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Warm, summer days linger well into fall here on the North Coast, allowing for a longer food and flower growing season. Abundance is the nature of autumn.

The thing that begins to plague our gardens this time of year is a fungal disease called powdery mildew. Evidence is when leaves turn a powdery white. Warm, humid days combined with cooler, dewy nights encourage powdery mildew. Roses, dahlias, summer squash, cucumbers and apple trees all fall prey to this disease soon or later. Some plants are more susceptible than others.

While you cannot completely eradicate powdery mildew from the garden, you can learn to manage it. The first step is to monitor plants closely and remove any leaves that begin to show signs of white coating. Upon removing leaves, spray entire plant with an organic fungicide. There are many available, such as Safer’s sulfur spray or Serenade, which contains Bacillus subtilis. You can also make simple and effective homemade organic spray. In one gallon of water, mix in one tablespoon of baking soda and a half teaspoon of dishwashing soap. The baking soda raises the pH on the leaf surface to discourage powdery from taking hold. The soap helps the spray stick to the leaves.

Controlling powdery mildew is most effective if plants are not covered with fungus. Heavily infected plants should be burned or thrown in the trash.

Terry Kramer is the site manager for the Humboldt Botanical Garden and a trained horticulturist and journalist. She has been writing a garden column for the Times-Standard since 1982. Contact her at vlngirl@yahoo.com.

 

 

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