On March 15, the U.S. Environmental Protection Agency (EPA) approved the label amendments that further restrict the use of over-the-top dicamba in Iowa and Minnesota. These changes came after the reports of high numbers of off-target dicamba injury incidents in Iowa and Minnesota in 2021. During the 2021 growing season, Iowa ranked second after Minnesota, for the highest reported number of off-target dicamba injury incidents at 528, but had the most affected acres of soybeans reported at 101,000 acres (EPA, 2021) Therefore, EPA stated that “these restrictions are intended to reduce the likelihood of volatility and offsite movement of over-the-top dicamba by avoiding application on days with high temperatures”. The revised labeling prohibits over-the-top applications of dicamba products (Xtendimax, Engenia, and Tavium) in dicamba-tolerant soybean after June 20 in Iowa, an amendment to the federal cut-off date of June 30.
In addition to the above amendment, applicators must follow all other restrictions for the use of those dicamba products in dicamba-tolerant soybean, which have been in effect since 2020. One of these restrictions include additional measures to protect the endangered species in specific counties. Currently, there are 12 counties in Iowa which are designated with Endangered Species. These include Allamakee, Cerro Gordo, Clayton, Delaware, Dickinson, Dubuque, Emmet, Hancock, Howard, Jackson, Kossuth and Osceola. While using over-the-top dicamba in these counties, both a 310-foot in-field wind-directional spray drift buffer and a 57-foot omnidirectional in-field buffer are required. Similarly, if applying dicamba with a hooded sprayer, both a 240-foot in-field wind-directional spray drift buffer and a 57-foot omnidirectional in-field buffer are required.
For the additional information on protecting endangered species, please check the EPA bulletins live (https://www.epa.gov/endangered-species/bulletins-live-two-view-bulletins).
It is critical to consider these amendments as dicamba use in soybean is likely to increase this year due to the shortage of key herbicides such as glyphosate and glufosinate.