A New Decade for Soy Rust

February 22, 2010 06:00 PM

Pam Smith, Farm Journal Seeds & Production Editor
The new decade may have started with Southerners shivering, but it wasn't enough to discourage the first outbreaks of soybean rust. The state of Florida turned red with the first positive soybean rust outbreak of the year on Jan. 4. Outbreaks in Louisiana and Georgia followed a few days later. Soybean rust has also been reported on jicama in the state of Tamaulipas in Altamira municipality in Mexico.
The disease was found in kudzu, the wily weed where soybean rust prefers to overwinter. Clayton Hollier, Louisiana State University Ag Center plant pathologist, says the disease could be evolving.
"I'm not certain if rust is getting tougher, but something interesting is going on with the survival of rust during colder temps lately,” he says. He points to newly formed rust pustules with new sporulation as evidence. By collecting the fresh spores, Hollier was able to get 10% germination. At this time of the year, kudzu that survives is generally in a protected area.
In 2009, soybean rust was found in 16 states and more than 576 counties in the U.S., and in three states and nine municipalities in Mexico. Last year, high levels of the disease spread across the Southeast and established early enough to require treatment in that region. Soybean rust spread as far north as northwestern Illinois in 2009, but arrived too late to threaten crop yields.
Hollier says fungicides have done a good job of controlling rust in Louisiana. "The growers in the southern half of the state are applying fungicides for other diseases and controlling rust too,” he reports. "Those in the mid- to upper states are applying for soybean rust as needed. There were a few incidences this past season where fungicides were applied too late and significant yield losses occurred.”
Follow soybean rust's path at USDA's Integrated Pest Management Web site: www.sbrusa.net.

You can email Pam Smith at psmith@farmjournal.com.

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