More than drought affecting wheat yields

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Ninety-five percent of these samples were diagnosed with the wheat streak mosaic virus. In addition, 50 percent of the samples contained maize red stripe virus, more commonly known as High Plains virus. Both diseases are vectored by the wheat curl mite, Allen said. And so far, there's no treatment for either the viruses or the mite.

The Great Plains Diagnostic Network is a part of a national plant disease monitoring system, which is divided into five regions. The Amarillo facility, a satellite lab to one at Kansas State University, is operated under the Experiment Station's plant pathology program, headed by Dr. Charlie Rush.

Samples came by mail, through Texas Cooperative Extension agents or were dropped off by producers, Allen said.

They came from as far north as Nebraska and as far south as Dallas and the Hill Country, Rush said, making this one of the most widespread years for wheat streak mosaic damage.

"Without question, wheat streak mosaic virus is the No. 1 pathogen of wheat year in and year out," he said.

An early indication this wheat crop would have more problems than normal was the arrival of samples in the middle of October, Allen said, "which is pretty rare to see virus that early. "We've had quadruple the number of samples as any previous year," he said.

Once a crop is diagnosed with one of the viruses, there is little the producer can do, Allen said. Widespread cases can reduce yields enough that only grazing or making silage from the crop can salvage any income. In many cases, the crop is "zeroed out" by insurance companies and plowed up.

This year's virus started early because of last year's crop, he said.

A hail storm across much of the region shortly before harvest knocked the grain from the heads, Allen said. These seeds germinated into a heavy volunteer wheat crop, which went uncontrolled through the summer.

The wheat curl mite over-summered on this "green bridge" and moved into the new crop.

Control of volunteer wheat this summer will be key to controlling the wheat curl mite that vectors the disease, Allen said.

Rush and Allen believe the Conservation Reserve Program grasses throughout the region also might harbor the wheat curl mite.

"We don't have a good understanding of the wheat curl mite and its ecology," Rush said. "It holds on some grasses, but there's lots of work to be done to understand what happens with these mites during the summer."

Right now, he said, the only other advice they can give to producers is to plant as late as possible to reduce chances of severe wheat streak problems again.

"We're trying to develop some cultivars that can be resistant to wheat streak mosaic and could be planted early and then grazed out," Rush said. "They would be popular in this region and serve an important purpose."

The problem now, he said, is any resistance breaks down in high temperatures. And not enough is known about the wheat curl mite to tell producers when or what to spray.

"There are big gaps in our knowledge," Rush said. "But we are making progress and have things working in the field that should provide answers in the next couple of years.\\\

Texas A&M University—Agricultural Communications