Cause The fungi Septoria tritici, which infects only leaves, and Stagonospora nodorum (formerly known as Septoria nodorum), which infects both leaves and glumes, survive between crops on infected wheat, barley, or oat stubble, and on leaves of volunteer wheat as well as grassy weed hosts. S. nodorum may be seedborne, but the importance of this in the disease cycle is unknown.
The fungi spread by wind and splashing water. Wet or humid conditions when temperature is 68 to 82°F promote Septoria leaf and glume blotch. The diseases have been a problem only west of the Cascades, where frequent spring rains have been associated with severe disease development. In the Willamette Valley of Oregon, leaf blotch has been more common than glume blotch.
Symptoms Leaf blotch appears first on lower leaves as light green or yellow, water-soaked spots between leaf veins. Spots spread rapidly, forming yellowish, lens-shaped areas that turn into reddish-brown, irregular blotches that tend to follow the leaf veins. Blotches are rectangular when infection is caused by S. tritici and roundish when infection is caused by S. nodorum. 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 blotch appears first as brown areas on tips of chaff or glumes. These areas progress downward, and tiny, black dots form as pycnidia develop. Seed from infected heads is shrunken and wrinkled.
- The cultivar 'Foote' currently has good resistance. 'Hill 81', 'Madsen', 'Yamhill' and 'Goetze' are moderately resistant to both pathogens and commonly show about half the level of disease as the susceptible cultivars '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 Cascades, when spring rains are frequent, and for the cultivars 'Gene', 'Stephens', or 'Malcolm'. Chemical control gave an economic yield advantage in some years when '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:
- Bumper 41.8 EC at 4 fl oz/A. May be applied until Feekes growth stage 10.5. Do not feed treated forage or cut green crop for hay or silage. 12-hr reentry.
- Proline 480 SC at 4.3 to 5.0 fl oz/A on 14-day intervals. Preharvest interval is 30 days. 48-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. 24-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 30 days of harvest for forage or hay. 12-hr reentry.
- Dithane DF Rainshield at 2.1 lb/A or 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.
- 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 WP at 1.5 to 2 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 two (2) applications 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. Do not apply later than the end of flowering (Feekes 10.5). Do not harvest wheat hay within 14 days of last application. 12-hr reentry.
- Quadris Flowable at 4 to 12 fl oz/A up to late head emergence (Feekes 10.5). Do not apply more than two (2) foliar applications of Quadris or other Group 11 fungicide before alternating to a labeled fungicide with a different mode of action. Do not apply within 14 days of harvest for forage and hay; 45 days of harvest for grain and straw. 4-hr reentry.
- 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.
- Premixes of Group 3 + 11 fungicides are available for use. Do not make more than two (2) applications per season.
- Quilt or Quilt Xcel 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 30 days for forage and hay. 12-hr reentry.
- Stratego at 10 fl oz/A. Do not apply after flag-leaf emergence (Feekes stage 8). Do not apply within 35 days of harvest. 12-hr reentry.