In 2016, the majority of the cotton acreage in the southeastern portion of Missouri was planted with dicamba-tolerant (DT) varieties. A limited number of DT soybean varieties were also planted throughout the state. However, during the 2016 growing season, the Environmental Protection Agency had not approved any dicamba herbicide formulations for post-emergence application to DT cotton or soybean. Although investigations are ongoing, apparently a subset of growers made illegal applications of dicamba to their DT cotton and/or soybean, which resulted in off-target movement of dicamba to a variety of sensitive crops, including large acreages of non-DT soybean. In southeastern Missouri alone, over 125 dicamba injury complaints were filed with the Missouri Department of Agriculture. These injury complaints occurred on over 40,000 acres of soybean, 1,000 acres of cotton, 700 acres of peaches, 400 acres of purple hull peas, 200 acres of peanuts, 32 acres of watermelon, 9 acres of cantaloupe, 6 acres of alfalfa, 2 acres of tomatoes, and on numerous homeowner’s gardens, trees, and ornamental bushes. Some of the primary factors that contributed to the off-site movement of dicamba will be discussed, as well as the impacts that this situation has had and will continue to have on Missouri agriculture.
Soil Science Extension
University of Wisconsin Madison