Dicamba off target movement created disagreements between many. This occurred in South Dakota between farmers, farmers and companies, farmers and university weed scientists and companies with regulatory agencies. Of the total 170 total pesticide related investigations, the South Dakota Department of Agriculture had 117 cases related to dicamba. To put this into perspective, in 2015 & 2016, the South Dakota Department of Agriculture had only 82 investigations each year dealing with pesticide complaints.
Investigating Off-Target Movement
Last year multiple universities set-out to conduct research on the new post-applied dicamba products on the market for dicamba-tolerant soybeans. Their objectives where to assess off-target movement of Engenia and Xtendimax in field trials using 2017 labeled applications and determine if secondary movement contributes significantly to off-target movement of both formulations. Fexapan is also labeled for post-application, but was not part of this study.
These studies were completed in Arkansas, Indiana, Nebraska and Tennessee by university researchers: Dr. J.K. Norsworthy, G. Kruger, D. Reynolds, L. Steckel, K. Bradley and B. Young. In each, small plots (2-3.5 acres) were set up to be sprayed with either Engenia or XtendiMax. Wind speed during application at each site was at or between the label requirements of 3 to 10 MPH at application. Sprayer speed was 8 MPH, spray volume was 10 gpa and TTI 11003 type nozzles were used. A summary of the preliminary data is in Figure 1.
Assessing Plant Injury
Percent injury is on the Y-axis; distance of injury from plots on X-axis. Above each product (Engenia on left and Xtendimax on right) there is indicated if injury was from secondary movement or a combination of primary and secondary movement. Secondary movement is not affected by application but chemistry of herbicide. This research shows that their application of Engenia and Xtendimax had the largest off-target damage to susceptible plants 20 ft. away from plots, followed by 100 ft. with the second most injury and 200 ft. with the least in both primary + secondary and secondary alone.
There were no differences between formulations at any distance. A considerable portion of the total injury is attributable to secondary movement and the likelihood for some secondary movement of either product appeared high.
Figure 1. Off-Target Movement of Engenia and Xtendimax.