June 18, 2004
An Iowa State University plant disease expert says it is unlikely that soybean rust will reach the continental United States and impact soybean production this year.
X.B. Yang, a professor of plant pathology at Iowa State, has studied the disease since 1989. He said rust has hit every continent where soybeans are grown in the world except North America.
Yang and experts at St. Louis University are using maps and models to track winds that could carry the rust spores to the United States. Yang and other experts agree that the fungal disease will eventually arrive but is unlikely to be carried to North America by winds this year.
"The disease would take a long time to travel through the Amazon basin," Yang said.
Pulling out an atlas as big as his desktop, Yang leafs through its pages to point out how the Andes Mountains act as a barrier. He also points out that although rust has hit hard in Brazil, Argentina, a neighboring country, hasn't had many problems.
"Currently the disease is causing the most damage in the subtropical regions near the equator," Yang said.
Yang brings out another map that compares the spread of rust in China to what could occur in the United States. He and other experts have developed models that predict how the pathogen might travel if wind-borne spores land in the southern region of the United States.
"A model is built by inputting environmental information," Yang said. "This helps us predict what will happen with diseases just like a meteorology forecast predicts the weather. We want to forecast what will happen in Iowa as well as other states in the north central region."
Greg Tylka, plant pathology professor at Iowa State, said he's concerned about the apprehension over a disease that hasn't been found on this continent.
"This is the first time I've seen people so anxious before a problem shows up. I'm afraid that some are on the verge of overreacting," Tylka said.
To alleviate fears, Tylka said it's important to give farmers and crop professionals up-to-date information about soybean rust, which is the goal of the Iowa Soybean Rust Team formed last fall. The team includes representatives from Iowa State University, ISU Extension, Iowa Department of Agriculture and Land Stewardship, the Iowa Soybean Promotion Board/Iowa Soybean Association and the U.S. Department of Agriculture Animal and Plant Health Inspection Service.
Tylka advises people to look to the Iowa Soybean Rust Team for timely, accurate and science-based information. The team has developed a plan to train nearly 1,500 certified crop consultants, certified professional agronomists and independent crop consultants in July. The purpose of the training is to assist in the accurate and rapid identification of soybean rust if it arrives in Iowa.
"We want to emphasize that there a lot of people paying attention to this, that we have a good system to check for soybean rust and producers should be very cautious about any unverified information they hear," Tylka said.
Rust can be treated with fungicides and researchers are worried that farmers are stocking up on chemicals that have a short shelf life. Yang said he's heard of farmers purchasing tens of thousands of dollars in fungicides in anticipation of the disease.
"We believe that it will be very unlikely to have rust infestation this season in Iowa," Yang said. "Some may be stocking chemicals they won't need in the near future."
Tylka also believes that rust will not land in North America this growing season. And if it is carried by winds to the southern United States it would not appear in Iowa until later in the growing season.
"It likely won't arrive until August or later because it will take time to get established," Tylka said. "If this disease shows up with only a few weeks of the growing season left, it's not going to cause as much damage as it would if it were present throughout the season."
Asian soybean rust was first identified in Japan in 1902 and was carried by the prevailing winds to Australia in 1934 from there it traveled to Africa. It was found in South America in 2001.