Downy Mildew

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Symptoms of Downy Mildew

downy mildew
  • Downy mildew, or crazy top, causes distortion and/or stunting of the corn plant.
  • Tunneling usually kills the plant.
  • The tassel bracts may proliferate, resulting in a very bushy appearance of the top of the plant.


  • Downy mildew is a fungal disease that frequently occurs in areas of fields subject to flooding.
  • Seedlings are more susceptible than adult plants.

Life Cycle of Downy Mildew

  • Crazy top is caused by a soilborne fungus, which overwinters as oospores either within infected tissue or in the soil.
  • During periods of flooding, the oospores germinate and swimming zoospores are produced. The zoospores infect the growing point of the young corn plants.

Management of Downy Mildew

  • Avoiding areas prone to flooding and providing for adequate drainage of surface water are the best means of controlling downy mildew.