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1/4/2010 - 1/10/2010

Iowa Crop and Weather Report Week of Jan. 4

By Doug Cooper, Extension Communications and External Relations

Crop and weather report guests are Iowa State University Extension climatologist Elwynn Taylor and corn agronomist Roger Elmore. On the first Monday of 2010 with frigid cold covering the state, guests discuss the current cold wave and 2009 national corn yield contest.

Taylor discusses current Arctic polar outbreak and how the Arctic front has cycled around and belongs around Des Moines this year. He reports our weather is on the cold side of usual by 15 to 20 degrees for the most part, compared to normal.

Elmore and Cooper talk corn yields and how our unusual weather impacted yields. Elmore says a Keokuk producer had the top yield in the non-irrigated class of the national competition with a 298 bushel yield; this was also the best recorded yield in Iowa.

2009 Soybean Rust Summary

Daren Mueller, Department of Plant Pathology

Soybean rust once again did not make it to Iowa in 2009, but it wasn’t from a lack of trying. Rust was found early in Louisiana and eventually was found at high levels throughout the Southeast. These – overwintering finds and high levels of inoculum in the South – are two prerequisites for rust getting to Iowa.

Where did it peter out in 2009? There was a long time between the initial finds in Louisiana (Jan. 14) and the first finds during the season in Arkansas (Aug. 10) and Mississippi (Aug. 6). Why, I’m not quite sure. It probably has something to do with the levels of infection and how widespread the pathogen survived the winter. Although it was found early in Louisiana and it survived in some counties in Florida, the pathogen still has not survived overwinter at levels seen in South America. This likely has lengthened the time between overwintering finds and soybean rust finds during the season.

The weather conditions were ideal in early August for disease development, and rust really took off. While it did not reach Iowa, it did spread to an unprecedented 575 counties including most (or all) of the counties in Arkansas, Louisiana, Mississippi, Alabama and Georgia (see map). Soybean rust was found in 16 states, the furthest north being in Illinois. By comparison, in 2008 soybean rust was found in 392 counties.

soybean rust map

An interesting development during the 2009 season was that soybean rust finally established early enough in some states to require management. There were reports of growers spraying fields for rust and experiencing yield loss in fields that were not treated. However, these were all in the South as soybean rust has yet to cause yield loss in any Midwestern states.

With the widespread movement of soybean rust in 2009 throughout the southeast, we will be keeping an eye on how well the pathogen overwinters. Remember the pathogen needs living tissue to survive. Where and how much rust survives will influence the early season establishment of rust next year. The good news is that some cold snaps already dipped fairly far south.

This past season also marks the last year a Section 18 fungicide for soybean rust was available. The Section 18 labels for Punch and Topguard have expired. Punch will not be available for soybean and EPA still has not decided on Topguard.


Daren Mueller is an extension specialist with responsibilities in the Corn and Soybean Initiative. Mueller can be reached at (515) 460-8000 or by emailing

This article was published originally on 1/11/2010 The information contained within the article may or may not be up to date depending on when you are accessing the information.

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