Wow, I am very aware of the brown spot problem and it has absolutely NOTHING to do with water your St Augustine. It is grubs that are laid in the lawn by the Japanese beetle in the spring. At the end of summer towards fall the grub from the eggs feeds on grass roots. It looks like round brown spots like your dog pissed there. If you pull on the brown spot and it comes up like a patch that's further proof. I treated my back yard and it stopped. I didnt treat the front and it has brown patches and bare spots. Dig around before it gets too cold and you will find grubs......Organic treatment is Milky spore

I'm guessing that you are watering too frequently, possibly daily, which has led to the lawn developing a fungal disease. Notice that there is a distinct arc to the brown blades from the bottom right of the picture to the middle left...that is another clue that it's a fungal disease and not caterpillars (worms). Quite often a fungal disease will form a near perfect circle. Can you post another picture? Get about 3 inches away from some of the grass at the edge of the brown area. The best pictures are taken on a cloudy day or in the shade to reduce the contrast. Fungal diseases show up on the blades of grass. If it is a fungal disease, my recommendation would be to apply ordinary corn meal at a rate of 20 pounds per 1,000 square feet. Corn meal attracts a predatory fungus which feeds on the disease fungus. It goes to work immediately but it takes about 3 weeks to see the improvement as the green grass returns. I have used corn meal successfully every year since 2002 to eradicate disease in my St Aug. Although, now that I have Floratam in the back yard, the grass fights off the disease faster than it can spread. I still see signs of disease...and then it's gone. If you don't have Floratam now, you might consider putting down one flat of it and letting it spread into the lawn. If you had Floratam in the lawn currently, it would be spreading into the thin (brown) areas and taking over even while the disease is present. Cool stuff. Oh and as to the watering, this time of year you should be watering no more frequently than once every 2 weeks in your area. If you get high temps in the 70s, then you could back off to once every 3 weeks. If you are not doing that, please write back and tell us what you are doing so we can get you backed off to watering less often.

You tricked me. I was going to guess that you lived in Texas (calcium soil) and have been subject to the heavy rains we've had over the past few weeks. Still you have the same issue. Your soil needs iron. I would start with Milorganite fertilizer. Give that 3 full weeks and see how it looks then. If it seems to be a little better, repeat. If you can find a product with glauconite, use that at 40 pounds per 1,000 square feet. In Texas it's called Texas Greensand, but sometimes they leave the Texas off. It is a greenish sandy material that is rich in all kinds of minerals. It works to green up this washed out soil when nothing else works. Do you know how much water your system puts out in 5 minutes? The best watering schedule for you would be to water 1 full inch, all at one time, and do that once every 1-2 weeks depending on whether your temps are in the 90s or 80s. Put some cat food or tuna cans around the yard, turn on the sprinklers and time how long it takes to fill the cans. That's how long you should be watering every week or two. You cannot go cold turkey with this watering if your grass is currently getting almost daily water. That would kill it because your roots are only as deep as they need to be to get that almost daily dose of very little water. Deeper and less frequent watering will develop deeper roots which are able to get iron at greater soil depths. If you are currently watering 4x per week, try watering deeply (during your can test), and then watch the grass carefully to see how long it can go without looking wilted. At the first sign anywhere of wilting, water it again for half the time it takes to get the inch. Then watch again and water 1/2 inch at the first sign of wilting. Now the grass should start to go longer before it looks wilted. When the grass can go 4 days without water, then give it a full inch and repeat the same regimen of watching for wilting. Soon enough it should go a week to 10 days before wilting. Then you can adjust your schedule. But at no time should you be watering more than once per week. And why do I say all that. Weed seeds need continual moisture to germinate and take root. When you water every other day, the weed seeds get exactly what they need. If you allow the surface of the soil to dry out completely before you water again, the weeds can't get started. You'll end up using less water, less fertilizer, and just about zero herbicide.

How did I miss a blatantly St Augustine topic? I'm thinking the soil is water logged. My St Augustine in San Antonio and in the Hill Country goes 3 weeks without water standing on its head. What is your watering schedule? How often do you water and for how long? Do you know how long it takes your sprinklers to apply an inch of water? Did you or someone leave some toys, garden trimmings, branches, leaves, or anything in that spot on the side yard? St Augustine is very intolerant of being cut off from air flow. One night of being covered can start the fungal disease process that leads to spots just like what you're seeing. Once that starts it doesn't matter how much or little you water, but I'm still interested in your watering. Oh and start calling around to feed stores to find corn meal in 50-pound bags. Corn meal is going to get your grass back into shape on the side and will help in the back. My St Aug spreads as much in the spring as in the fall. Key to spreading is to arrange for the air temp to be in the 70s.