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East-Central and Southeast Iowa Crop Information


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April 4

April 4, 2012


Do I Really Have to Wait Until Mid-April to Plant Corn? 

          With the record breaking temperatures in March and soil temperatures well above 50F, it is very tempting to get some corn in the ground. I know there are at least a few hundred acres of corn planted in the area with most of it up already. It could turn out to be a good decision. On the other hand I remember it was just 2 years ago that we had a freeze on May 9. Any March planted corn would likely need to be re-planted if we have another freeze in May this year. Most of the corn that got frozen 2 years ago still had the growing point below ground, so it did re-grow, but some found out it did not completely recover from that stress and so yields were reduced. With some forecasts predicting temperatures in the 20s later this week in parts of Iowa, I think I’d be more comfortable with the seed still in the bag. I agree with Roger Elmore’s recommendation to at least wait until the April 11 crop insurance date and then see what the soil temperature and forecast is. For more discussion on when to plant corn see Roger Elmore’s article at


Will We Have More Insect Problems Because of the Mild Winter? 

            The insects I would be most concerned about are those that over-winter as adults, since they are a little more vulnerable to winter temperatures. This would include bean leaf beetles, corn flea beetles, and alfalfa weevils. Before this winter we had several colder than normal winters, which may have helped to reduce problems with these insects. Hopefully it will take more than one mild winter for populations to rebound. According to the accumulated growing degree days, it is already time to start scouting for alfalfa weevils, which is over a month earlier than normal. There have already been reports of alfalfa weevils near the economic threshold in NE Iowa. The easiest way to scout for alfalfa weevil is to start with a sweep net just to survey a field.  If you catch some alfalfa weevil in the net, then follow the proper scouting procedure in the following ICM article (in the paragraph above Table 1) to determine if the economic threshold is reached.   Table 1 only goes up to $100 per ton alfalfa hay value, so a bit of common sense extrapolating of the economic threshold beyond the $100/ton hay value price may be warranted.


Killing Cover Crops 

For those using winter rye as erosion control cover, not as a forage crop for harvest, it’s time to kill it off.  You don’t want it to get too tall for several of reasons:   1) the more growth, the harder to kill, 2) the more growth, the more allelopathic compounds produced that could interfere with the following corn crop yield, and 3)   killing off the winter rye earlier will conserve soil moisture.  If you have 25 minutes, an excellent webinar on Managing a Winter Rye Cover Crop by Jeremy Singer is available for viewing at:    It’s the third webinar below the “2011 ILF Webinar Archives” heading.  The discussion of spring management on killing off the rye ahead of corn planting is about half-way through the presentation.  In addition to the webinar, Dr. Singer has a publication on this subject at:



          The warm temperatures have produced a bumper crop of winter annual weeds in some no-till fields. It probably makes more sense to take care of those soon with some 2,4-D and/or Roundup, and come back later with the residual soil herbicides. The larger weeds may take more than the pint/A rate of 2,4-D. Soybeans can be planted 30 days after the quart rate of 2,4-D.


25th Anniversary Celebration of ISU SE Research & Demonstration Farm – Crawfordsville

June 21 2012 

Details Available Later


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

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Last Update: April 4, 2012
Contact: Jim Fawcett

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