How to Get Rid of Powdery Mildew?

Comment Se Débarrasser de L'Oïdium ?

Powdery mildew is a common fungus that affects a wide variety of plants. It is easily identifiable and appears as gray or white powdery spots, usually on infected leaves, but can also be found underneath, or on stems, flowers, fruits or vegetables. The spots spread and will eventually cover most of the plant's leaves, with new growth being the most susceptible.

Powdery mildew thrives in hot, dry climates; however, it also needs relatively high humidity, such as warm days and cool nights from late spring to early summer. A lack of sunlight and poor air circulation also contribute to favorable conditions forpowdery mildew.

Although rarely fatal, if left unchecked it can ultimately cause serious damage to your plants by depriving them of water and nutrients. Most infections cause minor damage, such as yellow or wilted or distorted leaves, but plants can also become weak, bloom less and grow more slowly.


Here are some steps you can take to control powdery mildew before it sets in:

  • Thin out existing plants which can improve air circulation within the plant.
  • Maintain adequate spacing between plants and keep them far enough away from walls and fences to provide good air circulation and help reduce relative humidity.
  • Place plants according to their sunlight needs.
  • Maintain healthy plants by removing dead or diseased foliage.
  • Disinfect pruning shears or shears after using them on infected plants. (See Tool care and maintenance)
  • As new growth is more susceptible, be careful not to over-fertilize and cause a flush of new foliage.
  • Treat regularly with an organic fungicide containing sulfur as the active ingredient. This can be used as a preventative as well as a treatment for existing powdery mildew.
  • When purchasing plants, choose varieties with increased resistance to powdery mildew.


    Although most products on the market are more focused on preventing powdery mildew, there are many home remedies for treating an existing infection.
    Spray mixtures will only kill what they come into contact with, so be sure to cover all affected areas thoroughly. It may take several applications for a complete treatment.
    Apply once a week for three to four weeks, then wait to see the results. Reapply if necessary.

    • Baking soda solution:
      Mix 1 tablespoon of baking soda and ½ teaspoon of liquid soap such as Castile soap (non-detergent) in 4 quarts of water.
      Spray liberally, covering leaf surfaces above and below, as well as affected areas.
      This method may work best as a preventative measure, although it also has some effect on existing powdery mildew.
    • Bicarbonate of potassium:
      Mix 1 tablespoon of potassium bicarbonate and ½ teaspoon of liquid soap (non-detergent) in 4 liters of water.
      Spray liberally on all affected areas.
      This mixture may be more effective than baking soda in treating existing infections.
    • Milk :
      Mix 1 part milk with 2 to 3 parts water and spray thoroughly.
      Although the science behind this solution is not fully understood, it seems to work well, especially on zucchini, melons and cucumbers.
      Compounds naturally found in milk are believed to not only fight disease, but also strengthen the plant's immune system.
    • Huile de neem:
      Alone, neem oil has mixed opinions on its effectiveness for treating powdery mildew, but it can be added to the mixtures above for added effect. (Learn more about using neem oil.)
    • Powdery mildew fungicide:
      Use organic fungicides containing sulfur as both prevention and treatment of existing infections.
    • Prune or prune:
      Remove any affected leaves, stems, buds, fruits or vegetables from the plant and discard them.
      Some perennials can be cut back to ground level and new growth will emerge.
      Do not compost damaged or diseased foliage, as spores can spread and persist in the composted material.
      Disinfect pruners and all tools after using them on infected plants.


      Powdery mildew spores are dispersed by wind in hot, dry weather, but do not spread well when conditions are rainy and cool.
      Powdery mildew strains are specialized for certain plant groups and generally do not spread to other plant families.
      Spores can survive over winter in leaf piles and on plants, so it is important to discard and not compost any plant debris that has fallen from infected plants to prevent spread or allow it to reappear the following spring.


      Basically, there are no plants that are completely immune to any form of powdery mildew, including vegetables, roses, trees and shrubs.
      There are some plants that are more susceptible to powdery mildew than others, such as:

      • Bégonias
      • Sunflowers
      • Chrysanthemums
      • Dahlias
      • Roses
      • Zinnias
      • Melons
      • Courgettes
      • Squash
      • Lettuce
      • Cucumbers
      • Potatoes
      • Parsley
      • Pumpkins
      • Raisins
      • Peppers
      • Tomatoes

      If you have recurring problems with powdery mildew, look for varieties that are noted to have better disease resistance — this should be noted on the plant's label.


      Remove and discard any affected leaves, as well as any that have fallen to the ground, and treat the rest of the plant as a preventative measure.
      If you see powdery mildew on the buds, cut them off and throw them away too. Thoroughly clean and disinfect all cutting tools used in the process. Apply one of the treatments above, such as a fungicide, baking soda, potassium bicarbonate or milk mixture once a week for 3 to 4 weeks and wait to see results.
      Prevent new breakouts with regular applications every two weeks or follow directions on product labels.

      Ultimately, the results will be much better if the infection is detected at the first signs and treated promptly.
      Try these roses that offer increased resistance to powdery mildew:

      • Oso Easy Double Red
      • Oso Easy Double Pink
      • Dreamy


        The milk mixture mentioned above seems to give better results than other methods.
        Again, the science behind its effectiveness is still being discovered, but it appears to not only prevent powdery mildew infection but also boost the plant's immunity.


        Read more

        Un guide pour cultiver des plants de poivrons
        Comment Cultiver des Herbes ? - Jardins d'Herbes intérieurs et extérieurs

        Leave a comment

        All comments are moderated before being published.

        This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.