Delayed planting has complicated weed management for Iowa farmers this year. Gaps in the soybean canopy, especially in 30-inch rows, will favor the survival of late-emerging weeds, says Mark Licht, Iowa State University Extension cropping systems specialist.

As the calendar turns to July, farmers also need to consider the effect of later herbicide applications on next year’s crop cycle, he points out.

“One thing to at least place some caution with is understanding what the rotational interval is. If it’s a soybean field going to corn next year, we want to make sure that the herbicide allows that rotation to occur without any potential injury,” he explains. “It’s...