As of Dec. 10, nine U.S. states had confirmed cases of Asian soybean rust, a fungus that causes up to 80% yield loss in heavily infected fields. The affected states are Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, Missouri, South Carolina and Tennessee.

It's believed the spores rode Hurricane Ivan's winds into the southern tier of U.S. states from South America last fall. Fortunately, the transfer occurred after most of the soybean crop had been harvested.

Most soybean varieties grown in the U.S. have little or no known resistance to the fungus, but foliar fungicide applications have proven effective in controlling soybean rust in Brazil.