I am in Houston and trying to maintain my front yard of St. Augustine. This spot popped up recently and I don't know if this is from a lack of water or a bug or a fungus. The yard is on a automatics sprinkler system and I believe is getting adequate water. I have also fertilized in early spring as well as again in early June. The yard has a canopy of live oaks above it so that doesn't help promote good growth but I did have the trees thinned out last year so the grass does get some sunlight.

Does this look familiar and is there something I need to do to treat it?

That is either Bud Light or Pearl. Seen same thing in my spot , I mean yard.

Have you seen any white moths?

Google sod webworms

If you think that is what you have, buy some of this and a sprayer. I'm still using the bottle I bought 2 summers ago.

https://www.amazon.com/HOME-OUTDOOR-Bifenthrin-Control-Insecticide-Concentrate/dp/B00ESB7EPG/ref=sr_1_3?crid=2ZYI6L73KSWEX&dchild=1&keywords=bifen+xts&qid=1594606792&sprefix=bifen+xts%2Caps%2C193&sr=8-3

I do have some Biffen. I used it on my oak trees and it does great. I don't even know if I have a bug problem or if this is just as simple as this area needs more water. I'll spray it anyway and see what happens.