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Corn+Soybean Digest

Soybean Rust Marches North

A case of Asian soybean rust has been confirmed about 5° north of the equator in South America by USDA's Agricultural Research Service and the Animal and Plant Health Inspection Service.

This confirmation, north of Cali, Colombia, signals the advancement of spores in the direction of the continental U.S., says American Soybean Association Chairman Ron Heck, a soybean producer from Perry, IA.

“Prevailing wind patterns around the equator served as a temporary barrier to a natural transmission of soybean rust spores,” Heck explains. “If soybean rust becomes established on host plants in Colombia, South America, it would, at least theoretically, be easier for airborne spores to be carried directly to the U.S. across the Caribbean Sea, or by way of the land bridge formed by Central America.”

Based on weather models and past experience with other diseases, experts predict spores would most likely enter the U.S. through the southern tier of states along the Gulf of Mexico.

Soybean rust spores are easily transported in air currents and spread rapidly over wide distances. Limited data are available on how long spores can survive, but studies have shown that under the right circumstances, spores can be viable for more than 50 days.

For more information, see “Vigilance A Must For Rust,” pages 22-24, August 2004 or log on to

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