Powdery Mildew

The Problem

  • Powdery Mildew (and its associated Downy Mildew) if a fungal disease which probably leads to more loss of harvestable produce in our garden than any other cause.  
  • Powdery mildew spreads rapidly from a single infested plant, so all gardeners should be vigilant in monitoring for it — not only to protect your own crops, but those of all the other gardeners as well.


  • Appearance: Powdery mildews are easily identified by spots or patches of white to grayish, talcum-powder-like growth. They usually show up first on the underside of leaves, so it’s best to check the underside of susceptible plants often.
  • Signs of damage: A severe infestation will leech nutrients from the plant, causing the leaves to wither and yellow. If left untreated, leaves dry up.


  • Sanitation is the absolutely number one best way to control powdery mildew not only in your own garden plot, but to keep it from spreading to your neighbors.
  • Infected plants and leaves have to be removed and disposed of well away from the garden — and not in compost as that will help it overwinter and reestablish itself early the next season.
    • When removing infested plants and leaves, keep them as still as possible to avoid shaking loose and spreading the powder-like mildew spores to healthy plants.


  • A home-made spray is the best control
  • Sprays won’t get rid of mildew infestations that are already established, but can help prevent their spread.
  • Some of the most common sprays are:
    • A mixture of 1 tablespoon of baking soda, 1/2 teaspoon of liquid non- detergent soap, and 1 gallon of water.
    • A mixture with a 40/60 ratio of whole milk to water.
      • This spray works best when applied in bright sunlight since it depends on the protein in milk fat creating an antiseptic effect when exposed to sunlight.


Do Not Compost Diseased Plant Material!


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