Water heavily, and hope. Not much else you can do.

Dont worry your weed and feed contained moss killer which turns moss black when applied.Rake out as planned aerate lawn by spiking and mix grass seed with sharp sand and apply a handful every square yard.

Sorry Tug this quite a common problem in UK not sure you see much moss in Arizona ?

It might be dead moss, but I have to say it does sound more like uneven application as its in stripes. I'd water heavily, as Tug suggests, to try and wash it out more quickly.

Bonkersbon: Moss is pretty rare here. Even in overwatered shade, Our alkaline, salty water keeps it down. Algae, on the other hand.... : )

Algae on your lawn Tug ? Yuk glad mine stays in the pond ..suppose you hose it off ?

Re weed and feed I personally do not like to use a moss killer and struggle to find treatments without it included.I ve seen heavy applications of weed and feed and these have tended to scorch grass rather than blacken it.

Having used a spreader up and down , which would account for stripes surely weed and feed could not have been applied to such an extent it would blacken grass ? If heavily compacted with moss though it would account for black patches as moss turns sooty black when treated.

It's just a green stain or crust on the earth, Bonkersbon, and it only happens in overwatered shade. Changing the watering and/or applying gypsum does for it. The last time I overfertilized, the next day the damage showed up as extremely dark green, "cooked" patches, which later faded to straw color. So it wouldn't surprise me if it was the grass instead of moss that turned "black".

Probably me Tug but assuming Arizona usually hot dry and predominantly desert possibly due to images of the Grand Canyon and the odd cowboy film ..we have areas of heavily compacted clay soil that lend itself to moss invasion.

Our rainfall levels quite high which keeps us looking green we rarely get the sort of temps you would regard as normal and many years since we ve ever felt cooked.Back in the 1970s we had a few months of temps at the 90F it baked everything and we Brits were wilting .. guess that would be a normal day for you.

We get water from a whole system of dams on the Salt and Colorado rivers, so there is a lot of lush, green gardens here in the middle of the desert. The time is coming when we will regret this waste.

Thanks Tug yes sure you are right .. wonder if this guest will ever benefit from our wealth of international knowledge ? lol Probably not ..so guess they need to join and ask others .