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Corn+Soybean Digest


Nationwide, rust experts urge you to keep your guard up and stay vigilant for Asian soybean rust this year. Even though the disease spread slowly last year, they believe this year could be different.

“The hysteria is gone,” says Gary Schmitz, technical field manager for BASF. “We realize rust is manageable and that we may not have it every year.”

Last year, it's possible weather conditions in the South were too hot or dry at key times for the disease to develop and spread, says Dean Malvick, Extension plant pathologist at the University of Minnesota. He says that temperatures ranging from 66° to 80° are ideal for soybean rust, while temperature above 86° may retard the disease development. In addition, rain and dew are needed for the disease to become established and to spread.

A worry this year is that there's “a lot more inoculum in kudzu” than last year, says Marty Wiglesworth, technical manager for Syngenta Crop Protection. He adds that finding rust in Texas is more significant for the North than finding it in Florida because winds could blow inoculum northward.

In 2005, wind direction generally was unfavorable for spreading spores north, says X.B. Yang, plant pathologist at Iowa State University. “More winds in May through August moved from west to east, not north,” he says. “Also, last year was dry and not good conditions for rust. Yang also says the experts watch other plant rusts, like common corn and wheat rust, to get a sense of what will happen with soybean rust. “So far, the risk of having an epidemic this summer is not high,” he says.

If it does hit this year, however, you need to treat quickly because there's a short time window to spray, says John Pawlak, product development manager for Valent. “If you see it when you drive down the road at 60 mph, it's too late. It requires intensive scouting to identify,” he adds.

While there's still plenty to learn about rust and its spread, Malvick says to be prepared to manage it during the upcoming growing season.

  1. Track development and movement of soybean rust throughout the U.S.

  2. Scout for the disease at key times.

  3. Have a plan for fungicide use in case there's an outbreak.

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