Minimizing Lawn Disease in the Fall

Crisp autumn air is a welcome relief after a long, hot summer — unless you’ve been overwatering your lawn. Cooler temperatures and increased moisture make your grass susceptible to fungal disease.

Cooler temperatures and increased rainfall multiply the chances of disease problems in local lawns. Bermuda, zoysia and St. Augustine grasses can be susceptible to fungal diseases if the following conditions are present: overwatering or high soil moisture, high soil pH, poor soil fertility or improper mowing height.

Let’s take a look at the common fungal turf diseases that are possible in San Antonio.

  • Take-All Root Rot, or Take-All Patch, is a very common fungal disease in St. Augustine characterized by yellowing of the grass and tiny puzzle piece-shaped fungal structures called hyphopodia on the stolons. Reducing water application where possible and applying sphagnum peat moss or ammonium sulfate fertilizer to the lawn helps reduce pH in the soil. Fungicide products should be applied before this fungus becomes a problem, because it’s very difficult to cure once established.
  • Brown Patch Fungus, or Rhizoctonia, is another disease that appears when nighttime temperatures drop below 68 degrees and daytime temps stay in the mid-80s, combined with extended periods of increased humidity. Avoid applying too much nitrogen fertilizer and reduce thatch levels in the grass to help reduce moisture. Infected grass blades can be easily pulled off of the stolons. There are many fungicide products available on the market that will cure this fungus when applied properly.
  • Gray Leaf Spot fungus effects St. Augustine grass in late summer as the result of high humidity and proper conditions. The leaf spots are grayish in color with purple margins. Grass infected with this fungus should not be given nitrogen fertilizers until the disease is cured. There are products available to help treat this disease.

Fungal diseases are usually the result of high moisture and humidity combined with cooler temperatures. Reducing the amount of water applied to the lawn, utilizing core aeration to reduce compaction and proper fertilization of the soil can help you reduce the chances of fungal diseases in your turf.

For green healthy lawns, always follow the dictum, “Less is best.” Less water, less fertilizer and less compaction.

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