.
- Compaction. Packed soil drains slowly and weakens the grass.
- Acidic soil. Soil below pH 6.0 can make it more severe, except in centipedegrass, which prefers acidic soil.
How It Survives and Spreads
The fungus lives in the soil and thatch all year. It rides out summer heat and winter cold in old grass debris, then becomes active again each fall when the soil cools. It grows through the thatch to the base of the leaves near the soil surface and rots the leaf sheath, the wrapper where each leaf attaches to the runner. Once the base rots through, the leaf can no longer get water and turns yellow or orange, then brown.
Here’s the catch: much of the infection happens in fall, when the grass is already slowing for winter, so you may see nothing until spring. As the lawn tries to green up, the infected areas show up as patches — the worst outbreaks often come two to eight weeks after spring green-up. Within a lawn, the fungus grows outward through the thatch, so patches widen in a ring and often return in the same spots, larger each year. It moves to new areas on mowers, aerators, shoes and moved soil, and into new lawns on infected sod or plugs.
Where It Hits Hardest: Regional Notes
Large patch is a problem wherever warm-season lawns are grown in humid climates: the Southeast, the Gulf Coast and Texas, and the transition zone from Virginia and North Carolina west through Tennessee, Missouri and Kansas. In the Deep South, symptoms can appear anytime from late summer through May. In Missouri, it is the most important disease limiting zoysiagrass lawns. In the North and other cool-season regions it is essentially absent, because Kentucky bluegrass, tall fescue and the other cool-season lawn grasses aren’t hosts. Those lawns get Brown Patch instead, a summer disease caused by a different strain of the same fungus.
Large Patch Diagnostic Profile
Check what you see against the full set of signs. The more that match, the more likely this is your problem.
What You’ll See
Symptom Color
Tan or Straw
Yellow
Brown
Red, Pink or Purple
Orange or Rust
Black or Dark
Visible Signs
None Usually Visible
Lawn Pattern
Circular Patches
Rings or Frog-Eyes
Irregular Patches
Overall Thinning
Patch Size
6 to 12 Inches
1 to 3 Feet
Over 3 Feet
Blade Symptoms
Tip Dieback
Rotted Leaf Base or Crown
When and Where
Weather Triggers
Cool & Wet
Warm Days, Cool Humid Nights
Long Leaf Wetness (Dew or Rain)
Wet or Poorly Drained Soil
Where in the Lawn
Shade
Low or Wet Spots
Compacted or High-Traffic Areas
Open, Sunny Lawn
Controlling Large Patch
Care changes are the foundation of control, and on bermudagrass or a lawn with a few small patches, they are often all you need. Each one removes something the fungus depends on: wet leaf bases, soft new growth during the cool months, or thatch to live in.
- Time nitrogen to the growing season. Don’t fertilize within 6 weeks before your grass goes dormant in fall, and wait until 3 weeks after spring green-up begins. Use slow-release nitrogen and never more than 1 lb of nitrogen per 1,000 sq ft in a single application. If patches are active in spring, hold all nitrogen until the lawn has fully greened up and is growing strongly.
- Water early and less often. Water before or around sunrise, when the grass is already wet with dew and the sun will dry it, so you don’t add hours of leaf wetness. Water only when needed — about 1 inch a week, wetting the soil 4–6 inches deep — and no more than once a week in spring and fall.
- Mow at the right height. Mow St. Augustinegrass at 2–3 inches, zoysiagrass at 1–2 inches, centipedegrass at 1½–2 inches, common bermudagrass at 1–2 inches and hybrid bermudagrass at 1–1½ inches. If the lawn has had large patch, keep it at the upper end of its range; more leaf means more energy for recovery.
- Mow dry, mow patches last. Mow after the dew dries, bag clippings during cool, moist weather, mow diseased areas last and wash the mower afterward, so you don’t spread infected grass bits.
- Control thatch. Keep thatch under ½ inch with core aeration, vertical mowing or power raking, done in early summer while the grass is growing fast enough to recover.
- Fix drainage and compaction. Core aerate compacted areas and regrade or install drainage in low spots that stay soggy. Saturated soil is one of the strongest drivers of severe large patch.
- Open up shade. Limb up low tree branches and thin crowded shrubs so sun and wind can dry the lawn faster.
- Follow a soil test. Keep potassium and calcium at the upper end of the “sufficient” range, and keep pH where your soil test recommends for your grass. Don’t acidify St. Augustinegrass, zoysiagrass or bermudagrass below pH 6.0.
Fungicides are sometimes worth it: on St. Augustinegrass, zoysiagrass or centipedegrass lawns that get large patch year after year, a fall preventive program is the most reliable way to hold it back, but on bermudagrass or a lawn with a few small patches, care changes are enough.
Timing is everything, because fungicides protect healthy tissue; they can’t repair leaf bases that have already rotted. Spraying the patches you see in spring is late — that damage started in fall.
- First fall application. For zoysiagrass, spray when the soil temperature (measured about 2 inches deep) drops to 70°F and stays there for several days. For St. Augustinegrass and centipedegrass, NC State recommends starting earlier, once soil drops to 80°F for 5 days in a row, which can be as early as mid-August. In South Carolina, the 70°F mark typically arrives in mid-to-late October.
- Second fall application. Repeat about 3–4 weeks later, before the grass goes dormant. Two well-timed fall sprays often give season-long control.
- Spring. A single spray as the lawn begins to green up can help a lawn with a bad history that wasn’t treated in fall, but it is a backup, not a fix — Texas A&M calls spring sprays not cost-effective.
