Cause Pyrenophora avenae (asexual: Drechslera avenae; syn. sexual: Helminthosporium avenaceum; asexual: D. avenaceum), a fungus that overwinters on old straw or stubble.
Symptoms Long, brick-red blotches appear on young plants in the three- or four-leaf stage. New leaves show blotches as they grow out. Old leaves shrivel and die. Root systems develop poorly. Infected plants may break off at the soil line and lodge.
Cultural control Rotating crops and plowing under infected straw reduces the amount of disease.
Chemical control Registered seed treatments for oats either are ineffective or give only fair control.
- Copper formulations (Group M1) are registered for use.
- Badge SC at 0.5 to 1.8 pints/A on no shorter than 10-day intervals. Preharvest interval is 0 days. 48-hr reentry.
- Kocide 2000 at 1 to 1.5 lb/A at early heading and reapply 10 days later. 48-hr reentry. O
- Nu-Cop 50 DF at 1 lb/A. Make first application at early heading and reapply 10 days later. 48-hr reentry. O
- 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.
- 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. Preharvest interval is 7 days for forage and hay. 12-hr reentry.
- Tilt (Group 3) at 4 oz/A at flag-leaf emergence (Feekes stage 8) up to Feekes 10.5. Do not apply within 7 days of harvest for forage or hay; 45 days of harvest for grain and straw. 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.