Minnesota Dicamba Temperature, Cutoff Dates Credited for Less Off-Target Movement

However, they combined with rampant rainfall to prevent later dicamba applications.

The clock is ticking for dicamba use in dicamba-tolerant soybean systems, as its two-year conditional release expires November 9. An announcement by the Environmental Protection Agency regarding dicamba use in this system in 2019 is expected any day. Here’s what various parties are saying about dicamba’s performance in 2018.

Backing by Bayer

Off-target dicamba damage to soybeans and other crops did occur in 2018. However, it was down from 2018, according to Bayer Crop Science officials. (Bayer bought Monsanto and the accompanying Roundup Ready 2 Xtend system and accompanying Xtendimax herbicide in 2018. BASF makes another dicamba herbicide for the system called Engenia.)

In 2017, inquiries regarding off-target dicamba in the Roundup Ready 2 Xtend system tallied 99 inquires per 1 million acres. This year, it’s down to 13 per 1 million acres, and most revolved around weed-control issues, says Brett Begemann, Bayer Crop Science chief operating officer. Xtend soybean acreage is up, though, having doubled from last year’s 25 million acres to this year’s nearly 50 million acres. 

Ryan Rubischko, product manager and marketing lead for Bayer Crop Science, credits this to the nearly 100,000 farmers and applicators who went through dicamba classroom training before the 2018 application season. 

“It covered practical aspects of the (dicamba) label, with real-world scenarios,” he says. 

Training covered steps including:

  • Knowing what crops are planted on neighboring fields.
  • Applying dicamba at optimal times of the day (included on the label) to apply dicamba. For example, AMS – a common herbicide tank additive – cannot be used with Xtendimax, Rubischko says.
  • Applying within proper label wind speed and wind direction parameters.
  • Using only labeled tank additives.

After two years, U.S. farmers have planted nearly 50 million dicamba-tolerant soybeans acres out of approximately 89.6 million acres in 2018, according to Bayer Crop Science officials. 

“It’s a huge footprint for a technology that is two years old,” says Jesus Madrazo, who heads agricultural affairs and sustainability for Bayer Crop Science. Medrazo addressed dicamba at last week’s Future of Farming Dialogue held at Bayer’s headquarters in Monheim, Germany. He acknowledges complications like off-target movement has occurred during this quick ramp-up.  

“But the encouraging thing is that when you hear the feedback from farmers, more than 97% of that feedback is they are extremely satisfied with the performance of the product. They’re seeing the cleanest fields ever when they apply the technology.  

“We’ve also seen a significant reduction of (off-target) claims,” Madrazo says. “That’s the result of farmers getting more familiar with the technology. It’s the result of a lot of work that has been taking place by governmental authorities, our company, and so many others who provide training. It will only get better as this technology continues to work.”

State Cutoffs

Off-target dicamba movement was down in some states like Minnesota. After 2017, the Minnesota Soybean Growers Association formed a dicamba task force that included officials from the:

  • Minnesota Department of Agriculture (MDA)
  • University of Minnesota (U of M) Extension 
  • Agrichemical industry
  • Commercial applicators
  • Farmers

Two 24c restrictions to the federal label came out of that process, says Jeff Gunsolus, U of M Extension weed specialist. 

  • 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.

“The data was clear in 2017 that (off-target) incidents increase after June 20 and especially in July,” says Gunsolus. 

Compared with states that did not have cutoff dates, Minnesota had limited complaints of off-site dicamba movement in 2018, says Gunsolus. In 2017, there were over 250 reports of dicamba damage, he says. In 2018, MDA has so far fielded 52 reports of dicamba damage covering 1,850 acres, says Joshua Stamper, director of the pesticide and fertilizer management division for the MDA. Of those acres, most were soybeans but not all, he says. 

Gunsolus says applicator training did help reduce off-target movement of dicamba in many states. However, states with no additional state restrictions like Illinois had problems with off-target dicamba movement in 2018. 

The Illinois Department of Agriculture has so far recorded 330 dicamba complaints in 2018. That’s up from 246 in 2017. With no temperature and/or date cutoffs, complaints continued to come in through July and August, says Jean Payne, president of the Illinois Fertilizer and Chemical Association. “Nearly all are soybean related,” she says.

Cutoff Drawbacks

Rubischko says dicamba works well, especially when applied early in the growing season. Besides being more effective on small weeds, applying a product like Bayer’s Xtendimax or BASF’s Engenia gives farmers more flexibility in case factors like excessive wind dash the day’s spraying plans, he says. Spraying early enables applicators to come back and apply under label parameters and still obtain excellent weed control, he says. 

However, Bayer officials don’t favor temperature or date cutoffs like those in Minnesota. 

“Date restrictions or temperature cutoffs are not warranted,” he says. “Minnesota is an example of an unwarranted cutoff data that led to complications for farmers.” 

Excessive rainfall prevented many farmers with significant weed pressure from applying dicamba in dicamba-tolerant soybeans after the cutoffs, he says. 

“Many of the growers who planted dicamba-beans were not able to apply registered dicamba products prior to the cutoff date, due to the federal label restrictions and the temperature cutoff for Minnesota,” says Stamper. “For many growers, it was just too wet to get into the field, and when it was dry enough to get in the field, the wind was blowing 25 mph or it was too hot.”

Still, the cutoff dates helped to reduce cases of off-target dicamba, he says. 

“It was very sobering to see the hundreds of dicamba damage complaints in some of the states that did not have application cutoff dates," he says.  

Early applications also have the best fit for dicamba, says Gunsolus.  

“Extension weed scientists I talk to see the best use for dicamba in Xtend soybeans is from burndown up to an early postemergence application,” says Gunsolus. “The target species are weeds like common lambsquarter and common and giant ragweed. Because waterhemp is a later emerging weed — emerging well into July — the dicamba fit is not as good, and this is where the off-target troubles begin.”

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