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Cercospora Leaf Spot or Blight - Cercospora
spp.
 Clemson University, USDA Cooperative
Extension
Slide Series, www.ipmimages.org  HOSTS: Beets, carrots, celery, cucurbits (cucumber, squash), eggplant, tomatoes (different species
on each vegetable). Also found on perennial flowers, Dogwood, and Viburnum leaves. DESCRIPTION:
Spots
with tan-pale, round centers and dark margins are visible. Symptoms
appear on older leaves first and can cause defoliation. LIFE
CYCLE: The
fungus overwinters on plant residue. Spores are carried on the wind
relatively long distances. Infection requires free water on leaf
surfaces and temperatures of 79-90° F. CONTROLS:Cultural: Grow resistant varieties. Soak seed in 122° F. water for 25 minutes before sowing. Use a three-year rotation between each susceptible vegetable crop (ie: tomatoes, carrots, lettuce). Keep water off leaves. Increase air movement by staking if possible. Chemical: Spray sulfur or copper at first sign of the disease. (Cucurbits are very copper sensitive; test your varieties before spraying; use copper sprays very sparingly, and never on bright, sunny days with temperatures above 80 to 85° F) To encourage new leaf growth, use foliar fish fertilizer each time you irrigate. |
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