What disease is this

That looks like pythium blight. Try to compare it to images from google. Time is of the essence. It kills turf and spreads fast.

http://turfdiseaseid.ncsu.edu/diseasedetail.aspx?disease=PYTAP

Azoxy (Scotts DiseaseEX)will be fairly good. You could get it tonight at Lowes, Walmart, Meijer. The excellent post from Suburdan Jungle life listed above has other options. Within it there is a link by Turfguy93 that list each fungus and what is effective for each one.

But, first try to make sure that it is PB. The images don't look like dollar spot to me (trust me this year I had a lot of exposure to dollar spot).