Wheat (Triticum aestivum)-Stagonospora nodorum Blotch

See:

Wheat (Triticum aestivum) - Septoria tritici Blotch

Cause The fungus, Phaeosphaeria nodorum (anamorph Stagonospora nodorum, formerly known as Septoria nodorum) , infects both leaves and glumes. This fungus survives between crops on infected wheat, barley, or oat stubble, and on leaves of volunteer wheat as well as grassy weed hosts. But the strains from other grassy host other than wheat are only weakly virulent on wheat (and vice versa). Stagonospora nodorum may be seedborne.

The fungus spreads under windy, wet conditions. Wet or humid conditions when temperature is 68°F to 81°F promote disease and symptom development. The diseases have been a problem only west of the Cascade Range, where frequent spring rains have been associated with severe disease development. Stagonospora nodorum blotch commonly co-occurs with Septoria tritici blotch in the same field or on the same plant. In the Willamette Valley, Septoria tritici blotch has been more common than Stagonospora nodorum blotch.

Symptoms Light-yellow spots appears first on lower leaves. Spots spread rapidly, forming yellowish, lens-shaped areas that turn into reddish-brown, irregular, roundish blotches that tend have yellow margins. As spore production begins, the reddish-brown tissues turn grayish and tiny, dark dots develop; these are the fruiting bodies known as pycnidia, which contain spores. Glume infections appears first as brown areas on tips of glumes. Purple-brown to grayish-brown blotches or streaks develop and progress downward, and tiny, black dots form as pycnidia develop. Seed from infected heads is shrunken and wrinkled.

Cultural control

• Variety Foote currently has good resistance. The varieties Hill 81, Madsen, Yamhill, and Goetze, are moderately resistant to and commonly show about half the level of disease as the susceptible varieties Gene, Malcolm, and Stephens.
• Late planting may help avoid infection from fall inoculum.

Chemical control Seed treatment with Vitavax plus Thiram or Dividend only partly controls the seedborne phase of the disease.

Spray a fungicide at early flag-leaf emergence (Feekes stage 8 to 8.3) unless otherwise noted. Recommended for areas west of the Cascade Range, when spring rains are frequent, and for the varieties Gene, Stephens, or Malcolm. Chemical control gave an economic yield advantage in some years when varieties, Yamhill, Madsen, or Hill 81 were grown. There was no economic advantage from applying a second fungicide.

• Demethylation-inhibiting (DMI) fungicides (Group 3) are labeled for use and include the following fungicides as well as other formulations:
  • Alto 100SL at 1.5 to 5.5 fl oz/A applied between Feekes Stage 8 and 10.5.1. Preharvest interval is 21 days forage and hay; 30 for grain and straw. 12-hr reentry.
  • Bumper 41.8 EC at 4 fl oz/A. May be applied until Feekes growth stage 10.5. Do not treat within 30 days of harvest 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
  • Proline 480 SC at 4.3 to 5.0 fl oz/A on 14-day intervals. Preharvest interval is 30 days. 12-hr reentry.
  • PropiMax EC at 4 fl oz/A no later than the end of flowering (Feekes 10.5). Do not graze or feed treated forage to livestock or harvest treated crop for hay or silage. After harvest, straw may be used for bedding. Do not apply within 40 days of harvest. 12-hr reentry.
  • Tebuzol 3.6F at 2 to 4 fl oz/A (4 oz for glume blotch) at flag-leaf emergence up to the end of flowering. Do not apply within 30 days of harvest. 12-hr reentry.
  • Tilt at 4 fl oz/A at flag-leaf emergence (Feekes stage 8) but no later than Feekes 10.5. Do not apply within 7 days of harvest for forage or 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.
• Dithane F-45 Rainshield at 1.6 quarts/A. Start applications at the onset of disease or when plants are in the tillering to jointing stage and repeat on 7- to 10-day intervals. Do not apply after Feekes 10.5 or heading. 24-hr reentry.
• Kocide 2000 at 1 to 1.5 lb/A at early heading and reapply 10 days later. 48-hr reentry. O
• Manzate 75 DF at 2 lb/A. Do not apply within 26 days of harvest. Do not graze treated areas prior to harvest. 24-hr reentry.
• Nu-Cop 50 DF at 1 lb/A. Make first application at early heading and reapply on 10 days later. 48-hr reentry. O
• 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.
  • Aftershock at 2 to 4 fl oz/A on 14- to 21- day intervals up to late head emergence (Feekes 10.5). Make no more than one (1) application prior to harvest of wheat forage. Do not apply within 7 days of harvest for forage and hay; 40 days of harvest for grain and straw. 12-hr reentry.
  • Headline at 6 to 9 fl oz/A. Do not apply later than the end of flowering (Feekes 10.5). Preharvest interval is 14 days for hay and forage. 12-hr reentry.
  • Quadris Flowable at 4 to 12 fl oz/A up to late head emergence (Feekes 10.5). Do not apply within 7 days of harvest for forage and hay and 14 days of grazing. 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.
  • Vertisan 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. 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 Max (Group M3 + 11) at 2.1 lb/A on 7- to 10-day intervals. Applications may be applied up to Feekes growth stage 10.5. Preharvest interval for hay is Feekes growth stage 10.5, but no less than 26 days; grain and straw is 45 days. 24-hr reentry.
  • Dexter Xcel (Group M3 + 11 +3) at 48 fl oz/A. The single application may be applied up to Feekes growth stage 10.54. 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 immediately after flag leaf emergence but no later than the beginning of flowering (Feekes 10.5). Preharvest interval is 7 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 10 fl oz/A or Stratego YLD at 4 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 35 days of harvest. See label for grazing, forage, and hay restrictions. 12-hr reentry.

Reference Bergstrom, G.C. 2010. Stagonospora nodorum blotch and Stagonospora avenae blotch. p. 75-77 in Compendium of Wheat Diseases, 3rd Edition. Bockus, W.W., Bowden, R.L., Hunger, R.M., Morrill, W.L., Murray, T.D., and Smiley, R.W., (eds.). St. Paul, MN: APS Press.