White Powdery Mildew

[Tom Speight]

I have been struggling for the last year with a white powdery fungus
that gets on my African Violets and ferns  and selected other
houseplants within our new home. I place the infected plants outside for
a week or so and the fungus disappears but it reappears within days of
returning them inside. It also leaves a sticky substance on the carpets
and nearby furniture so I really want to get rid of this. Tried Orthonex
[sp?] and several other fungal sprays, but they don't seem to work. Is
there any treatment for this?