Published October 11, 2026
Brown circles showing up in a St. Augustine lawn in Central Texas this month are most likely large patch, a fungal disease that wakes up when the nights cool off and the soil stays wet. The rings have orange or yellow edges, and the grass inside pulls loose with a gentle tug. Large patch does not kill a lawn overnight, but the damage stays until spring, so October is the month to slow it down.
Large patch is a turf disease caused by the fungus Rhizoctonia solani, and it hits warm-season grasses in spring and fall. Texas A&M AgriLife Extension's guide, E-633, calls it the most chronic and economically important disease of both St. Augustinegrass and zoysiagrass in Texas. Those two grasses cover a lot of yards in Georgetown, Round Rock and Cedar Park.
Many people still call it brown patch. AgriLife Today explains that the two names belong to different groups of the same fungus: brown patch affects cool-season grasses, and large patch affects warm-season grasses like St. Augustine and zoysia. If your lawn is St. Augustine, the brown circles you are looking at are large patch.
Large patch shows up in October because that is when temperatures drop into the range the fungus likes. AgriLife's E-633 says the disease occurs when temperature is below 70 degrees Fahrenheit, and that the fungus survives summer heat but thrives in cooler temperatures when the soil is wet.
The fungus never leaves. AgriLife's Williamson County office points out that Rhizoctonia solani sits in the soil year-round and takes advantage of cool temperatures and wet soil. A sprinkler schedule still set for August, combined with the first fall rains, gives it exactly that.
Large patch makes circles, and the grass at the edge of a circle pulls loose easily. Here is what AgriLife says to look for:
Chinch bugs are the common look-alike, and the shape gives them away. AgriLife's chinch bug guide says disease damage usually runs in a circular or semi-circular pattern, while chinch bug feeding leaves irregular patches. Chinch bug damage also builds fastest in sunny spots during hot, dry weather, next to driveways, sidewalks and brick walls, and it normally appears at approximately 20 to 25 chinch bugs per square foot. A circle in a shady, damp corner in October points to large patch. A ragged patch by the driveway in July points to bugs.
If the signs are mixed, get it confirmed before spending money. AgriLife Today notes that diagnosis by a certified nursery professional or turfgrass specialist is the best option for accuracy.
Water, late fertilizer, short grass and thatch make large patch worse. E-633 lists the conditions that promote infection: over-fertilization late in the fall, poor drainage, over-irrigation, low mowing height and excess thatch. The Williamson County office says large patch thrives in lawns that have poor drainage and are over-fertilized. Most of that list is under a homeowner's control.
Cut the watering back now that the heat has broken. AgriLife's guidance is to water evenly and only when necessary, water early in the morning, and reduce how long the leaves stay wet. Evening watering leaves the grass wet all night, which is exactly what the fungus needs. Our irrigation maintenance visits reset controller schedules for the season and find the heads that are soaking one spot.
Keep St. Augustine at 2 to 3 inches and zoysia at 1 to 2 inches. E-633 says mowing turfgrass to appropriate heights will discourage the disease, and AgriLife Today adds a second rule: avoid mowing wet turfgrass. Scalping a St. Augustine lawn to tidy it up for fall works against you. Our mowing maintenance crews keep the cut at the height the grass needs.
Do not push nitrogen into a St. Augustine lawn late in the fall. E-633 puts the ideal fertilizer timing at 6 weeks before the first frost and 3 weeks after spring green-up. The National Weather Service Austin climate summary puts the average first freeze at December 1, so the fall feeding window closes around the third week of October. That timing is part of how we schedule lawn treatment through the year.
A fungicide helps most when it goes down before the circles appear, and helps much less after. AgriLife's E-633 says the best time to apply is when soil temperature drops below 70 degrees Fahrenheit in the fall, that the key in Texas is treating before or immediately after the disease begins in October to November, and that efficacy is limited once symptoms have appeared.
Read the label before buying anything. E-633's fungicide table marks several products as not for residential turf or home lawns. Spring applications, according to the same guide, are not cost-effective.
Lightly damaged St. Augustine usually fills back in, but not until spring. E-633 says damaged grass will not recover until the following spring, and that new growth fills the patches during the summer as temperatures rise. Where the disease has caused extensive crown and root damage, the grass may not recover and resodding is often necessary.
Expect it to come back next fall in the same spots. The Williamson County office says large patch will probably return in the fall, and E-633 says the disease recurs under certain conditions every year, which is why prevention matters more than cure.
If your yard in Georgetown or nearby already has orange-edged circles, the steps are the same either way. Water less, mow high, skip the late fertilizer, and keep an eye on the edges of each ring until it gets cold.
CTX Mowing keeps the mowing height, sprinkler schedule and lawn treatment calendar working against large patch instead of for it. Get a free quote today.
