Cause The fungal pathogen, Bipolaris sorokiniana (syn. Cochliobolus sativus), may be carried on seed or overwinter on infected plant residues or as spores in soil.
Symptoms Spots can develop at all stages of plant development. Leaf spots on adult plants are round to oblong and dark brown with yellow margins. Spots on seedlings are more rounded. Spots may coalesce to form blotches over large areas of the leaf. Older spots may turn olive-black from the spores being produced. Severely affected leaves senesce prematurely.
Cultural control
- Use pathogen-free seed.
- Plant resistant varieties, such as 'Foster'.
- Rotate crops to nongrass species if feasible.
- Practice tillage that buries or accelerates breakdown of residues.
Chemical control Foliar fungicide application is helpful under severe disease pressure or when raising an unusually susceptible variety.
- Demethylation-inhibiting (DMI) fungicides (Group 3) are labeled for use.
- 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. 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.
- Strobilurin fungicides (Group 11) are labeled for use. Do not make more than one (1) application of a Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
- Headline at 6 to 9 fl oz/A. Begin applications in order to protect the flag leaf stage of growth from infection. Do not apply 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.
- Succinate dehydrogenase inhibitors (SDHI) fungicides (Group 7) are labeled for use and include the following fungicide as well as other formulations. SDHI fungicides should always be mixed with a DMI fungicide to avoid selection for fungicide resistance.
- Miravis Ace A 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.
- Vertisan at 14 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. 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.
- 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.