October 25, 2008


Asian soy rust reaches US soy belt


Asian soy rust has moved into the core of the US soy belt. It was discovered Thursday for the first time this season in Illinois, Missouri and Oklahoma, states forecast to harvest 20 percent of the nation's 2.983 billion bushel soybean crop this fall.


The disease was detected on soy in McLean County in central Illinois, in Scott County in eastern Missouri, and in Bryan County in southern Oklahoma, reported the USDA, through the agency's official rust Web site. "The disease has now been detected in 15 states this year" compared to 18 as of late October 2007.


Although the airborne plant fungus has now spread to within about 125 miles of Chicago, it is not expected to produce significant yield losses, occurring near the end of the growing season at a time when many fields have already been harvested.


"In spite of the rust find in Bryan County this week, there is no need to scout or treat for rust in soybeans in Oklahoma," said Oklahoma State University plant pathologist Jahn Damicone. "Soybeans in the state have advanced past vulnerable growth stages or have been harvested. The current rust find - and any future rust finds - are of biological significance, but are not economically important and cannot damage the current crop because pods have already filled."


The USDA warns that soy rust will continue to spread northward until a fall frost ends the annual growing season.


"Winds are expected to transport spores across the eastern US, as well as Ontario and Quebec, later this week," said the agency in its latest risk assessment. "Expected rain and clouds in the region will create a moderate risk for spore deposition and survival throughout all areas east of the Mississippi River through Saturday."


Soy rust, which cuts grain-yield by causing premature defoliation of infected plants, is a major plant pest in South America. It first appeared in the continental US about five years ago, but has thus far failed to become a significant agronomic threat.

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