When it come's to turfgrass disease's, they are just to numerous and complicated to guess at. Trust me on this, i've been growing grass for more than 25 year's and while i can be pretty accurate on a lot of disease's i know that the lab can do a better job than i can and i will defer to them almost every time.
I'm glad your sending off a sample. How long will it take to get a answer? How much did it cost? See what i mean about air movement? Most people don't realize how important that is.