Orange ring of large patch disease around a green zoysia circle marked 70°F

Large Patch Fungicide in Fall: When to Spray and What to Buy

ByRyan
The Short Answer

Large patch infects warm-season grass in fall, but the circles don’t show until spring. The window that matters is when soil temperature drops to 70°F for several days in a row. Spray a preventive fungicide then, spray a different fungicide group about three weeks later, and add one more pass at spring green-up. If you spray after you can see the patch, you’re mostly paying to watch it spread.

What to buy: Azoxy 2SC Select, generic azoxystrobin (~$55.78 a pint) · Prime Source Propiconazole 14.3 Select (~$33.56 a pint) · no sprayer: Scotts DiseaseEx granules (price not verified). All picks.

It’s early October, your zoysia still looks fine, and that’s the problem. Large patch does its damage while the lawn is green. By the time you see orange rings in March, the infection happened five months earlier and the fungicide window closed with it.

This article is the buying and timing half of the story. Jump to the quick answer. If you still need to confirm what you’re dealing with, the large patch diagnosis guide walks through the basal sheath test and the look-alikes. Here the question is narrower: it’s fall, you’ve had patches before or you’re on a susceptible grass, and you want to know when to spray, what to spray, and what it costs.

Which Lawns Need This

Not every lawn does. NC State Extension ranks centipedegrass and seashore paspalum as the most susceptible, then zoysia, then St. Augustine. Bermudagrass is rarely affected and grows out of it quickly when it is. Tall fescue and bluegrass are close to immune, though they have their own brown patch season in summer.

The trigger temperature differs by grass, and most articles skip that. NC State says to start centipede and St. Augustine at 80°F soil temperature held for 5 or more consecutive days, which can be mid-August. Zoysia starts at 70°F for 5 or more days. If you run centipede or St. Augustine and you’re just now reading this, your first window already passed, so go straight to the second application and the spring one.

I grow zoysia in Peachtree City, Georgia. I haven’t grown centipede, St. Augustine, or bermudagrass myself, so what I say about those comes from extension sources, not from my own turf.

When to Spray: Watch Soil, Not the Calendar

Mississippi State Extension puts it plainly: make the first application after the 2-inch soil temperature has been at 70°F or cooler for three consecutive days. NC State asks for five. In their Mississippi trial plots, the section treated in mid-September at that trigger showed no symptoms by late October, while the difference from the untreated side was clear. Pick the stricter of the two and you won’t be early.

Clemson gives calendar dates for South Carolina, based on 2014 to 2018 soil averages: first application around October 15 for the Upstate (Clemson, Greenville, Rock Hill), October 20 for Columbia, Florence, Aiken, and Myrtle Beach, October 25 for the coast (Charleston, Beaufort). Second application three weeks after the first. Georgia’s Piedmont sits close to that Upstate group, but treat those dates as a starting guess and let a thermometer overrule them. A cheap soil thermometer pushed 2 inches into the turf at the same time every morning does the job, or use the free soil temperature lookup if you don’t want to buy one.

Then there’s spring. Clemson recommends one more application once the lawn starts greening up, because the pathogen is active again as soils warm through the same range. That makes three passes in a bad-history lawn: two in fall, one in spring. NC State says two well-timed applications may give season-long control in many situations, and that severe sites can repeat every 4 to 6 weeks while soil stays above 50°F.

Why Two Different Products

Fungicides are sorted into fungicide groups by how they kill. Azoxystrobin is group 11. Propiconazole is group 3. Spraying group 11 twice in a row repeats the same attack on the same fungal population, which is how resistance builds. Clemson’s advice for single-ingredient products is to alternate: one group first, a different group for the follow-up. Products that already carry two active ingredients (Headway G, for example) can be repeated, but they cost more per pass.

That’s why the cheap program is two jugs, not one. The full rotation logic, plus which diseases each group handles, lives in the lawn fungicide guide. For mixing both in one tank, check the tank mixing guide first, and read both labels.

The Math

Take an 8,000-square-foot lawn. Azoxy 2SC Select lists a turf broadcast rate of 0.38 to 1.35 oz per 1,000 square feet in 2 to 4 gallons of water. That’s roughly 3 to 11 oz per pass on this lawn, so a $55.78 pint covers somewhere between one and five passes depending on where on the label range you land. Prime Source Propiconazole 14.3 Select lists 0.5 to 4.0 fl oz per 1,000 square feet. At the top of that range, a $33.56 pint treats about 4,000 square feet, so a lawn this size wants the gallon ($93.00) or you accept a thinner rate.

