Diagnosing Brown Spots in Bermuda Grass Near AC Drainage

When Bermuda grass dies in a localized area where air conditioner condensation drains, the culprit is often fungal disease fueled by constant moisture. A homeowner in Suwanee, Georgia, noticed spreading dead patches exactly where their AC unit discharged water—despite drought conditions and watering restrictions limiting irrigation elsewhere.

Why Excess Moisture Causes Problems

Bermuda grass thrives in well-drained soil and full sun. Continuous water from AC condensation creates saturated conditions that suffocate roots and invite fungal pathogens. Warm temperatures and organic matter (thatch, grass clippings) provide ideal conditions for fungi like Rhizoctonia (brown patch) or Pythium (root rot). The disease spreads outward from the wettest zone, explaining the expanding dead area.

Steps to Confirm and Treat

1. Inspect for fungal signs: Look for gray-white mycelium in early morning, lesions on blades, or a "smoke ring" at patch edges.
2. Apply a fungicide: Products containing azoxystrobin, propiconazole, or thiophanate-methyl are effective against common turf fungi. Follow label rates and timing.
3. Redirect drainage: Extend the AC condensate line away from the lawn, or create a gravel-filled catch basin to disperse water.
4. Improve cultural practices: Reduce thatch, aerate compacted soil, and avoid nitrogen-heavy fertilizers during hot, wet periods.

When to Consider Other Causes

If fungicide treatment fails, heavy metals from the AC system (copper, zinc) could be accumulating in the soil. A soil test with metal analysis or plant tissue testing can rule this out, but it's a last resort. Fungus remains the most likely cause.

By addressing the moisture source and treating the fungus, the grass can recover. Overseed or plug bare areas once the disease is controlled and drainage is corrected.