In an era of herbicide-resistant pigweed, kochia, waterhemp and marestail, controlling weeds is not easy. But it’s also not easy to watch your cash crop perish due to off-target herbicide application.

So far in 2017, farmers have reported hundreds of complaints of dicamba herbicide damage on various cash crops, ornamentals, trees and vine crops in several southeast and Midwest states. 

As a result, by July 11, Missouri and Arkansas have prohibited the sale of dicamba herbicide. 


History lesson

The dicamba-tolerant trait was developed at the University of Nebraska, and licensed to Monsanto in 2005. Under the terms of the licensing agreement, Monsanto has exclusive license to integrate the trait into commercial crop lines. According to a 2005 release from Monsanto, dicamba is “…effective against most broadleaf weeds, including weeds that are hard to control. However, it is harmful to crops such as soybeans, canola and cotton, which also are broadleaf plants. The new technology will allow the development of soybean and other broadleaf crops that are highly tolerant to treatment with dicamba.” 

Monsanto released Xtend soybeans in time for the 2016 crop year, although neither the company’s XtendiMax with VaporGrip Technology herbicide nor other low-drift dicamba formulations (including BASF’s Engenia and DuPont’s FeXapan plus VaporGrip Technology) were approved by the Environmental Protection Agency for that crop year. 

The EPA did approve XtendiMax, FeXapan and Engenia for application in the 2017 crop. All three dicamba formulations are labeled as low-drift products. Yet, there is definite damage due to dicamba. Ohio State University weed specialists Bill Johnson and Mark Loux write in a newsletter that in many cases, injury is indicative of both particle drift and volatility. 

“However, an alarmingly high number of fields seem to show we have more offsite movement due to volatility than we thought would happen based on past experience with dicamba use in corn and the development of lower volatility formulations of dicamba products labeled for use in Xtend beans. This is not to say that spray particle drift is not occurring. It is evident that in many situations, dicamba is being applied in too much wind or with no buffer left between the treated beans and adjacent non-Xtend soybeans,” the pair wrote. 

On July 7, the Missouri Department of Agriculture issued a temporary Stop Sale, Use or Removal Order on all dicamba products in Missouri. Arkansas issued a similar statement that went into effect July 11.

In response, Monsanto issued a statement reading in part: “We sympathize with any farmers experiencing crop injury, but the decision to ban dicamba in Arkansas was premature since the causes of any crop injury have not been fully investigated. While we do not sell dicamba products in Arkansas, we are concerned this abrupt decision in the middle of the growing season will negatively impact many farmers in Arkansas. 

“We strongly encourage farmers using dicamba in other states to make their voice heard. Share how important this tool is to your farm and how you are using it responsibly. We have heard those stories. To ensure your continued access to dicamba products, make sure your elected officials and relevant agencies hear those stories, too.”


Hundreds of complaints

As of July 10, the number of dicamba drift calls to state departments of agriculture includes:

• Arkansas—330;

• Missouri—130; and

• Kansas—30.


Stewardship requirements

Growers using this technology must meet several label requirements, including: spraying within a wind speed of 3 to 10 miles per hour, no spraying if a rain is forecast within 24 hours and no tank mixtures are approved. Applicators using these products can only apply via ground rig using a TT11004 nozzle, and must leave a 110- to 220-foot buffer strip, and an additional buffer in the case of sensitive areas. 

Jason Norsworthy, weed specialist at the University of Arkansas, said many of the label requirements contradict weed management. “This is a resistance management nightmare. If you are not killing weeds on the edge of the field, you are selecting for herbicide resistance. One of the keys in preventing herbicide resistant weeds is to take care of weeds at the edge of the field,” he said. 

“Also, the individual who applies the herbicide is solely responsible and liable for off-target movement,” Norsworthy added. “That’s the local co-op, or the grower who sprays. Not the chemical company.” 

Bill Spiegel can be reached at 785-587-7796 or

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