June 4, 2004
By Jim Paul
Source: Associated Press
URBANA, Ill. - Researchers led by a University of Illinois professor are developing a tool that could give American farmers early warning of the approach of soybean rust, a relentless disease farmers worry could destroy soybean crops if it arrives in the United States undetected.
The U.S. Department of Agriculture says the disease's arrival here is inevitable and has acknowledged it will be impossible to eradicate. Isard and his colleagues have developed a computer model that could help farmers make critical decisions regarding their soybean planting and show just when fungicide, which can limit crop loss, should be applied.
"We can run our models on forecast weather data and then we can divide the country into high-risk areas, medium-risk areas and low-risk areas on a daily basis," said Scott Isard, an aerobiologist and geography professor at the university's Urbana-Champaign campus.
Soybean rust disease has been moving around the planet for the past 30 years, with outbreaks in Australia, Africa and South America so far. In the past three years, it has taken hold in Paraguay, Brazil, Argentina and Bolivia.
The disease thrives when it is warm and moist and causes premature leaf loss, which leads to a smaller number of bean pods, fewer seeds per pod and reduced yield. Fungicides can reduce the damage, but when left uncontrolled the disease has caused as much as 80 percent loss in some fields.
As an aerobiologist, Isard studies the movement of organisms through the atmosphere. Backed by a $104,000 grant from the Animal and Plant Health Inspection Service of the USDA, he and colleagues last July began developing a way to use computers to simulate the spread of soybean rust.
The spores that cause the plant-destroying fungus travel on the wind until they are killed by exposure to the sun or washed out by rain, Isard said. If they land on a soybean plant or another host plant, they can take hold, reproduce and spread again.
The researchers have plotted several potential paths of travel that could advance the disease northward, Isard said.
Next they want to learn more about the disease's traits and apply that information to weather forecasts rather than historical data, Isard said. A separate, $900,000 USDA grant will help establish a field trial in Paraguay, where soybean rust is present, so researchers can learn how spores get out of a field and into the atmosphere and how that's affected by the weather, he said.
"It's extremely important," said Glen L. Hartman, a National Soybean Research Laboratory scientist and soybean rust researcher who is not directly involved in the computer modeling. "This gives us an idea about what the potential spread will be like should it get into the United States."
Soybean rust's arrival in the United States has been delayed because the Southern Hemisphere's growing season is opposite that of North America. Once the fungus crosses the equator, it's just a matter of time, wind and rain when it will jump the Caribbean Sea and Gulf of Mexico or spread through Central America, Isard said.
"Once it gets north of the equator, it could be a matter of months" before it's found in the United States, Hartman said.
Brazil lost about $1.3 billion to the disease in 2003, much of that spent on the fungicides that helped keep crop losses to about 5 percent, according to the USDA.
Efforts are under way to breed soybeans that are resistant to rust, but those efforts are unlikely to produce results for several years