Diagnosing Yellow Patches in Centipede Grass Lawns

Investigating Localized Chlorosis in Centipede Grass

A South Carolina lakefront homeowner with a new centipede lawn noticed small yellow/brown patches. The expert (a microbiologist/botanist) outlined a systematic diagnostic approach.

Potential Causes Checklist

1. Chemical spills: Chlorinated pool water, herbicide drift, fuel leaks.
2. Physical obstruction: Temporary shade from objects, debris.
3. Grub damage: Dig up affected turf; look for white C-shaped larvae eating roots. Treat with appropriate insecticide.
4. Fungal disease: Examine blades for lesions, spots, mycelium. Apply fungicide if confirmed.
5. Bacterial/viral: Rare; requires lab diagnosis; may need turf replacement.
6. Iron deficiency (chlorosis): Common in centipede. High pH locks up iron. Treat with iron sulfate or chelated iron (Ironite).

Managing Summer "Hot Spots"

• Identify areas that decline above 85°F.
• Top-dress with compost or quality topsoil to improve moisture retention.
• Optimize soil organic matter before summer heat arrives.

Watering Wisdom

• Avoid clock-timer irrigation unless computer-controlled with rain sensor.
• Water visually: When turf doesn't spring back from footprints.
• Deep, infrequent: 1-3 inches/week in one soaking. Promotes deep roots.
• Night watering reduces evaporation loss.

Fertilizing Principles

• Never fertilize during drought.
• Soil test to match NPK to actual needs.
• Compost top-dressing annually improves soil long-term.
• Earthworms are indicators of healthy soil; introduce if absent.

Key Takeaway

Centipede grass is sensitive to high pH and excess nitrogen. Yellow patches in small areas often indicate localized soil variation or pest/disease issues rather than whole-lawn problems. Treat specifically after diagnosis.