St. Augustine Disease Management
Large Patch (Rhizoctonia solani) is the primary fungal disease. It activates in fall and spring when soil temps are 60-75°F with wet conditions. Symptoms: circular patches of yellowing/thinning turf, stolons pull away easily at the infection point with a dark rotted lesion. Preventive fungicide (azoxystrobin or propiconazole) when soil temps drop to 75°F in fall and again when they rise to 60°F in spring. Take-All Root Rot (TARR): roots turn black and rotten, grass thins and yellows in irregular patterns. Treat TARR with soil acidification — peat moss topdressing at 1/2 inch plus fungicide. Do NOT confuse TARR with chinch bug damage — pull up a stolon and inspect the roots.
Frequently Asked Questions
What is the most common St. Augustine disease?
Large Patch (brown patch) is the most common, appearing as large circular brown areas in fall and spring when soil temps are 60-75°F. Preventive fungicide is the best defense.
What is Take-All Root Rot?
TARR attacks the roots, causing yellow then brown patches that don't respond to fertilizer or water. Pull up affected grass — if roots are short and black, it's likely TARR. Acidify soil with sulfur and apply fungicide.
When should I apply preventive fungicide to St. Augustine?
Apply in early fall when soil temps drop to 75°F, and again in early spring when they rise to 60°F. These are the two Large Patch infection windows.
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