Where weather conditions are favorable for its development, leaf rust is starting to pop up in hard red winter wheat in parts of the Plains where harvest is just weeks away.

Some varieties in Oklahoma test plots are showing high susceptibility to the disease, according to Oklahoma State University Extension wheat pathologist Bob Hunger. But, it's been held to areas where the weather's favored leaf rust's development. The disease thrives in wet

"One report I received from near Hinton, Oklahoma (about 50 miles west of Oklahoma City) indicated that leaf rust in unsprayed fields of Jagger was 'covering the flag leaves,' Hunger says. "Similar reports of severe leaf rust have come from the experiment station at Lahoma (about 15 miles west of Enid. Oklahoma)."

Not all varieties are affected by leaf rust, however. Hunger says the varieties showing highest levels of susceptibility right now are Jagalene, Jagger and Lakin.

Finding leaf rust in your wheat fields? If so, you stand to lose some yield potential and test weight, according to Kansas State University Extension plant pathologist Robert Bowden.

"The earlier leaves are lost, the more severe the yield loss. Losses may vary depending on the variety's ability to fill from the stem, glumes and awnns," Bowden says. "Susceptible varieties can be protected from rust with foliar fungicides. Although systemic fungicides can give very good control of leaf rust, they are relatively expensive. Therefore, fungicide use in Kansas is limited to fields with high yield potential (at least 45 bushels per acre) and high disease potential."

In diagnosing leaf rust in the field, Bowden says to look for orange pustules on the leaf surface, sometimes surrounded by a "narrow yellow or white halo.

"When rust severity is high, field scouts may notice the orange dust on hands and clothing," he adds. "Leaf rust typically occurs uniformly across a field. In overwintering locations, it is most severe on the bottom leaves. When it blows in from distant fields, it will be most severe on upper leaves."

Where weather conditions are favorable for its development, leaf rust is starting to pop up in hard red winter wheat in parts of the Plains where harvest is just weeks away.