Iowa Public Television


Asian Soybean Rust Spreading

posted on October 19, 2007

In its latest "guesstimate," the Agriculture Department predicted U.S. growers will harvest 2.6 billion bushels of soybeans this fall -- down nearly 20 percent from last year. Exports, on the other hand, are at all-time highs.

According to the United Soybean Board, soybean exports totaled a record 1.1 billion bushels for the marketing year that ended last August. China retains its title from last year as the top consumer of U.S. soybeans, importing 420 million bushels in the past year -- up 18 percent from the previous year.

Hoping to capitalize on increased demand, U.S farmers are expected to increase soybean acreage significantly next year. Increasingly though, growers must contend with a fungus the rest of the soybean-producing world knows all too well.

Asian Soybean Rust Spreading

Asian soybean rust, which can cut yields by as much as 80%, will not have much effect on yields this year even though the fungus has been found in 216 counties in 18 different states. That's a dramatic increase from a year ago when only 88 counties in 8 states reported rust sightings.

Tracy Blackmer, Iowa Soybean Association: "Some of the stories we've heard now in South America, in a matter of a week, you can go from something that looks healthy, where you aren't seeing many symptoms, to the point where the whole field can be dead."

Before being found in two fields in Louisiana in 2004, North America was the only soybean-producing continent unaffected by the disease. The spores of the fungus that cause the rust are dependant on winds to spread and need proper temperatures and moisture to infect susceptible hosts.

Tracy Blackmer, Iowa Soybean Association: "Now that we've had it for several years in some of the southern states, you know the question is will we be getting more of it closer to the frost line in certain years, that won't be as cool and kill it as much. And, what weather patterns have we got moving it up for it to really spread and take hold."

In Iowa, the nation's top soybean producing state, growers are taking a proactive approach to battling the fungus. Field tests are being conducted to compare yields of soybeans treated with a fungicide, with plants in the same field that did not receive treatment.

Dennis Bogaards, Pella, Iowa: "Well this year after we combined them, we found somewhere around 5 to 7 bushel yield difference between sprayed versus not sprayed. This about the third year that we've done fungicide trials and the previous 2 years has been about break even. Running anywhere from 2 to 4 bushels yield advantage, and this year we found economic yield advantage to spraying them."

The tests are expected to give growers a better idea of when a fungicide is a cost effective deterrent in the battle against soybean rust.


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