Milk! It Does a Rose Bush Good!

We have powdery mildew. It's the worst on the Phoenix rose Rob transplanted in front of the fence.

I found this milk cure online. It worked great, but I didn't do a second application soon enough, so the mildew's back in full force on Phoenix.

The other roses are pretty much cured from the first treatment, but I'm going to use milk as a preventative...