November, north Florida.

You are about to lose the lawn.

1. The Diagnosis: In North Florida in November, 3–6 ft circular yellow-brown patches in low areas are classic Large Patch (Rhizoctonia solani). It activates when soil temps drop to 70°F and moisture is high. Your low spots hold water, creating the perfect incubator.

2. Why the Tech’s Plan Kills Grass:

• Daily Irrigation: Large Patch requires leaf wetness and saturated soil. Daily watering in November (low ET, dormant growth) guarantees 24/7 moisture. You are fertilizing the fungus, not the grass. Stop watering. Let the top 2 inches dry.
• 20-0-0 (High Nitrogen): Nitrogen on a warm-season grass entering dormancy (or already dormant) with active Large Patch is rocket fuel for the pathogen. It forces tender, susceptible tissue and suppresses root carbohydrate storage needed for spring green-up. UF/IFAS recommends ZERO nitrogen after Sept 15 in North FL.
• Mowing at 2.5 inches: St. Augustine cultivars (Floratam, Palmetto, CitraBlue) require 3.5–4 inches. Scalping to 2.5" removes photosynthetic leaf area, exposes stolons to frost/desiccation, and stresses the plant, reducing its ability to fight the fungus.

3. Immediate Corrective Action:

• Irrigation: Off. Rain only. If bone dry for 14+ days, run once (½ inch).
• Fungicide: Apply a DMI (propiconazole, myclobutanil) or SDHI (azoxystrobin) now per label rates for Large Patch curative control. Water in lightly (⅛ inch) to move to crown/stolon zone.
• Mowing: Raise deck to 4 inches. Do not mow dormant/brown grass.
• Fertility: Zero Nitrogen until soil temps hit 65°F at 4-inch depth for 7 consecutive days (usually late March/April). Potassium (0-0-16 to 0-0-22) is acceptable now for stress tolerance.

Code/Standard: UF/IFAS ENH5/LH010 (St. Augustinegrass for Florida Lawns); UF/IFAS PP333 (Large Patch).

The proposed fix will likely worsen the problem.

Circular yellow-brown patches 3–6 feet across in St. Augustine grass in north Florida in November strongly suggest large patch disease (caused by Rhizoctonia solani AG 2-2 LP), a common fungal disease in warm-season turf during cool, wet fall conditions. It thrives when daytime temps are 60–80°F and nights are cool—exactly November in north Florida.

Why the tech’s plan backfires:

• Daily irrigation → increases leaf wetness and soil moisture, creating ideal conditions for fungal spread. St. Augustine needs less water in fall; overwatering promotes disease.
• 20-0-0 (high N fertilizer) → stimulates lush, tender growth that is more susceptible to fungal infection. Nitrogen should be avoided in fall for St. Augustine to reduce disease risk.
• Mowing at 2.5 inches → too low for St. Augustine (ideal height: 3.5–4.5 inches). Scalping stresses the turf, reduces root depth, and opens wounds for infection. It won’t “blend in” patches—it will weaken healthy grass and invite invasion.

What’s about to happen: The patches will expand rapidly as the fungus spreads under wet, fertilized, stressed turf. By spring, you’ll see larger dead zones, weed invasion (especially crabgrass and doveweed), and thinning that may require sod replacement.

Correct action (per UF/IFAS Extension):

• Stop nitrogen now; apply potassium if soil test shows deficiency (e.g., 0-0-60).
• Reduce irrigation to only when grass shows wilt (1/2–3/4 inch per application, max 1x/week).
• Apply a fungicide labeled for large patch (e.g., azoxystrobin, flutolanil, or propiconazole) — follow label.
• Mow at 4 inches; collect clippings if disease active.
• Improve drainage and aerate in spring if compacted.

Bottom line: This is a disease issue, not drought stress. The tech’s approach treats symptoms incorrectly and will accelerate decline. Recommend a licensed turf professional or county extension agent for diagnosis and treatment. (UF/IFAS ENH11, SS-PLP-003)