check with you local extension office... could be Brown patch or some sort of fungus... this is what I had

I agree, most likely a fungus. Your watering schedule is most likely what's causing the problem. Deep and infrequent watering is what you want. Water a full inch all at once, one time per week if the temps are in the 90's. By watering every day the grass is staying wet for too long and causing a fungus problem. Get some close up photos of the affected area preferably when it is cloudy or late in the evening and post them. There's a good chance someone on here can tell you the type of fungus you have.

Even though you're watering program is crazy, I disagree about the fungus, at least not unless I see something else.

Your watering program could not be any worse. It would be helpful to know where you live, but your watering program has developed a grass with practically nonexistent roots and possibly hydrophobic soil.

I am one of those neighbors who never fertilizes and never waters. I mean NEVER. Here is a picture I took today.

{{gwi:102789}}

I took the picture because it shows the contrast. The grassy area under the trees used to look like the foreground. We came out of a severe drought in 2012 and suddenly all that grass was there. I had not watered it...until I saw it was there. Since then I have watered about 5 times in there. All I can think of is there was some straggler St Augustine from years ago before I moved in. We must have had some perfectly timed rain, because that's 2,000 square feet of lawn I didn't have before the drought. I might add that I live on the more humid edge of the Texas desert. It gets very hot and dry when you drive west, but we get temps in the 100s every summer. My point is that you're watering waaaaaaaaaay too frequently to have healthy lawn. Many times people write back here to say that all they changed was their watering and that cured their problems.

Here's what I see with your situation. You have short little roots. Why? Because they are still saturated from yesterday. They do not even need to enter the soil although they will have some presence there. So at the slightest provocation the roots can dry out leaving the grass looking like that. You respond by raking out the old grass (fescue I presume), adding more topsoil, and reseeding. Adding more topsoil raises the soil level above the surrounding soil causing a mounding effect. That mound requires slightly more moisture because you get a slight bit of runoff...because it is a mound (opposite of a hole). Third, you have the confluence of two slabs of steaming hot concrete right there at the corner of the lawn. I am betting that that area gets full sun during the day to heat up the concrete. That hot concrete remains warm all night heating up the soil and increasing soil evaporation. I'm also guessing that your sprinkler only barely touches that corner of the lawn. If that is true then this is probably the only good thing you have going on. But I think you have the "perfect storm" of events: Short roots, mounded soil, and hot concrete.

The solution for that would be to wean your lawn off the daily watering and be certain that corner gets as much water as the rest. You'll end up watering the concrete along with the grass. Ideally this time of year, if you have regular daytime temps in the 90s, you should be watering once per week. If you haven't yet reached the 90s, then water once every 2 weeks. At this point you're shouting back at your computer to call me crazy. But remember how much I water?? What you need to do is deepen the roots on your grass. By withholding water bit by bit, and watering deeply when you do water, the grass roots will grow deeper and deeper.

Put some cat food or tuna cans in the yard and time how long it takes to fill them from your sprinkler. That is your target time for watering. Every time you water that is how long you should do it. Then you can adjust from there for factors like shade, cloud cover, temperature, wind, humidity, soil type, mowing height, etc. I have obviously backed way off of weekly watering even with temps in the 90s. There are other circumstances in my yard, but you won't likely benefit from what I'm doing, so there you go.

First, I would like to say thank you to all of you for responding. That helped a lot!

I live in a town called Lewiston in Idaho. It's at 700 SL on the Washington border and gets in the low 100s in July/Aug.

Now that I read your posts, I do not think it is fungus. I think dchall and ForsheeMS are correct that it is a issue of my over frequent watering. I also think you are right I've mounded up the area and yes my sprinkler barely touches that corner.

I will try the tuna can method, that makes perfect sense.

What I don't understand is your statement about: "That hot concrete remains warm all night heating up the soil and increasing soil evaporation. I'm also guessing that your sprinkler only barely touches that corner of the lawn. If that is true then this is probably the only good thing you have going on."

What would be good about my sprinkler not touching that corner?

Thanks again for all the info guys!

Sort of depends. If you are over watering every time, then the parts of the lawn getting the least water might be expected to do better. When you combine those areas with hot concrete, then maybe there is no benefit at all.

Just figure out the watering and you should see some recovery at the corner.