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Alfalfa

Identifying Diseases—Establishing a Stand

On this page
  • Common leafspot
  • Downy mildew
  • Sclerotinia rot

Look for symptoms of diseases that can occur during stand establishment. Compare field symptoms to the photos below and keep records of symptoms you see. Some diseases can be reduced by adjusting harvest or irrigation practices. Names link to more information on identification and management.

Click on photos to enlarge
Symptoms (field view) Close-up view
Common leaf spot
Common leafspot
Identification tip: Leaves of infected plants are covered with small brown-to-black spots.
Close-up of common leaf spot
Common leafspot
Identification tip: Infected leaves have raised fruiting bodies in the middle of brown leaf lesions.
Downy mildew
Downy mildew
Identification tip: Leaves infected with downy mildew are spotted with a distinctive pale-green color.
Close-up of downy mildew
Downy mildew
Identification tip: Blotches on the upper sides of infected leaves are gray-green to tan.

Sclerotinia rot
Sclerotinia rot
Identification tip: Stems of plants infected with Sclerotinia rot are covered with white mycelia.

Close-up of Sclerotinia rot
Sclerotinia rot
Identification tip: Hard black sclerotia resting bodies form on the mat of white mycelium.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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