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Alfalfa

Identifying Diseases and Disorders—Summer

On this page
  • Phytophthora root and crown rot
  • Rhizoctonia
  • Scald
  • Southern anthracnose
  • Stagonospora crown and root rot

Several diseases and disorders occur in alfalfa in the summer. Compare field symptoms to the photos below and keep records of diseases you see. Adjusting irrigation practices can reduce some diseases and disorders. Names link to more information on identification and management.

Click on photos to enlarge
Field view Close-up view

Phytophthora infected leaves
Phytophthora root and crown rot
Identification tip: Leaves of infected plants turn yellow or tan and drop. Phytophthora can infect large areas of alfalfa in a field.

Phytophthora infected root tips
Phytophthora root and crown rot
Identification tip: Red-orange to yellow streaks spread up from infected root tips.

No photo available.

Rhizoctonia
Rhizoctonia Root Canker
Identification tip: Brown rotted roots caused by seedling disease known as damping off, due to Pythium sp., Rhizoctonia sp., or Fusarium sp.

Field exhibiting serious damage from scald
Scald
Identification tip: Plants that sustain waterlogging combined with high soil temperatures will uniformly turn yellow and wilt. This condition, called scald, can also occur with soils that remain saturated for long periods under cooler temperatures.

No photo available.

 

Plants infected with southern anthracnose
Anthracnose
Identification tip: Infected plants' stems eventually become bleached and bent.
Close-up view of lesions on stems
Anthracnose
Identification tip: Southern anthracnose stem lesions (right) are darker and lack the distinct fruiting bodies that appear in Stagonospora lesions (left).

Stagonospora leaf spots
Stagonospora crown and root rot
Identification tip: Stagonospora leaf spots are irregularly shaped tan lesions with brown borders.

Stagonospora lesions
Stagonospora crown and root rot
Identification tip: Stagonospora lesions are spotted with tiny, round, black fruiting bodies.


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