Why many Minnesota farmers are facing an early 2022 dicamba application cutoff date
The Minnesota Department of Agriculture (MDA) is recommending a Minnesota 2022 cut-off date of June 12 to the Environmental Protection Agency (EPA) for dicamba formulations labeled for dicamba-tolerant soybeans planted south of Interstate Highway 94.
This area encompasses much of central and southern Minnesota. Soybean farmers north of Interstate Highway 94 — including much of northwestern Minnesota — may apply dicamba formulations on dicamba-tolerant soybeans up until June 30. This is the same cutoff date as the federal label approved in October 2020.
“There is value in dicamba,” said Joshua Stamper, director of MDA’s pesticide and fertilizer management division to those attending this month’s Minnesota crop pest management short course. “It is still a very effective herbicide, and we are in a situation where we don’t have a lot of very effective herbicides left.”
Dicamba’s weak point, though, is that it doesn’t always stay at home. “Dicamba is a highly volatile chemical that causes lots of damage through off-target movement,” says Stamper.
Why the Early Date?
In 2017, the Environmental Protection Agency approved matching XtendiMax (Bayer), Engenia (BASF), and FeXapan (Corteva Agriscience, discontinued earlier this year) postemergence dicamba formulations for dicamba-tolerant soybeans. (In 2019, Syngenta launched Tavium, a dicamba formulation labeled for application on dicamba-tolerant soybeans though the V4 growth stage.)
That year, the MDA received 253 complaints of alleged off-target dicamba movement, with 55 of those requiring investigations. This impacted an estimated 265,000 acres. The number may have tallied closer to 1 million acres, as farmers don’t like to turn in other farmers, Stamper believes.
“Driving to Farmfest (near Morgan in southwestern Minnesota) that year, I could not spot a (soybean) field that didn’t look like it had been damaged,” says Stamper. In 2018, Minnesota stakeholders revised the federal label. Two 24c restrictions to the federal label came out of this process.
- No dicamba applications in dicamba-tolerant soybeans after June 20.
- No dicamba applications in dicamba-tolerant soybeans if the daily high temperature is forecast to be over 85°F.
Following this, 2018 complaints dropped to 53 impacting over 1,800 acres, with 29 formal investigations requested. Complaints dropped even further in 2019, with just 21 reports impacting 760 acres, says Stamper.
However, complaints increased in 2020, with 104 complaints filed. Out of these, nearly one-half requested investigations, says Stamper. In 2021, nearly 300 complaints were filed, with 132 requesting investigations.
One factor that likely led to fewer complaints in 2018 and 2019 was cooler and wet weather, says Stamper.
Rainfall doesn’t necessarily make the symptoms of dicamba injury such as cupped leaves go away, but it does allow plants to continue to grow, says Aaron Hager, University of Illinois Extension weed specialist. “A lot of times, you won’t see symptomology on the next set of leaves,” he says.
Still, the increase in the number of complaints in 2020 and 2021 with investigation requests reveals that people are tiring of enduring damage, believes Stamper. Failure to comply with the label is a contributing factor, Stamper adds. “In the period of time from 2018 to 2020, we didn’t have a single person that had a complaint filed against them demonstrate that they complied with the dicamba label,” he says.
Legal applications do exist, he says.
“Quite frankly, commercial applications are not the bulk of our issues,” Stamper adds. “Most issues are with private applicators and non-commercial applicators (including farmers).”
What to Do
If you’re a parent, have you ever told your sons or daughters “nothing good ever happens after midnight?” It’s akin to “nothing good happens with dicamba applied later in the season,” says Stamper.
That’s the rationale for the June 12 cutoff proposal, he adds. In 2021, Minnesota followed the federal cutoff date of June 30. An analysis of 2021 complaints reveals that a June 20 cutoff date would have reduced complaints only 15%. Meanwhile, a June 12 cutoff date would have reduced complaints about 75%.
“We need to be using products like dicamba early,” says Stamper. “Using products like dicamba late in the growing season is a recipe for getting your neighbors pissed at you. You will have problems.”
North of Interstate Highway 94, the federal label cutoff date of June 30 will stand. Complaints typically have been lower in northwestern Minnesota than other areas, Stamper notes.
Both areas will have temperature restrictions. No applications shall be made if the air temperature of the field at application time exceeds 85°F. or if the National Weather Service’s forecasted high temperature for the nearest available location for the day exceeds 85°F.
The state-specific restrictions will require EPA approval and would appear on the federal label for each product. The MDA will also require product makers to provide approved education and training for applicators. Stamper says the MDA is also working with manufacturers on these changes.
Bayer, which sells the dicamba formulation XtendiMax, released this statement on MDA’s proposal: We are aware of the proposal from the Minnesota Department of Agriculture (MDA) and will work with them to ensure this important tool is available to Minnesota soybean growers and applicators for the 2022 growing season and beyond.
Symptom, not the Problem
Dicamba damage symptoms are just part of a bigger picture that revolve around herbicide resistance, says Stamper.
“When you see news articles about antibiotic resistance and you replace the word antibiotic with pesticide, it’s the exact same article,” he says. University weed scientists have already confirmed weeds that resist dicamba in states that include Tennessee and Illinois. That’s why rotating herbicide sites of action and layering preemergence residual herbicides are key for not only effective control, but for forestalling resistance, Stamper says.
“The challenges that we have with dicamba damage are more than anything a reflection of the fact that we are losing chemistry at a rate that is entirely unsustainable,” he says.