- Target your sprays. Mark or photograph where the patches are each spring. Patches return in the same places, so you can spot-treat those areas the following fall and cut costs.
These active ingredients are sold in homeowner lawn products and rated for large patch by Clemson Extension:
| Active ingredient | FRAC group | Protection per application | Large patch rating |
|---|---|---|---|
| Azoxystrobin + propiconazole | 11 + 3 | Up to 28 days | Excellent |
| Pyraclostrobin + triticonazole | 11 + 3 | Up to 28 days | Excellent to good |
| Azoxystrobin | 11 | 28 days | Good |
| Fluoxastrobin | 11 | 28 days | Good |
| Propiconazole | 3 | 14 days | Good |
| Myclobutanil | 3 | 14 days | Fair |
Two-ingredient products can be reused because they already combine two modes of action. With single-ingredient products, alternate between a Group 11 and a Group 3 product so the fungus doesn’t become resistant. Lawn “fungus control” products with similar names can contain different ingredients, so always check the active-ingredient panel. Some active ingredients in professional fungicide tables, including chlorothalonil and iprodione, are not labeled for home lawns.
Water granular products in right away with ½ inch of irrigation so the fungicide reaches the leaf bases and thatch, where the fungus is. Liquids, applied in at least 2 gallons of water per 1,000 sq ft, give slightly better coverage of the leaf bases than granules.
Recovery and Repair
Most lawns recover on their own once the grass is growing strongly in late spring and summer and the heat shuts the fungus down. Bermudagrass fills in within weeks; St. Augustinegrass, zoysiagrass and centipedegrass can take several weeks to a few months. Grass damaged in late fall won’t start filling in until it greens up the next spring.
Recovery speeds up when the grass is mowed at the top of its recommended range, fertilized only after full green-up, and watered deeply but not often. Thin patches invite weeds, but hold off on herbicides in the patches themselves until the grass recovers, because herbicides add stress to already-weakened grass.
If patches are still bare by early summer, the crowns are dead and won’t come back. Rake out the dead grass, fix whatever caused the outbreak (drainage, thatch, compaction), then resod or plug the bare areas in late spring to early summer, while the grass is growing actively. Don’t patch in fall or early spring: new sod roots slowly in cool soil, and that is exactly when large patch strikes.
When to Call a Pro
Send a sample to your state’s extension plant diagnostic lab if the tug test doesn’t give a clear answer, if patches are still bare or spreading in early summer when they should be filling in, or if they keep growing after you’ve fixed watering, nitrogen timing and drainage. A lab can tell large patch from take-all root rot and spring dead spot, which matters because they are managed differently. It’s also worth a lab confirmation before you commit to spraying every fall.
Take the sample from the active edge of a patch, not the dead center, so it holds both sick and healthy grass: a plug about 4 inches square and a few inches deep, with the soil and roots attached. Wrap the soil in plastic, leave the leaves exposed, don’t add water, and ship it early in the week so it doesn’t sit in transit over a weekend. Call a lawn professional when drainage or grading needs real earthwork, or when bare areas are too large to resod yourself.
Frequently Asked Questions
These answers are synthesized from plant pathology research and diagnostic guidance published by university extension services and plant disease clinics.
Related, but not the same. Both are caused by the fungus Rhizoctonia solani, and older Southern publications still call large patch “brown patch.” But large patch is a different strain that attacks warm-season grasses in fall and spring, while brown patch hits cool-season lawns like tall fescue in hot, humid summer weather. The timing and the advice are different, so make sure any guide you follow is about your grass.
The fungus never leaves. It survives in the thatch and soil of the old patch through summer and winter, then grows outward again when fall weather turns cool and wet, so patches often return in the same places and a bit larger each year. Those spots usually share a cause too, like poor drainage, shade or thick thatch. Fixing the site problem and spot-treating those areas in fall breaks the cycle.
Yes, if it goes down too early. Nitrogen applied before the lawn has fully greened up produces soft new growth the fungus invades easily, at a time when the grass is still too slow to replace the damage. Wait until 3 weeks after green-up begins, and avoid weed-and-feed products on active patches, because the herbicide adds stress to grass that is already struggling.
Only if the problem keeps coming back despite good care. NC State calls a less susceptible grass the most effective long-term fix. Bermudagrass recovers far faster than St. Augustinegrass, zoysiagrass or centipedegrass, and in the transition zone, tall fescue is immune to large patch. A switch only makes sense if the new grass suits your sun, climate and how you use the lawn.
Scientific Authority
This profile is built on plant pathology research and diagnostic guidance from university extension services and plant disease clinics. We prioritize accurate identification and cultural control first, recommending fungicides only where research shows they are justified, and naming them by active ingredient rather than brand.
Primary Resources
- Clemson Cooperative Extension (HGIC) — Brown Patch & Large Patch Diseases of Lawns (HGIC 2150)
- Clemson Cooperative Extension (HGIC) — Large Patch Disease Control in Warm Season Lawns
- NC State Extension — Large Patch in Turf
- Texas A&M AgriLife Extension — How to Diagnose and Manage Large Patch Disease in Warm-Season Turfgrass (E-633)
- Texas A&M AgriLife Extension — Take-All Root Rot (E-615)
- LSU AgCenter — Louisiana Home Lawn Series: Large Patch
- University of Missouri Extension — Large Patch (Turfgrass Disease Profiles)
- University of Georgia Extension — Lawn Disease Update: Rhizoctonia Large Patch
- University of Georgia Extension — Dead Patches in Your Warm-Season Lawn? It Could Be Rhizoctonia Large Patch
- Kansas State Research and Extension — Zoysiagrass in Kansas (MF683)