No-tlll corn growers have two options for pre-plant weed control — they can incorporate a residual herbicide in the fall, or burn down weeds in the spring with a contact herbicide.

A burndown product with contact activity used in the spring will eliminate weeds and crop residue, an option confidently recommend by many weed specialists. Burndown herbicides also control a broader spectrum than residuals. However, both fall and spring programs have their benefits.

Which Is Best?

Weed scientists say that your best option depends on several factors, including geography, seasonal weather, soil type, target weeds and terrain.

For example, James Martin, University of Kentucky Extension weed scientist at the Western Kentucky Research Center in Princeton, Ky., recommends taking a close look at the history of the field. No-tillers who typically have problems getting into wet fields in the spring might want to consider fall spraying.

Specific weed challenges should be taken into consideration, Martin says. Some weeds are more conducive to a fall herbicide application, such as annual ryegrass in corn.

“Annual ryegrass is a menace in no-till corn,” he says. “It emerges in the fall and over winters. Even with Gramoxone Max or a glyphosate product, it is hard to control in the spring.”

Giant ragweed is another weed that is difficult to control, particularly when spring burndown applications are not applied in a timely manner.

“Fall applications that contain a soil residual herbicide such as Princep may sometimes help control giant ragweed plants before they begin to emerge…