Monday, September 5, 2011

Powdery Mildew On Phlox

Powdery Mildew On Phlox

Powdery Mildew has long been a common fungal problem for garden Phlox (P. paniculata), as well as several other species of susceptible plants such as Bee Balm, Asters, Zinnias, Roses, Pulmonaria and Lilacs.

Although each plant species is prey to its own fungus species the cause can usually be attributed to improper watering or poor air circulation. Phlox and Zinnias are more prone to powdery mildew when their leaves stay moist for long periods (high humidity is a definite contributor). Species like Bee Balm and Pulmanaria are more susceptible when grown to dry.

To treat powdery mildew or to help prevent future outbreaks in your garden try these tips:
  • Grow your Phlox (or other powdery mildew sensitive plants) in full sun.
  • Water your plant from the base rather than over head watering. This will help the leaves to stay drier.
  • Maintain a consistent soil moisture.
  • Plant resistant varieties. 'David', 'Katherine', 'Natascha', 'Carolina' and 'Delta Snow' are a few phlox varieties that are seldom affected by powdery mildew.
  • Improve the air circulation around susceptible plants.
  • Thin your phlox by removing 1/3 to 1/2 of  the stems to the ground.
  • Spray the plant yearly with horticultural oil.

Baking soda is known to have fungicidal properties and can be useful in treating powdery mildew. Try this natural remedy below when powdery mildew appears in your garden.

1 teaspoon baking powder

1 L water

A few drops of mild liquid dish soap

1 teaspoon cooking oil

(Put the ingredients into a spray bottle and mist directly onto the plant leaves, both sides.  Re-shake the bottle once and a while to keep the soda from settling on the bottom of your bottle.)


Note: Do not spray your plants during the heat of the day, which can burn them. Evenings are also not a good choice as the leaves may not have a chance to fully dry before dark. Early morning is the best time to spray.

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