Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


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May 18, 2010



Post Herbicides on Stressed Corn


Although we didnít have as much frost injury in the area as in some other parts of the state, the corn has been under stress with this cold, wet weather. This makes it more vulnerable to herbicide injury. Ironically it makes the weeds less vulnerable to be killed by the herbicides, since the best herbicide activity is seen when the weeds are healthy and actively growing. Because of this it would be best to wait an extra day or two before making the herbicide applications if the weed and crop size and weather forecast will allow it. It definitely would not be advisable to be using UAN as a carrier if the corn has emerged, since this will increase the corn injury. If the corn has emerged and the application was planned to be applied preemergence, make sure the label allows for applications after corn emergence. For additional comments on the subject, see Bob Hartzlerís article at




Check Plants for Seedling Diseases


The cool, wet weather may result in increased seedling diseases in both crops this spring. When checking plant stands, itís important to do some digging and check the health of the below ground portions of the plant. Seedling rots often affect the mesocotyl in corn (part between the seed and nodal roots). Check to see if it is firm and white or becoming brown and mushy. Fungicide seed treatments help to protect the developing corn seedlings, but with the extended period of cool weather, seedling diseases can still develop. See the Alison Robertson and Gary Munkvold article for some additional discussion and pictures of seedling rot at


For soybeans emerged or not, we need to evaluate the hypocotyls and roots.  The hypocotyls should be firm. Emerging soybean fields should still be watched for a short while after emergence just to be sure that damping-off is still not an issue.  If germinated seedlings were infected during this cold spell, itís possible to have a ďpost-emergenceĒ damping-off as discussed in the following publication:




Farm Progress Hay Expo, Strawberry Point

June 17-18


For details about the program, exhibitors, etc. go to:






The Spring Field Day of the Southeast Research and Demonstration Farm (Crawfordsville) will be on the afternoon of Thursday, June 24, 2010 at the farm.  Certified Crop Advisor (CCA) credits will be available.  The field day will feature Erin Hodgson on new advances in soybean aphid management, Matt Helmers on Tile Drainage Research results, Emily Heaton, on Miscanthus and other Cellulosic Ethanol Crops, and Johns Sawyer on Nitrogen Management and Cover Crops. In addition, Certified Crop Advisors can obtain additional hours of credit (including soil and water) by attending a special session in the morning (9:00 a.m.) followed by the afternoon tour (1:00 p.m.).  Soil drainage will be featured in this special session. More details will be posted at


Northeast ISU Research Farm Field Day, Nashua

June 30



Field day speakers include:   Ken Pecinovsky, Farm Superintendent, Robert Hartzler, ISU Extension Weed Scientist, Alison Robertson, ISU Extension Plant Pathologist, John Sawyer, ISU Extension Soil Fertility Specialist, Chad Ingels, ISU Extension Program Specialist, and Brian Lang, ISU Extension Agronomist. CCA Credits available for a fee.



If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: May 18, 2010
Contact: Jim Fawcett

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