Wet weather has delayed soybean planting in many areas. As a result, growers may skip applications of soil-residual herbicides. If so, the herbicides may still be applied before the crop emerges, according to Aaron Hager, University of Illinois Extension weed specialist.  

But if soybeans are emerging or a certain number of days has elapsed since planting, growers need to check herbicide labels before proceeding with an application.

Hager says only a few preemerge herbicides may be applied after soybeans emerge. Active ingredients in some preemerge products may cause severe damage to the soybean plant. The damage may occur if the product is applied to the plant or even near the plant.

“Labels often restrict applications to within a certain number of days after planting and/or before there are any visible signs of soybean emergence,” Hager said. “Keep in mind that, in general, the potential for soybean injury can increase as the interval between application and planting decreases.”

Another problem is the soil-residual soybean herbicides may not control emerged weeds when they are applied after soybeans are emerged. Hagar says a postemergence herbicide may then be needed.

For more information on post-emergence applications of the more traditional soil-applied soybean herbicides, read the May 26 edition of The Bulletin from University of Illinois Extension.