Winter wheat showing signs of disease stress

Stripe rust continues to increase across Oklahoma, reports Bob Hunger, Extension wheat pathologist at Oklahoma State University.

In his weekly update, Hunger says there are severe stripe rust "hot spots" in Grant County, Oklahoma, the north-central part of the state near the Kansas border.

"In Major County, which is immediately south of Grant County, an agronomist with Syngenta found a 'high incidence of stripe rust' in that company's wheat plots near Carrier, Oklahoma," Hunger wrote.

Near Stillwater, Oklahoma, Hunger observed severe stripe rust in spreader strips of the susceptible variety Pete. And, near Perkins, Oklahoma, Jeff Wright, coordinator of production operations at OSU, says a field of the old variety Triumph 64 was almost entirely yellow due to the incidence of stripe rust. Fungicide application on those affected fields will protect green leaves, but yellowed leaf tissue will be killed from the infection in that field, Hunger says.

"This is a good example of the importance of applying a fungicide to a susceptible variety sufficiently early to prevent such widespread infection," he says. "What and how such a big and uniform infection occurred is puzzling to me, but I suspect that is related to overwintering of the stripe rust fungus in the field."

Moving North

On Twitter, several instances of diseases moving into Kansas have been cited.

• Near Leoti in western Kansas, wheat streak mosaic virus is hitting susceptible fields, according to farmer Rick Horton.
• Near Great Bend in central Kansas, stripe rust is occurring on susceptible varieties, notes Stacy Campbell, Extension crop specialist. The disease is confirmed as far north as Interstate 70 in central Kansas.
• Meanwhile, back in Oklahoma, Hunger says powdery mildew is severe in susceptible varieties, and Barley yellow dwarf also is easily found in many trials and varieties.