Discovery of Rust Late in 2007 Was No Surprise

Soybean rust findings this year in Iowa are significant for future crop management.

As Iowa soybean growers finished harvesting the 2007 crop, Iowa State University were scouting late planted fields for signs of Asian Soybean Rust. And they found it in 14 counties across the state.

Asian soybean rust has been confirmed in 2007 in Adair, Dallas, Des Moines, Fremont, Hancock, Iowa, Johnson, Lee, Muscatine, Polk, Pottawattamie, Ringgold, Story and Washington counties. Although the development of rust in Iowa fields happened too late in the growing season to cause any real damage, it is a significant discovery for soybean producers.

"Discovering soybean rust in multiple counties clearly indicates that the disease reached northern production regions. Data suggest that the spores reached southwestern Iowa as early as August this year," says X.B. Yang, plant pathologist at Iowa State University.

August weather prompted the infections

The discovery of rust in Iowa this year was no great surprise to some. Checkoff-funded research conducted at ISU predicted the possibility. Yang has been refining a weather-based computer model to track the movement of rust spores from known infected locations and predicts where the disease may develop based on climate conditions. ISU leads the field in these efforts.

August rains are the likely culprit that sprinkled rust spores over Iowa soybean fields. When discovered, the disease was in its very earliest stages of development in most fields with the exception of Fremont County where disease development had progressed to 20% incidence.

Those scouting for the disease are individuals from the Iowa Soybean Rust Team First Detectors, a group of 700 highly qualified crop professionals trained to identify the disease by Iowa State University through a partnership with the Iowa Soybean Association. Iowa State University and the soybean checkoff began training First Detectors during the summer of 2004, before rust was found in the United States.

"Soybean producers need to continue to be vigilant and manage their soybean crop to optimize yield and profitability," says David Wright, director of contract research, Iowa Soybean Association. "Producers should increase the management of their soybean crop through increased scouting efforts."
Online resources for soybean growers include,, and  

Checkoff-funded Research on Asian Soybean Rust

The Iowa Soybean Association began investing soybean checkoff dollars into research on Asian soybean rust in 2002, two years before the pathogen arrived in the United States. The association has taken a global approach to finding ways to minimize yield loss from soybean rust.

ISA's initial investments focused on finding genetic resistance to the disease and determining the effectiveness of fungicides available to manage the disease. In 2002, ISA worked with the USDA and the United Soybean Board to utilize the disease containment facility at Fort Detrick, Md. to screen current commercial varieties for genetic resistance. We also worked with the USDA to test the fungicides against soybean rust in countries like Paraguay, Zimbabwe and Uruguay.

ISA's Key Investments

National Sentinel Plot Network – the main component of the U.S. safety network tracks known locations of Asian soybean rust. We have dozens of dedicated people monitoring Iowa's sentinel plots weekly.

Computerized prediction models – There are several models being developed, but the one ISA has been funding is the one at Iowa State University. Dr. X.B. Yang is one of the world's foremost experts on Asian soybean rust, working on it since 1989 when he worked at the USDA's research facility at Fort Detrick, Md. He collaborates with climatologists at St. Louis University using climate models to predict the movement of rust spores from known locations and predict where they might be moved to and where the disease is most likely to show up.

One of our most productive investments has been an investment in University of Florida Research station at Quincy, Fla.; an investment made through the North Central Soybean Research Program. USDA scientists told us that rust will likely show up in Iowa four years out of 10. So we as a checkoff board needed to find a way to enable scientists to conduct research on soybean rust without waiting for it to show up in Iowa.

Working with the North Central Soybean Research Program, the soybean checkoff enabled the University of Florida to allow Midwest researchers to conduct research at the research station in Quincy, Fla. As a result more than 50 man-years of research have been conducted on soybean rust in just two years.

ISA has helped Iowa State University train more than 700 Certified Crop Advisors to expertly identify soybean rust.

ISA invested checkoff dollars with the USDA to test fungicides against soybean rust and evaluate carrier volumes for best results. Because of this research we know that the fungicides available to us are effective against soybean rust if they are applied at the recommended rates and at high carrier-volumes (15-20 gpa).

Researchers at Iowa State are looking at how one of the four known resistance genes works. Through this research we may be able to improve the plant's resistance to soybean rust. This is long-term research but we feel it is necessary for the long-term profitability of Iowa's soybean producers.

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