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.
- Bicarbonates are registered to control powdery mildew. Thorough coverage is essential.
- Carb-O-Nator at 2.5 to 5 lb/100 gal of water on 5- to 14-day intervals, depending on disease pressure. Preharvest interval is zero (0) days for all listed crops. 4-hr reentry. O
- Kaligreen at 2.5 to 3 lb/A on 7- to 10-day intervals. May be applied up to the day before harvest. 4-hr reentry. O
- MilStop SP at 2 to 5 lb/A on 7- to 14-day intervals. Can be applied up to and including the day of harvest. 1-hr reentry. O
- 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.
- Topguard at 10 to 14 fl oz/A on 7-day intervals. Preharvest interval is 0 days for forage, 15 days for hay, and 30 days for grain.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.
- 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. Does not benefit from the addition of an adjuvant. 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.
- Miravis Ace (Group 3 + 7) at 13.7 fl oz/A. Apply between Feekes 10.3 and 10.5.4. Harvest interval is 7 days for forage and hay. 12-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.