Some growers who own cattle are often tempted to let their volunteers grow and provide late-fall forage for the livestock, but this is a dangerous practice for neighboring wheat fields, Falk Jones added. Although they prefer the newest, most tender plant tissue, wheat curl mites can live on any part of the plant that is green.

"If you're grazing the top of the wheat, they can still survive near the base of the plant, so while you might be decreasing populations of those mites, there are still ones out there that can move and cause problems," she cautioned.

Although the mites prefer wheat, they can also survive on certain grassy weed species, particularly jointed goat grass, field sandbur and many foxtail species.

When a host plant dies and dries out, the mites move to the top of the plant and use the ever-reliable Kansas winds to drift to new plants and, eventually, new fields.

"One way to think about how they move is like smoke fanning out from a single source," Falk Jones explained. "They can easily move a quarter of a mile, but can move farther on wind currents."

Wheat streak mosaic symptoms in a field often display this same pattern, with symptoms at their most severe near the source of the infection and gradually dissipating farther away, she added.

This mobility has turned the mite into a community crisis, with every farmer's management affecting his or her neighbors.

Engler has seen this dynamic up close in his region. Absentee landowners and the sudden turnover of rental land can leave some fields without good weed and volunteer control -- and doom their neighbors' wheat.

In 2017, one un-tended field spread wheat streak mosaic to other fields around it for miles and cost Engler and his neighbors a lot of yield. "It's really out of your hands -- there's nothing to do once it gets started," he said.

"There has to be a neighborhood effort to control this," said Falk Jones.

PICK VARIETIES CAREFULLY

Since 2015, Engler sees wheat varieties differently.

"We certainly look at wheat streak mosaic resistance more than we used to," he said. "I probably wouldn't pick a variety unless it had some decent tolerance to it now."

Growers have a smattering of options here, Falk Jones said. Wheat varieties Joe, Clara CL and Oakley CL show good resistance to the virus, but that protection starts to break down when temperatures climb above 75 degrees. TAM 112, Byrd and Avery varieties can also offer some virus protection, by slowing mite reproduction, Falk Jones said.

Planting wheat a little later in the fall can reduce the risk that the crop will emerge when wheat curl mite populations are large and looking to move, Falk Jones added.

Kansas State University researchers are also actively breeding wheat with a new resistance gene, WSM3, which will protect wheat from all three mosaic viruses -- and this type of resistance will persist even in higher temperatures. However, varieties with this new gene are still several years from commercialization.

Read more about wheat streak mosaic virus and its management from Kansas State University here: https://www.bookstore.ksre.ksu.edu/…

Read more and from Kansas Wheat here:

http://kswheat.com/…

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee

(PS/AG)

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