So first off, I know I should have fixed this problem earlier and I've let it get too far where I might not have any great options now. We had our first kid last year and it's thrown off my yard game.

This corner of my yard though has been getting worse and worse since probably early to mid July. I thought at first it was just lack of water since it started to get pretty dry around here, so I started watering it fairly regularly (you can see the rest of the yard looks okay.)

I also actually treated for chinch bugs and put down a fungicide in late August because I thought that might be the problem, but it didn't seem to improve, and now another grass is invading pretty quickly (all of that green has come up in the last few weeks.)

This part of the yard gets full sunlight for most of the day (most of the rest of the yard is shaded by a big tree)

Thoughts? Suggestions?

Have you dug up to check for chinch bugs or grubs?

Late August seems like a pretty late treatment.

Yeah, I got in there with my hands pretty good to look for chinch bugs but didn't see anything. I went ahead and treated for them just in case, but it seemed to still keep spreading. Maybe I didn't look hard enough though.

I didn't look for grubs though.

Web worms. They got me last year. I sprayed yard 3x in 14 days as recommended. Apparently it worked - I'm still seeing some moths fly around this season, but nothing like last year. Last year if I walked the yard in the evening I would spook up hundreds and hundreds of moths. This year only a handful.

I haven't seen any moths though either, and I usually mow in the evening.

looks like grub worms damage

To check for grubs, try grabbing the dead turf and pulling. If it peels up pretty easily like the roots have been cut, there's a good chance it's grubs.

Also, how does the green turf look on the edges of the dead patches? Any spots on the blades, irregular damage like chunks eaten out of sides of blades, etc.?

It comes up pretty easy. Is it worth putting anything out for grubs at this point of the year or is the damage already done and over with?

Just an FYI for the future, chinch bugs will continue to affect the grass even after treated. They inject a toxin in the grass that continues to work. Grubs need to be treated earlier in the year.

The grass filling in is probably bermuda. It will fill in quicker than SA. The SA should take over the bermuda over time. The grass is already slowing down so I doubt you'll see anything recover this year.

Maybe I should put a border around the bermuda, get a reel mower, and turn that part of the yard into a putting green.

Lol idk how well native bermuda would do as a putting green, but I like the thought!

Between that and my wildly sloped front yard it would be horrible.

Thanks everyone for the help/diagnosis. Hopefully I'm more on top of it this year and spot problems earlier.