Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Carrot (Daucus carota) -- Aster Yellows
 
Cause: Candidatus (Ca.) Phytoplasma aster is spread by leafhoppers. Phytoplasmas survive the winter on weed hosts. Aster yellows also occurs in lettuce, endive, tomato, parsley, onion, salsify, squash, many weeds, and several ornamental flowering plants.
Symptoms: New leaves in the plant's heart are yellow, reduced in size, deformed, and dense in growth. Older leaves may have a purple or reddish color. Carrot roots frequently are deformed and develop dense tufts of hairlike rootlets. Dormant buds in the crown may develop so the plant takes on a witches' broom appearance.

 
Cultural control:

  1. Remove infected plants as soon as detected.
  2. Control measures against the leafhopper vectors have reduced disease in some areas but are economical only in areas with significant crop losses. For details of materials and application rates, see the PNW Insect Control Handbook.
Content edited by: Cynthia M. Ocamb on January 1, 2010
 
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