Dicamba has been in the headlines the last two weeks. In case you’ve missed it, here are the highlights:
On June 3 the United States Court of Appeals for the Ninth Circuit ruled against the Environmental Protection Agency and its 2018 registration of over-the-top dicamba products Xtend, Engenia, and FeXapan and vacated their registrations. The suit did not include a fourth over-the-top dicamba herbicide, Tavium. The ruling can be viewed here: https://cdn.ca9.uscourts.gov/datastore/opinions/2020/06/03/19-70115.pdf
Between June 3 and June 8, state regulators across the middle part of the country were forced to interpret the ruling, with some choosing to ban the products and others continuing to allow them. Extension row crop weed scientists across the county pulled together recommendations for managing broadleaf weeds without dicamba, including Purdue (https://extension.entm.purdue.edu/newsletters/pestandcrop/article/well-now-what-do-i-do-if-i-cant-spray-a-dicamba-product-in-xtend-soybean/).
On June 8 the EPA issued a cancellation order for the three dicamba products, but allowed applicators to use products in their possession. The product had to be purchased on or before June 3 and must be used by July 31. The full order can be found here: https://www.epa.gov/sites/production/files/2020-06/documents/final_cancellation_order_for_three_dicamba_products.pdf
What does all of this mean for the future of over-the-top auxin herbicides and off-target risk to sensitive crops?
The Indiana cut-off date for over-the-top dicamba application was June 20. This date has not changed. Many other states have similar cut-off dates well before the EPA deadline of July 31.
The three dicamba herbicides affected by the court’s ruling and the EPA cancellation order were only registered for two years with their registrations ending in 2020. It is expected that there will be new formulations of dicamba for over-the-top use in 2021.
Time will tell what effect these events will have on off-target movement to sensitive crops. For this reason it is important for applicators to practice good herbicide stewardship and for producers of sensitive crops to remain vigilant.
New fact sheet series about dicamba and 2,4-D drift now available online.
Scientists with Purdue University, Ohio State University, along with the North Central Integrated Pest Management Center and a nation-wide working group of weed scientist have developed a series of fact sheets to help specialty crop producers navigate issues related to dicamba and 2,4-D drift. Although the emphasis is on auxinic herbicides, the principles laid out in the fact sheets can be more broadly applied to other types of herbicide drift. Printed versions of the fact sheets will be available this fall.
Overview of Dicamba and 2,4-D Drift Issues: https://ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/overview-dicamba-and-24-d-drift-issues
Frequently Asked Questions: https://ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/frequently-asked-questions
Preparing for Drift Damage: https://ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/preparing-drift-damage
Responding to Drift Damage: https://ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/responding-drift-damage
More Resources: https://ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/more-resources
A tomato displaying epinasty (stem and petiole twisting), a symptom of auxinic herbicide exposure.