The labels set the legal rate for your disease and your grass. Read them before you mix anything. Both are professional-formulation concentrates sold to homeowners. DoMyOwn won’t ship some products to a few states, so confirm yours at checkout.

One more cost cut from NC State: map the patches in spring, then spot-treat those areas in fall. If your lawn only blew out in two or three circles, you don’t need to broadcast the whole yard, and a pint goes a very long way.

Do Not Buy

  • A fungicide in spring once the circles are visible, expecting a cure. It can slow the edge, but the sheath damage is done and recovery takes a growing season.
  • Two group 11 products back to back. Heritage G followed by Scotts DiseaseEx is the same chemistry twice. Rotate to a group 3 product for the second pass.
  • A fall “winterizer” with nitrogen on a warm-season lawn. Clemson flags that most winterizers contain nitrogen, and nitrogen in fall feeds the pathogen. Our warm-season nitrogen cutoff guide has the dates.
  • A weed and feed bag in the same window. The fertilizer half works against you here, as the weed and feed breakdown explains.
  • Any of this for Pythium. Groups 3 and 11 do essentially nothing against water mold. If the lawn is waterlogged and rotting, get a diagnosis first.

Three Ways to Do This

Tier 1: Cost, for the Rationalist. Two generic liquids, one sprayer, and your own thermometer. Azoxy 2SC Select: DoMyOwn, $55.78 (pint). Prime Source Propiconazole 14.3 Select: DoMyOwn, $33.56 (pint). Together that’s $89.34 for the two jugs, and the azoxystrobin pint alone can cover more than one pass. Azoxystrobin is the same active ingredient that sits in the name-brand granulars. Artavia 2 SC is the same chemistry at $65.10 a pint if the Azoxy 2SC Select is out of stock: DoMyOwn, $65.10 (pint).

Tier 2: Effort, for the Minimalist. No sprayer, no mixing. Clemson lists Scotts DiseaseEx (azoxystrobin) and Bayer BioAdvanced Fungus Control for Lawns granules (propiconazole) as an excellent pair when applied together, and either granule must be watered in with at least half an inch of irrigation. Scotts DiseaseEx: Amazon, price not verified this run. You pay more per square foot for the convenience, and you still need to hit the same soil-temperature window.

Tier 3: Goal, for the Nut. Map every patch in spring, log soil temperature daily from late September, spot-treat the problem zones in fall at the 70°F trigger, and broadcast only if the history says the whole lawn is at risk. Pair the spray with the free fixes: morning irrigation only, no fall nitrogen, mowing at the recommended height, and thatch under control. Fungicide is the last 10 percent of this program, as the large patch guide lays out.

Where I Stand

My lawn is zoysia in Peachtree City, Georgia, which is exactly the grass and climate this disease likes. I don’t put nitrogen down once soil temperatures start sliding toward 70°F, and spring feeding waits until the 4-inch soil temperature is past 65°F and rising. The fungicide timing in this article comes from NC State, Clemson, and Mississippi State extension work, not from a spray log of mine, so use their numbers and your own thermometer.

Quick Reference

The disease: Rhizoctonia solani infects warm-season turf in fall and shows up in spring.

  • Zoysia trigger: soil at 70°F for 3 to 5 consecutive days (2-inch depth).
  • Centipede and St. Augustine trigger: 80°F for 5 or more days, often mid-August.
  • Second application: about 3 weeks after the first, from a different fungicide group.
  • Spring: one more application once the lawn greens up.
  • No fall nitrogen. Water granules in with at least half an inch.

Do not buy: a spring fungicide as a cure, two group 11 products in a row, or a nitrogen winterizer.

What to buy:

  • Azoxy 2SC Select (group 11): DoMyOwn, $55.78 (pint)
  • Prime Source Propiconazole 14.3 Select (group 3): DoMyOwn, $33.56 (pint), $93.00 (gallon)
  • Scotts DiseaseEx (group 11 granules): Amazon, price not verified

Products Mentioned in This Article

Some links on this page are affiliate links. If you buy through one, I may earn a commission at no extra cost to you. It doesn’t change the picks. How I choose products.

Sources: NC State Extension, Large Patch in Turf; Clemson HGIC, Large Patch Disease Control in Warm Season Lawns; Mississippi State Extension, The Plant Doctor: Large (Brown) Patch of Warm-Season Turfgrasses.

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