Sandell and Owen both rank velvetleaf as the fifth-most-difficult weed to control in corn, mostly due to its prevalence, competitiveness and the longevity of seed in the soil.

“Velvetleaf is common in cornfields all across Nebraska,” Sandell says. “It can be difficult to control if an application isn’t timely or is made too early or late in the day. Research has demonstrated lower levels of control with glyphosate are possible when velvetleaf’s photosynthetic rate is slower in the early morning or late day.”

Velvetleaf tends to be less of a problem in Illinois than in states further west, says Hager, who ranks annual morningglory as the fifth-most-difficult weed to control for corn in Illinois, partly due to how swiftly it spreads. “Timing is extremely important with morningglory, because it can get away from you very quickly,” he says.

Control problems also can occur with this weed when relying on glyphosate alone, Hager points out. “Annual morningglory is not as effectively controlled with glyphosate as other weeds are,” he says. “So for glyphosate to be effective, you’ll need to tank mix a product that offers good morningglory control.”