> Hi, me again!
> I have a Gallica rose (Duchesse de Montebello) that I noticed today has
> some powdery mildew on the
> leaves. I'd rather treat it with something organic if possible, but will
> resort to sprays if necessary. Everything I've read says to use an
> antifungal spray or sulfur, lime-sulfur or Bordeaux mix. Does anyone
> (Victoria, help!) know of an organic concoction I can whip up?
Since your Gallica rose has finished blooming for the year, the mildew is
essentially only a cosmetic problem at this point. So you really don't
have to do anything.
Mildew can only grow during warm, dry days. You can just leave it alone
and it will go away on its own when the weather cools or it starts raining.
However, you should pick up any dropped leaves to remove as many of the
spores as you can.
If you feel you must do something, and you don't want to use a fungicide, a
horticultural oil spray (AT SUMMER RATE!!) can reduce mildew. Some
sensitive to any hort oil in warm weather, so try out an inconspicuous stem
watch for foliage burning, or the cure will be worse than the disease.
Some sources recommend adding baking soda to the hort oil, or using
baking soda alone, but we have found that baking soda will damage the
foliage that the mildew is growing on.
Personally, we don't do anything specifically for mildew on our
Nick - NJ - Zone 7a
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