Cause The fungus, Pyrenophora teres (asexual stage: Drechslera teres), causes net blotch. The pathogen soverwinters on barley residues and can also be transmitted by seed. Infection is favored by long periods of high humidity or moisture.
Symptoms Lesions first appear as small circular spots. They enlarge into narrow, dark brown stripes extending across and down the leaf, forming a distinct net-like pattern. The affected part turns brown, and the entire leaf may die if infection is severe. Stems, sheaths, and kernels may be affected.
Cultural control
- Use pathogen-free seed.
- Plant resistant varieties, such as 'Merit', 'Foster', and 'Legacy'.
- Plow under infected barley straw or stubble.
- Rotate with nonsusceptible crops for at least two seasons.
Chemical control
- Demethylation-inhibiting (DMI) Fungicides (Group 3) are labeled for use.
- Bumper 41.8 EC or Bumper ES at 4 fl oz/A on a minimum of 14-day intervals for no more than two (2) applications, one (1) application maximum if harvesting for forage or hay. Do not apply within 45 days of harvest for grain and straw; 30 days 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.
- Tilt at 4 fl oz on a minimum of 14-day intervals for no more than two (2) applications, one (1) application maximum if harvesting for forage or hay. 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.
- Miravis Ace A (Group 7) 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.
- Strobilurin fungicides (Group 11) are labeled for use. Do not make more than one (1) application of any Group 11 fungicide per season.
- Headline at 6 to 9 fl oz/A. Apply no 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.
- 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.
- Priaxor (Group 7 + 11) at 4 to 8 oz/A. 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. 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.