If you imagine a lush, thick, dark green yard of St. Augustine grass (Stenotaphrum secundatum), then prepare to function at it. Although this potent perennial grass requires little upkeep in warm, rainy, coastal areas, inland it needs regular irrigation in addition to fertilization and mowing to maintain a dense, weed-free turf. Several fungal diseases assault St. Augustine grass including brownpatch and gray leaf spot which thin and tighten the grass. To control and prevent bacterial diseases, first employ good maintenance and cultural control practices and consider the need for fungicide. Fungicides are more effective as preventatives compared to remedies.
Limit fertilization to ward off bacterial disease. Over-fertilization, especially with nitrogen, encourages rapid and lush grass growth and invites a respiratory disease. But too little nitrogen also creates an environment which encourages bacterial infection, so the goal is to implement enough but not too far. When planting, apply a balanced, complete fertilizer, then insert nitrogen each month at a rate of 1 pound per 1,000 square feet.
Cut your grass short, but not so brief as to stress it. A mix of moist foliage and warm weather encourages bacterial diseases. Maintain the grass at a height of 1 to 3 inches. Mow frequently enough that you never remove more than one-third the height of the grass blades. Keep your mower blades sharp so that they cut the grass blades instead of ripping them. If your St. Augustine grass is attacked by a bacterial infection, allow the blades to grow more. The more the grass, the leaf tissue for photosynthesis, resulting in more energy for your turfgrass to combat the disease.
Limit irrigation to when the grass blades curl. Fungal pathogens need water on the grass blades or high humidity to begin the disease procedure. Water early in the morning between 2 a.m. and 8 a.m. so the grass may dry completely during the day. Water enough to saturate the root zone, no more. The grass blades should never be wet for more than six hours.
Apply a fungicide at the first indication of brown patches in your lawn. Utilize a systemic fungicide which has preventative and therapeutic properties. Unlike contact fungicides which you apply to the plant leaves to create a protective barrier, systemic fungicides are absorbed by the plant. Read and follow label instructions carefully, such as how much of the product to use, how much water to use and how often to use the fungicide. Mix the correct quantity of the fungicide using water and spray the lawn after mowing and raking, thoroughly covering the grass blades. Depending on the fungicide as well as the bacterial disease, you may have to reapply the fungicide in two- or three-week periods.