Another day free of soybean rust

By Jean Caspers-Simmet

NASHUA, Iowa -- Midwest; soybean growers have dodged the Asian soybean rust bullet so far, and each day that goes by is one day closer to not having a problem this season, says Iowa State University Extension Pathologist Greg Tylka.

Speaking at last week's field day at the Northeast Iowa Research Center at Nashua, Tylka provided an update on where rust has been found.

Rust was found Nov. 10 in Louisiana and by the time the dust settled it had been identified in 9 states.


"I don't mean to worry you but soybean rust needs green leaf tissue to survive and by mid-November there are a lot of places that have no green leaf tissue,'' Tylka said.

Tylka said USDA's soybean rust web site shows that for 2005, the disease has been reported on soybeans in Baldwin County, Alabama; Marion County, Florida; and Seminole County, Georgia. The Alabama and Florida finds were in sentinel plots, while the George find was on volunteer soybeans which have since been destroyed. Six counties in Florida have reported soybean rust on kudzu.

Tylka said intensive scouting continues wherever soybeans are grown.

"No rust has been found in any soybean production fields in the country,'' Tylka said. "In December, I would have wagered $1,000 that soybean rust would have been found in many production fields in the United States by now.''

Tylka said there are look alike diseases. Brown spot, bacterial blight and bacterial pustule have some similar symptoms. Cercospora is a leaf blight that appears mid- to late-season and turns leaves a bronze color, and has also been confused with soybean rust. ISU, the USDA and the Iowa Department of Agriculture and Land Stewardship have set up a fast track system to assist producers identify soybean rust, Tylka said. Six-hundred first detectors are trained in Iowa. Their names are available at or from local ISU Extension offices. If a first detector agrees a soybean sample looks like it is infected with rust, they contact one of 40 ISU Extension triage members. They decide if a sample should be sent to the ISU Plant Disease Clinic at Ames. The first couple of times soybean rust is identified in Iowa, samples will be sent to the USDA Lab in Beltsville, Md. for confirmation.

"My gut feeling?" Tylka said. "I can't believe it's July 1 and there is no rust. Each day that passes I more optimistic that if it does get here, it will be so late it won't matter much.''

Tylka said the tropical storms and hurricanes are a wildcard because they move things around more "but they can't move something that's hardly there in the first place.''

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