Steady rain is causing field flooding in many locations in the Red River Valley. Yield potential may decline with extended periods of soil saturation. If the wheat yield potential is worth protecting from Fusarium head blight, now is the time to consider your options. This weather is promoting the potential for an epidemic of FHB to occur.

NOTE: The forecasting model may be underestimating disease epidemic risk since its forecasts are based on weather during the last 7 days. An extended wet weather pattern, like many RRV locations have experienced, will promote spore production by the fungus.

For current outlook: http://mawg.cropdisease.com

FUSARIUM HEAD BLIGHT. If you have FHB susceptible wheat in a high-moisture locale that is approaching the early-flowering growth stage that has good yield potential, the crop will need to be protected with a fungicide application. My recommendation is the “3 x 3” fungicide mix containing 3 fl. oz./A Proline (prothioconazole) and 3 fl. oz./A Folicur (or any generic tebuconazole product listed below) applied at early flower. This tank mix has a slightly greater disease management efficacy than either active ingredient product applied alone. If you have a moderately resistant variety, a 4 fl. oz./A application of tebuconazole (Folicur, Orius, TebuStar, Embrace, Tebuzol, Integral, or Muscle) may be adequate. Slightly better management would be expected from the fungicide mix, however moderately resistant varieties will benefit less than susceptible varieties.

WHEAT LEAF RUST continues to spread. Ardelle Knudsvig, MN Dept. Ag, reports a field near Fosston with a high LEAF RUST incidence, but as of yet a low severity. Doug Holen, UM Regional Extension Educator reports a field of Oxen (nurse crop for alfalfa) in west central MN with high LEAF RUST incidence and severity. Severity of susceptable varieties may increase rapidly with this weather. In general, a fungicide application is not recommended on wheat for RUST until the early-flowering growth stage when FUSARIUM HEAD BLIGHT management is also possible. This year it may be doubly important to apply fungicide at early flower—to manage scab and rust diseases. Scout infected fields that are planted to susceptible varieties every few days to determine if a fungicide application can safely be delayed until then.

Dr. Charla Hollingsworth, Plant Pathologist
Univ. of Minnesota Extension