Wheat (Triticum aestivum)-Septoria tritici Blotch

By C. Hagerty, C. Mundt, and C. M. Ocamb

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Cause The fungus, Zymoseptoria tritici (syn. Mycosphaerella graminincola, anamorph Septoria tritici), infects wheat leaves. This fungus survives on infected wheat plants or wheat stubble. The fungus produces ascospores on infected residues, which are spread by wind and infect new plants starting in the fall. Asexual spores (conidia) are produced by pycnidia in leaf spots as temperatures warm, and conidia are moved by splashing water. Time from new infection until conidia occur is shortest (11 days) when temperature is 59°F to 77°F. This disease has been a problem west of the Cascade Range, where frequent spring rains have been associated with severe disease development. Septoria tritici blotch commonly co-occurs with Stagonospora nodorum blotch (formerly known as Septoria nodorum; leaf and glume 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 Tan blotches with yellow margins appear first on lower leaves, especially those touching the soil. Tiny, black dots develop in the oblong leaf spots; these are the fruiting bodies known as pycnidia. Spots that develop on leaves higher up turn into reddish-brown, somewhat rectangular blotches that tend to follow the leaf veins. The entire leaf blade may be killed, and disease may spread to the leaf sheath.

Cultural control

  • The varieties, Bobtail, LCS Biancor, and LCS Drive currently are less susceptible than other varieties.
  • Late planting may help avoid infection from wind-blown spores in the fall.

Chemical control 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, especially on susceptible varieties and when spring rains are frequent.

  • 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.
  • 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.
  • Dithane F-45 Rainshield (Group M3) 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 (Group M1) 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 (Group M1) 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 but do not provide disease control due to strobilurin fungicide resistance in western Oregon. 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.
    • 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.
  • 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.
    • 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.
    • Trivapro (Group 3 + 7 + 11) at 9.4 to 13.7 fl 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, 14 days for grain. 12-hr reentry.

Reference Shaner, G. 2010. Septoria tritici blotch. p. 56-58 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.