pelirojaroja

I'm in a sad state with my tuberous begonia plants. I have 10 or so (2 very
large ones) in containers on the shady front porch (Cleveland OH Zone 6). I
bought them all from local nurseries in spring, and all have been doing
wonderfully until about 3-4 weeks ago. First one plant, then all the
others, have gradually developed first brown (prematurely brown) flowers and
then white filigreed spots on leaves. The flowers aren't just spent -- they
are attached quite firmly but are dead-brown and papery.

Are the plants goners? My research on the web shows a powdery mildew fungus
the likely cause, although they are on a protected porch, and I never water
the leaves and am careful not to over-water.

On advice from the local nursery, I've sprayed all plants with a
Daconil-type fungicide, but the result was awful. The plants now look even
worse -- white residue coating all the leaves, and the fungicide has killed
all the remaining flowers it touched.

Do I keep up with the weekly application of fungicide and put up with the
unsightly residue/no flowers? What's the point of that, I wonder? However,
I have so much $$ invested in these beautiful plants that I hate to give
them up to the fungus. Any advice appreciated!

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-- pelirojaroja
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"There is a garden in every childhood,
an enchanted place where colors are brighter,
the air softer, and the morning more fragrant
than ever again."

-- Elizabeth Lawrence