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  • Rhododendron Problem

    Created by Mickie G on

    Hello, I have a Rhododendron plant that appears to have a disease growing on its leaves. They are brown spots in color, with a predominant number of spots growing in the shade spots of the plant. My question, is what is it and how do I cure the plant of this problem?

    Thank you

  • Author
  • #239136

    Eric Vinje

    Hi Mickie –

    Several plant diseases are known to attack rhododendron plants throughout the year. Leaf Spot is a common fungal problem that shows up as brown or black water-soaked spots on the foliage, sometimes with a yellow halo, usually uniform in size. The spots enlarge and will run together under wet conditions.

    Prevention & Treatment:

    • Choose resistant varieties whenever possible.
    • Prompt removal and destruction of infected plant parts helps breaks the life cycle of the disease in individual shrubs.
    • It is important to rake up and remove any fallen leaves or debris from under plants.
    • Prune occasionally to improve air circulation. Also, water from below to keep from wetting blossoms and foliage.
    • Ready to use sulfur sprays or copper-based fungicides should be applied weekly to infected plants starting early in the year and continuing throughout the growing season. If at all possible, time applications so that 12 hours of dry weather follows application.
    • Safely treat most fungal and bacterial diseases with SERENADE Garden. This broad spectrum bio-fungicide uses a patented strain of Bacillus subtilis that is registered for organic use. Best of all, SERENADE is completely non-toxic to honey bees and beneficial insects.

    Good luck!

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