Dicamba drift sows trouble in Arkansas

Arkansas is considering a 120-day ban on the use of dicamba herbicide on cotton and soybeans. The ban would be a response to farmers who say dicamba drifted to their fields from other farms and damaged crops.

Dicamba is used to control broadleaf weeds, including those such as Palmer amaranth that have developed resistance to the herbicide glyphosate. Herbicide-resistant weeds have become a major problem for farmers, particularly in the southern U.S.

This year, cotton and soybean farmers had the option to plant crops genetically modified to tolerate being sprayed with dicamba. The Arkansas State Plant Board approved a new dicamba formulation—BASF’s Engenia—for use during the growing season.

Engenia is an N,N-bis-(3-aminopropyl)methylamine salt of dicamba developed by BASF to reduce drift. To ensure the herbicide stays put, farmers are required to use Engenia rather than older formulations and follow detailed application instructions.

Even with those controls in place, the Arkansas plant board has received 135 complaints from farmers alleging off-target damage from dicamba across 17 counties. Confirming the cause requires investigators to go to each site to examine plant symptoms and pesticide records.

The board says it has investigated a higher-than-normal volume of dicamba-related complaints since the new crop trait became available. Reports of dicamba drift have also emerged in Mississippi, Tennessee, and Missouri.

Monsanto and DuPont have their own low-drift formulations of dicamba based on diglycolamine salts. They were not approved for use in Arkansas after April 15 but can be applied in other states during the growing season.