According to Wisconsin soybean growers, our stakeholders, waterhemp (Amaranthus tuberculatus) continues to be the most difficult-to-control and concerning weed species in Wisconsin's corn-soybean production systems.

During the summer of 2023, UW-Extension Weed Specialist, Dr. Rodrigo Werle, received several calls regarding lack of complete post-emergence waterhemp control with Callisto and/or dicamba in corn and with Enlist One in soybeans. Thanks to support from the Wisconsin Soybean Marketing Board, we've been able to launch an immediate investigation into why this is happening through,

Werle explains to Pam Jahnke that Wisconsin farmers, agronomists, and industry representatives are being invited to collect waterhemp seeds this fall from Wisconsin corn and soybean production fields where Callisto, dicamba, and/or Enlist One didn’t provide satisfactory post-emergence waterhemp control and submit them to the UW-Madison’s Wisconsin Cropping Systems Weed Science lab for herbicide resistance screenings.

Werle intends to screen the waterhemp samples in the greenhouse for resistance to Callisto (mesotrione; Group 27), Enlist One (2,4-D; Group 4), dicamba (Group 4), and glufosinate (Liberty; Group 10). Results will be made available to those who submit the samples after the greenhouse screenings are completed.

There is no cost associated with the herbicide resistance screenings. The only cost will be your time to collect the seed samples, thanks in part to Wisconsin soybean checkoff dollars made available through the Wisconsin Soybean Marketing Board.