Soybean Rust and Late Planted Soybeans

August 6, 2008

By Daren Mueller, Department of Plant Pathology
Iowa producers are asking if soybean rust will affect the late planted soybean crop. Taking a look at current U.S. locations of soybean rust and understanding the movement of the rust, helps answer the question for Iowa producers.

Where is soybean rust currently?
Soybean rust is reported in five states - Florida, Georgia, Alabama, Louisiana and Texas, with the majority of the finds in Florida. Outside of Florida, soybean rust only has been reported in seven counties, the furthest north and west being in a kudzu patch in eastern Texas.  

How fast is soybean rust moving?
Compared to 2007, soybean rust is moving much slower in the southern states, namely Louisiana and Texas. On April 19th, a trace amount of soybean rust was found on the new growth of kudzu at a kudzu sentinel site in Polk County, Texas in the eastern part of that state.

Since that find, the weather turned dry throughout the southern half of Texas, and soybean rust has not moved out of that kudzu patch. In fact, drier than normal conditions continue to plague much of the southeastern U.S. (see Figure), which has slowed the movement of soybean rust, much like 2005 and 2006.

So will the late planted soybean crop in Iowa be at risk?
Right now, the chances of soybean rust moving into the Midwest anytime soon appear to be low. Movement of soybean rust in late September and October has been the trend the past few years, and this year appears to be no different.

According to Palle Pedersen, late planted soybeans will reach growth stage R6 (full seed) September 10 - 20. We will continue to monitor movement of soybean rust to be sure these late-season crops will not be affected, but for now there is not much movement to monitor.

Soybean rust - Mueller. 2008

Monitor weekly soybean rust updates
The Iowa State University Soybean Rust website has been overhauled. The new version highlights weekly messages written throughout the growing season that provide up-to-date information on soybean rust.

Individuals can sign up to have these reports e-mailed to them. The website also provides the basics and management of soybean rust, as well as fast facts about soybean rust.

 

Daren Mueller is an extension specialist with responsibilities in the Corn and Soybean Initiative.

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