5 St Augustine Grass Diseases

Published Categorized as Pest Control
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St. Augustine is among the most vulnerable grass varieties to fungal diseases, pests, and weed infestation. These St Augustine diseases could affect your lawn significantly, making it unsightly. Early identification and management of these St. Augustine grass problems are vital to keeping your turf healthy and magnificent. So, which are the common St Augustine grass diseases?

St Augustine grass diseases include brown patch, gray leaf spot, take-all root rot (TARR), fairy ring, St. Augustine decline, and nigrospora stolon rot.

Although this turf type is relatively resistant to diseases, it is still vulnerable to these fungal diseases. One St Augustine grass disease can kill your lawn and start over. Therefore, act quickly to save your grass if your lawn shows vivid signs of stress, like brown patches.

St Augustine Grass Diseases Pictures: How to Diagnose

St Augustine grass diseases

You can identify problems with St. Augustine grass if you notice the following symptoms;

i. If the Saint Augustine grass stolons start turning brown, that’s a fungal infection.

ii. Random yellowing of turf leaves signifies fungi, weeds, or pest infestation. Excessive shading may also cause the yellowing of grass blades.

iii. Roots pulling out effortlessly indicates fungal issues.

iv. Once you notice irregular brown patches in your lawn, it signifies the presence of fungal problems.

v. If the leaf blades start to brown at the base, that’s a fungal infestation issue.

Which Are the Common Problems With St Augustine Grass?

Here are St Augustine grass diseases pictures you need to beware of:

1. Brown patch disease

St Augustine Grass Diseases

Brown patch disease or Rhizoctonia solani attacks your Saint Augustine grass, mainly in winter or fall. The disease thrives when the temperatures are low, the ground has excessive moisture, or the yard has too much thatch.

You can identify the disease by seeing dark brown spots in leaf blades, thinning out edges, or loose grass.

2. Gray leaf spot

St Augustine Grass Diseases

This St Augustine grass disease is caused by Pyricularia grisea. It flourishes in areas with high temperatures, excessive water, or shaded areas. Nitrogen deficiency or excess fertilizer use in your lawn also accelerates the spread of gray leaf spots.

You can first identify it with oval and round patches on the turf with dark brown margins.

3. Take-all root rot (TARR)

Take-all root rot spread quickly during April and May. It mainly affects the root system and is caused by excessive shading, over-watering, under-watering, extreme temperatures, and herbicide injury.

If you notice yellowing of turf blades, root rotting leaves thinning, or irregular brown spots, that’s a take-all root rot problem.

4. Fairy ring

St Augustine Grass Diseases

Fairy ring diseases are caused by Basidiomycetes fungus and are predominant in areas with sandy soil and excessive thatch. This problem forms a fungal mat in the ground preventing proper water absorption into the soil.

It’s characterized by dark green circles in the turf enclosed by a ring of dead lawn.

5. Nigrospora stolon rot

This disease is triggered by Nigrospora sphaerica fungus and is dominant in summer, drought periods, or dry spring. It prevents proper absorption of nutrients and water by the grass, making the leaves thin and yellow. The problem eventually causes the roots to rot and decay.

Other Saint Augustine Grass Problems

St Augustine Grass Diseases

Your St. Augustine grass may stunt or die because of other issues apart from fungal diseases. These grass problems include;

  • Pests infestation, especially Chinch bugs attacks and white grubworms
  • Weeds invasion
  • Excessive shading
  • Over-watering and under-watering
  • Cold damage

St Augustine Grass Diseases FAQs

Q: How do you treat Saint Augustine grass diseases?

A: You can treat St. Augustine grass diseases by spraying the lawn with fungicides like propiconazole, azoxystrobin, thiophanate-methyl, or myclobutanil. Water the grass straightaway after application and do proper fertilization.

Q: Which factors contribute to St Augustine grass issues?

A: Factors that cause Saint Augustine grass issues include prolonged drought conditions, freezing temperatures, diseases, pests, and weeds infestation. Over-watering, under-watering, and excessive shading are other elements that lead to lawn problems.

Final Remarks

Although St. Augustine grass is fairly disease-resistant, it is still vulnerable to diseases, especially in summer and spring.

Common St Augustine grass diseases are brown patch, gray leaf spot, take-all root rot, fairy ring, and Nigrospora stolon rot. Low temperatures, excessive moisture, drought, excessive thatch, excessive shading, and improper lawn maintenance are the leading causes.

You can treat these diseases by applying fungicides like propiconazole, azoxystrobin, thiophanate-methyl, or myclobutanil.


University of Arkansans System Division of Agriculture

Clemson University