Welcome to lawn care...and stop watering!! You are killing your lawn with kindness. I'll explain. Look carefully at this picture. See how the spot forms an oval right in the middle of the drainage swale? What you have is standing water right there that has contributed to a fungal disease. I'm going to make the wild assertion that all your dead grass is due to a fungal disease simply because you are watering wrong. St Augustine grass, especially in Houston and especially this time of year, only needs to be watered once every 10 days or so. You are watering more like you were establishing a new lawn. Now you need to back off. I would wean it by skipping days and increasing the time. To start with you should water about an inch every time you water. Measure how long it takes to fill a tuna can using your sprinkler system. Then water for that length of time when you water. Watch the grass for signs of wilting to get the timing for your watering. Sometimes you can go 14 days in the spring and fall. In the winter go to a monthly schedule even if the grass is dormant. When the summer heat cranks back up, you can go to every 7 days and maybe to a 5-day schedule if 7 isn't working. The big point is that you are watering shallow and often. You should be watering deep and infrequently. Frequent watering is also the reason for your weeds. Grass and weed seeds need frequent watering in order to sprout. By backing off on the watering you will cut off the supply of water at the very surface of the soil and virtually stop the new weeds. The reason your attempts to kill the weeds has not worked is you are using the wrong product. Weed n Feed comes up in the forums all the time. It just doesn't do what you expect it to do. The reason seems to do with timing of the product. Weeds die best when they are well fertilized. But by the time the fertilizer part of the WnF product kicks in, the herbicide is long gone. You will have much better results using a plain fertilizer at the recommended rate and then, spot spray individual weeds with something like Weed-B-Gone two weeks after the fertilizer. You will also save a lot of money and frustration. If you want to try that again but you're afraid of killing the grass with too much fertilizer, you can use organic fertilizer instead. The two types of fertilizer have absolutely no cross interactions that would cause you to worry. But in the case of organic, it takes 3 full weeks to see results, so wait 3 weeks instead of 2 before you use the WbG. The last thing with St Augustine is to keep it mowed at the mower's highest setting. There is never any reason to lower the mowing height of St Aug. One more last thing, whatever that weed is should die out from Weed-b-Gone. Be sure to use the Weed-b-Gone in the black bottle with the purple label. That is the only one safe for St Augustine. But do not spray and breath the spray or get it on your or pets. Keep the kids and pets away until it has dried. The less of that you can get away with using the better. Your lawn looks very good, by the way...except for the minor amount of dead stuff. We see some pretty crappy lawns in the forums. Hopefully yours will never become one of those.

You picked a doozy of a topic to reference. I don't think I've ever seen so many people piggybacking onto one thread. The spots you see on your grass are the same as those I posted in that other topic. The corn meal should help. Give it 3 full weeks. This is not a shade issue or a watering issue. St Aug will be thinner in the shade but it should be healthy looking with zero spots or yellow blades. Here's a picture of my lawn in San Antonio growing in deeper shade than you had. The point of this picture is 1) no spots, and 2) lots of shade. I took this picture to illustrate chlorosis in St Augustine caused by too much rain. The yellow blades in the center are from the rain. The point you cannot see is that this area looked horrible a month earlier from disease. You could see the soil, leaves, stolons, and spots on the few living blades of grass. Note that you can still see through the turf a little to the stolons underneath. If this was in full sun it would be so packed in the blades would be growing straight up. I'll get a picture of my new lawn in Bandera looking straight down. It's very hard to push a mower through that stuff. Okay I have to comment on the TAMU pamphlet on growing St Augustine. Generally when I see something from TAMU I read it and do the opposite. Truth! Here's my experience this year. I live in Bandera now, so think Texas Hill Country. Our temps ran in the mid to high 90s this year. We got our first rain on Memorial Day and it nearly washed my belongings out of the garage. It was 11 inches in 3 days with most coming the first night. That's too much rain so I was expecting to get some disease. I did but only about 1 square foot was affected. But since Memorial Day I have watering the actual grass one time. Fortunately we got some rain relief last week, so from June 1 to Aug 19 I did not water. Had I followed TAMU I would have watered it every 5 days. Had I followed my own advice (below) I would have watered it every 7 days. What the TAMU people did was over simplify watering, but then they went into too much detail on how to achieve the simple watering. Watering is slightly harder than they suggest but setting it up is easier than they suggest. Here's my take on watering after reading and moderating lawn forums for 10 years. 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. I guess I should add that if it rains 11 inches, reset your calendar back by a month at least. Mowing height. If you read the topic you referenced you saw pix of my dog in the tall grass. (We found her and she's up at the new house in Bandera). From those pictures you can see that tall St Aug is pretty healthy. I seriously did not water, mow, fertilize, or weed that lawn from October 2011 through Feb of 2015. All it got was rainfall. 2011 and 2013 were drought years, and it thrived. Point is keep your st Aug as tall as you can stand it. Set the mower to the highest setting and weld it in place. Contrary to what TAMU says, mowing it low does not make a better turf. Fertilizing. If I was on a rigorous fertilizer schedule I would use organics 5x per year following the federal holiday schedule (Washington's birthday, Memorial Day, 4th of July, Labor Day, and Thanksgiving). If I was on a casual schedule I would fertilize on Memorial Day, Labor Day, and Thanksgiving. If you decide not to use organic fertilizer, I would still strongly suggest you use it at least once a year in addition to, or in lieu of, one of your fertilizer apps. The general experience of the universe of lawn care websites is that lawns that get no organics for 10 years or so will develop issues where the chemical fertilizer seems to not be effective. One dose of organics will reset the soil biology and the chemical fertilizers will work again. I think you can avoid that issue by preempting it. Organic fertilizer is much less expensive per 1,000 square feet than compost. The fertilizer is also much easier to apply than compost.

