Good idea on the fungicide. You can cut it out and plug or, depending on the size of the patch, let the grass fill in naturally.

With those temps, you might actually have areas that did not get enough water and became injured in the hot sun.

If I were you, I'd water well, once a day, everyday, in the early morning (6 AM).

You can also water during the hot sun times to cool off the grass, but most of that water will evaporate.

Hopefully it's not St Augustine Decline.

Hmmmm...

I was going to say you weren't watering enough. Three intervals of three minutes isn't very much. And in 100 degree temps, I'd say what little bit of water that's being applied is evaporating very quickly.

But after after backing off you're finding the worst areas are still "WET" and in poor-draining, heavily-shaded spots, you've probably overwatered those areas.

I'd continue to keep watering as you currently are. Good job waiting until you see signs of wilting. But I'd also only hand-water those areas that are showing signs of wilting. Hold off on the poor-draining, well-shaded areas until they start to wilt.

The good news is that if your patches of brown aren't too large, the St. A will fill it in rather quickly once you get your watering dialed in. (I had a 10' diameter bare patch where the kids' pool was last year that filled in in about 8 weeks this spring.)

I just did some research on SAD, and that's what I am now. I am 85% sure that this lawn is infected with St Augustine Decline. The infected areas show yellow mottling on the blades that is very similar to some high definition photos I found of leaves infected by the virus.

I was under the impression that SAD usually affected older lawns? This lawn is not even 4 months old, and I don't use a landscaping company to maintain it. In addition, I bought a brand new lawn mower that has never touched any other grass but this lawn. There was also no lawn here before I planted this sod. Everyone, please correct me if I am wrong, but doesn't this mean that the sod came to me infected with the virus?

Possible, but I thought SAD progressed much more slowly. It really sounds like overwatering to me. When I laid my St.A back in 2007 we had torrential downpours for the following month. I had some spots die off due to too much water, and as it died, it looked similar to SAD.

Can you post some pics?

Palmetto is quite susceptible to SADV but the question is how it got in the first place. That's what happened to mine but I never could figure out how that happened. I use my own mower for that lawn only. Maybe a bird that infected it? Who knows? Fortunately Sapphire and Floratam filled in rapidly for me (by accident when I didn't know it was happening).

Alrighty then. Figured out a way to post a photo.

There is an additional piece of information that I thought of yesterday, and that is that this lawn probably had over-spray from tree insecticide (systemic and contact for borers)in june. It already had some thinning spots then, but the thinning has progressed substantially with many additional stressors like increased heat and shade. Was thinking that the spray could have killed off many of the helpful turf critters. Opinions on that?

My current approach, on which I would love feedback, is to dethatch brown spots, use a sod plugger to remove 3' plugs from healthy spots and transplant into dethatched areas followed by thin compost for the whole lawn. Thoughts?

Has anyone tried cornmeal and/or potassium bicarbonate for fungal disease symptoms? Any luck?

Here is a link that might be useful: {{gwi:112216}}

I'm not a disease expert - fortunately. But this looks just like the areas I had die off after my new sod was overwatered my mother nature.

I would not bother plugging That small area will fill in in a month or less. Seriously - I had a 10' diameter dead patch that filled in in two months. I would just rake out all of the dead material so the existing grass has bare soil to spread into, and make sure you put down your next fertilizing right on schedule.