Pictures are a big help! Thanks Firstly: yes, that is St Augustine. The next to last picture does show fungal lesions. The easiest treatment for that, especially with our warm weather, is ordinary corn meal. I realize that seems hard to believe, but it is a microbiological solution. Corn meal attracts various fungi to decompose it. After the population of those fungi grows from eating the corn meal, then another fungus comes in as a predator on the first fungi. Once the population of the secondary fungus grows large enough, it will spread and "eat" the fungus causing your disease and kill it. I have gotten that same disease almost every year since 2001. It will continually spread if you don't stop it. Corn meal was the one thing that worked for me. Apply at 20 pounds per 1,000 square feet now and repeat in 3 weeks. Get the corn meal at your local feed store. Call first because there is another product they are familiar with called corn GLUTEN meal. You don't want that. You want ordinary whole ground corn meal. Cracked corn will work, too. Deer corn will work but it will give you a field of corn. Being in Brownsville, you can get a 25-pound bag of corn flour at HEB. Don't get the stuff that is tortilla mix. That has baking powder in it. You just want plain ground corn. There are almost no insects that hurt St Augustine. Fire ants might smother part or eat the roots, but generally they are just a nuisance...as you well know. The red ants are not a problem. Any tiny hopping insects you see are not a problem. By the way, corn meal is a low grade organic fertilizer. You will see the lawn green up about 3 weeks after you apply it. With the second application of corn meal, you may not need to fertilize again until next April (after the spring flush of rapid growth is over). If you stick with Milorganite, you can apply that any time and not have a problem. Keep checking to see that the sod is knitting down into the underlying soil.

You have a disease, but why? I suspect you have a broken water line behind the meter in the pipe going into the house. Turn off all the water and check your meter to see if it is moving. It should be perfectly still. Once you get the leak fixed and pipe replaced, I would apply ordinary corn meal at a rate of 20 pounds per 1,000 square feet to stop it. You can do that now even while it is hot. Be sure when the remove the soil to dig out the old pipe that they return all the soil they dug out back into the trench. It should mound up almost an inch, but it will settle back down to level in 3 years.

See the tan colored spots with the dark brown edges? Those are fungal disease spots. That's what's taking out your grass. This should respond to ordinary corn meal if you have not already applied a fungicide. Call your local feed stores to find it in 50-pound bags. If they don't have it you'll find corn flour at any grocery store in FL and especially those that cater to the Hispanic population. If you get it at a grocery store there are different products packaged in very similar bags. You don't want the stuff that already has baking soda/power in it. Apply at the rate of 20 pounds per 1,000 square feet. Apply to the entire lawn or else you'll have green spots. Corn is a fertilizer. The reason corn meal works against fungal disease is through the decomposition process a predatory fungus takes over the final stages. Once the predator finishes with the corn meal it takes over killing the disease fungus in your yard. This is a biological process that takes about 3 weeks. You can apply in the heat of summer or whenever you feel the need. During the 3 weeks you should see new grass coming in but it might still get the spots. After 3 weeks the new grass should not get the spots. Most people in FL are watering wrong - at least the ones writing in here report that everyone waters every day. That's wrong. Here's more. Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

Looks like it to me. Here is a link to some more information, which you might have already found. I would assume the grass came with the disease which got much worse with the rain. Take a note and don't buy grass from that supplier again. Being an organic kind of guy, I would be hitting the grass with ordinary corn meal at 15 pounds per 1,000 square feet every 3-4 weeks for the rest of the summer. This is INSTEAD of using a fungicide. As discussed in the link above, this is a soil borne disease. These problems are caused by an imbalance of beneficial versus pathogenic microbes - essentially an unhealthy soil. The fastest way to restore the soil to health is to use organic fertilizer, NOT fungicide. Corn meal has the additional benefit of heavily populating the soil with a predatory, but beneficial fungus called Trichoderma (try koh DER mah). Not all fungi cause disease. If you cannot find ordinary corn meal at your local feed stores (call first), then cracked corn will work. If you cannot find either one, then look for a grocery store catering to the Hispanic market. They will have 25-pound bags of corn flour. They will also have 25-pound bags of tortilla ready-mix which has baking soda and baking powder in it. The bags are almost identical, but you want the plain corn flour. Ask for help if you cannot tell them apart. If you have any doubts about the effectiveness of organic fertilizer, please ask. I think you ran into an unfortunate weather situation - unlucky timing. The grass could have been afflicted before you bought it, but that's hard to prove. It may have a guarantee or you might get a discount on buying again from the same supplier.