Barley (Hordeum vulgare)-Powdery Mildew

Cause A fungus, Blumeria graminis (= 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. Dense stands, over-application of nitrogen, high humidity, and low temperatures favor disease development.

Symptoms Powdery, gray-white, or buff-color spore masses develop on leaves, leaf sheaths, and heads. Yellowing, browning, and death of the leaves follows heavy infection.

Cultural control

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

Chemical control Foliar fungicide application is helpful under severe disease pressure or when raising an unusually susceptible variety.

  • Badge SC (Group M1) at 0.5 to 1.8 pints/A on no shorter than 10-day intervals. Preharvest interval is 0 days. 48-hr reentry.
  • Demethylation-inhibiting (DMI) Fungicides (Group 3) are labeled for use.
    • Bumper 41.8 EC or Bumper ES at 4 fl oz/A on a minimum of 14-day intervals for no more than two (2) applications, one (1) application maximum if harvesting for forage or hay. Do not apply within 45 days of harvest for grain and straw; 30 days for forage or hay. 12-hr reentry.
    • Miravis Ace B at 4 fl oz/A at flag-leaf emergence (Feekes stage 8) but not after Feekes 10.5.4. Do not apply within 7 days of harvest for forage or hay. 12-hr reentry.
    • Tilt at 4 fl oz on a minimum of 14-day intervals for no more than two (2) applications, one (1) application maximum if harvesting for forage or hay. Apply when the flag leaf is 50% to fully emerged, up to late head emergence (Feekes 10.5). Preharvest interval is 7 days for forage and hay. 12-hr reentry.
  • Miravis Ace A (Group 7) at 10.3 fl oz/A beginning at flag-leaf emergence (Feekes stage 8) but not after full head emergence (Feekes 10.5.4). Do not apply within 7 days of harvest for forage or hay. 4-hr reentry.
  • MilStop SP (85% potassium bicarbonate) at 2 to 5 lb/A. 1-hr reentry.
  • Regalia (Group P5) at 1 to 2 quarts/A on 7- to 10-day intervals starting prior to infection. Under high-disease pressure, use in combination with another fungicide. 4-hr reentry. O
  • Strobilurin fungicides (Group 11) are labeled for use. Do not make more than two (2) applications of any Group 11 fungicide per season. Do not make more than one (1) application of any Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
    • Headline at 6 to 9 fl oz/A. Apply no later than 50% head emergence (Feekes 10.3). Preharvest interval is 14 days for hay and forage. 12-hr reentry.
    • Quadris Flowable at 9 to 12 fl oz/A applied prior to disease development, up to late head emergence (Feekes 10.5). Do not apply within 7 days of grazing. Preharvest interval is 7 days for forage and hay. 4-hr reentry.
  • Premixed fungicides are available for use. Do not make more than one (1) application of any Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
    • Dexter Xcel (Group M3 + 11 + 3) at 48 fl oz/A. The single application may be applied up to Feekes growth stage 10.5.4. Preharvest interval is 30 days. 24-hr reentry.
    • Priaxor (Group 7 + 11) at 4 to 8 oz/A. Do not apply after 50% head emergence (Feekes stage 10.3). Preharvest interval is 14 days for forage and chopped feed. 12-hr reentry.
    • Quilt or Quilt Xcel (Group 3 + 11) at 10.5 to 14 fl oz/A when the flag leaf is 50% to fully emerged. Applications may be made no closer than a 14-day interval and may be applied up to Feekes growth stage 10.5. Do not make more than two (2) applications per season. Preharvest interval is 7 days for forage and hay. 12-hr reentry.
    • Stratego (Group 3 + 11) at 7 fl oz/A or Stratego YLD at 2.3 fl oz/A. Do not apply after flag-leaf emergence (Feekes stage 8). Do not make more than two (2) applications per season. Do not apply within 40 days of harvest. See label for grazing, forage, and hay restrictions. 12-hr reentry.
    • Trivapro (Group 3 + 7 + 11) at 9.4 to 13.7 oz/A beginning when the flag leaf is 50% to fully emerged, up through full head emergence. Do not make more than two (2) sequential applications of Trivapro or other Group 7 or Group 11 fungicides. Preharvest interval is 7 days for forage and hay, 45 days for grain and straw. 12-hr reentry.

Biological control Efficacy in the PNW is unknown.

  • Ballad Plus at 1 to 4 quarts/A on 7- to 14-day intervals. Can be applied up to and on the day of harvest.4-hr reentry. O
  • Serenade ASO (Group BM02) at 0.5 to 2 quarts/A. Applications can be made up to and the day of harvest. 4-hr reentry. O