Sorry to disagree with you weed. That is fungal disease. How long did your grass sit on the pallet before you put it down. St Aug is very prone to disease when it does not get good air circulation. Here is a picture of iron chlorosis in otherwise healthy St Aug... Only the grass in the very center of the photo is affected and only barely affected. I happened to catch it right before the entire lawn turned yellow. I have a much better picture of St Aug chlorosis but on a different computer. Your instinct to spray with a fungicide was correct. I would not have used a spray because I have excellent experience using ordinary corn meal on St Augustine. If the spray does not work, you can still use corn meal but you will have to use a little compost first. Corn meal is a biological solution and your spray has upset the natural biology of the soil. Compost will restore that biology and then you can use corn meal. Yes, this is the corn meal you eat. As a comment on your previous die-offs: the first one was not due to a major freeze. I don't know what it was, but if St Aug survives almost every winter in Dallas, it is much more likely to survive absolutely EVERY winter in Florida. Second one was chinch bugs...or was it lack of water and mowing too low? Established St Aug must be watered at least monthly to remain alive. It needs to be watered weekly during the heat of summer to thrive. If you have sandy soil yours might need it more frequently. And most St Aug should be mowed at your mower's highest setting. Mow too low and you need to use more water...and you get weeds.

It is never too late for either compost or corn meal. Corn meal is good for many of the lawn diseases and it is also an organic fertilizer. It can be applied any day of the year for either fungus control or fertilizer. If you only use the corn meal on the disease part of the lawn, chances are you will miss some of that area. And if you only use it on the disease part of the lawn, in 3 weeks you will have a very dark green spot where the disease was and the rest of the lawn will look yellow. For both of those reasons I suggest applying corn meal to the entire lawn if you are going to treat for disease. Unless you have done something harmful to your soil's microbes, you probably do not need to apply compost. However, if you want to apply it anyway, apply the compost first. Which way you do it is not critical but I "think" it will work better if the corn meal goes on top.

Before dchall replies can you take him a picture from about 3 inches away. Get one of the grass that is still green at the perimeter of the brown area too. Also what is your definition of "water when needed" Debo you do seem to be reading my mind...or any of about 500 posts asking for the same thing. LOL. I've used corn meal successfully in St Augustine since 2002. There was one year when it seemed to be only good enough to stop the spread. This year might be one of those years. It has to do with how much rain we got since October. As Debo started to explain, corn meal works biologically. It attracts the Trichoderma fungus which is predatory on other fungi. It seems to feed on most of the lawn disease fungi, so it is considered to be beneficial. The application rate is 20 pounds per 1,000 square feet. It can take 3 weeks to see the new blades of grass coming out and not turning brown or getting spots on them. Here's what the spots look like. ...well for some reason GardenWeb is not letting me load a picture. Here's a link to the picture. I get corn meal at a feed store in plain brown, 50-pound, bags but you can also get it in 25 pound bags at grocery stores catering to the Hispanic population. It's something like Masa Maiz. Read the ingredients to see if it has any baking powder in it. You don't want or need that. Just get plain corn meal or corn flour.

If you had not already applied a chemical fungicide I could have helped you. Recheck the label on your fungicide to be sure it works in the temperatures you are getting now. Most tell you to not use above 80 or 85 degrees F. If that's on your label then stop using it now. The easy solution to the problem, had you not already used the chemical, is to apply ordinary corn meal at rate of 20 pounds per 1,000 square feet. If you cannot find corn meal in 50 pound bags at your local feed store, you can also use cracked corn or corn flour from the grocery store. You can find it in 25 pound bags in stores that cater to the Hispanic community. Corn meal works by attracting a beneficial predatory fungus which kills the disease fungus. So if you have already used a fungicide, then the beneficial fungus is gone. If the temps are too high for your chemical fungicide, then wait 2 months and try the corn meal. Or you might be able to speed up the recovery by using compost at a rate of 1 cubic yard per 1,000 square feet along with the corn meal. Compost contains the beneficial fungus you need and will reinoculate the soil with it. Here are before and after pictures using corn meal. The grass in the pictures were in deep filtered shade of a large live oak tree. That was about as dense as it ever got in that area with zero hours of direct sunlight. St Augustine does not get thatch except under the most ridiculous maintenance practices. It would require daily watering and weekly fertilizing with a liquid spray. I have seen it, but only on one yard. And as soon as the management on that yard went back to normal the thatch disappeared. That lawn was growing entirely on top of the soil. Aerating won't help. Would you characterize your soil as sand or something else? Okay I just read back. This is Floratam? Floratam is the most disease resistant variety of St Aug. It is also the most sensitive to chemicals. Stop mowing it low and let it grow up for several weeks until it is higher than your mower's highest setting. Then mow every 2-3 weeks. The idea is to grow deeper roots which can get nutrition from deeper down in the soil/sand. You should see the new Floratam growing in at a faster rate than the disease can progress. You MIGHT still need corn meal to get rid of it, but tall Floratam in full sun can outrun a disease. Deeper rooted Floratam needs much less water and even less fertilizer. I have grown it up to 32 inches high in the Texas heat and drought, and it never needed either irrigation or fertilizer over a 2 year period. I'm not suggesting you do that, but the grass loves being tall. Here are some other tips to keep disease out of your lawn. Never put anything on the grass and leave it overnight. No toys, no yard clippings, no trash, no yard tools, nuthin that would cut off the airflow overnight. Disease will form in the morning dew if the dew cannot evaporate easily. Also be sure your soil drains well both downward and outward so it never puddles anywhere. You can improve downward percolation by spraying the entire yard with any clear shampoo at a rate of 3 ounces per 1,000 square feet and follow that up with 1/2 to 1 inch of irrigation or rain. And one last question: what is your watering regimen? How often and for how long do you water when it is not raining?