As recently as November, only Louisiana was known to harbor the deadly soybean rust spore pushed northward from South America in 2004 by Hurricane Ivan.

In just a few weeks, a fungal disease that can cut yields by 80 percent or more had spread to eight other states, including as close to Nebraska as southeast Missouri.

Depending on the depths of winter temperatures and the heights of summer humidity readings here, Rising City farmer Bart Ruth and others in the nation's fifth-leading soybean state could face trouble in a matter of months.

"I think everybody from academics to farm groups thought that it wasn't a matter of if it gets here, but when it gets here," Ruth said as he looked ahead to another round of soybean planting in May.

In Brazil and elsewhere in South America, soybean growers are using fungicides to keep rust under control and to keep their yield losses in the 10-15 percent range. But the cost to treat in dollars can easily rise as high as $15 an acre, Ruth said, and it can take as many as three treatments to get the job done.

And those aren't the only reasons to regard rust as one of the worst disease problems since soybeans caught on as a significant part of field crops in Nebraska decades ago.

"It's very hard to diagnose," said Victor Bohuslavsky of the Nebraska Soybean Board in Lincoln. "The average individual is not going to catch it. And by the time he sees something that makes him recognize what it is, it's already too late."

Beyond that, resistant soybean varieties are probably at least five years away.

Still, Ruth, former national president of the American Soybean Association, and Loren Giesler, a plant pathologist at the University of Nebraska-Lincoln, point out that Nebraska has some natural advantages to hold the disease in check.

Primary among them is a requirement of green plant tissue for disease spores to last from one growing season to the next.

That is much less likely to be the case in Nebraska in the middle of winter than in leading soybean states farther south.

"We're far enough north that the spores can't over-winter," Ruth said. "If we get it, most people put the odds at less than 50 percent for annual infestations."

Furthermore, Nebraska is not as much in the path of the humid air and airborne spores that typically move northward from the Gulf of Mexico toward such prominent soybean states as Iowa and Illinois.

Giesler said rust still ranks as "the most destructive disease of soybeans that we will have in the United States."

However, "there's been a lot invested in being ready for when this would occur."

It may even turn out that Nebraska can turn adversity to advantage. If colder winters block the spores' advance, farmers in a state better known for corn production might be able to profit from the higher prices that go with reduced soybean acres farther south.

And being able to spare the fungicide treatments might give Nebraska some niche markets in importing countries concerned about any related health risks.

"Rust," said Giesler, "could potentially increase profits for Nebraska producers."

Reach Art Hovey at 523-4949 or at ahovey@alltel.net.