Powdery Mildew on Roses

Rose Fungus

row of roses

Do you Know what Powdery Mildew on Roses looks like?. View a picture of this rose fungus, and find an organic treatment. This is a common rose fungus that primarily affects rose foliage.

The flowers and new shoots can also be affected. The fungus appears as powdery white or light grey patches on the leaves (thus the name). Powdery mildew on roses, is mainly seen on the tender new growth of the rose plant. You will see white powdery leaves, and rose buds also covered with it.

The powdery coating is made up of a tangle of mycelium with chains of spores. The spores germinate in high humidity but not in the actual drops of water.

Identify Powdery Mildew on Rose Leaves

Infections of Powdery Mildew usually occur when high humidity is present. High daytime temperatures with cool nights usually cause high humid conditions perfect for this fungus. Day time temps from 65 to 80 degrees and cooler night time temps. Late Summer is the most common time for this Mildew to be prevalent. Roses that are in too much shade, and those with little air circulation could be affected.

Peak time is in cool, dry, overcast conditions while the rose plants are in active growth.

powdery mildew on rosesPowdery Mildew

A severe infection of the fungus will cause the affected young leaves to twist and be distorted. Plants may be deformed, or even dwarfed.

The only treatments I use on my roses are Organic ones! I feel good using products that are safe. Often you will see this type of mildew on perennial plants such as Phlox, or Lilac. Although a different fungus, the same treatment can be used on these plants with good results also.

Organic Recipe to Treat Powdery Mildew

Mix one tablespoon baking soda with one tablespoon horticultural oil (or dish soap) and a gallon of water. Spray both the tops and undersides of foliage.  This usually prevents this fungus.

Here you'll find another version of this easy to make recipe for powdery mildew!

Organic sulfur based fungicides work well on this powdery mildew, along with rust and black spot

Note: The sulfur is a last resort; it is rather smelly... and should only be used when the temperature is below 85 degrees.


Remember; plenty of Sun, good air circulation, and having soil that is healthy, will increase the roses resistance to powdery mildew, and other rose diseases.

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See the complete Spray Guide for Roses

more rose diseases and pests like Powdery Mildew on roses


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