One issue is the idea that a fall application suggests you can skip a spring herbicide application. That's a worry given the changing nature of weeds and the fact that even the best herbicide won't be waiting around to stop a spring weed germination flush. However, the rising concern of winter annuals, along with the rising issue of marestail control, complicates the issue.

"Weeds like marestail that behave as an early spring germinator and a winter annual, a fall herbicide application along with what you're using from a spring-applied residual herbicide perspective will help," Owen adds. "It also depends on the likelihood that you'll go forward with the fall application and follow with a spring application. This year a lot of people saw that intention get lost in the shuffle of wet weather. As Bob Burns said, the best laid plans…"

Bill Johnson, Purdue weed scientist, asks whether you're using conventional or no-till as a cultural practice. If you have weeds that can be controlled with a fall tillage pass your need for fall herbicide diminishes. But those winter annuals are a concern. "They can slow spring soil warming and drying," he notes. In a no-till situation that can be problematic.

As for that pesky marestail? "We are sort of in an evolution phase here with the marestail issue," he says. "Here in the Eastern Corn Belt we're almost to the point of making a blanket recommendation for a fall-applied, limited residual herbicide."