St. Augustine grass is a popular warm-season turf known for its thick, carpet-like growth. Dead patches, caused by disease, pests, or environmental stress, compromise the lawn’s uniform appearance and allow weeds to invade. Restoring a damaged St. Augustine lawn requires a methodical approach, starting with accurate diagnosis, preparation, targeted repair, and preventative maintenance.
Identifying the Cause of Grass Death
Identifying the cause is the first step, as solutions for pests differ from those for fungal diseases. First, determine if the grass is truly dead or just stressed. Use the “pull test”: if the blades resist a gentle tug, the grass is stressed but alive; if they lift easily, the roots are dead or rotted.
Chinch bugs are a common culprit, particularly in hot, sunny areas near sidewalks or driveways. Damage appears as irregular yellow patches that turn brown, often with a yellow halo around the dead zone. The grass will feel spongy when walked upon. You can confirm their presence by parting the grass near the edge of a damaged area and looking for the small, black insects with white, diamond-shaped patches on their wings.
Fungal diseases typically favor wet, humid conditions. Brown Patch disease appears as circular patches of yellowing or brown grass. A key symptom is that the grass blades easily slip from the stolons because the fungus has rotted the stems. Gray Leaf Spot thrives in shade and excessive moisture, showing up as small, diamond-shaped lesions on the blades with gray centers and dark brown edges.
Water stress can mimic disease or pest damage, but the pattern is usually more general. Drought damage appears uniformly across the lawn or in areas with poor irrigation coverage. Overwatering encourages fungal growth and can lead to root rot. If the grass pulls up easily, it may also indicate Take-All Root Rot (TARR), a fungal disease associated with high soil pH that rots the roots.
Preparing the Area for Repair
After identifying the cause, preparing the soil ensures the new grass can thrive. If the cause was an active pest or disease, treat the area first with the appropriate insecticide or fungicide, following label instructions.
The dead material must be physically removed to expose the soil, as St. Augustine grass does not spread well over thick thatch. Rake out the dead grass and debris to loosen the topsoil and encourage better root growth. This light raking improves air circulation and water penetration.
St. Augustine grass performs optimally in a soil pH range of 6.0 to 7.5. If a soil test reveals the pH is too high, applying sulfur can gradually lower it, which helps prevent fungal issues like Take-All Root Rot. For compacted areas, core aeration helps relieve pressure, allowing air and water to reach the deeper root zone.
Reviving or Replacing Dead Patches
The repair method depends on the extent of the damage. For minor damage or stressed grass that is still rooted, revival is possible. Start with a deep, slow watering session and proper cultural adjustments, such as withholding nitrogen fertilizer if fungus is present. If a pest or disease was identified, apply the necessary treatment immediately.
For completely dead patches, replacement is necessary since St. Augustine grass does not grow reliably from seed. The two primary methods are using plugs or laying sod. Plugs are small, cost-effective sections of established grass used for smaller, scattered bare spots.
Using Plugs
When planting plugs, dig holes 12 to 18 inches apart in a staggered pattern. Ensure the holes accommodate the plug’s roots without burying the crown. Press the plugs firmly into the holes to ensure full contact with the soil, then water thoroughly to settle the area.
Laying Sod
Laying sod involves placing larger sections of turf over the entire prepared area for instant restoration. The new sod must be rolled to ensure good contact with the soil and then immediately watered deeply.
After installation, keep the soil consistently moist for the first one to two weeks to help the new roots establish. Avoid watering so heavily that it causes puddling or waterlogging. Gradually reduce the frequency of watering over the next few weeks, transitioning to a deep, less-frequent schedule as the grass spreads.
Long-Term Maintenance to Prevent Recurrence
Preventative maintenance is essential to avoid future problems and maintain the turf’s strength against pests and disease. St. Augustine grass benefits from a high mowing height, typically 2 to 4 inches, with the higher range improving shade tolerance and drought resistance. Mowing at this height encourages deeper root growth and provides more leaf surface area for energy production.
Established St. Augustine grass requires about one inch of water per week, delivered through deep, infrequent watering sessions. Avoid light, daily sprinkles, as deep watering encourages a more resilient root system. Watering in the early morning is ideal because it allows the grass blades to dry quickly, reducing the prolonged moisture needed for fungal diseases to develop.
Fertilization should be guided by a soil test to ensure the proper balance of nutrients. Applications should occur during the active growing season, beginning after the grass has fully greened up in the spring. Avoid applying high-nitrogen fertilizer too late in the season, as this encourages growth susceptible to fungal diseases like Brown Patch. Proactive pest and disease management, including the timely application of pre-emergent herbicides, helps maintain dense, healthy turf.