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Soybean Rust: New Invasive Threat to Soybean Growers - December 2004
December 21, 2004
UNIVERSITY PARK, PA - A newly confirmed disease has the potential to cause serious losses to the nation's soybean crop, but researchers at Penn State are working to keep ahead of the spreading problem.
Soybean rust is a fungal disease that could cause large crop and economic losses to soybean growers because of decreases in yeild and/or increased fungicide application costs. Scientists have been tracking the spread of the rust as it made its way from Africa to Brazil and then northward across the Caribbean Sea.
One year before soybean rust was first discovered in Louisiana last November, the first confirmed sighting in the U.S., researchers at Penn State started working collaboratively with other agencies and the private sector to determine the potential movement of the disease and what effects it would have on soybean growers. According to Scott Isard, professor of aerobiology at Penn State, soybean rust originated in Asia over a century ago and has slowly spread to India, Africa and South America. Recently, it was confirmed in nine southern states. Symptoms of the disease include tan or brown lesions on the foliage of the plant, particularly on the underside of leaves. In addition to soybeans, the rust can infect about 100 other species, including sweet peas, green beans, yellow sweet clover and kudzu.
Researchers believe the airborne fungus arrived in the U.S. as a result of the high winds during the active hurricane season. Working with ZedX, Inc., an information technology company based out of Bellefonte, Pa, Isard was able to correctly predict that one of the hurricanes in the Caribbean this season had the potential to move the spores northward from South America. Weather-based transport models developed by ZedX and Penn State confirmed that Hurricane Ivan blew the spores to Louisiana from Colombia. "When the spores were discovered on a Louisiana State University research farm, we looked at images of diseased plants emailed to us and immediately recognized that the spores had been in the fields for about four to six weeks. ZedX then ran the spore transport model for all active source regions, and we were successfully able to track the spread of the disease," Isard explained. Field visits to scout for the disease, guided by maps produced by the spore transport model, confirmed its spread to eight other states, capping off the most accurate invasive species prediction effort to date.
Isard emphasizes that if the disease had to come to the U.S., it arrived at the best possible time. "Since it entered the U.S. at the end of the growing season, there were no yield losses. In addition, we have all winter to prepare for the next growing season and time to register and produce fungicides that are effective against soybean rust," Isard said.
Currently, Isard is leading a United States Department of Agriculture (USDA) Animal and Plant Biosecurity project that will take him and a Penn State graduate student to South America as part of a large team to study the aerial transport of soybean rust. "We'll be studying the progression of the disease and the movement of the fungus to determine best management strategies," he explains.
In addition, Isard will continue working with ZedX in a project funded by USDA Animal Plant Health Inspection Service (APHIS) to develop a system for forecasting soybean rust spore movement. By using over 24 years of daily weather data, they will develop models to create risk maps that will indicate where the pathogen could overwinter, and best places to monitor for the disease in the spring. "We'll also run the spore transport model to predict the movement of spores each day, and assess the risk of disease in soybean growing areas throughout the U.S. The model takes into consideration factors such as rain, which can wash the spores out of the air; ultraviolet radiation, which kills the spores while they travel; and wind to predict spore movement and survival," says Isard. "This will enable us to provide timely information to a grower on whether he needs to spray a fungicide, and the timing of the sprays."
In most years, Pennsylvania farmers will find their risk of soybean rust low to minimal. However, the disease still has the potential to cause 10 to 100 percent losses in individual fields. In a recent study, the USDA Economic Research Service indicated that the disease could cause losses up to $1.3 billion nationwide in its first year of establishment, depending on the extent and severity of the outbreak. Currently, research is being done around the world to find a resistant soybean cultivar. In addition, Isard also hopes to work with ZedX to further develop a Web-based decision support system that stakeholders could use to assess their risk and to select best management tactics.
For more information on soybean rust, see Web site https://netfiles.uiuc.edu/ariatti/www/SBR/index.htm. Funded by APHIS and sponsored by Penn State, ZedX, the ARS National Soybean Research Facility in Illinois and North Carolina State University, the Web site includes information on the life cycle of the disease, risk assessment, source area maps, project reports, and other information. To find out more about the economic impacts of soybean rust, download USDA's report at http://www.ers.usda.gov/publications/ocs/Apr04/OCS04D02/.
ZedX, Inc.is an information technology company that specializes in the development of weather-dependent, decision-support products for specific industries such as agriculture and energy. For more information on services offered ZedX, see the company's Web site at http://www.zedxinc.com/.
The Pennsylvania IPM program is a collaboration between the Pennsylvania State University and the Pennsylvania Department of Agriculture aimed at promoting integrated pest management in both agricultural and nonagricultural situations. For more information, contact the program at (814) 865-2839, or Web site http://paipm.cas.psu.edu/. To view our archived news releases, see Web site http://paipm.cas.psu.edu/10.htm.