At least 16 cases of Asian soybean rust have been confirmed in six southeastern states this year, raising concerns about next year’s crop.

No damage has been done to this year’s soybeans in Iowa, because they have already been cultivated. But soybean producers are concerned that the rust may spread north in the next growing season.

Soybean rust, or Phakopsora pachyrhiz, is a contagious fungal disease that destroys soybean plants within three weeks of infection, said Alison Robertson, assistant professor of plant pathology.

It was located in Louisiana, Alabama, Arkansas, Georgia, Mississippi and Florida this past season. In Florida, the disease was confirmed to be present on kudzu, a weed-like plant that could host the disease and further spread it.

Some southern states are considering replacing soybeans with a different crop, said Xiao Bing Yang, professor of plant pathology, because the disease could incubate in about 90 other host plants like kudzu.

Greg Tylka, professor of plant pathology, said the disease is not easy to contain.

“There is not much that can be done to prevent the spread of this disease,” Tylka said. “It is a disease that can easily be moved from field to field by spores blown on the wind. But temperatures and moisture levels dictate whether or not the fungus thrives and causes a lot of yield loss.”

The environment has an important role in the effect of soybean rust.

“If we have a season like this past year, which was wet and cold, it could be pretty devastating,” Robertson said. “But, if it’s dry and hot, those conditions are not conducive for soybean rust, so it will not be as big a problem.”

Depending on weather conditions and wind patterns, the rust could spread through Iowa after the winter frost.

“It will spread very quickly,” Robertson said.

“It’s a very aggressive disease. It can defoliate a soybean plant in three weeks.”

Soybean rust can reduce soybean yield by up to 80 percent and could cost U.S. soybean producers from $240 million to $2 billion annually, according to the ISU plant pathology Web site.

“It’s predicted that 30 percent of soybean farmers in Brazil will be out of business in the next few years,” Yang said. “Iowa is not going to be that bad, because environmental conditions aren’t the same. I think Iowa is much better educated, and we have been preparing for years. We’re in a good position to handle it.”

Iowa State is providing training and education on the fungus for soybean producers, which will help minimize any possible breakout in Iowa.

“We’re doing a lot of training, teaching people how to identify the rusts,” Robertson said. “There are a lot of diseases similar to the rust.”

Rust identification and management programs are also being conducted at Iowa State, to help soybean producers learn how to deal with rust if it gets here. Currently, the only way to kill the fungus is with fungicide.

With fungicide, Brazil lost only 6 percent of its soybean yield, but without it, production losses can be extreme, she said.