Where do you live? What is your watering regimen (frequency and duration)? Can you take a picture of the edge of the remaining grass from a distance of 3 inches? I need to see the blades of green grass and blades of any yellowing/browning grass up very close. You're getting plenty of light. St Aug grows very well in full shade as long as it gets light from somewhere. For example it will grow poorly under the low canopy of a magnolia tree but it will grow fine under the canopy of any tree with bottom limbs 6 feet high or more.

Literally everyone who writes in here from Florida is watering every day - literally every day. Literally everyone with no exceptions, except you. Thank you for that. I'm sort of familiar with the Maseca products. I think the instant one is the right one. Their labeling could not be more confusing - at least to me. When I see the word instant, I start thinking all the additives are in there so you just add water, but not with Maseca.

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.

I'm going to assume it is a fungal disease. Your watering is wrong enough to possibly get a root rot going. Would you mind posting a picture? The best garden pictures are taken on an overcast day to reduce the contrast between brights and shadows. For this the distance should be about 6 inches away. I have had a similar disease issue in my St Aug where it returned time after time, but mine was a surface disease and not affecting the roots. Mine did not go away until I treated it with corn meal - yes, the same stuff you eat. Apply at 20 pounds per 1,000 square feet over the entire yard. You can buy it in 50-pound bags at a feed store. Call first to see if they have it. Ask for the price. It should be well under $15 and more like $5. If the price is above $20 then it's not corn meal but corn gluten meal. That won't work. You want ordinary corn meal. Cracked corn will work, but don't use whole corn. Whole corn will turn your yard into a corn field (easily mowed down). Corn meal works biologically and not chemically. The corn decomposes with bacteria and fungi already living in the soil. One of the fungi that seems to accumulate especially well on corn is Trichoderma (try ko DER mah or trick oh DER ma). This is a predatory fungus that feeds on the disease causing fungus. Give it three full weeks to show improvement. If it seems like it is working, but you want to really hammer it home, reapply. If you have already used a chemical fungicide in the past few weeks, then corn meal won't work. Why? Because the Trichoderma has been killed off by the fungicide. In the future you should change your watering. I realize 99% of all Floridians water daily, but they are all wrong. All of them including the sprinkler guys who set everyone up. Here's more about watering. 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.