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  • How do you treat powdery mildew on plants?

    Created by Sumi on


    I need some help figuring out what treatment to buy to rid my New Zealand Flax plants of a powdery white substance growing at the base of the leaves. I tried Garden Safe Fungicide 3 but it did not appear to do anything after 2 weeks’ application. I see there are many different products offered on your site but I’d like to get some expert advice before choosing one. I can email photos.

    Thank you,
    San Francisco, CA

  • Author
  • #290576

    Eric Vinje

    Hi Sumi –

    Common on many plants, powdery mildew is a fungal disease found throughout the United States. Infected leaves become covered with a white to gray powdery growth, usually on the upper surface; unopened flower buds may be white with mildew and may never open.

    Here’s how to treat powdery mildew disease on plants using time-tested, organic and natural techniques.

    1. Prune or stake plants to improve air circulation. Make sure to disinfect your pruning tools (one part bleach to 4 parts water) after each cut.

    2. Remove diseased foliage from the plant and clean up fallen debris on the ground.

    3. Add a good amount of organic compost or mulch under plants. Mulches will prevent the fungal spores from splashing back up onto flowers and leaves.

    4. Water in the morning, so plants have a chance to dry during the day. Drip irrigation and soaker hoses will help keep the foliage dry.

    5. Apply sulfur or copper-based fungicides to prevent infection of susceptible plants. For best results, apply early or at first sign of disease. Spray all plant parts thoroughly and repeat at 7-10 day intervals up to the day of harvest.

    Hope it helps!

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