More farmers are switching from herbicide dicamba, but that leaves their crops vulnerable to those who still use it

"Among the many moving targets to keep an eye on this season is off-target dicamba injury in soybeans. And it’s already evident in Midwestern states," Megan Schilling reports for Successful Farming. Agronomists and others in Iowa say they've seen what appear to be dicamba injuries to soybeans that aren't genetically modified to resist the herbicide. "There are reports of widespread damage to soybeans in southern Illinois and complaints of pesticide misuse that specifically mention damage to trees. The signs are cupping in soybean leaves and bare trees in July and August."

Agronomists had hoped to see less off-target damage this year since many farmers switched from using dicamba-based herbicides to Enlist, a Dow Chemcial system developed to replace Roundup (both contain glyphosate), Schilling reports. The widespread adoption of Enlist means that, even though less dicamba has been sprayed overall, more acres are vulnerable to it.

"As long as we have dicamba, it's not a question of if we ever will see off-target injury in a year, the only unknown is how extensive it will be," Aaron Hager, associate professor and faculty Extension specialist at the University of Illinois Urbana-Champaign, told Schilling.

The heat doesn't help, Hager said: "When there is widespread use of a volatile product like dicamba at times of the growing season where temperatures are much higher than normal, we continue to see the effects across the landscape." Researchers have found that plenty of rain or weekly irrigation are the best ways to help dicamba-injured soybeans recover, but drought can put those options out of reach. Windbreaks with multiple rows of perennial trees and shrubs have also been found to minimize damage, Schilling reports.