That sounds like what they generically call "powdery mildew". I
haven't had a problem with it on my Phlox, but it does affect my Peony
and it is famous on Zinnia.

My understanding is that although it looks bad, it doesn't usually
hurt the plant. I have read that good ways to reduce instances of this
are full sun, good air circulation and clearing out dead leaves and
other Autumn debris. I also think that there are potions that are
supposed to deal with it too.

JD

On Sun, 12 Aug 2007 11:41:32 +0100, "Mary Fisher"
wrote:


John - Pa. wrote in message
.. .
Flocks of Phlox, in fact.

My phlox leaves are always covered with a white powder - don't know if it's
a fungus or what but it's unsightly. The flowers are unaffected.

I'd pull them up but they were given to me by a neighbour who died last year
and it seems ungrateful. I just wish the hens would eat them but they don't!

Mary