St. Augustine Grass Care

St. Augustine grass is susceptible to many problems that may cause patches of it to turn brown, including: 
Take All Root Rot (TARR), Chinch Bugs, Gray Leaf Spot, White Grub Worms and Brown Patch.

Since the treatment for each is radically different, it is important to first identify the culprit. 

Take-All Root Rot 

Take-All Root Rot (TARR) is a fungal disease that often affects turfgrass. This disease has the ability to destroy large sections of turfgrass if left uncontrolled. Symptoms of TARR usually appear in April and May.

To check for Take-All Root Rot:

• The first symptom is often yellowing of the leaves which eventually die.
• Turf becomes thin as roots, nodes and stolons become infected.
• Unlike Brown Patch (see below), leaves of TARR infected plants do not easily separate from the plant when pulled.
• Roots become rotted, so damaged stolons are easily pulled from the ground, similar to white grub damage (see below).

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Chinch Bugs

The southern chinch bug is an insect pest of turfgrass. Chinch bug infestations are characterized by expanding, irregular patches of dead or stunted grass surrounded by a halo of yellowing, dying chinch bugs. Symptoms of a chinch bug infestation usually appear June through the summer. Chinch bug damage can be difficult to distinguish from that caused by drought, therefore detecting significant numbers of the insects themselves is the best proof of chinch bug damage. 

To check for chinch bugs:

• If you have patches of bermuda grass that appear untouched in an otherwise suffering St. Augustine lawn, you may have chinch bugs.
• Spread the St. Augustine turf near the soil with your hands and look for chinch bugs. A magnifying glass may help as chinch bugs are so small.
• Another common method needs a metal cylinder that is open on both ends or has had both ends removed such as a used coffee can.
  • First, pick a patch of lawn and stick the metal cylinder 2-3 inches into the soil, then fill the cylinder 3/4 full of water.
  • Next, agitate the turf that is underwater. If you have chinch bugs, they will float to the top of the water.
• Adults are small and slender, measuring ⅙ to ⅕ of an inch long.They have black bodies with white wings. Recently hatched nymphs are wingless, yellow or pinkish-red with a light-colored band across their backs. 

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Gray Leaf Spot

Gray Leaf Spot is a fungal disease that tends to affect areas of the lawn that are shady and damp. Symptoms of Gray Leaf Spot usually appear June through early fall.

To check for Gray Leaf Spot:

• Leaf spots first appear as tiny brown to ash-colored spots with purple to brown margins that enlarge and become diamond-shaped.
• In severe cases, the leaves wither and die, causing thinning of the turfgrass and eventually giving the lawn a "scorched" appearance.

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White Grub Worms

White grub worms are an insect pest of turfgrass, and are actually the larval stage of several different beetles in our area (i.e. the well-known June beetle). If you've been digging around in your landscape, chances are you've come across one or two of them. Unfortunately, these larvae feed on the root structures of many species of turfgrass, slowly causing patches of the lawn to loosen and die. Symptoms of a white grub worm infestation usually appear in October. 

To check for white grub worms:

• Focus on parts of the lawn that appear to be declining, and are more susceptible to invasion by weeds.
• Turfgrass with roots damaged by white grub worms will pull out easily from the soil (similar to TARR, because both conditions affect the roots).
• To confirm whether you need to treat for grubs, examine several soil sections at least 3 to 4 inches across and 4 inches deep, paying particular attention to edges surrounding areas of suspected grub worm damage. Finding more than five white grubs per square foot may treatment, although some lawns with even higher numbers of grubs may show no damage.
• In lieu of chemical treatment, many effective mechanical and biological treatment solutions for white grub worms exist.

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Brown Patch

Brown Patch is a fungal disease that often affects turfgrass.  Symptoms of Brown Patch often appear as a result of over-irrigation or unusually wet weather.

To check for Brown Patch:

• Brown patch symptoms usually occur in a circular or semi-circular pattern, as opposed to the irregular-shaped areas of dead and dying grass that result from chinch bug feeding. 
• An easy way to tell the difference between TARR and Brown Patch is to give the grass leaves a tug! Grass blades with Brown Patch can be slipped easily from the stolon because the fungus has rotted the stems.
• Infected leaves often have a slimy, dark brown lesion at the base of the leaf.

Learn more

 

Treatment

The Integrated Pest Management (IPM) approach is recommended for maintaining healthy lawns. When adhering to IPM principles: cultural, mechanical and/or biological solutions to pest problems are preferred, and use of chemical pesticides is always as a last resort.

 

Additional Resources

• The Earth-Wise Guide to Lawn Problems is a handy reference with easy-to-read flow charts that help you diagnose your problem.
• When chemical control becomes absolutely necessary, this resource from TAMU details some common Chemical Controls for Turfgrass Diseases.
• Finally, learn more about Maintaining Healthy St. Augustine Grass Lawns in Texas with this article from TAMU.