Just make sure the sod is being given adequate water to set its roots. Its cooler now---not so much heat, so the grass will grow for a time.
I'm not that familiar with St Aug grass as far as when you should cut it.....ask your neighbors---especially the ones that have a nice lawn of the same type of grass.
I think St Augustine grass grows best when allowed to grow a bit higher...3"....4" ....it will shade out the weeds.

If you must apply a herbicide (weed killer) do so with a hand sprayer to hit the weed....not the young grass....you don't want the young establishing roots to be harmed.
I wouldn't have put the fertilizer down at this time without some guidance.....does the package say you can apply it to growing sod.
Give the grass a chance to set its roots and grow some before mowing.

As far as yellowing grass, that could be nothing but some sod pieces drying out from sun after it has been hit with water.
Try sprinkling the sod 2- 3 times a day instead of trying to do it all at once. Morning....early afternoon, early evening.
This way you wont endanger the sod pieces being drowned.

Weeds: you need to identify them as either grassy weeds or broadleaf weeds. Grassy weeds look like a different kind of grass. For those you can usually just let the St Augustine grow up really tall (5-6 inches) before mowing. That means mow every other week at your mower's highest setting. For broadleaf weeds you will need to dig them out or use a spray with Atrazine. Most broadleaf weed killers will also kill St Aug, but Atrazine seems to work okay as long as the temperature is not going to be above 85 degrees for a couple days. Spectracide makes on in a black bottle with a purple label. We just got a cold front come through. Don't know where you are but you must be south of San Antonio to have gotten the daily rains. If you are not too far south, the temps might be cooling off for you, too.

Fertilizer: You are perfectly fine with the Milorganite. Any organic can be used at any time. You might start checking prices at your local feed stores for ordinary corn meal.

Brown spots: If this is a fungus (and I would need to see a picture), then apply the corn meal at a rate of 20 pounds per 1,000 square feet once now and again 3 weeks later.

This is the time of year that St Augustine really spreads and thickens. If this cold front hit you, too, look for runners spreading as much as 5 feet in the next few weeks.

Unless you specifically ordered a dwarf variety, always mow St Aug at the mower's highest setting. It uses less water, survives better in the heat, and survives dry soil better.

Establishing the lawn: As goren mentioned, the sod needs to be moist all the time for about 3 weeks. It does NOT need to be saturated. You only need to moisten the sod and the very top level of the underlying soil so the roots will grow into it. Watering too long, 3x per day, will often kill St Augustine. Just keep it alive and the roots will knit into the underlying soil in a couple weeks.

Once you get the grass established, start deep watering. Deep means 1 full inch to start. Time your sprinkler to see how long it takes to get an inch. Use cat food or tuna cans to measure. Water the grass at that depth and watch it carefully. See if it will go a full week without the grass looking wilted or the color changing to a darker green. Also watch for the grass blades folding together. Any of those signs means it needs another inch of water. Eventually, and pretty soon, you will be watering only once every week, and then 2, 3, and 4 weeks as the grass roots deepen.

Next time you put in a new yard, do not rototill it. That fluffy soil is starting to settle now but it will not finish settling for 3 years. When it does finally settle, you will have a very bumpy surface. You'll start noticing the bumpiness next spring. If you soil is too soggy to mow, do not worry. I have St Aug in George West that is anywhere from 12 inches to 32 inches high. That grass loves being tall. You can mow it when the soil dries out. Never mow St Aug when there is dew on it or the soil is too soft. Just wait for it to dry.

If you take pictures, take them on a cloudy day (like last week!). If the Sun is shining bright, the contrast is too much to see what we're looking for. Also for the yellow and brown grass, please get the camera about 3 inches away. Take a picture of the grass that is yellow and the green grass at the edge of the brown grass.

Thank you for responding. I live in Brownsville,Tx. Like I said we have had rain everyday, today is the first day without any. I took pics but I took them today. Certain areas look bad, but I don't know if that's normal. I'm afraid of losing the lawn and I just want to make sure I'm doing ok. How long does it take for the the sod to root? I have been pulling at areas and some have small white roots and other areas seem they are already in the ground. Also I have seen fire ants around and in the lawn. I treated that today with a product from Walmart, do red ants affect the sod? I have uploaded some pics, and thanks again for your help! I was told this was SA grass, can you confirm with these pics?

Picture

Close up...

Pic...

Pic...

I don't know if these pics help, I took them with my iPad.

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.

Thank you so much, I will go and buy the corn meal today and apply this afternoon. I appreciate your time and help!!!

Ok, I applied corn meal to my lawn on 09/23/13 when I got home. I was wondering what should I be looking for. Should the lawn continue to yellow, brown out? Or should it not spread? Also I wanted to know about watering, the last time I watered was on Saturday. I haven’t watered since, like I had mentioned we got a lot of water the first 3 weeks of when I laid down the sod and I don’t want to over water. At this point how frequently should I be watering, this is the 4th week since laying down the sod…… Thanks!

Watch for the blades with lesions to die. They will be replaced with new blades. Those new blades should not have the disease and should not get it.

Watch the grass very carefully. As soon as any of it looks wilted, water it immediately. Water a full inch. I know it is warming back up...we had 92 again today in George West. By stretching out the time you water, it forces the roots to grow deeper. Tough love. If the grass looks okay still on Saturday, go ahead and water an inch. Then I would look to really extend for next time. See if it will go 10 days, but be ready at any time. And I would not mow until it gets up to 5 inches. Then mow it back to 4.