According to a report by the National Wildlife Federation, the Prairie Rivers Network, and the Xerces Society for Invertebrate Conservation, the synthetic herbicide dicamba has devastated more than five million acres of American crops since the Environmental Protection Agency (EPA) conditionally approved its use in 2016. The report found that the herbicide poses “significant threats” to crops, native plants, and the wildlife that depend on them, even when applied as prescribed on the manufacturers’ labels.
The herbicide was first introduced in the 1960s and has been used for “broadleaf weed control in crops, lawns, and turfgrass,” traditionally at the beginning of the growing season to kill annual weeds before planting crops. Dicamba’s active ingredients function by mimicking plant hormones that work by disrupting their growth.
The herbicide is characterized by high volatility and mobility, meaning that it evaporates quickly from plant and soil surfaces, then drifts away from use areas. This affects nearby cultivation and indigenous growth, particularly during temperature inversions and hot weather in southern and midwestern states, where its use is prevalent.
Since 2015, agricultural giants like Monsanto (recently acquired by Bayer), BASF, Dow Agrosciences, and DuPont (now DowDuPont, with the agricultural division Corteva Agriscience) have developed and released dicamba-resistant soy and cotton seeds. Revised dicamba herbicidal formulations, marketed as having reduced vapor drift, received conditional approval from the EPA for “over-the-top” crop applications for the aforementioned dicamba-resistant crops in late 2016. Yet, dicamba drift and damage to both crops and natural areas have been widely reported since.
To avoid short and long term consequences, the report recommended that policymakers step in. It argued for four key implementations, including that the EPA does not renew any dicamba over-the-top product registrations until independent research can demonstrate that dicamba will not cause off-target damage. The report also suggested that the EPA conduct “full risk assessments” for Endangered Species Act-listed aquatic life, birds, and pollinators exposed to dicamba.
The environmental groups urge the United States Department of Agriculture not to deregulate dicamba-resistant crop strains, arguing that this would cause more widespread use of the herbicide. Finally, they recommended greater resource devotion to the research, development, and popularization of sustainable, multi-tactic weed management solutions to reduce reliance on harmful herbicides like dicamba.
