See:
Fungicide Effectiveness as Seed Treatments for Cereal Diseases
Cause A fungus, Puccinia coronata, which may overwinter on volunteer and wild oats. Alternate hosts are species of Rhamnus (buckthorn). This is not a serious problem most years in Oregon and is not known to be in Idaho.
Symptoms Orange-yellow pustules (uredinia) form on leaves, stems, and sometimes heads. Rust pustules first are round to oblong but soon coalesce to form irregular, orange-yellow patterns. Black spores (teliospores) form in autumn. Heavy infection causes lodging and premature ripening.
Cultural control Resistant varieties are available elsewhere, but most varieties commonly grown in the Pacific Northwest either are susceptible or their reaction is unknown.
Chemical control
- Seed treatment reduces infection during the seedling stage.
- Raxil MD at 5 to 6.5 fl oz/100 lb seed plus a dye. See label for reentry restrictions.
- Foliar applications when the disease is severe.
- Bumper 41.8 EC (Group 3) at 4 fl oz/A. Highest yields are normally obtained when applied to the emerging flag leaf. Applications may be applied until the ligule of the flag leaf emerges (Feekes growth stage 8). Preharvest interval is 30 days for forage or hay; 45 days for grain and straw. 12-hr reentry.
- Miravis Ace B (Group 3) 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.
- Quadris Flowable (Group 11) at 6 to 12 fl oz/A applied prior to disease development, up to late head emergence (Feekes 10.5). Do not apply more than two (2) applications of Quadris or other Group 11 fungicide per season. Do not apply within 7 days of grazing. Preharvest interval is 7 days for forage and hay. 4-hr reentry.
- Tilt (Group 3) at 4 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 45 days of harvest for grain and straw; 7 days for forage and hay. 12-hr reentry.
- Vertisan (Group 7) at 10 to 24 fl oz/A on 7- to 14-day intervals through flowering (Feekes 10.5.1). Do not make more than two (2) sequential applications before alternating to a labeled fungicide with a different mode of action (non-Group 7). Preharvest interval is 0 days for forage and hay. 12-hr reentry.
- Premixed fungicides are available for use.
- Priaxor (Group 7 + 11) at 4 to 8 oz/A. Do not apply after 50% head emergence (Feekes stage 10.3). Do not make more than two (2) sequential applications. 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. 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 late head emergence (Feekes 10.5.4). 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, 14 days for grain. 12-hr reentry.