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1 March 2019 Off-target Movement of DGA and BAPMA Dicamba to Sensitive Soybean
Gordon T. Jones, Jason K. Norsworthy, Tom Barber, Edward Gbur, Greg R. Kruger
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It is well established that dicamba can cause severe injury to soybean that is not resistant to dicamba. Dicamba-resistant (DR) cotton became available in 2015, followed by DR soybean in 2016; in late 2016 came the release of new dicamba formulations approved for topical use in cotton and soybeans. Until this approval, use of dicamba was limited to primarily corn, small grains, range and pasture, and eco-fallow acres. Hence, studies were conducted in 2015 and 2016 to examine off-target movement of two dicamba formulations using non-DR soybean as a bio-indicator. Diglycolamine (DGA) and N,N-Bis(3-aminopropyl)methylamine (BAPMA) dicamba were applied simultaneously at 560 g ae ha–1 in the center of two side-byside 8-ha fields to vegetative glufosinate-resistant soybean. On the same day, a rate response experiment was established encompassing nine different dicamba rates of each formulation. Results from the rate response experiment indicate that soybean is equally sensitive to DGA and BAPMA dicamba. In 2015, a rain event occurring 6 to 8 h after application of the large drift trial probably limited off-target movement by incorporating some of the herbicide into the soil. As a result, secondary drift was less in 2015 than in 2016. However, minimal secondary injury (<5%) occurred 12m farther into DGA dicamba plots in 2015. In 2016, secondary movement was decreased by 72m when BAPMA dicamba was used compared to DGA dicamba. Appreciable secondary movement of both DGA and BAPMA dicamba is possible following in-crop applications of either formulated product to soybean in early to mid-summer. Additionally, the risk for secondary movement of BAPMA dicamba is slightly less than for DGA dicamba.

Nomenclature: Dicamba; glufosinate; cotton, Gossypium hirsutum L.; soybean, Glycine max (L.) Merr.

© Weed Science Society of America, 2019. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Gordon T. Jones, Jason K. Norsworthy, Tom Barber, Edward Gbur, and Greg R. Kruger "Off-target Movement of DGA and BAPMA Dicamba to Sensitive Soybean," Weed Technology 33(1), 51-65, (1 March 2019).
Received: 8 September 2018; Accepted: 19 December 2018; Published: 1 March 2019

dicamba symptomology
dicambaresistant cotton
dicamba-resistant soybean
leaf malformation
Off-target movement
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