I'm a little unclear. At this point, how often is it getting watered? From week 3 to now, week 4, how have you been watering?

If you stick your finger in the soil, is it dry, mostly dry, slightly damp, damp, moist, wet, or squishy? Is that true in the green and brown areas, or does it vary?

Do you have a dog or two?

No dogs & we have stayed off the lawn.

We were watering regularly for shorter periods up through week 3. At the end of week 3 we changed & watered once/day for longer periods. I believe the soil was damp. Then we cut it and we've continued with the longer watering once/day in a.m. I just checked the brown spots & the soil is slightly damp. The color is the true in the brown & green areas.

The temp here has been high 80's for the last week, hotter than the weeks prior.

Slightly damp is about right and perhaps a bit too wet at the one month mark--you definitely don't want grass to be soaking wet at this point! Damp from 1" down, sure.

If that's what you're maintaining, it's definitely not burning out or browning out, and you didn't remove overmuch grass when you mowed (you can be fairly mean with the mowing as long as the grass isn't stressed or dry).

So I'm leaning in the direction of Something Wrong, but we don't have the correct photos to determine that, if we can. Could we get closeups of the grasses in the brown areas, from just a few inches away, under shadowed or (better) overcast conditions? We're looking to see webbing, lesions, discolorations, or other odd looking things like bugs in there.

I just did a soil test, the surface of the soil is dry. Here are 2 photos taken in two different areas, at dusk. The brown areas feel course, almost hay-like. The green grass is very green.

I appreciate the time you've taken to possibly help my situation.

I feel like Sherlock Holmes here. :-) The edges are very demarcated, and with what you're reporting, the surface may be dry, but with the watering you're doing, the under-soil is damp and, at four weeks, the sod is fully rooted.

And that sharp edge screams "disease," probably fungus. As to which one, I can't tell, although I have two highly-probable candidates in mind. Both of which will be set off by a lot of watering (inevitable with getting new sod established).

DiseaseEx by Scott's or, really, any other anti-fungal you find at the big box store or garden/landscape store that advertises it's effective against dollar spot and brown patch will be effective here, I'm thinking. I don't like doing it on sod this young but, in this instance, we don't have much choice.

Hit the whole thing. The disease is everywhere, it just hasn't struck everywhere. Yet.

Even in the SF Bay area, I don't recommend feeding in late June, plus it's simply going to encourage the disease. Hold off until around Labor Day and feed at that point with any good lawn food at the bag rate. Personally, I'd recommend Milorganite or any other organic, but that's just me. I'm perfectly comfortable with you choosing a synthetic fertilizer if you prefer.

Thank you!! I'll head out tomorrow to buy some DiseaseEx tomorrow!!! I would hate to wake up & have my whole lawn look like hay.

I read somewhere to push a screwdriver into the lawn 6 inches to see what the soil feels like. I did that at dusk too & when I put my finger in the hole, the soil felt damp, with the surface feel of the soil dry.

Last question: Do J stop watering it if your investigation leads you to believe it's fungus possible caused by over-watering?

You're in a very strange state here, kind of like, totally quantum, dude.

The grass is a bit young to stop watering, although I think I'd step back to every other day or every third day if you can get away with it. You might not be able to, and new sod is going to be touchy through the entire first summer, even in the SF area (particularly if you're in the warmer, sunnier part of that area, since it's pretty big).

Fungal infections stop if you stop watering, or at least generally slow down (there are exceptions, this is not one of them). But see above.

So I'd say slow down if you can, but realize the grass may not be happy about that and demand you step it back up. If the grass wants you to, do it--and use another fungicide if you have to in about a month. Just make sure the active ingredient is different because we don't want that infection becoming immune to what you're using.

This looks like your standard dry spots in new sod. Sod needs to be overwatered the first month or two because the small starter roots can get dry. I would suggest even more watering and putting down some sulfur-coated slow-release fertilizer (16-16-16). This is a basic and non-aggressive fertilizer you can get from your local hardware store and should help in addition to watering.