Sharp eyespot reappears in Willamette Valley wheat
Oregon State University plant pathologist Chris Mundt reported at Hyslop Farm Field Day May 27 that sharp eyespot is back infecting Willamette Valley wheat, and doesn’t appear to be leaving any time soon.
“We were hoping it would go away,” Mundt said, “but that’s not the case.”
Sharp eyespot appeared in the valley at unheard of levels last year, causing yield losses as high as 50 percent in one field and between 10 and 20 percent in others, according to Mundt.
The disease was indiscriminate last year, appearing in wheat fields up and down the valley and on nearly all the common varieties, he said.
This year appears no different. Sharp eyespot is just as prominent, he said, and has been spotted in Central Oregon wheat stands as well, dousing hopes that last year’s outbreak was an anomaly that wouldn’t be repeated.
Mundt said he is finding it in every clump of wheat he pulls up in the valley.
Plants infected with the disease will exhibit black areas on stems, Mundt said, and at high infestation levels will lodge.
Mundt is speculating that a new strain, or population, of the sharp eyespot fungus, Rhizoctonia cerealis, is responsible for the infestation. He said literature shows it also is appearing in China.
The disease has appeared sparingly in the valley over the years, Mundt said, but never at high levels.
Among research being conducted on the disease, researchers are studying whether certain fungicides, such as the strobilurins, are effective at controlling it. “We’ll know at the end of this year,” Mundt said.
Researchers also are planning to put out trials this fall to study whether delaying planting can lower plant susceptibility.
Mundt also reported that barley yellow dwarf virus is appearing at unusually high levels in Willamette Valley wheat this year.
“This is the worst barley yellow dwarf I’ve ever seen in the valley,” he said.
He speculated that last fall’s high temperatures facilitated aphid survival, contributing to the spread of the disease. Aphids transmit barley yellow dwarf virus between plants.
Mundt said certain varieties, such as Bobtail, are showing better resistance to barley yellow dwarf than others. And, he said, if growers can hold off planting wheat until the end of October, it can help slow the spread of the disease.
“If you have any way to back off seeding to mid- to late October, it would be good not only for your individual farm, but for the valley as a whole,” he said.
In general, Mundt said, planting late lowers plant exposure to diseases.