This picture is a close-up of some of the brown patches.

And an overall view of the affected area

Is it always that shady? I cannot grown SA without a few hours of good sun.

In the morning it tends to get more sun. Shady during the heat of the afternoon. The sod company recommended Sapphire SA as a shade-tolerant variety, not sure how accurate that is.

That should be plenty of sun for St Aug. I have parts of my lawn that have not seen direct sunlight since the 1980s.

Yours is not a close up. This is a close up...

{{gwi:92453}}

More specifically that is a close up of diseased St Augustine. You can see the fungal lesions which look like water spots. Look in your grass for the same thing. Even the brown grass will have those spots where they show a different color of brown.

The reason you have dead grass is that you are over watering and have been for months. Once the new grass knit down to the underlying soil/sand, then you should have begun the process of backing off. For a mature grass, which yours should be just about mature by now, you should be watering only once every week or two. If your daytime temps are in the 80s, then once every other week. With temps in the 90s, once per week. With temps above 100, then every 5 days. But NEVER do you go to once every other day or every 3rd day. If you lived in Las Vegas, in full sun, where the sand holds no water, temps above 105, and humidity below 10%, then you might need to water once every 5 days. Your sand holds much more water than the Las Vegas sand. Plus you never have humidity lower than 60% and the wind is always full of moisture. Add your shade and once per week in July would be puh-LENTY.

Beach sand is my preferred fill material for St Augustine. My house in San Antonio was a wash-out when we bought. We filled with top soil in places and sand in places. The sandy soil is the best we have. So I will not accept that your sandy soil is a problem.

If you have not already measured your sprinkler output, do it using cat food or tuna cans. Time how long it takes to get a full inch in all the cans. That is the time you should shoot for every time you water. Then don't water until the surface of the soil is dry/warm down an inch (or to your first knuckle). The idea is to grow deep roots which will be able to get moisture from the cooler sand/soil deeper underground. Also adjust your mower to the highest position. Tall St Aug needs much less water than short St Aug. I have an ongoing experiment in a lawn in George West, Texas, on the edge of the Texas desert. One large part of that lawn has received no supplemental water since October 2011. Of course the grass got up to 32 inches tall, but the point was definitely made. The water district called me to ask if I had moved out, because I wasn't using as much water as the previous owners. Then they thought my water meter wasn't working, so they replaced that. Tall grass does not need as much water. With that in mind, my mower is set to the highest position and I only mow every 2nd or 3rd week. That lets the grass get up tall for the best root production before I mow it down.

Now what do you do with your lawn?
My suggestion would be to apply ordinary corn meal at a rate of 20 pounds per 1,000 square feet. I know that sounds like crazy talk, but it works. It is the only "fungicide" that has worked for me since forever. The problem with chemical fungicides in the deep south is the only day it is safe to apply is something like January 4th. All the rest of the time it is too hot or too wet. Read the label very carefully if you decide to use chemicals. On the other hand, corn meal attracts a beneficial fungus called trichoderma (try koh DER ma). The trichoderma fungus is predatory on other fungi and will literally eat up the disease over a period of 3 weeks. Corn meal, obviously, is harmless to you, your children, and pets. If you think you didn't get enough put down, you can always apply more without fear of hurting anything. Corn meal is also a mild organic fertilizer, so there is really no downside to using it. Although if you don't use it on your entire lawn, you might end up with dark green spots where you used it and lighter green elsewhere. You can find corn meal in bulk at your local feed store. Call first to see if they have it. Cost should be around $15 for a 50-pound bag. I would continue to use corn meal as your only fertilizer for the rest of the season to make sure the disease does not return. If you use it once per month that would speed the regrowth of the lawn.

So stop the frequent watering, mow high, and fertilize with corn meal. The first two are free and the third is safe and effective.

Dchall,

Thank you very much for your input. I just went out and adjusted the sprinklers to 1x per week. As far as the overwatering, again I was just following the instructions from the sod farm and actually cut back from their advice. Now I know better. Also, here is a more close up view, it doesn't have the spots that your photo indicated. Would you still recommend the cornmeal as a preventative and fertilizer?

Again, thank you for your response.

I had something similar happen. Did you ever find a resolution?
I can't be out there too much though because my body cant take it.

I have bad allergies lol.

Here is a link that might be useful: How to stop sneezing

I did not see the last post by the OP on this. I would have still suggested the corn meal to treat for fungus.

Drenrawr, where do you live?
How often do you water and for how long?
How high/low are you mowing?
Is shade an issue in the landscape?
And do you know what variety of St Aug you have?
When were the last two times you fertilized and what did you use?
Have you used any herbicide or insecticide or fungicide in the past season?