Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Barley (Hordeum vulgare) -- Powdery Mildew
 
Cause: A fungus, Erysiphe graminis f. sp. hordei, that overwinters on stubble and straw or volunteer barley and certain wild grasses. Heavy, succulent growth favors mildew development. Not usually a problem in Oregon or Idaho. Disease is favored by dense stands, nitrogen overfertilization, high humidity, and low temperatures.
Symptoms: Powdery, gray-white, or buff-colored spore masses develop on leaves, leaf sheaths, and heads. Yellowing, browning, and death of the leaves follows heavy infection.
Cultural control:

  1. Plant resistant varieties.
  2. Reducing rates of nitrogen fertilization gives some control if the disease is severe.
  3. Clean plowing and crop rotation help reduce the disease.
Chemical control:

  1. Seed treatment will reduce mildew in the seedling stage for spring-planted crops.
    1. Baytan 30 at 1.5 fl oz/100 lb seed. See label for reentry restrictions.
  2. Foliar fungicide application is helpful under severe disease pressure or when raising an unusually susceptible variety.
    1. Bumper 41.8 EC at 4 fl oz/A. Highest yields are normally obtained when applied to the emerging flag leaf. May be applied until the ligule of the flag leaf emerges (Feekes growth stage 8). Do not feed treated forage or cut green crop for hay or silage. 24-hr reentry.
    2. Headline at 6 to 9 fl oz/A. Begin applications in order to protect the flag leaf stage of growth from infection. Do not make applications later than 50% head emergence (Feekes 10.3). Do not harvest barley hay within 14 days of last application. 12-hr reentry.
    3. MilStop (85% potassium bicarbonate) at 2 to 5 lb/A. 1-hr reentry.
    4. Quadris at 12 fl oz/A applied prior to disease development from Feekes 6 up to Feekes 10.5. Do not make more than two (2) foliar applications of Quadris or other Group 11 fungicides per acre per season. Do not harvest treated barley for forage. Do not apply within 14 days of harvest for hay. Do not apply within 45 days of harvest for grain and straw. 4-hr reentry.
    5. Tilt at 4 fl oz/A in not less than 15 gal/A water (ground) or 5 gal/A water (air). Apply when the flag leaf is 50% to fully emerged. Do not apply within 30 days of harvest for forage, 40 days for grain and straw and 45 days for hay. 12-hr reentry.
Biological control:
  1. Ballad Plus at 1 to 4 qt/A on 7- to 14-day intervals. Can be applied up to and on the day of harvest. 4-hr reentry.
Content edited by: Cynthia M. Ocamb on January 1, 2009
 
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