Dave,

You will have to treat it with a fungicide. I have used sprays in the past.
I used a preventative treatment last year and did not have any problems. The
stuff I got contained a fungicide called Bayleton. I did a quick check and
found that Bayer Advanced now carries a lawn fundicide that not only cures
many fungi (included red thread), but also acts as systemic preventative.
The chemical is absorbed by the grass plants and helps the grass become more
resistant to future infections.

Good luck.

Andrew in KC