WSU Extension


Downy mildew 

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Caption: Snapdragon rust
Photo by: R.S. Byther
Snapdragon : Rust
(revision date: 4/23/2014)

Rust is caused by a fungus that is spread by water or on clothes and in diseased cuttings. It is not carried in seed but seeds can be contaminated by the fungus on the outside. Upper leaf surfaces have diffuse pale or yellow spots. Under the leaf are concentric rings of chocolate-brown pustules. Pustules are on stems and flowers also. The infected plant may appear stunted and dry.
Management Options

Non-Chemical Management
  • Space plants to encourage good air circulation.
  • Do not water foliage or water only in morning or in the middle of the day when the foliage will dry quickly.
  • Rust-resistant snapdragon cultivars are available.
Select non-chemical management options as your first choice!

Chemical Management

Focus on cultural management options for best results.


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Caption: Snapdragon rust
Photo by: R.S. Byther