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Ohio farmers escaped soybean rust for a second straight year, but whether the disease will arrive next season is literally up in the air.

"It all depends on the winter and the spring (and) what the weather does," said Anne Dorrance, an Ohio State University plant pathologist.

While the disease overwintered in Georgia and Alabama, drought conditions in the Southeast thwarted its spread this spring.

"Under those dry conditions, soybean rust just can't do anything," Dorrance said.

The lack of cool, moist weather, on which the disease thrives, even caused the presence of rust to decline from February to May, Dorrance said. In one case, soybean rust disappeared completely from a site in Montgomery, Ala. where it was detected early this year.

As of print time, rust has been found on soybeans and kudzu in 36 counties in seven states, according to the U.S. Department of Agriculture's tracking system. The northernmost detection is in South Carolina, although recent precipitation in some affected areas is increasing the spread of rust. Soybean rust will continue to build up in the southern United States through the fall.

After collecting two years of data, Dorrance now believes there must be a significant amount of rust in Tennessee by early July for growers in Ohio to be concerned.

"If the weather conditions are not conducive, we don't get buildup," she said.

In the meantime, researchers are continuing work to identify soybean varieties resistant to rust.

"There are some lines that are showing some resistance. Crosses have been made. And so we'll just see how fast we can get this moved into the germplasm," Dorrance said.

She said the rust resistance trait will likely operate similar to gray leaf spot resistance, which slows the rate that the disease takes over the plant.

"With that type of resistance, we should cut our fungicide use dramatically," she said.