Ample soil moisture and warm temperatures are resulting in rapid corn growth as well as rapid weed development. In order to get the most effective results from postemergence herbicides, University of Illinois Extension Weed Specialist Aaron Hager offers a few recommendations.

“Before you apply, scout corn fields to accurately determine the crop’s growth stage,” Hager says. “Adverse environmental conditions can result in corn plants that are physiologically older than their height suggests, so assess the plant’s developmental stage by evaluating leaf/collar number in addition to plant height.”

Look for the maximum corn stage listed on the respective herbicide label and do not apply the product if corn exceeds the labeled stage, he adds. If tankmixing two or more products, follow the most restrictive corn growth stage listed on any of the tankmix component labels.

With the increased occurrence of glyphosate-resistant weed populations and weed species that are inherently less sensitive to glyphosate, tankmixing products with glyphosate to control these challenging species has become a more common practice.
 

http://cornandsoybeandigest.com/inputs/herbicides/good-weed-weather-herbicide-0526/