Okay then good news about the top dressing. It could be so old that it was never graded properly the first time. Or it could be optical illusions. My inlaws in El Monte had a perfectly flat lawn where the soil met the concrete at the driveway and sidewalk with no bulges, so in that respect it was perfect. They didn't water, so it was a mess, but... Yes, dig for grubs just for your own edification. You might find as much as a few per square feet. That's fine up to a dozen per square feet. If you find it squishy with hundreds of grubs, then you should have treated it in July. Treating now is like closing the door after the horses are out. They have stopped feeding for this year. Hot? Okay here's the watering schedule broken down by temperatures. 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. If once every 5 days works in Phoenix at 115 degrees, then 2x per week would never be right for the San Gabriel Valley. It is likely, too, that 1/2 hour is not enough to get an inch. Here's another tip: spray the yard with any clear shampoo at a rate of 3 ounces per 1,000 square feet followed by 1/2 into to 1 inch of irrigation or rain. That will help the soil absorb the water much deeper. j4 is a non-believer in corn meal. I don't know if he's tried it, but it has worked for me every year for the past 14. I have never let my lawn get as bad as your mother's is. It does look dead. I have recovered a dead lawn, but it was from the outside in and required serious patience. Mine was in the Texas (almost) desert and caused by a broken sprinkler system before I moved in. St Aug only spreads when temps are in the 70s, so fixing it in the heat took a little longer than I had hoped. I fixed it with deep and infrequent watering. You might be surprised to see new grass popping up in the middle of the dead. Or not. Just because everyone is mowing short in the area, that won't make mowing short the right thing to do. St Aug will absolutely thrive at 32 inches tall. Here's a picture of my dog walking through my semidesert St Aug. You can see her tail and ears. That grass was never fertilized (or mowed) in the 2.5 years I lived there. When the grass grows up tall it grows deeper roots which can get moisture and nutrients from much deeper in the soil. These roots were in uncharted territory picking up nutrients from way deep down. As it turns out you don't have to water nearly as frequently when the grass is up tall like that. I had one spot that grew up to 32 inches quickly. I never watered that area in 30 months through a full year of drought and then some rains. This hyperinfrequent watering was the point of growing the grass that tall.

More important than the fuzz are the brown lesions on the grass blades in pictures 2 and 3. Mushrooms mean you have far too much water. At this point it is too late to adjust the water and get rid of the disease. If you have the Floratam variety of St Aug, it will fight back but will take a long time to fully recover. I have had success with this type of fungus by using ordinary corn meal applied at a rate of 20 pounds per 1,000 square feet. You can buy corn meal at feed stores in 50 pound sacks for under $10. Call first to be sure they have it. Corn meal works biologically rather than chemically. Corn is decomposed by various fungi. One of the fungi that comes in with the decomposition is a predatory fungus. It feeds on other fungi including the one that causes the disease you are seeing. Apply the corn meal now and in 3 weeks you should see the browning stop and no more lesions. If you cannot find corn meal at a feed store then buy corn flour at a grocery store catering to Hispanic shoppers. Cost should be $7 for a 25-pound bag. Be sure you don't get the stuff with baking powder in it. That's like the Bisquick for making tortillas. You want the plain corn flour, masa de maiz. Maseca is a popular brand. You should back way off on watering frequency. I would give it a week to dry out watching for wilting. In fact I might go until it starts to wilt somewhere just to make sure it is dry enough to water. Then start with deep watering. Start with 1/2 inch of water, twice a week. If it rains, don't water for a week or possibly longer depending on how many inches of rain you got. When this is mature it should easily go a week in the summer heat without watering.