About a week ago I noticed a white chalky substance clinging to the individual blades of grass around a section of my lawn...about 10-12 feet diameter. Yesterday, I noticed the grass is still covered with this "chalk" and large portions of grass have turned yellow and died. This area is a ways back from my "normal" dog walking route so I didn't really notice the progressing damage. I figure there's no reversing it now, but what is it and how do I fix the problem. If I walk on it will I spread it via my shoes. Any help is greatly appreciated.