Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Yucca -- Leaf Spot
 
Cause: Coniothyrium bartholomaei, a fungus, has been found in Oregon. Mycosphaerella tassiana has been reported from Washington, and Paraphaeosphaeria obtusispora has been reported for both Oregon and Washington.
Symptoms: Coniothyrium - small spots start out purple but become zoned with a center that turns light grayish brown. Concentric rings of tiny, black, fruiting bodies (pycnidia) develop in the spots. Spots generally are an inch or more in diameter and have a purple border. They coalesce on severely infected leaves which eventually die. Generally more severe on lower portion of the plant.

Notice the dark spots on these leaves.

Note the dark fruiting bodies (pycnidia) in the center of the tan zone of this leaf spot.

 
Cultural control:

  1. Remove and destroy infected leaves.
Chemical control:

  1. Champ Formula 2 at 0.6 pint/100 gal water. Champion WP can be used for organic production. 24-hr reentry.
  2. Copper-Count-N at 1 quart/100 gal water. 12-hr reentry.
  3. Nu-Cop 50 DF at 1 lb/100 gal water. 24-hr reentry.
  4. Mancozeb-based products. 24-hr reentry.
    1. Pentathlon DF at 1 to 2 lb/A or per 100 gal water.
    2. Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
  5. Spectro 90 WDG (chlorothalonil plus thiophanate methyl) at 1 to 2 lb/100 gal water. 12-hr reentry.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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