In article DQYRa.94052$H17.28625@sccrnsc02, James Curts
wrote:

I have one rose. Not special rose, just a small thorny thing, but an old
buddy. Every Spring it suffers from white powdery mildew and I try various
things on it which may or may not works well. This Spring I was gone a lot
and it suffered to the point it did not provide the first set of flowers. I
finally got time with it and trimmed back severely and treated with some off
the shelf stuff which seemed to work.

What do I use early on before serious infestation occurs to help this rose?

An expensive but very effective maybe organic method is called Erase.
It is made from jojoba oil and will have a dramatic and immediate
effect of PM. Unfortunately, it doesn't last long. If you want to use
an organic approach, I recommend it highly. Sorry it's so expensive,
but a quart will last a long time.