Issue No. 7, Article 8/May 6, 2005
Delayed Applications of Soil- Applied Corn Herbicides
Soil-applied herbicides continue to be widely utilized for weed management in Illinois cornfields. Of the planted acres scheduled to receive some application of a soil-applied herbicide, most were treated prior to planting or prior to corn emergence. It is likely, however, that some cornfields were planted before the herbicide was applied, and the crop has now emerged.
Can a soil-applied corn herbicide be applied after the crop has emerged? Many, but not all, soil-applied corn herbicides can be applied after corn emergence. Not all of these herbicides will control emerged weeds, so additional management procedures (such as the use of a rotary hoe or the addition of a herbicide that has postemergence activity) may be needed. Atrazine and atrazine-containing premixes can provide postemergence control of certain annual broadleaf (2 to 3 inches) and grass (1.5 inches or less) weed species. We again caution growers about the potential for enhanced corn injury if these products are applied during periods of crop stress, such as stress caused by excessive soil moisture or frost. Table 3 summarizes information about postemergence applications of the more traditional soil-applied corn herbicides. Consult the respective product label for additional information.
--Aaron Hager and Dawn Nordby