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Insect & Disease ID And Diagnosis Guide: Rusts And Mildew

Diagnose pest and disease issues that manifest as rusts and mildew.

 

January 21, 2009

  •  Daylily leaves show orange spore pustules on the back when infected with rust.  © 2009
    Daylily leaves show orange spore pustules on the back when infected with rust.
  •  The undersurfaces of coleus leaves with downy mildew are sometimes covered with thick sporulation.  © 2009
    The undersurfaces of coleus leaves with downy mildew are sometimes covered with thick sporulation.
  •  Downy mildew on snapdragons may cause systemic infections that make foliage chlorotic and stunted.  © 2009
    Downy mildew on snapdragons may cause systemic infections that make foliage chlorotic and stunted.
  •  White grainy or gray water-soaked spots may be powdery mildew on begonia. Look for fungus strands on leaf surfaces.  © 2009
    White grainy or gray water-soaked spots may be powdery mildew on begonia. Look for fungus strands on leaf surfaces.
  •  Fuchsia rust may form purple-rimmed leaf spots when seen from the upper surface, and this apricot-colored sporulation on the undersurface.  © 2009
    Fuchsia rust may form purple-rimmed leaf spots when seen from the upper surface, and this apricot-colored sporulation on the undersurface.
  •  Downy mildew will produce purpling above and white sporulation on the undersurface of osteospermum.  © 2009
    Downy mildew will produce purpling above and white sporulation on the undersurface of osteospermum.
  •  Chrysanthemum white rust causes yellow spots on leaves, with white spore pustules on the reverse side.  © 2009
    Chrysanthemum white rust causes yellow spots on leaves, with white spore pustules on the reverse side.
  •  Sporulation on the undersurfaces of coleus leaves is sometimes hard to see.  © 2009
    Sporulation on the undersurfaces of coleus leaves is sometimes hard to see.
  •  Impatiens leaves with downy mildew may be bronzed on the undersurface and curl downward.  © 2009
    Impatiens leaves with downy mildew may be bronzed on the undersurface and curl downward.

Seeing rust on your crops? Take a look at these pictures to see common diseases that can lead to rusts.

Scouting tip: If you are shipping fresh plant material and/or living insects, use a 24 to 48 hour delivery service, preferably the former. Avoid shipping on Thursday or Friday, if possible.

Daylily leaves show orange spore pustules on the back when infected with rust.

The undersurfaces of coleus leaves with downy mildew are sometimes covered with thick sporulation.

Downy mildew on snapdragons may cause systemic infections that make foliage chlorotic and stunted.

White grainy or gray water-soaked spots may be powdery mildew on begonia. Look for fungus strands on leaf surfaces.

Fuchsia rust may form purple-rimmed leaf spots when seen from the upper surface, and this apricot-colored sporulation on the undersurface.

Downy mildew will produce purpling above and white sporulation on the undersurface of osteospermum.

Chrysanthemum white rust causes yellow spots on leaves, with white spore pustules on the reverse side.

Sporulation on the undersurfaces of coleus leaves is sometimes hard to see.

Impatiens leaves with downy mildew may be bronzed on the undersurface and curl downward.

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