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Corn+Soybean Digest

Hurricanes Likely Soybean Rust Carrier

This year's unusually active hurricane season may have provided the conduit for Asian soybean rust to land in the U.S., says an Iowa State University expert on the disease.

X.B. Yang, Iowa State plant pathologist, says the unusual weather increased precipitation, which may have provided a vehicle for spores from Colombia to rain down on soybean plants in the southern U.S..

"The number of hurricanes and precipitation events this year increased the possibility of spore dispersal" Yang says. "Rain is a factor in the survival of spores. This hurricane season was a once-in-40-year event, which may help explain how soybean rust was blown into the United States this year."

USDA announced the first incidence of soybean rust in North America in Louisiana. Now it’s also been found in Mississippi and Florida. A USDA report indicates that soybean rust has been found in 14 Louisiana counties.

Yang is a leading expert on soybean rust and spent part of last week examining soybean fields in Louisiana. He is a member of the USDA assessment team that responded to the confirmation of Asian soybean rust. The USDA team examined a 10,000-square-mile area. Team members searched late-maturing soybean fields and high-density kudzu areas. Kudzu is a common, vigorously growing weed found in southern states that may act as a host for soybean rust.

Yang has studied soybean rust since 1989 and uses weather models and maps to track wind movements that could carry rust spores. Yang and other researchers agree that soybean rust spores will be carried by winds into Iowa from the southern states sometime during the 2005 growing season. Researchers are now trying to estimate when and how soybean rust could impact Iowa.

"Soybean rust will not overwinter in Iowa. We will have to wait for the spores to travel from the south every season. It's too early to make predictions, but we need to make predictions based on spring rust occurrence in the south and early summer weather systems, such as tropical storms, that may influence its travel," Yang says.

Asian soybean rust is an aggressive fungal disease that can reduce soybean yield substantially, says Greg Tylka, Iowa State plant pathologist. The disease has the potential to cause extensive damage to soybean plants and can travel quickly through infected areas, depending on environmental conditions.

Tylka coordinated training sessions last summer for more than 400 certified crop consultants, certified professional agronomists and independent crop consultants as first detectors in a "fast-track" reporting system.

The fast-track system was developed to speed up reporting of soybean rust. The system is simple: producers submit samples to first detectors at no cost. First detectors send suspect samples to triage personnel, who are Iowa State Extension field staff, for further diagnosis. The triage person then forwards suspect samples to the Iowa State University Plant Disease Clinic.

The fast track system was prepared by the Iowa Soybean Rust Team to quickly identify soybean rust and efficiently manage samples submitted to the Iowa State Plant Disease Clinic. The team has worked for the past two years preparing to respond to the introduction of Asian soybean rust into the U.S. and Iowa.

Team members represent Iowa State University, the Iowa Department of Agriculture and Land Stewardship, the Iowa Soybean Association/Iowa Soybean Promotion Board and the USDA Animal and Plant Health Inspection Service. More information about the team and its action plan are available at .

Prior to the recent rust announcement, the Iowa Department of Agriculture and Land Stewardship applied and received permits from the EPA to allow producers to apply certain fungicides to manage soybean rust. The permits became effective as soon as the USDA confirmed reports of soybean rust in the U.S..

Asian soybean rust was first recorded in Japan in 1902. The pathogen moved throughout Asia, Australia and Africa before it was discovered in South America in 2000.

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