This post describes using potassium bicarbonate to control powdery mildew, but doesn't give any more info.

So I'm looking for the following:

Efficacy? Mixing rate? Application rate? Application frequency?

And finally, are there different types of potassium bicarbonate and, if so, can they all be used for this purpose?

  • I don't use bicarb for this, its a hell of a lot easier to use cow's milk - 1 part cow's milk to 9 parts water.
    – Bamboo
    Aug 14, 2015 at 13:40

1 Answer 1


I tried this and it did not work for powdery mildew on lupins or Monarda. Your mileage may vary:

  • add one tablespoon potassium bicarbonate to a quart of water
  • consider adding a bit of vegetable oil as a "sticker"
  • pour in to a hand powered sprayer
  • agitate vigorously to get a suspension
  • spray, agitate, repeat

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