Recipe for Fighting Pansy Downy Mildew

pansy downy mildewThis year’s extended winter weather has left many gardeners craving any spot of floral color out in the yard this month. Coaxing spring bulbs and pansies to hang on until temperatures are safe for the summer annuals is probably as good as it will get. 

But what is that grayish white film coating the pansies? Peronospora violae, or pansy downy mildew, is a fungus-like organism specific to pansies. Cooler temperatures, humidity and rainfall cause it and stems and lower leaves are particularly vulnerable. Downy mildews also attack roses, grapes and impatiens.

Peronospora violae penetrates the tissue of a host plant over time without killing it. Eventually, mildew spores wind up in the air or the soil and can start new infections. However, the pathogen cannot live without a living organism as a host.

If left untreated, mildew can affect photosynthesis, causing leaves to yellow and flowers to diminish. So what can be done to preserve those spring pots of pansies a bit longer? Read on.

Best Ways to Avoid Downy Mildew

  • Keep plants as dry as possible. For example, plant facing the morning sun to dry dew. Avoid top watering or splashing water on the leaves.
  • Space plants to allow adequate air flow. Plant in open, uncrowded areas if possible.
  • Remove discolored leaves as soon as possible. Don’t be afraid to pinch back leggy growth. But don’t remove all the leaves and don’t discard diseased leaves in the compost bin.
  • Rake debris and use coarse mulch under plants in the spring. Disease can overwinter in old mulch, fallen leaves, and in the soil.
  • For containers, sterilize pots and change out the soil seasonally, and don’t plant pansies in the same spot in consecutive years.

pansy downy mildew spray recipe

While pansy downy mildew is unsightly, it may not warrant a chemical control, such as a systemic fungicide. Maintaining the gardening practices mentioned in the list above should keep it under control, or at least prevent further infection.

Non-Toxic Downy Mildew Spray Recipe

Many gardeners subscribe to using an organic home remedy to treat this problem, in lieu of a fungicide. The common ingredient bicarbonate of soda, or baking soda, is the main ingredient of the concoction. This works best in the early stages of the disease and may not be a full-blown cure. It may also be used as a preventative. Unlike a systemic fungicide, rain will wash it off.

Using a baking soda plant spray for mildew has often been studied. It is thought that it works by making conditions more alkaline. It does not kill fungus; it prevents it from growing.

Comparisons of various mixtures seem to indicate that the addition of soap and cooking or horticultural oil to baking soda and water work best. A test patch is recommended, as it is possible to hurt plants due to mixture proportions. Similar mixtures have been used for powdery mildew and black spot.

Downy Mildew Spray:

  • 1 gallon of water
  • 1 tablespoons baking soda
  • 1 tablespoon vegetable oil
  • 2 drops dish soap

Spray plants until they drip. Also wet the soil. Retreat in one to two weeks.

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