Sill looks like drought stress and gone dormant.

Have you tried to push a screwdriver into the ground in that area to see if the ground is hard or soft?

I agree but Chinch bugs are not normally a problem in Bermuda grass as that is the plague of Saint Augustine and Centiwede grass. Now if you are in Florida or a neighborhood surrounded by Saint Augustine grass, then you might very well have a Chinch bug infestation.

Pretty to check and the best method is to take a coffee can, cut the top and bottom out and sink it into the ground a couple of inches. Then fill with water and maintain the water level for 5 minutes with a couple of drops of an insecticide in it like pyrethrin. If you have Chinch bugs you will see them clearly floating on top of the water in just a few short minutes.

But I am going to stick to my guns here and say number 1 suspect is drought stress from improper watering.

It is a process of elimination to find the cause. As mentioned the first elimination test is for watering problem and by all means the screw driver test is fast and accurate. If that checks OK, then look for insect problem.

Thursday after work I put my sprinkler system on test to see how my coverage was in that area. I walked out and stood right in the brown areas and got soaked, so I would say my coverage is pretty good.

So, I think I have it down to two possible causes. The area where it starts turning brown near the top of the pic all the way to the tree is a gradual downward slope all the way to the base of the tree, so maybe the water isnt soaking in like on the flat parts of the lawn.

My second guess is that I have too much tatch for the grass to grow in full. I picked around that entire area and it's much thinner with a good amount of mulched grass covering the soil. I am in the process of trying to find a dethatcher to rent, but it looks like I might have to go the town over to get one.

Hard to tell from the picture, but that looks like typical end of season scalping from bermuda being cut too high.

I should clarify scalping since it can mean different things in different context.

For this, I'm not talking scalping down to the dirt. I'm talking removal of the green leaves and leaving brown leggy stems behind. I bet if you look at your grass, only the top 1/4" or so is green and the remaining height is brown.

That is not accurate. In fact you are maintaining your Bermuda extremely high which greatly increases your chances of scalping, especially this late in the season. Get a little late on cutting just a day or two, and you will scalp the grass leaving it brown or scalped. It is very common.

My grass has been cut at the same height all summer and my side yard and back yard which is about 5000 sq feet all look great. This one area just cropped up at the end of August.

If I am keeping it too long shouldnt I just wait until next spring to start cutting it shorter? It seems a little late in the season to start channing anything.

Thanks for your help.

The only way to tell how much water you are putting out is to measure it. We normally use cat food or tuna cans. Put several out and time how long it takes to fill them. My system takes 8 hours but my neighbor's takes 20 minutes. If you are putting 2 inches of water per week, that is probably 3x more than you need right now. Normally we move from 1 inch per month in the cool months to 1 inch per week in the hottest heat of summer. But we always apply all at one time. Then we watch the grass to see if we can delay the next watering. This time of year you should be delaying and delaying more and more as the temps cool off. In the late spring you would be moving it up to increase the frequency.