Wichita ? An unidentified wheat virus has agricultural scientists in Kansas scratching their heads.

The pathogen causes wheat leaves to yellow and die, but it’s not caused by wheat streak mosaic, head death or freeze.

“We’re pretty sure it’s a virus,” said wheat breeder Joe Martin, who works at the Kansas State University research station at Hays. “It showed up early and, at first glance, we thought it was streak mosaic. But it’s not. It kills the oldest leaves of the plant and finally kills the head.”

Researchers don’t know what the virus is, where it came from or how it spreads.

Martin said he had seen evidence of the virus in almost every field he had checked in western Kansas, but it hadn’t taken over the crop. He encouraged farmers to be on the lookout when checking their fields.

Dallas Seifers, a plant pathology professor at Fort Hays State University, is trying to determine how the pathogen works and what it might be.

“It’s possible that this is something that has been identified somewhere else in the world, even something that has shown up in a different crop, corn or rice or something,” Seifers said.

Seifers, with the help of some virologists in Winnipeg, Canada, is trying to identify the protein that causes the virus’ symptoms. That’s complicated by the fact that most affected plants found in the field are already dead.

Seifers is trying to grow his own supply of infected plants to study, but the effort hasn’t been as successful as he hoped.

“The worst-case scenario is I won’t be able to maintain it long enough, and I’ll have to wait until next spring and start over,” Seifers said.

Once researchers do identify the protein’s genetic sequence, they can compare it with known pathogens to find a match, or one that is in the same family.

Seifers said it was possible that the virus was showing up now because of recent unusual weather patterns, and that it wouldn’t show up in a normal year.