Insect & Disease ID And Diagnosis Guide: Rusts And Mildew

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.