Tips For Applying Soil-Residual Herbicides In Post-Emergence Scenarios

U of I's Aaron Hager says depending on the herbicide, growers may be able to apply a soil residual in a post-emergence situation.

Published on: May 20, 2013

Rain events have put Illinois farmers squarely behind the eight ball.

As University of Illinois weed specialist Aaron Hager notes in a recent issue of The Bulletin, many are running into a time crunch with corn planting and applying soil-residual herbicides. If corn has not yet emerged, Hager recommends spraying the residual herbicide as planned.

But, what if the corn has emerged and the soil-residual herbicide has not been applied?  Can the application proceed as planned, or will a different product need to be selected?  The answer depends on the respective herbicide.

Hager says most, but not all, soil residual herbicides can be applied after corn has emerged. 

Tips For Applying Soil-Residual Herbicides In Post-Emergence Scenarios
Tips For Applying Soil-Residual Herbicides In Post-Emergence Scenarios

"Products such as Balance Pro, Fierce, Prequel, Sharpen and Verdict must be applied before corn begins to emerge; applications of these products to emerged corn can result in significant corn injury," he notes. "Be cautious about applying a soil-residual herbicide in UAN carrier if corn has emerged as this can increase the potential for corn injury."

Several soil-residual herbicides can control small, emerged summer annual weeds.  Additional management procedures (such as the addition of an herbicide that has postemergence activity) will be needed for those products that lack the ability to control emerged weeds. In all situations, Hager advises reading the respective product label for tankmix and additive recommendations.

"Labels usually indicate a maximum corn growth stage beyond which applications should not occur," he notes. "These growth stages can range from as early as two leaf collars to as late as 40-inch tall corn, so be sure to consult the respective product labels.  Products containing atrazine must be applied before corn exceeds 12-inches tall, although the labels of some atrazine-containing products specify a smaller corn height."

Source: University of Illinois