Integrated Crop Management News

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Improving glyphosate performance in Roundup Ready soybean

July 3, 2008

By Bob Hartzler, Department of Agronomy

Although glyphosate resistant weeds have been documented in states surrounding Iowa, at this time our only confirmed glyphosate-resistant species is horseweed/marestail (Conyza canadensis).  However, over the past decade we have selected for a weed spectrum that possesses a higher level of tolerance than was present at the start of the Roundup Ready era of weed management.  Because of this, glyphosate control failures are more common now than they were ten years ago.

Corn Following Corn in 2008

July 3, 2008
Plant height differences between sorn following soybeans and corn following corn

By Mahdi Al-Kaisi, Roger Elmore, Antonio Mallarino, Palle Pedersen, Alison Robertson, John Sawyer, and Jon Tollefson

Degree Days Continue to Lag

July 1, 2008
Image of base 50 degree F degree days in regions of Iowa from May 1 to June 29, 2008

By Rich Pope, Department of Plant Pathology

Another week of slightly cool days with scattered storms has Iowa farmers facing uneven stands in many fields. Cumulative heat during the week of June 23 lagged behind long term averages by 10 to 25 degree days in Iowa. The cool temperatures and still wet soils provide stresses to struggling crops, and those stresses are showing up in poor growth.  As we get more heat the corn and soybean should recover, but this early summer has predisposed the crops to future stresses.