Oidium sp.

What is Powdery Mildew

Powdery mildew is a fungus which spreads a white or ash-grey film over the upper and lower surfaces of the leaves of plants-usually the older leaves. Powdery mildew fungus favours high humidity and dry conditions. Water splash and air currents spread the spores of powdery mildew which grows on the surface of the leaf only. Powdery mildew is a common disease of roses, crepe myrtles, dahlias, zinnias, calendulas, sweet peas, cucurbits and vine crops.



Appearance of a whitish film on leaves and buds. New growth is distorted and older leaves become blackened. Flower buds may fail to open.


Plants impacted

  • Roses
  • Crepe Myrtles
  • Dahlias
  • Zinnias
  • Calendulas
  • Sweet Peas
  • Cucurbits 
  • Vine crops

Recommended products

Yates Nature's Way Fungus Spray

Protects against a very wide range of fungal and bacterial diseases. It is formulated from copper and sulfur, which are naturally occurring compounds.

Yates Fungus Gun - Ready to Use

A broad spectrum fungicide that works systemically within the plant, providing both protectant and curative activity to prevent and control fungal diseases.

Yates Rose Gun Spray - Ready to Use

A combination of systemic fungicide and contact insecticide. Kills pests and mites on contact and works from within the plant to control black spot, powdery mildew and rust on roses and ornamentals in the home garden.

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Downy Mildew

Downy Mildew is often more widespread in younger plants and is recognised by downy, whitish tufts or spores on the underside of the leaves.

Sooty Mould

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Myrtle Rust

Myrtle Rust is a fungal disease which attacks the new growth of plants from the Myrtaceae family such as pōhutukawa, rātā, mānuka and eucalypts.