( y cases the crop is zeroed out by in...)More than drought affecting wheat yields

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 tellproducers 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."