Iowa State University (ISU) Extension weed scientists are re­­commending only pre-emergence applications of dicamba on Roundup Ready 2 Xtend soybean fields in 2018 after widespread reports of off-target damage oc­­curred this year.

“We are fully aware that this very much limits the utility of the technology,” Extension Weed Specialist Mike Owen said last week at the annual ISU Integrated Crop Management Conference in Ames. “We (feel) the benefits do not outweigh the risks.”

New low-volatility dicamba formulations, including BASF’s Engenia and Monsanto’s Xtendimax with VaporGrip technology, were approved for over-the-top application on Xtend soybeans for the first time this year. A third low-volatility formulation, FeXapan by Dupont, was also approved but used on a smaller number of acres.

An estimated 3.6 million acres of soybeans were injured by off-target dicamba applications across the United States this year, according to information compiled by Kevin Bradley, a University of Missouri weed scientist. In Iowa, dicamba-related soybean injury totaled about...